8 .ds RF FORMFEED[Page %]
17 Network Working Group P. Riikonen
19 draft-riikonen-silc-spec-01.txt 6 October 2000
25 Secure Internet Live Conferencing (SILC),
26 Protocol Specification
27 <draft-riikonen-silc-spec-01.txt>
32 This document is an Internet-Draft and is in full conformance with
33 all provisions of Section 10 of RFC 2026. Internet-Drafts are
34 working documents of the Internet Engineering Task Force (IETF), its
35 areas, and its working groups. Note that other groups may also
36 distribute working documents as Internet-Drafts.
38 Internet-Drafts are draft documents valid for a maximum of six months
39 and may be updated, replaced, or obsoleted by other documents at any
40 time. It is inappropriate to use Internet-Drafts as reference
41 material or to cite them other than as "work in progress."
43 The list of current Internet-Drafts can be accessed at
44 http://www.ietf.org/ietf/1id-abstracts.txt
46 The list of Internet-Draft Shadow Directories can be accessed at
47 http://www.ietf.org/shadow.html
49 The distribution of this memo is unlimited.
55 This memo describes a Secure Internet Live Conferencing (SILC)
56 protocol which provides secure conferencing services over insecure
57 network channel. SILC is IRC [IRC] like protocol, however, it is
58 not equivalent to IRC and does not support IRC. Strong cryptographic
59 methods are used to protect SILC packets inside SILC network. Two
60 other Internet Drafts relates very closely to this memo; SILC Packet
61 Protocol [SILC2] and SILC Key Exchange and Authentication Protocols
75 1 Introduction .................................................. 3
76 2 SILC Concepts ................................................. 3
77 2.1 SILC Network Topology ..................................... 4
78 2.2 Communication Inside a Cell ............................... 5
79 2.3 Communication in the Network .............................. 6
80 2.4 Channel Communication ..................................... 7
81 2.5 Router Connections ........................................ 7
82 3 SILC Specification ............................................ 8
83 3.1 Client .................................................... 8
84 3.1.1 Client ID ........................................... 9
85 3.2 Server .................................................... 10
86 3.2.1 Server's Local ID List .............................. 10
87 3.2.2 Server ID ........................................... 11
88 3.2.3 SILC Server Ports ................................... 11
89 3.3 Router .................................................... 12
90 3.3.1 Router's Local ID List .............................. 12
91 3.3.2 Router's Global ID List ............................. 13
92 3.3.3 Router's Server ID .................................. 13
93 3.4 Channels .................................................. 14
94 3.4.1 Channel ID .......................................... 15
95 3.5 Operators ................................................. 15
96 3.6 SILC Commands ............................................. 15
97 3.7 SILC Packets .............................................. 16
98 3.8 Packet Encryption ......................................... 16
99 3.8.1 Determination of the Source and the Destination ..... 17
100 3.8.2 Client To Client .................................... 17
101 3.8.3 Client To Channel ................................... 19
102 3.8.4 Server To Server .................................... 19
103 3.9 Key Exchange And Authentication ........................... 20
104 3.10 Algorithms ............................................... 20
105 3.10.1 Ciphers ............................................ 20
106 3.10.2 Public Key Algorithms .............................. 21
107 3.10.3 MAC Algorithms ..................................... 21
108 3.10.4 Compression Algorithms ............................. 22
109 3.11 SILC Public Key .......................................... 22
110 3.12 SILC Version Detection ................................... 24
111 4 SILC Procedures ............................................... 25
112 4.1 Creating Client Connection ................................ 25
113 4.2 Creating Server Connection ................................ 26
114 4.3 Joining to a Channel ...................................... 27
115 4.4 Channel Key Generation .................................... 28
116 4.5 Private Message Sending and Reception ..................... 29
117 4.6 Private Message Key Generation ............................ 29
118 4.7 Channel Message Sending and Reception ..................... 30
119 4.8 Session Key Regeneration .................................. 30
120 4.9 Command Sending and Reception ............................. 30
121 5 SILC Commands ................................................. 31
122 5.1 SILC Commands Syntax ...................................... 31
123 5.2 SILC Commands List ........................................ 33
124 5.3 SILC Command Status Types ................................. 56
125 5.3.1 SILC Command Status Payload ......................... 56
126 5.3.2 SILC Command Status List ............................ 57
127 6 Security Considerations ....................................... 61
128 7 References .................................................... 61
129 8 Author's Address .............................................. 62
136 Figure 1: SILC Network Topology
137 Figure 2: Communication Inside cell
138 Figure 3: Communication Between Cells
139 Figure 4: Router Connections
140 Figure 5: SILC Public Key
141 Figure 6: SILC Command Status Payload
147 This document describes a Secure Internet Live Conferencing (SILC)
148 protocol which provides secure conferencing services over insecure
149 network channel. SILC is IRC [IRC] like protocol, however, it is
150 not equivalent to IRC and does not support IRC.
152 Strong cryptographic methods are used to protect SILC packets inside
153 SILC network. Two other Internet Drafts relates very closely to this
154 memo; SILC Packet Protocol [SILC2] and SILC Key Exchange and
155 Authentication Protocols [SILC3].
157 The protocol uses extensively packets as conferencing protocol
158 requires message and command sending. The SILC Packet Protocol is
159 described in [SILC2] and should be read to fully comprehend this
160 document and protocol. [SILC2] also describes the packet encryption
161 and decryption in detail.
163 The security of SILC protocol and for any security protocol for that
164 matter is based on strong and secure key exchange protocol. The SILC
165 Key Exchange protocol is described in [SILC3] along with connection
166 authentication protocol and should be read to fully comprehend this
167 document and protocol.
169 The SILC protocol has been developed to work on TCP/IP network
170 protocol, although it could be made to work on other network protocols
171 with only minor changes. However, it is recommended that TCP/IP
172 protocol is used under SILC protocol. Typical implementation would
173 be made in client-server model.
179 This section describes various SILC protocol concepts that forms the
180 actual protocol, and in the end, the actual SILC network. The mission
181 of the protocol is to deliver messages from clients to other clients
182 through routers and servers in secure manner. The messages may also
183 be delivered from one client to many clients forming a group, also
186 This section does not focus to security issues, instead basic network
187 concepts are introduced to make the topology of the SILC network
192 2.1 SILC Network Topology
194 SILC network is a cellular network as opposed to tree style network
195 topology. The rationale for this is to have servers that can perform
196 specific kind of tasks what other servers cannot perform. This leads
197 to two kinds of servers; normal SILC servers and SILC routers.
199 A difference between normal server and router server is that routers
200 knows everything about everything in the network. They also do the
201 actual routing of the messages to the correct receiver. Normal servers
202 knows only about local information and nothing about global information.
203 This makes the network faster as there are less servers that needs to
204 keep global information up to date at all time.
206 This, on the other hand, leads to cellular like network, where routers
207 are in the center of the cell and servers are connected to the router.
209 Following diagram represents SILC network topology.
229 ---- ---- ---- ---- ---- ----
230 | S8 | S5 | S4 | | S7 | S5 | S6 |
231 ----- ---- ----- ----- ---- -----
232 | S7 | S/R1 | S2 | --- | S8 | S/R2 | S4 |
233 ---- ------ ---- ---- ------ ----
234 | S6 | S3 | S1 | | S1 | S3 | S2 | ---- ----
235 ---- ---- ---- ---- ---- ---- | S3 | S1 |
236 Cell 1. \\ Cell 2. | \\____ ----- -----
238 ---- ---- ---- ---- ---- ---- ---- ------
239 | S7 | S4 | S2 | | S1 | S3 | S2 | | S2 | S5 |
240 ----- ---- ----- ----- ---- ----- ---- ----
241 | S6 | S/R3 | S1 | --- | S4 | S/R5 | S5 | ____/ Cell 4.
242 ---- ------ ---- ---- ------ ----
243 | S8 | S5 | S3 | | S6 | S7 | S8 | ... etc ...
244 ---- ---- ---- ---- ---- ----
249 Figure 1: SILC Network Topology
252 A cell is formed when a server or servers connect to one router. In
253 SILC network normal server cannot directly connect to other normal
254 server. Normal server may only connect to SILC router which then
255 routes the messages to the other servers in the cell. Router servers
256 on the other hand may connect to other routers to form the actual SILC
257 network, as seen in above figure. However, router is also normal SILC
258 server; clients may connect to it the same way as to normal SILC
259 servers. Normal server also cannot have active connections to more
260 than one router. Normal server cannot be connected to two different
261 cells. Router servers, on the other hand, may have as many router to
262 router connections as needed.
264 There are many issues in this network topology that needs to be careful
265 about. Issues like the size of the cells, the number of the routers in
266 the SILC network and the capacity requirements of the routers. These
267 issues should be discussed in the Internet Community and additional
268 documents on the issue will be written.
272 2.2 Communication Inside a Cell
274 It is always guaranteed that inside a cell message is delivered to the
275 recipient with at most two server hops. Client who is connected to
276 server in the cell and is talking on channel to other client connected
277 to other server in the same cell, will have its messages delivered from
278 its local server first to the router of the cell, and from the router
279 to the other server in the cell.
281 Following diagram represents this scenario:
295 Figure 2: Communication Inside cell
298 Example: Client 1. connected to Server 1. message sent to
299 Client 4. connected to Server 2. travels from Server 1.
300 first to Router which routes the message to Server 2.
301 which then sends it to the Client 4. All the other
302 servers in the cell will not see the routed message.
305 If client is connected directly to the router, as router is also normal
306 SILC server, the messages inside the cell are always delivered only with
307 one server hop. If clients communicating with each other are connected
308 to the same server, no router interaction is needed. This is the optimal
309 situation of message delivery in the SILC network.
313 2.3 Communication in the Network
315 If the message is destined to server that does not belong to local cell
316 the message is routed to the router server to which the destination
317 server belongs, if the local router is connected to destination router.
318 If there is no direct connection to the destination router, the local
319 router routes the message to its primary route. Following diagram
320 represents message sending between cells.
325 1 --- S1 S4 --- 5 S2 --- 1
326 S/R - - - - - - - - S/R
336 Figure 3: Communication Between Cells
339 Example: Client 5. connected to Server 4. in Cell 1. message sent
340 to Client 2. connected to Server 1. in Cell 2. travels
341 from Server 4. to Router which routes the message to
342 Router in Cell 2, which then routes the message to
343 Server 1. All the other servers and routers in the
344 network will not see the routed message.
347 The optimal case of message delivery from client point of view is
348 when clients are connected directly to the routers and the messages
349 are delivered from one router to the other router.
353 2.4 Channel Communication
355 Messages may be sent to group of clients as well. Sending messages to
356 many clients works the same way as sending messages point to point, from
357 message delivery point of view. Security issues are another matter
358 which are not discussed in this section.
360 Router server handles the message routing to multiple recipients. If
361 any recipient is not in the same cell as the sender the messages are
364 Server distributes the channel message to its local clients who are
365 joined to the channel. Also, router distributes the message to its
366 local clients on the channel.
370 2.5 Router Connections
372 Router connections play very important role in making the SILC like
373 network topology to work. For example, sending broadcast packets in
374 SILC network require special connections between routers; routers must
375 be connected in specific way.
377 Every router has their primary route which is a connection to another
378 router in the network. Unless there is only two routers in the network
379 must not routers use each other as their primary routes. The router
380 connections in the network must form a circular.
382 Example with three routers in the network:
392 S/R1 - > - > - > - > - > - > - S/R2
395 \\ - < - < - S/R3 - < - < - /
400 Figure 4: Router Connections
403 Example: Network with three routers. Router 1. uses Router 2. as its
404 primary router. Router 2. uses Router 3. as its primary router,
405 and Router 3. uses Router 1. as its primary router. There may
406 be other direct connections between the routers but they must
407 not be used as primary routes.
409 The above example is applicable to any amount of routers in the network
410 except for two routers. If there are only two routers in the network both
411 routers must be able to handle situation where they use each other as their
414 The issue of router connections are very important especially with SILC
415 broadcast packets. Usually all router wide information in the network is
416 distributed by SILC broadcast packets.
420 3. SILC Specification
422 This section describes the SILC protocol. However, [SILC2] and
423 [SILC3] describes other important protocols that are part of this SILC
424 specification and must be read.
430 A client is a piece of software connecting to SILC server. SILC client
431 cannot be SILC server. Purpose of clients is to provide the user
432 interface of the SILC services for end user. Clients are distinguished
433 from other clients by unique Client ID. Client ID is a 128 bit ID that
434 is used in the communication in the SILC network. The client ID is
435 based on the nickname selected by the user. User uses logical nicknames
436 in communication which are then mapped to the corresponding Client ID.
437 Client ID's are low level identifications and must not be seen by the
440 Clients provide other information about the end user as well. Information
441 such as the nickname of the user, username and the hostname of the end
442 user and user's real name. See section 3.2 Server for information of
443 the requirements of keeping this information.
445 The nickname selected by the user is not unique in the SILC network.
446 There can be 2^8 same nicknames for one IP address. As for comparison to
447 IRC [IRC] where nicknames are unique this is a fundamental difference
448 between SILC and IRC. This causes the server names to be used along
449 with the nicknames to identify specific users when sending messages.
450 This feature of SILC makes IRC style nickname-wars obsolete as no one
451 owns their nickname; there can always be someone else with the same
452 nickname. Another difference is that there are no limit of the length
453 of the nickname in the SILC.
459 Client ID is used to identify users in the SILC network. The Client ID
460 is unique to the extent that there can be 2^128 different Client ID's.
461 Collisions are not expected to happen. The Client ID is defined as
465 128 bit Client ID based on IPv4 addresses:
467 32 bit ServerID IP address (bits 1-32)
469 88 bit Truncated MD5 hash value of the nickname
471 o Server ID IP address - Indicates the server where this
472 client is coming from. The IP address hence equals the
473 server IP address where to the client has connected.
475 o Random number - Random number to further randomize the
476 Client ID. This makes it possible to have 2^8 same
477 nicknames from the same server IP address.
479 o MD5 hash - MD5 hash value of the nickname is truncated
480 taking 88 bits from the start of the hash value. This
481 hash value is used to search the user's Client ID from
485 Collisions could occur when more than 2^8 clients using same nickname
486 from the same server IP address is connected to the SILC network.
487 Server must be able to handle this situation by refusing to accept
488 anymore of that nickname.
490 Another possible collision may happen with the truncated hash value of
491 the nickname. It could be possible to have same truncated hash value for
492 two different nicknames. However, this is not expected to happen nor
493 cause any problems if it would occur. Nicknames are usually logical and
494 it is unlikely to have two distinct logical nicknames produce same
495 truncated hash value.
501 Servers are the most important parts of the SILC network. They form the
502 basis of the SILC, providing a point to which clients may connect to.
503 There are two kinds of servers in SILC; normal servers and router servers.
504 This section focus on the normal server and router server is described
505 in the section 3.3 Router.
507 Normal servers may not directly connect to other normal server. Normal
508 servers may only directly connect to router server. If the message sent
509 by the client is destined outside the local server it is always sent to
510 the router server for further routing. Server may only have one active
511 connection to router on same port. Normal server may not connect to other
512 cell's router except in situations where its cell's router is unavailable.
514 Servers and routers in the SILC network are considered to be trusted.
515 With out a doubt, servers that are set to work on ports above 1023 are
516 not considered to be trusted. Also, the service provider acts important
517 role in the server's trustworthy.
521 3.2.1 Server's Local ID List
523 Normal server keeps various information about the clients and their end
524 users connected to it. Every normal server must keep list of all locally
525 connected clients, Client ID's, nicknames, usernames and hostnames and
526 user's real name. Normal servers only keeps local information and it
527 does not keep any global information. Hence, normal servers knows only
528 about their locally connected clients. This makes servers efficient as
529 they don't have to worry about global clients. Server is also responsible
530 of creating the Client ID's for their clients.
532 Normal server also keeps information about locally created channels and
536 Hence, local list for normal server includes:
539 server list - Router connection
550 client list - All clients in server
558 channel list - All channels in server
561 o Client ID's on channel
562 o Client ID modes on channel
571 Servers are distinguished from other servers by unique 64 bit Server ID.
572 The Server ID is used in the SILC to route messages to correct servers.
573 Server ID's also provide information for Client ID's, see section 3.1.1
574 Client ID. Server ID is defined as follows.
577 64 bit Server ID based on IPv4 addresses:
579 32 bit IP address of the server
583 o IP address of the server - This is the real IP address of
586 o Port - This is the port the server is bound to.
588 o Random number - This is used to further randomize the Server ID.
591 Collisions are not expected to happen in any conditions. The Server ID
592 is always created by the server itself and server is responsible of
593 distributing it to the router.
597 3.2.3 SILC Server Ports
599 Following ports has been assigned by IANA for the SILC protocol:
606 If there are needs to create new SILC networks in the future the port
607 numbers must be officially assigned by the IANA.
609 Server on network above privileged ports (>1023) should not be trusted
610 as they could have been set up by untrusted party.
616 Router server in SILC network is responsible for keeping the cell together
617 and routing messages to other servers and to other routers. Router server
618 is also a normal server thus clients may connect to it as it would be
619 just normal SILC server.
621 However, router servers has a lot of important tasks that normal servers
622 do not have. Router server knows everything about everything in the SILC.
623 They know all clients currently on SILC, all servers and routers and all
624 channels in SILC. Routers are the only servers in SILC that care about
625 global information and keeping them up to date at all time. And, this
626 is what they must do.
630 3.3.1 Router's Local ID List
632 Router server as well must keep local list of connected clients and
633 locally created channels. However, this list is extended to include all
634 the informations of the entire cell, not just the server itself as for
637 However, on router this list is a lot smaller since routers do not keep
638 information about user's nickname, username and hostname and real name
639 since these are not needed by the router. Router keeps only information
643 Hence, local list for router includes:
646 server list - All servers in the cell
653 client list - All clients in the cell
657 channel list - All channels in the cell
659 o Client ID's on channel
660 o Client ID modes on channel
665 Note that locally connected clients and other information include all the
666 same information as defined in section section 3.2.1 Server's Local ID
671 3.3.2 Router's Global ID List
673 Router server must also keep global list. Normal servers do not have
674 global list as they know only about local information. Global list
675 includes all the clients on SILC, their Client ID's, all created channels
676 and their Channel ID's and all servers and routers on SILC and their
677 Server ID's. That is said, global list is for global information and the
678 list must not include the local information already on the router's local
681 Note that the global list does not include information like nicknames,
682 usernames and hostnames or user's real names. Router does not keep
683 these informations as they are not needed by the router. This
684 information is available from the client's server which maybe queried
687 Hence, global list includes:
690 server list - All servers in SILC
696 client list - All clients in SILC
699 channel list - All channels in SILC
701 o Client ID's on channel
702 o Client ID modes on channel
707 3.3.3 Router's Server ID
709 Router's Server ID's are equivalent to normal Server ID's. As routers
710 are normal servers as well same types of ID's applies for routers as well.
711 Thus, see section 3.2.2 Server ID. Server ID's for routers are always
712 created by the remote router where the router is connected to.
718 A channel is a named group of one or more clients which will all receive
719 messages addressed to that channel. The channel is created when first
720 client requests JOIN command to the channel, and the channel ceases to
721 exist when the last client has left it. When channel exists, any client
722 can reference it using the name of the channel.
724 Channel names are unique although the real uniqueness comes from 64 bit
725 Channel ID that unifies each channel. However, channel names are still
726 unique and no two global channels with same name may exist. Channel name
727 is a string which begins with `#' character. There is no limit on the
728 length of the channel name. Channel names may not contain any spaces
729 (` '), any non-printable ASCII characters, commas (`,') and wildcard
732 Channels can have operators that can administrate the channel and
733 operate all of its modes. Following operators on channel exist on SILC
737 o Channel founder - When channel is created the joining client becomes
738 channel founder. Channel founder is channel operator with some more
739 privileges. Basically, channel founder can fully operate the channel
740 and all of its modes. The privileges are limited only to the particular
741 channel. There can be only one channel founder per channel. Channel
742 founder supersedes channel operator's privileges.
744 Channel founder privileges cannot be removed by any other operator on
745 channel. When channel founder leaves the channel there is no channel
746 founder on the channel. Channel founder also cannot be removed by
747 force from the channel.
749 o Channel operator - When client joins to channel that has not existed
750 previously it will become automatically channel operator (and channel
751 founder discussed above). Channel operator is able administrate the
752 channel, set some modes on channel, remove a badly behaving client from
753 the channel and promote other clients to become channel operator.
754 The privileges are limited only to the particular channel.
756 Normal channel user may be promoted (opped) to channel operator
757 gaining channel operator privileges. Channel founder or other channel
758 operator may also demote (deop) channel operator to normal channel
766 Channels are distinguished from other channels by unique Channel ID.
767 The Channel ID is a 64 bit ID and collisions are not expected to happen
768 in any conditions. Channel names are just for logical use of channels.
769 The Channel ID is created by the server where the channel is created.
770 The Channel ID is defined as follows.
773 64 bit Channel ID based on IPv4 addresses:
775 32 bit Router's Server ID IP address (bits 1-32)
776 16 bit Router's Server ID port (bits 33-48)
779 o Router's Server ID IP address - Indicates the IP address of
780 the router of the cell where this channel is created. This is
781 taken from the router's Server ID. This way SILC router knows
782 where this channel resides in the SILC network.
784 o Router's Server ID port - Indicates the port of the channel on
785 the server. This is taken from the router's Server ID.
787 o Random number - To further randomize the Channel ID. This makes
788 sure that there are no collisions. This also means that
789 in a cell there can be 2^16 channels.
796 Operators are normal users with extra privileges to their server or
797 router. Usually these people are SILC server and router administrators
798 that take care of their own server and clients on them. The purpose of
799 operators is to administrate the SILC server or router. However, even
800 an operator with highest privileges is not able to enter invite-only
801 channel, to gain access to the contents of a encrypted and authenticated
802 packets traveling in the SILC network or to gain channel operator
803 privileges on public channels without being promoted. They have the
804 same privileges as everyone else except they are able to administrate
805 their server or router.
811 Commands are very important part on SILC network especially for client
812 which uses commands to operate on the SILC network. Commands are used
813 to set nickname, join to channel, change modes and many other things.
815 Client usually sends the commands and server replies by sending a reply
816 packet to the command. Server may also send commands usually to serve
817 the original client's request. However, server may not send command
818 to client and there are some commands that server must not send. Server
819 is also able to send the forwarded command packets. For example,
820 SILC_COMMAND_JOIN is always forwarded packet. See [SILC2] for more
821 about packet forwarding.
823 Note that the command reply is usually sent only after client has sent
824 the command request but server is allowed to send command reply packet
825 to client even if client has not requested the command. Client may,
826 however, choose ignore the command reply, but should not.
828 It is expected that some of the commands may be miss-used by clients
829 resulting various problems on the server side. Every implementation
830 should assure that commands may not be executed more than once, say,
831 in two (2) seconds. This should be sufficient to prevent the miss-use
834 SILC commands are described in section 5 SILC Commands.
840 Packets are naturally the most important part of the protocol and the
841 packets are what actually makes the protocol. Packets in SILC network
842 are always encrypted using, usually, the shared secret session key
843 or some other key, for example, channel key, when encrypting channel
844 messages. The SILC Packet Protocol is a wide protocol and is described
845 in [SILC2]. This document does not define or describe details of
851 3.8 Packet Encryption
853 All packets passed in SILC network must be encrypted. This section
854 defines how packets must be encrypted in the SILC network. The detailed
855 description of the actual encryption process of the packets are
856 described in [SILC2].
858 Client and its server shares secret symmetric session key which is
859 established by the SILC Key Exchange Protocol, described in [SILC3].
860 Every packet sent from client to server, with exception of packets for
861 channels, are encrypted with this session key.
863 Channels has their own key that are shared by every client on the channel.
864 However, the channel keys are cell specific thus one cell does not know
865 the channel key of the other cell, even if that key is for same channel.
866 Channel key is also known by the routers and all servers that has clients
867 on the channel. However, channels may have channel private keys that
868 are entirely local setting for client. All clients on the channel must
869 know the channel private key before hand to be able to talk on the
870 channel. In this case, no server or router knows the key for channel.
872 Server shares secret symmetric session key with router which is
873 established by the SILC Key Exchange Protocol. Every packet passed from
874 server to router, with exception of packets for channels, are encrypted
875 with the shared session key. Same way, router server shares secret
876 symmetric key with its primary route. However, every packet passed
877 from router to other router, including packets for channels, are
878 encrypted with the shared session key. Every router connection has
879 their own session keys.
883 3.8.1 Determination of the Source and the Destination
885 The source and the destination of the packet needs to be determined
886 to be able to route the packets to correct receiver. This information
887 is available in the SILC Packet Header which is included in all packets
888 sent in SILC network. The SILC Packet Header is described in [SILC2].
890 The header is always encrypted with the session key who is next receiver
891 of the packet along the route. The receiver of the packet, for example
892 a router along the route, is able to determine the sender and the
893 destination of the packet by decrypting the SILC Packet Header and
894 checking the ID's attached to the header. The ID's in the header will
895 tell to where the packet needs to be sent and where it is coming from.
897 The header in the packet does not change during the routing of the
898 packet. The original sender, for example client, assembles the packet
899 and the packet header and server or router between the sender and the
900 receiver must not change the packet header.
902 Note that the packet and the packet header may be encrypted with
903 different keys. For example, packets to channels are encrypted with
904 the channel key, however, the header is encrypted with the session key
905 as described above. However, the header and the packet may be encrypted
906 with same key. This is case, for example, with command packets.
910 3.8.2 Client To Client
912 Process of message delivery and encryption from client to another
913 client is as follows.
915 Example: Private message from client to another client on different
916 servers. Clients do not share private message delivery
917 keys; normal session keys are used.
919 o Client 1. sends encrypted packet to its server. The packet is
920 encrypted with the session key shared between client and its
923 o Server determines the destination of the packet and decrypts
924 the packet. Server encrypts the packet with session key shared
925 between the server and its router, and sends the packet to the
928 o Router determines the destination of the packet and decrypts
929 the packet. Router encrypts the packet with session key
930 shared between the router and the destination server, and sends
931 the packet to the server.
933 o Server determines the client to which the packet is destined
934 to and decrypts the packet. Server encrypts the packet with
935 session key shared between the server and the destination client,
936 and sends the packet to the client.
938 o Client 2. decrypts the packet.
941 Example: Private message from client to another client on different
942 servers. Clients has established secret shared private
943 message delivery key with each other and that is used in
944 the message encryption.
946 o Client 1. sends encrypted packet to its server. The packet is
947 encrypted with the private message delivery key shared between
950 o Server determines the destination of the packet and sends the
951 packet to the router.
953 o Router determines the destination of the packet and sends the
954 packet to the server.
956 o Server determines the client to which the packet is destined
957 to and sends the packet to the client.
959 o Client 2. decrypts the packet with the secret shared key.
962 If clients share secret key with each other the private message
963 delivery is much simpler since servers and routers between the
964 clients do not need to decrypt and re-encrypt the packet.
966 The process for clients on same server is much simpler as there are
967 no need to send the packet to the router. The process for clients
968 on different cells is same as above except that the packet is routed
969 outside the cell. The router of the destination cell routes the
970 packet to the destination same way as described above.
974 3.8.3 Client To Channel
976 Process of message delivery from client on channel to all the clients
979 Example: Channel of four users; two on same server, other two on
980 different cells. Client sends message to the channel.
982 o Client 1. encrypts the packet with channel key and sends the
983 packet to its server.
985 o Server determines local clients on the channel and sends the
986 packet to the Client on the same server. Server then sends
987 the packet to its router for further routing.
989 o Router determines local clients on the channel, if found
990 sends packet to the local clients. Router determines global
991 clients on the channel and sends the packet to its primary
992 router or fastest route.
994 o (Other router(s) do the same thing and sends the packet to
997 o Server determines local clients on the channel and sends the
998 packet to the client.
1000 o All clients receiving the packet decrypts the packet.
1004 3.8.4 Server To Server
1006 Server to server packet delivery and encryption is described in above
1007 examples. Router to router packet delivery is analogous to server to
1008 server. However, some packets, such as channel packets, are processed
1009 differently. These cases are described later in this document and
1010 more in detail in [SILC2].
1014 3.9 Key Exchange And Authentication
1016 Key exchange is done always when for example client connects to server
1017 but also when server and router and router and router connects to each
1018 other. The purpose of key exchange protocol is to provide secure key
1019 material to be used in the communication. The key material is used to
1020 derive various security parameters used to secure SILC packets. The
1021 SILC Key Exchange protocol is described in detail in [SILC3].
1023 Authentication is done after key exchange protocol has been successfully
1024 completed. The purpose of authentication is to authenticate for example
1025 client connecting to the server. However, Usually clients are accepted
1026 to connect to server without explicit authentication. Servers are
1027 required use authentication protocol when connecting. The authentication
1028 may be based on passphrase (pre-shared-secret) or public key. The
1029 connection authentication protocol is described in detail in [SILC3].
1035 This section defines all the allowed algorithms that can be used in
1036 the SILC protocol. This includes mandatory cipher, mandatory public
1037 key algorithm and MAC algorithms.
1043 Cipher is the encryption algorithm that is used to protect the data
1044 in the SILC packets. See [SILC2] of the actual encryption process and
1045 definition of how it must be done. SILC has a mandatory algorithm that
1046 must be supported in order to be compliant with this protocol.
1048 Following ciphers are defined in SILC protocol:
1051 aes-cbc AES in CBC mode (mandatory)
1052 twofish-cbc Twofish in CBC mode (optional)
1053 blowfish-cbc Blowfish in CBC mode (optional)
1054 rc6-cbc RC6 in CBC mode (optional)
1055 rc5-cbc RC5 in CBC mode (optional)
1056 mars-cbc Mars in CBC mode (optional)
1057 none No encryption (optional)
1061 All algorithms must use minimum of 128 bit key, by default. Several
1062 algorithms, however, supports longer keys and it is recommended to use
1063 longer keys if they are available.
1065 Algorithm none does not perform any encryption process at all and
1066 thus is not recommended to be used. It is recommended that no client
1067 or server implementation would accept none algorithms except in special
1070 Additional ciphers may be defined to be used in SILC by using the
1071 same name format as above.
1075 3.10.2 Public Key Algorithms
1077 Public keys are used in SILC to authenticate entities in SILC network
1078 and to perform other tasks related to public key cryptography. The
1079 public keys are also used in the SILC Key Exchange protocol [SILC3].
1081 Following public key algorithms are defined in SILC protocol:
1088 Both of the algorithms are described in [Scheneir] and [Menezes].
1090 Additional public key algorithms may be defined to be used in SILC.
1094 3.10.3 MAC Algorithms
1096 Data integrity is protected by computing a message authentication code
1097 (MAC) of the packet data. See [SILC2] for details how to compute the
1100 Following MAC algorithms are defined in SILC protocol:
1103 hmac-sha1 HMAC-SHA1, length = 20 (mandatory)
1104 hmac-md5 HMAC-MD5, length = 16 (optional)
1105 none No MAC (optional)
1108 The none MAC is not recommended to be used as the packet is not
1109 authenticated when MAC is not computed. It is recommended that no
1110 client or server would accept none MAC except in special debugging
1113 The HMAC algorithm is described in [HMAC] and hash algorithms that
1114 are used as part of the HMACs are described in [Scheneir] and in
1117 Additional MAC algorithms may be defined to be used in SILC.
1121 3.10.4 Compression Algorithms
1123 SILC protocol supports compression that may be applied to unencrypted
1124 data. It is recommended to use compression on slow links as it may
1125 significantly speed up the data transmission. By default, SILC does not
1126 use compression which is the mode that must be supported by all SILC
1129 Following compression algorithms are defined:
1132 none No compression (mandatory)
1133 zlib GNU ZLIB (LZ77) compression (optional)
1136 Additional compression algorithms may be defined to be used in SILC.
1140 3.11 SILC Public Key
1142 This section defines the type and format of the SILC public key. All
1143 implementations must support this public key type. See [SILC3] for
1144 other optional public key and certificate types allowed in SILC
1145 protocol. Public keys in SILC may be used to authenticate entities
1146 and to perform other tasks related to public key cryptography.
1148 The format of the SILC Public Key is as follows:
1154 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
1155 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1156 | Public Key Length |
1157 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1158 | Algorithm Name Length | |
1159 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1163 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1164 | Identifier Length | |
1165 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1169 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1173 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1177 Figure 5: SILC Public Key
1181 o Public Key Length (4 bytes) - Indicates the full length
1182 of the public key, not including this field.
1184 o Algorithm Name Length (2 bytes) - Indicates the length
1185 of the Algorithm Length field, not including this field.
1187 o Algorithm name (variable length) - Indicates the name
1188 of the public key algorithm that the key is. See the
1189 section 3.10.2 Public Key Algorithms for defined names.
1191 o Identifier Length (2 bytes) - Indicates the length of
1192 the Identifier field, not including this field.
1194 o Identifier (variable length) - Indicates the identifier
1195 of the public key. This data can be used to identify
1196 the owner of the key. The identifier is of following
1200 HN Host name or IP address
1207 Examples of an identifier:
1209 `UN=priikone, HN=poseidon.pspt.fi, E=priikone@poseidon.pspt.fi'
1211 `UN=sam, HN=dummy.fi, RN=Sammy Sam, O=Company XYZ, C=Finland'
1213 At least user name (UN) and host name (HN) must be provided as
1214 identifier. The fields are separated by commas (`,'). If
1215 comma is in the identifier string it must be written as `\\,',
1216 for example, `O=Company XYZ\\, Inc.'.
1218 o Public Data (variable length) - Includes the actual
1219 public data of the public key.
1221 The format of this field for RSA algorithm is
1230 The format of this field for DSS algorithm is
1242 The variable length fields are multiple precession
1243 integers encoded as strings in both examples.
1245 Other algorithms must define their own type of this
1246 field if they are used.
1249 All fields in the public key are in MSB (most significant byte first)
1254 3.12 SILC Version Detection
1256 The version detection of both client and server is performed at the
1257 connection phase while executing the SILC Key Exchange protocol. The
1258 version identifier is exchanged between initiator and responder. The
1259 version identifier is of following format:
1262 SILC-<protocol version>-<software version>
1265 The version strings are of following format:
1268 protocol version = <major>.<minor>
1269 software version = <major>[.<minor>[.<build>]]
1272 Protocol version may provide both major and minor version. Currently
1273 implementations must set the protocol version and accept the protocol
1274 version as SILC-1.0-<sotware version>.
1276 Software version may provide major, minor and build version. The
1277 software version may be freely set and accepted.
1280 Thus, the version string could be, for example:
1290 This section describes various SILC procedures such as how the
1291 connections are created and registered, how channels are created and
1292 so on. The section describes the procedures only generally as details
1293 are described in [SILC2] and [SILC3].
1297 4.1 Creating Client Connection
1299 This section describes the procedure when client connects to SILC server.
1300 When client connects to server the server must perform IP address lookup
1301 and reverse IP address lookup to assure that the origin host really is
1302 who it claims to be. Client, host, connecting to server must have
1303 both valid IP address and fully qualified domain name (FQDN).
1305 After that client and server performs SILC Key Exchange protocol which
1306 will provide the key material used later in the communication. The
1307 key exchange protocol must be completed successfully before the connection
1308 registration may continue. The SILC Key Exchange protocol is described
1311 Typical server implementation would keep a list of connections that it
1312 allows to connect to the server. The implementation would check, for
1313 example, the connecting client's IP address from the connection list
1314 before the SILC Key Exchange protocol has been started. Reason for
1315 this is that if the host is not allowed to connect to the server there
1316 is no reason to perform a key exchange protocol.
1318 After successful key exchange protocol the client and server performs
1319 connection authentication protocol. The purpose of the protocol is to
1320 authenticate the client connecting to the server. Flexible
1321 implementation could also accept the client to connect to the server
1322 without explicit authentication. However, if authentication is
1323 desired for a specific client it may be based on passphrase or
1324 public key authentication. If authentication fails the connection
1325 must be terminated. The connection authentication protocol is described
1328 After successful key exchange and authentication protocol the client
1329 registers itself by sending SILC_PACKET_NEW_CLIENT packet to the
1330 server. This packet includes various information about the client
1331 that the server uses to create the client. Server creates the client
1332 and sends SILC_PACKET_NEW_ID to the client which includes the created
1333 Client ID that the client must start using after that. After that
1334 all SILC packets from the client must have the Client ID as the
1335 Source ID in the SILC Packet Header, described in [SILC2].
1337 Client must also get the server's Server ID that is to be used as
1338 Destination ID in the SILC Packet Header when communicating with
1339 the server (for example when sending commands to the server). The
1340 ID may be resolved in two ways. Client can take the ID from an
1341 previously received packet from server that must include the ID,
1342 or to send SILC_COMMAND_INFO command and receive the Server ID as
1345 Server may choose not to use the information received in the
1346 SILC_PACKET_NEW_CLIENT packet. For example, if public key or
1347 certificate were used in the authentication, server may use those
1348 informations rather than what it received from client. This is suitable
1349 way to get the true information about client if it is available.
1351 The nickname of client is initially set to the username sent in the
1352 SILC_PACKET_NEW_CLIENT packet. User should set the nickname to more
1353 suitable by sending SILC_COMMAND_NICK command. However, this is not
1354 required as part of registration process.
1356 Server must also distribute the information about newly registered
1357 client to its router (or if the server is router, to all routers in
1358 the SILC network). More information about this in [SILC2].
1362 4.2 Creating Server Connection
1364 This section descibres the procedure when server connects to its
1365 router (or when router connects to other router, the cases are
1366 equivalent). The procedure is very much alike when client connects
1367 to the server thus it is not repeated here.
1369 One difference is that server must perform connection authentication
1370 protocol with proper authentication. Proper authentication is based
1371 on passphrase or public key authentication.
1373 After server and router has successfully performed the key exchange
1374 and connection authentication protocol, the server register itself
1375 to the router by sending SILC_PACKET_NEW_SERVER packet. This packet
1376 includes the server's Server ID that it has created by itself and
1377 other relevant information about the server.
1379 After router has received the SILC_PACKET_NEW_SERVER packet it
1380 distributes the information about newly registered server to all routers
1381 in the SILC network. More information about this in [SILC2].
1383 As client needed to resolve the destination ID this must be done by the
1384 server that connected to the router, as well. The way to resolve it is
1385 to get the ID from previously received packet. Server must also start
1386 using its own Server ID as Source ID in SILC Packet Header and the
1387 router's Server ID as Destination when communicating with the router.
1389 If the server has already connected clients and locally created
1390 channels the server must distribute these informations to the router.
1391 The distribution is done by sending packet SILC_PACKET_NEW_CHANNEL.
1392 See [SILC2] for more information on this.
1396 4.3 Joining to a Channel
1398 This section describes the procedure when client joins to a channel.
1399 Client may join to channel by sending command SILC_COMMAND_JOIN to the
1400 server. If the receiver receiving join command is normal server the
1401 server must check its local list whether this channel already exists
1402 locally. This would indicate that some client connected to the server
1403 has already joined to the channel. If this is case the client is
1404 joined to the client, new channel key is created and information about
1405 newly joined channel is sent to the router. The new channel key is
1406 also distributed to the router and to all clients on the channel.
1408 If the channel does not exist in the local list the command must be
1409 forwarded to the router which will then perform the actual joining
1410 procedure. When server receives the reply to the command from the
1411 router it must be distributed to the client who sent the command
1412 originally. Server will also receive the channel key from the server
1413 that it must distribute to the client who originally requested the
1414 join command. The server must also save the channel key.
1416 If the receiver of the join command is router it must first check its
1417 local list whether anyone in the cell has already joined to the channel.
1418 If this is the case the client is joined to the channel and reply is
1419 sent to the client. If the command was sent by server the command reply
1420 is sent to the server who sent it. Then the router must also create
1421 new channel key and distribute it to all clients on the channel and
1422 all servers that has clients on the channel.
1424 If the channel does not exist on the router's local list it must
1425 check the global list whether the channel exists at all. If it does
1426 the client is joined to the channel as described previously. If
1427 the channel does not exist the channel is created and the client
1428 is joined to the channel. The channel key is also created and
1429 distributed as previously described. The client joining to the created
1430 channel is made automatically channel founder and both channel founder
1431 and channel operator privileges is set for the client.
1433 When the router joins the client to the channel it must send
1434 information about newly joined client to all routers in the SILC
1435 network. Also, if the channel was created in the process, information
1436 about newly created channel must also be distributed to all routers.
1437 The distribution of newly created channel is done by sending packet
1438 SILC_PACKET_NEW_CHANNEL.
1440 It is important to note that new channel key is created always when
1441 new client joins to channel, whether the channel has existed previously
1442 or not. This way the new client on the channel is not able to decrypt
1443 any of the old traffic on the channel. Client who receives the reply to
1444 the join command must start using the received Channel ID in the channel
1445 message communication thereafter. However, client must not start
1446 communicating on the channel before it has received the packet
1447 SILC_PACKET_CHANNEL_KEY.
1449 If client wants to know the other clients currently on the channel
1450 the client must send SILC_COMMAND_NAMES command to receive a list of
1451 channel users. Server implementation, however, may send command reply
1452 packet to SILC_COMMAND_NAMES command after client has joined to the
1453 channel even if the client has not sent the command. Server should also
1454 send SILC_NOTIFY_TYPE_JOIN to all clients on the channel about a new
1455 client on the channel.
1459 4.4 Channel Key Generation
1461 Channel keys are created by router who creates the channel by taking
1462 enough randomness from cryptographically strong random number generator.
1463 The key is generated always when channel is created, when new client
1464 joins a channel and after the key has expired. Key could expire for
1467 The key must also be re-generated whenever some client leaves a channel.
1468 In this case the key is created from scratch by taking enough randomness
1469 from the random number generator. After that the key is distributed to
1470 all clients on the channel. However, channel keys are cell specific thus
1471 the key is created only on the cell where the client, who left the
1472 channel, exists. While the server or router is creating the new channel
1473 key, no other client may join to the channel. Messages that are sent
1474 while creating the new key are still processed with the old key. After
1475 server has sent the SILC_PACKET_CHANNEL_KEY packet must client start
1476 using the new key. If server creates the new key the server must also
1477 send the new key to its router. See [SILC2] on more information about
1478 how channel messages must be encrypted and decrypted when router is
1483 4.5 Private Message Sending and Reception
1485 Private messages are sent point to point. Client explicitly destines
1486 a private message to specific client that is delivered to only to that
1487 client. No other client may receive the private message. The receiver
1488 of the private message is destined in the SILC Packet Header as any
1489 other packet as well.
1491 If the sender of a private message does not know the receiver's Client
1492 ID, it must resolve it from server. There are two ways to resolve the
1493 client ID from server; it is recommended that client implementations
1494 send SILC_COMMAND_IDENTIFY command to receive the Client ID. Client
1495 may also send SILC_COMMAND_WHOIS command to receive the Client ID.
1496 If the sender has received earlier a private message from the receiver
1497 it should have cached the Client ID from the SILC Packet Header.
1499 Receiver of a private message should not explicitly trust the nickname
1500 that it receives in the Private Message Payload, described in [SILC2].
1501 Implementations could resolve the nickname from server, as described
1502 previously, and compare the received Client ID and the SILC Packet
1503 Header's Client ID. The nickname in the payload is merely provided
1504 to be displayed for end user.
1506 See [SILC2] for description of private message encryption and decryption
1511 4.6 Private Message Key Generation
1513 Private message may be protected by key generated by client. The key
1514 may be generated and sent to the other client by sending packet
1515 SILC_PACKET_PRIVATE_MESSAGE_KEY which travels through the network
1516 and is secured by session keys. After that the private message key
1517 is used in the private message communication between those clients.
1518 See more information about how this works technically in [SILC2].
1520 Other choice is to entirely use keys that are not sent through
1521 the SILC network at all. This significantly adds security. This key
1522 would be pre-shared-key that is known by both of the clients. Both
1523 agree about using the key and starts sending packets that indicate
1524 that the private message is secured using private message key. This
1525 is the technical aspect mentioned previously that is described
1528 If the private message keys are not set to be used, which is the
1529 case by default in SILC, the private messages are secured by using
1530 normal session keys established by SILC Key Exchange protocol.
1536 4.7 Channel Message Sending and Reception
1538 Channel messages are delivered to group of users. The group forms a
1539 channel and all clients on the channel receives messages sent to the
1542 Channel messages are destined to channel by specifying the Channel ID
1543 as Destination ID in the SILC Packet Header. The server must then
1544 distribute the message to all clients on the channel by sending the
1545 channel message destined explicitly to a client on the channel.
1547 See [SILC2] for description of channel message encryption and decryption
1552 4.8 Session Key Regeneration
1554 Session keys should be regenerated periodically, say, once in an hour.
1555 The re-key process is started by sending SILC_PACKET_REKEY packet to
1556 other end, to indicate that re-key must be performed.
1558 If perfect forward secrecy (PFS) flag was selected in the SILC Key
1559 Exchange protocol [SILC3] the re-key must cause new key exchange with
1560 SKE protocol. In this case the protocol is secured with the old key
1561 and the protocol results to new key material. See [SILC3] for more
1562 information. After the SILC_PACKET_REKEY packet is sent the sender
1563 will perform the SKE protocol.
1565 If PFS flag was not set, which is the default case, then re-key is done
1566 without executing SKE protocol. In this case, the new key is created by
1567 hashing the old key with hash function selected earlier in the SKE
1568 protocol. If the digest length of the hash function is too short for the
1569 key, then the key is distributed as described in section Processing the
1570 Key Material in [SILC3]. After both parties has regenerated the session
1571 key, both send SILC_PACKET_REKEY_DONE packet to each other. These packets
1572 are still secured with the old key. After these packets, following
1573 packets must be protected with the new key.
1577 4.9 Command Sending and Reception
1579 Client usually sends the commands in the SILC network. In this case
1580 the client simply sends the command packet to server and the server
1581 processes it and replies with command reply packet.
1583 However, if the server is not able to process the command, it is usually
1584 sent to the server's router. This is case for example with commands such
1585 as, SILC_COMMAND_JOIN and SILC_COMMAND_WHOIS commands. However, there
1586 are other commands as well. For example, if client sends the WHOIS
1587 command requesting specific information about some client the server must
1588 send the WHOIS command to router so that all clients in SILC network
1589 are searched. The router, on the other hand, sends the WHOIS command
1590 to further to receive the exact information about the requested client.
1591 The WHOIS command travels all the way to the server who owns the client
1592 and it replies with command reply packet. Finally, the server who
1593 sent the command receives the command reply and it must be able to
1594 determine which client sent the original command. The server then
1595 sends command reply to the client. Implementations should have some
1596 kind of cache to handle, for example, WHOIS information. Servers
1597 and routers along the route could all cache the information for faster
1598 referencing in the future.
1600 The commands sent by server may be sent hop by hop until someone is able
1601 to process the command. However, it is preferred to destine the command
1602 as precisely as it is possible. In this case, other routers en route
1603 must route the command packet by checking the true sender and true
1604 destination of the packet. However, servers and routers must not route
1605 command reply packets to clients coming from other server. Client
1606 must not accept command reply packet originated from anyone else but
1607 from its own server.
1614 5.1 SILC Commands Syntax
1616 This section briefly describes the syntax of the command notions
1617 in this document. Every field in command is separated from each
1618 other by whitespaces (` ') indicating that each field is independent
1619 argument and each argument must have own Command Argument Payload.
1620 The number of maximum arguments are defined with each command
1621 separately. The Command Argument Payload is described in [SILC2].
1623 Every command defines specific number for each argument. Currently,
1624 they are defined in ascending order; first argument has number one
1625 (1), second has number two (2) and so on. This number is set into the
1626 Argument Type field in the Command Argument Payload. This makes it
1627 possible to send the arguments in free order as the number must be
1628 used to identify the type of the argument. This makes is it also
1629 possible to have multiple optional arguments in commands and in
1630 command replies. The number of argument is marked in parentheses
1631 before the actual argument.
1636 Example: Arguments: (1) <nickname> (2) <username@host>
1640 Every command replies with Status Payload. This payload tells the
1641 sender of the command whether the command was completed successfully or
1642 whether there was an error. If error occured the payload includes the
1643 error type. In the next section the Status Payload is not described
1644 as it is common to all commands and has been described here. Commands
1645 may reply with other arguments as well. These arguments are command
1646 specific and are described in the next section.
1655 Arguments: (1) <nickname>[@<server>] (2) <message>
1658 The command has maximum of 3 arguments. However, only first
1659 and second arguments are mandatory.
1661 First argument <nickname> is mandatory but may have optional
1662 <nickname@server> format as well. Second argument is mandatory
1663 <message> argument. Third argument is optional <count> argument.
1665 The numbers in parentheses are the argument specific numbers
1666 that specify the type of the argument in Command Argument Payload.
1667 The receiver always knows that, say, argument number two (2) is
1668 <message> argument, regardless of the ordering of the arguments in
1669 the Command Payload.
1671 Reply messages to the command:
1674 Arguments: (1) <Status Payload> (2) [<channel list>]
1675 (3) <idle time> (4) [<away message>]
1677 This command may reply with maximum of 4 arguments. However,
1678 only the first and third arguments are mandatory. The numbers
1679 in the parentheses have the same meaning as in the upper
1680 command sending specification.
1682 Every command reply with <Status Payload>, it is mandatory
1683 argument for all command replies and for this reason it is not
1684 described in the command reply descriptions.
1691 SILC_STATUS_ERR_TOO_MANY_TARGETS
1692 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
1693 SILC_STATUS_ERR_NO_SUCH_NICK
1695 Every command reply also defines set of status message that it
1696 may return inside the <Status Payload>. All status messages
1697 are defined in the section 5.3 SILC Command Status Types.
1700 Every command that has some kind of ID as argument (for example
1701 <Client ID>) are actually ID Payloads, defined in [SILC2] that includes
1702 the type of the ID, length of the ID and the actual ID data. This
1703 way variable length ID's can be sent as arguments.
1707 5.2 SILC Commands List
1709 This section lists all SILC commands, however, it is expected that a
1710 implementation and especially client implementation has many more
1711 commands that has only local affect. These commands are official
1712 SILC commands that has both client and server sides and cannot be
1713 characterized as local commands.
1715 List of all defined commands in SILC follows.
1720 None. This is reserved command and must not be sent.
1723 1 SILC_COMMAND_WHOIS
1726 Arguments: (1) [<nickname>[@<server>]] (2) [<Client ID>]
1729 Whois command is used to query various information about specific
1730 user. The user maybe requested by their nickname and server name.
1731 The query may find multiple matching users as there are no unique
1732 nicknames in the SILC. The <count> option maybe given to narrow
1733 down the number of accepted results. If this is not defined there
1734 are no limit of accepted results. The query may also be narrowed
1735 down by defining the server name of the nickname.
1737 It is also possible to search the user by Client ID. If <Client ID>
1738 is provided server must use it as the search value instead of
1741 To prevent miss-use of this service wildcards in the nickname
1742 or in the servername are not permitted. It is not allowed
1743 to request all users on some server. The WHOIS requests must
1744 be based on specific nickname request.
1746 The WHOIS request must be always forwarded to router by server
1747 so that all users are searched. However, the server still must
1748 search its locally connected clients. The server must send
1749 this command to the server who owns the requested client. That
1750 server must reply to the command.
1752 Reply messages to the command:
1755 Arguments: (1) <Status Payload> (2) <Client ID>
1756 (3) <nickname>[@<server>] (4) <username@host>
1757 (5) <real name> (6) [<channel list>]
1760 This command may reply with several command reply messages to
1761 form a list of results. In this case the status payload will
1762 include STATUS_LIST_START status in the first reply and
1763 STATUS_LIST_END in the last reply to indicate the end of the
1764 list. If there are only one reply the status is set to normal
1767 The command replies include the Client ID of the nickname,
1768 nickname and servername, username and hostname and users real
1769 name. Client should process these replies only after the last
1770 reply has been received with the STATUS_LIST_END status. If the
1771 <count> option were defined in the query there will be only
1772 <count> many replies from the server.
1777 SILC_STATUS_LIST_START
1778 SILC_STATUS_LIST_END
1779 SILC_STATUS_ERR_NO_SUCH_NICK
1780 SILC_STATUS_ERR_WILDCARDS
1781 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
1782 SILC_STATUS_ERR_TOO_MANY_PARAMS
1787 2 SILC_COMMAND_WHOWAS
1790 Arguments: (1) <nickname>[@<server>] (2) [<count>]
1792 Whowas. This command is used to query history information about
1793 specific user. The user maybe requested by their nickname and
1794 server name. The query may find multiple matching users as there
1795 are no unique nicknames in the SILC. The <count> option maybe
1796 given to narrow down the number of accepted results. If this
1797 is not defined there are no limit of accepted results. The query
1798 may also be narrowed down by defining the server name of the
1801 To prevent miss-use of this service wildcards in the nickname
1802 or in the servername are not permitted. The WHOWAS requests must
1803 be based on specific nickname request.
1805 The WHOWAS request must be always forwarded to router by server
1806 so that all users are searched. However, the server still must
1807 search its locally connected clients.
1809 Reply messages to the command:
1812 Arguments: (1) <Status Payload> (2) <nickname>[@<server>]
1815 This command may reply with several command reply messages to form
1816 a list of results. In this case the status payload will include
1817 STATUS_LIST_START status in the first reply and STATUS_LIST_END in
1818 the last reply to indicate the end of the list. If there are only
1819 one reply the status is set to normal STATUS_OK.
1821 The command replies with nickname and username and hostname.
1822 Every server must keep history for some period of time of its
1823 locally connected clients.
1828 SILC_STATUS_LIST_START
1829 SILC_STATUS_LIST_END
1830 SILC_STATUS_ERR_NO_SUCH_NICK
1831 SILC_STATUS_ERR_WILDCARDS
1832 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
1833 SILC_STATUS_ERR_TOO_MANY_PARAMS
1836 3 SILC_COMMAND_IDENTIFY
1839 Arguments: (1) [<nickname>[@<server>]] (2) [<Client ID>]
1842 Identify. Identify command is almost analogous to WHOIS command,
1843 except that it does not return as much information. Only relevant
1844 information such as Client ID is returned. This is usually used
1845 to get the Client ID of a client used in the communication with
1848 The query may find multiple matching users as there are no unique
1849 nicknames in the SILC. The <count> option maybe given to narrow
1850 down the number of accepted results. If this is not defined there
1851 are no limit of accepted results. The query may also be narrowed
1852 down by defining the server name of the nickname.
1854 It is also possible to search the user by Client ID. If <Client ID>
1855 is provided server must use it as the search value instead of
1858 To prevent miss-use of this service wildcards in the nickname
1859 or in the servername are not permitted. It is not allowed
1860 to request all users on some server. The IDENTIFY requests must
1861 be based on specific nickname request.
1863 Implementations may not want to give interface access to this
1864 command as it is hardly a command that would be used by an end user.
1865 However, it must be implemented as it is used with private message
1868 The IDENTIFY must be always forwarded to router by server so that
1869 all users are searched. However, server must still search its
1870 locally connected clients.
1872 Reply messages to the command:
1875 Arguments: (1) <Status Payload> (2) <Client ID>
1876 (3) [<nickname>[@<server>]] (4) [<username@host>]
1878 This command may reply with several command reply messages to form
1879 a list of results. In this case the status payload will include
1880 STATUS_LIST_START status in the first reply and STATUS_LIST_END in
1881 the last reply to indicate the end of the list. If there are only
1882 one reply the status is set to normal STATUS_OK.
1884 The command replies with Client ID of the nickname and if more
1885 information is available it may reply with nickname and username
1886 and hostname. If the <count> option were defined in the query
1887 there will be only <count> many replies from the server.
1892 SILC_STATUS_LIST_START
1893 SILC_STATUS_LIST_END
1894 SILC_STATUS_ERR_NO_SUCH_NICK
1895 SILC_STATUS_ERR_WILDCARDS
1896 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
1897 SILC_STATUS_ERR_TOO_MANY_PARAMS
1903 Arguments: (1) <nickname>
1905 Set/change nickname. This command is used to set nickname for
1906 user. There is no limit of the length of the nickname in SILC.
1907 Nickname must not include any spaces (` '), non-printable
1908 characters, commas (`,') and any wildcard characters. Note:
1909 nicknames in SILC are case-sensitive which must be taken into
1910 account when searching clients by nickname.
1912 When nickname is changed new Client ID is generated. Server must
1913 distribute SILC_NOTIFY_TYPE_NICK_CHANGE to local clients on the
1914 channels (if any) the client is joined on. Then it must send
1915 SILC_PACKET_REPLACE_ID to its primary route to replace the old
1916 Client ID with the new one.
1918 Reply messages to the command:
1921 Arguments: (1) <Status Payload> (2) <New ID Payload>
1923 This command is replied always with New ID Payload that is
1924 generated by the server every time user changes their nickname.
1925 Client receiving this payload must start using the received
1926 Client ID as its current valid Client ID. The New ID Payload
1927 is described in [SILC2].
1932 SILC_STATUS_ERR_WILDCARDS
1933 SILC_STATUS_ERR_NICKNAME_IN_USE
1934 SILC_STATUS_ERR_BAD_NICKNAME
1935 SILC_STATUS_ERR_NOT_REGISTERED
1936 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
1937 SILC_STATUS_ERR_TOO_MANY_PARAMS
1943 Arguments: (1) [<Channel ID>] [<server>]
1945 The list command is used to list channels and their topics on
1946 current server. If the <Channel ID> parameter is used, only the
1947 status of that channel is displayed. Secret channels are not
1948 listed at all. Private channels are listed with status indicating
1949 that the channel is private.
1951 If the <server> argument is specified the specified server's
1952 channels are listed. In this case the command must be sent to
1953 the server who owns the channel that was requested.
1955 Reply messages to the command:
1958 Arguments: (1) <Status Payload> (2) <Channel ID>
1959 (3) <channel> (4) <topic>
1961 This command may reply with several command reply messages to form
1962 a list of results. In this case the status payload will include
1963 STATUS_LIST_START status in the first reply and STATUS_LIST_END in
1964 the last reply to indicate the end of the list. If there are only
1965 one reply the status is set to normal STATUS_OK.
1967 This command replies with Channel ID, name and the topic of the
1968 channel. If the channel is private channel the <topic> includes
1974 SILC_STATUS_LIST_START
1975 SILC_STATUS_LIST_END
1976 SILC_STATUS_ERR_WILDCARDS
1977 SILC_STATUS_ERR_NOT_REGISTERED
1978 SILC_STATUS_ERR_TOO_MANY_PARAMS
1979 SILC_STATUS_ERR_NO_SUCH_CHANNEL
1980 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
1981 SILC_STATUS_ERR_NO_SUCH_SERVER
1984 6 SILC_COMMAND_TOPIC
1987 Arguments: (1) <Channel ID> (2) [<topic>]]
1989 This command is used to change or view the topic of a channel.
1990 The topic for channel <Channel ID> is returned if there is no
1991 <topic> given. If the <topic> parameter is present, the topic
1992 for that channel will be changed, if the channel modes permit
1995 Reply messages to the command:
1998 Arguments: (1) <Status Payload> (2) <Channel ID>
2001 The command may reply with the topic of the channel if it is
2007 SILC_STATUS_ERR_NOT_ON_CHANNEL
2008 SILC_STATUS_ERR_WILDCARDS
2009 SILC_STATUS_ERR_NOT_REGISTERED
2010 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2011 SILC_STATUS_ERR_NO_SUCH_CHANNEL
2012 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
2013 SILC_STATUS_ERR_NO_CHANNEL_ID
2014 SILC_STATUS_ERR_BAD_CHANNEL_ID
2015 SILC_STATUS_ERR_TOO_MANY_PARAMS
2016 SILC_STATUS_ERR_NO_CHANNEL_PRIV
2019 7 SILC_COMMAND_INVITE
2022 Arguments: (1) <Client ID> (2) <Channel ID>
2024 This command is used to invite other clients to join to the
2025 channel. The <Client ID> argument is the target client's ID that
2026 is being invited. The <Channel ID> is the Channel ID of the
2027 requested channel. The sender of this command must be on the
2028 channel. This command must fail if the requested channel does
2029 not exist, the requested client is already on the channel or if
2030 the channel is invite only channel and the caller of this command
2031 does not have at least channel operator privileges.
2033 Reply messages to the command:
2036 Arguments: (1) <Status Payload>
2038 This command replies only with Status Payload.
2043 SILC_STATUS_ERR_NOT_REGISTERED
2044 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2045 SILC_STATUS_ERR_TOO_MANY_PARAMS
2046 SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
2047 SILC_STATUS_ERR_NO_CLIENT_ID
2048 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
2049 SILC_STATUS_ERR_NO_CHANNEL_ID
2050 SILC_STATUS_ERR_NOT_ON_CHANNEL
2051 SILC_STATUS_ERR_USER_ON_CHANNEL
2057 Arguments: (1) [<quit message>]
2059 This command is used by client to end SILC session. The server
2060 must close the connection to a client which sends this command.
2061 if <quit message> is given it will be sent to other clients on
2062 channel if the client is on channel when quitting.
2064 Reply messages to the command:
2066 This command does not reply anything.
2072 Arguments: (1) <Client ID> (2) [<comment>]
2074 This command is used by SILC operators to remove a client from
2075 SILC network. The removing has temporary effects and client may
2076 reconnect to SILC network. The <Client ID> is the client to be
2077 removed from SILC. The <comment> argument may be provided to
2078 give to the removed client some information why it was removed
2081 Reply messages to the command:
2084 Arguments: (1) <Status Payload>
2086 This command replies only with Status Payload.
2091 SILC_STATUS_ERR_WILDCARDS
2092 SILC_STATUS_ERR_NOT_REGISTERED
2093 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2094 SILC_STATUS_ERR_TOO_MANY_PARAMS
2095 SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
2096 SILC_STATUS_ERR_NO_CLIENT_ID
2099 10 SILC_COMMAND_INFO
2102 Arguments: (1) [<server>]
2104 This command is used to fetch various information about a server.
2105 If <server> argument is specified the command must be sent to
2106 the requested server.
2108 Reply messages to the command:
2111 Arguments: (1) <Status Payload> (2) <Server ID>
2114 This command replies with the Server ID of the server and a
2115 string which tells the information about the server.
2120 SILC_STATUS_ERR_WILDCARDS
2121 SILC_STATUS_ERR_NOT_REGISTERED
2122 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2123 SILC_STATUS_ERR_TOO_MANY_PARAMS
2124 SILC_STATUS_ERR_NO_SUCH_SERVER
2127 11 SILC_COMMAND_CONNECT
2130 Arguments: (1) <Server ID>
2131 (2) [<remote server/router>[ <port>]]
2133 This command is used by operators to force a server to try to
2134 establish a new connection to another router (if the connecting
2135 server is normal server) or server (if the connecting server is
2136 router server). Operator may specify the server/router to be
2137 connected by setting <remote server> argument. The separator
2138 between <remote server address> and <port> is whitespace (` ').
2140 Reply messages to the command:
2143 Arguments: (1) <Status Payload>
2145 This command replies only with Status Payload.
2152 SILC_STATUS_ERR_WILDCARDS
2153 SILC_STATUS_ERR_NOT_REGISTERED
2154 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2155 SILC_STATUS_ERR_TOO_MANY_PARAMS
2156 SILC_STATUS_ERR_NO_SUCH_SERVER_ID
2157 SILC_STATUS_ERR_NO_SERVER_PRIV
2158 SILC_STATUS_ERR_NO_ROUTER_PRIV
2161 12 SILC_COMMAND_PING
2164 Arguments: (1) <Server ID>
2166 This command is used by client and server to test the communication
2167 channel to its server if one suspects that the communication is not
2168 working correctly. The <Server ID> is the ID of the server the
2169 sender is connected to.
2171 Reply messages to the command:
2174 Arguments: (1) <Status Payload>
2176 This command replies only with Status Payload. Server returns
2177 SILC_STATUS_OK in Status Payload if pinging was successful.
2184 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2185 SILC_STATUS_ERR_TOO_MANY_PARAMS
2186 SILC_STATUS_ERR_NO_SERVER_ID
2187 SILC_STATUS_ERR_NO_SUCH_SERVER
2188 SILC_STATUS_ERR_NOT_REGISTERED
2191 13 SILC_COMMAND_OPER
2194 Arguments: (1) <username> (2) <authentication data>
2196 This command is used by normal client to obtain server operator
2197 privileges on some server or router. Note that router operator
2198 has router privileges that supersedes the server operator
2199 privileges and this does not obtain those privileges. Client
2200 must use SILCOPER command to obtain router level privileges.
2202 The <username> is the username set in the server configurations
2203 as operator. The <authentication data> is the data that the
2204 client is authenticated against. It may be passphrase prompted
2205 for user on client's screen or it may be public key
2206 authentication data (data signed with private key), or
2209 Reply messages to the command:
2212 Arguments: (1) <Status Payload>
2214 This command replies only with Status Payload.
2219 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2220 SILC_STATUS_ERR_TOO_MANY_PARAMS
2221 SILC_STATUS_ERR_NOT_REGISTERED
2222 SILC_STATUS_ERR_BAD_PASSWORD
2223 SILC_STATUS_ERR_AUTH_FAILED
2226 14 SILC_COMMAND_JOIN
2229 Arguments: (1) <channel> (2) [<passphrase>]
2232 Join to channel/create new channel. This command is used to
2233 join to a channel. If the channel does not exist the channel is
2234 created. If server is normal server this command must be forwarded
2235 to router who will create the channel. The channel may be protected
2236 with passphrase. If this is the case the passphrase must be sent
2237 along the join command.
2239 The name of the <channel> must not include any spaces (` '),
2240 non-printable characters, commas (`,') or any wildcard characters.
2242 Cipher to be used to secure the traffic on the channel may be
2243 requested by sending the name of the requested <cipher>. This
2244 is used only if the channel does not exist and is created. If
2245 the channel already exists the cipher set previously for the
2246 channel will be used to secure the traffic.
2248 The server must check whether the user is allowed to join to
2249 the requested channel. Various modes set to the channel affect
2250 the ability of the user to join the channel. These conditions
2253 o The user must be invited to the channel if the channel
2254 is invite-only channel.
2256 o The Client ID/nickname/username/hostname must not match
2259 o The correct passphrase must be provided if passphrase
2260 is set to the channel.
2262 o The user count limit, if set, must not be reached.
2264 Reply messages to the command:
2267 Arguments: (1) <Status Payload> (2) <channel>
2268 (3) <Channel ID> (4) <channel mode mask>
2269 (5) [<ban mask>] (6) [<invite list>]
2272 This command replies with the channel name requested by the
2273 client, channel ID of the channel and topic of the channel
2274 if it exists. It also replies with the channel mode mask
2275 which tells all the modes set on the channel. If the
2276 channel is created the mode mask is zero (0). If ban mask
2277 and/or invite list is set they are sent as well.
2279 Client must not start transmitting to the channel even after
2280 server has replied to this command. Client is permitted to
2281 start transmitting on channel after server has sent packet
2282 SILC_PACKET_CHANNEL_KEY to the client.
2287 SILC_STATUS_ERR_WILDCARDS
2288 SILC_STATUS_ERR_NOT_REGISTERED
2289 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2290 SILC_STATUS_ERR_TOO_MANY_PARAMS
2291 SILC_STATUS_ERR_BAD_PASSWORD
2292 SILC_STATUS_ERR_CHANNEL_IS_FULL
2293 SILC_STATUS_ERR_NOT_INVITED
2294 SILC_STATUS_ERR_BANNED_FROM_CHANNEL
2295 SILC_STATUS_ERR_BAD_CHANNEL
2296 SILC_STATUS_ERR_USER_ON_CHANNEL
2299 15 SILC_COMMAND_MOTD
2302 Arguments: (1) <server>
2304 This command is used to query the Message of the Day of the server.
2306 Reply messages to the command:
2309 Arguments: (1) <Status Payload> (2) [<motd>]
2311 This command replies with the motd message if it exists.
2316 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2317 SILC_STATUS_ERR_TOO_MANY_PARAMS
2318 SILC_STATUS_ERR_NOT_REGISTERED
2319 SILC_STATUS_ERR_NO_SUCH_SERVER
2322 16 SILC_COMMAND_UMODE
2325 Arguments: (1) <Client ID> (2) <client mode mask>
2327 This command is used by client to set/unset modes for itself.
2328 However, there are some modes that the client may not set itself,
2329 but they will be set by server. However, client may unset any
2330 mode. Modes may be masked together ORing them thus having
2331 several modes set. Client must keep its client mode mask
2332 locally so that the mode setting/unsetting would work without
2333 problems. Client may change only its own modes.
2335 Following client modes are defined:
2337 0x0000 SILC_UMODE_NONE
2339 No specific mode for client. This is the initial
2340 setting when new client is created. The client is
2344 0x0001 SILC_UMODE_SERVER_OPERATOR
2346 Marks the user as server operator. Client cannot
2347 set this mode itself. Server sets this mode to the
2348 client when client attains the server operator
2349 privileges by SILC_COMMAND_OPER command. Client
2350 may unset the mode itself.
2353 0x0002 SILC_UMODE_ROUTER_OPERATOR
2355 Marks the user as router (SILC) operator. Client
2356 cannot this mode itself. Router sets this mode to
2357 the client when client attains the router operator
2358 privileges by SILC_COMMAND_SILCOPER command. Client
2359 may unset the mode itself.
2361 Reply messages to the command:
2364 Arguments: (1) <Status Payload> (2) <client mode mask>
2366 This command replies with the changed client mode mask that
2367 the client is required to keep locally.
2373 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2374 SILC_STATUS_ERR_TOO_MANY_PARAMS
2375 SILC_STATUS_ERR_NOT_REGISTERED
2376 SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
2377 SILC_STATUS_ERR_BAD_CLIENT_ID
2378 SILC_STATUS_ERR_NOT_YOU
2379 SILC_STATUS_ERR_UNKNOWN_MODE
2380 SILC_STATUS_ERR_NO_RECIPIENT
2381 SILC_STATUS_ERR_NO_CLIENT_ID
2384 17 SILC_COMMAND_CMODE
2387 Arguments: (1) <Channel ID> (2) <channel mode mask>
2388 (3) [<user limit>] (4) [<passphrase>]
2389 (5) [<ban mask>] (6) [<invite list>]
2390 (7) [<cipher>[:<key len>]]
2392 This command is used by client to set or change channel flags on
2393 a channel. Channel has several modes that set various properties
2394 of a channel. Modes may be masked together by ORing them thus
2395 having several modes set. The <Channel ID> is the ID of the
2396 target channel. The client changing channel mode must be on
2397 the same channel and poses sufficient privileges to be able to
2400 When the mode is changed SILC_NOTIFY_TYPE_CMODE_CHANGE notify
2401 type is distributed to the channel.
2403 Following channel modes are defined:
2405 0x0000 SILC_CMODE_NONE
2407 No specific mode on channel. This is the default when
2408 channel is created. This means that channel is just plain
2412 0x0001 SILC_CMODE_PRIVATE
2414 Channel is private channel. Private channels are shown
2415 in the channel list listed with SILC_COMMAND_LIST command
2416 with indication that the channel is private. Also,
2417 client on private channel will no be detected to be on
2418 the channel as the channel is not shown in the client's
2419 currently joined channel list. Channel founder and
2420 channel operator may set/unset this mode.
2422 Typical implementation would use [+|-]p on user interface
2423 to set/unset this mode.
2426 0x0002 SILC_CMODE_SECRET
2428 Channel is secret channel. Secret channels are not shown
2429 in the list listed with SILC_COMMAND_LIST command. Secret
2430 channels can be considered to be invisible channels.
2431 Channel founder and channel operator may set/unset this
2434 Typical implementation would use [+|-]s on user interface
2435 to set/unset this mode.
2438 0x0004 SILC_CMODE_PRIVKEY
2440 Channel uses private channel key to protect the traffic
2441 on the channel. When this mode is set the client will be
2442 responsible to set the key it wants to use to encrypt and
2443 decrypt the traffic on channel. Server generated channel
2444 keys are not used at all. This mode provides additional
2445 security as clients on channel may agree to use private
2446 channel key that even servers do not know. Naturally,
2447 this requires that every client on the channel knows
2448 the key before hand (it is considered to be pre-shared-
2449 key). This specification does not define how the private
2450 channel key is set as it is entirely local setting on
2453 As it is local setting it is possible to have several
2454 private channel keys on one channel. In this case several
2455 clients can talk on same channel but only those clients
2456 that share the key with the message sender will be able
2457 to hear the talking. Client should not display those
2458 message for the end user that it is not able to decrypt
2459 when this mode is set.
2461 Only channel founder may set/unset this mode. If this
2462 mode is unset the server will distribute new channel
2463 key to all clients on the channel which will be used
2466 Typical implementation would use [+|-]k on user interface
2467 to set/unset this mode.
2470 0x0008 SILC_CMODE_INVITE
2472 Channel is invite only channel. Client may join to this
2473 channel only if it is invited to the channel. Channel
2474 founder and channel operator may set/unset this mode.
2476 Typical implementation would use [+|-]i on user interface
2477 to set/unset this mode.
2480 0x0010 SILC_CMODE_TOPIC
2482 The topic of the channel may only be set by client that
2483 is channel founder or channel operator. Normal clients
2484 on channel will not be able to set topic when this mode
2485 is set. Channel founder and channel operator may set/
2488 Typical implementation would use [+|-]t on user interface
2489 to set/unset this mode.
2492 0x0020 SILC_CMODE_ULIMIT
2494 User limit has been set to the channel. New clients
2495 may not join to the channel when the limit set is
2496 reached. Channel founder and channel operator may set/
2497 unset the limit. The <user limit> argument is the
2498 number of limited users.
2500 Typical implementation would use [+|-]l on user interface
2501 to set/unset this mode.
2504 0x0040 SILC_CMODE_PASSPHRASE
2506 Passphrase has been set to the channel. Client may
2507 join to the channel only if it is able to provide the
2508 correct passphrase. Setting passphrases to channel
2509 is entirely safe as all commands are protected in the
2510 SILC network. Only channel founder may set/unset
2511 the passphrase. The <passphrase> argument is the
2514 Typical implementation would use [+|-]a on user interface
2515 to set/unset this mode.
2518 0x0080 SILC_CMODE_BAN
2520 Ban mask has been set to the channel. The ban mask
2521 may be used to ban specific clients to join the channel.
2522 The <ban mask> argument is the set ban mask. When
2523 unsetting a ban mask the mask must be provided as
2524 argument. Channel founder and channel operator may
2525 set/unset this mode. Channel founder may not be
2526 added to the ban list. <ban mask> is comma (`,') separated
2527 list of banned clients in following format:
2529 [<nickname>!][<username>]@[<hostname>]
2531 Wildcards maybe used when banning clients.
2533 Typical implementation would use [+|-]b on user interface
2534 to set/unset this mode.
2537 0x0100 SILC_CMODE_INVITE_LIST
2539 Invite list has been set to the channel. The invite list
2540 can be used to mark the clients that is able to join
2541 channel without being invited when the channel is set to
2542 be invite-only channel. The <invite list> argument is the
2543 set invite mask. When unsetting entry from the invite list
2544 the entry must be provided as argument. Channel founder and
2545 channel operator may set/unset this mode. The <invite list>
2546 is command (`,') separated list of invited clients in following
2549 [<nickname>!][<username>]@[<hostname>]
2551 Wildcards maybe used when setting the invite list.
2553 Typical implementation would use [+|-]I on user interface
2554 to set/unset this mode.
2557 0x0200 SILC_CMODE_CIPHER
2559 Sets specific cipher to be used to protect channel
2560 traffic. The <cipher> argument is the requested cipher.
2561 When set or unset the server must re-generate new
2562 channel key. If <key len> argument is specified with
2563 <cipher> argument the new key is generated of <key len>
2564 length in bits. Only channel founder may set the cipher of
2565 the channel. When unset the new key is generated using
2566 default cipher for the channel.
2568 Typical implementation would use [+|-]c on user interface
2569 to set/unset this mode.
2572 To make the mode system work, client must keep the channel mode
2573 mask locally so that the mode setting and unsetting would work
2574 without problems. The client receives the initial channel mode
2575 mask when it joins to the channel. When the mode changes on
2576 channel the server distributes the changed channel mode mask to
2577 all clients on the channel by sending SILC_COMMAND_CMODE command
2581 Reply messages to the command:
2584 Arguments: (1) <Status Payload> (2) <channel mode mask>
2586 This command replies with the changed channel mode mask that
2587 client is required to keep locally.
2592 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2593 SILC_STATUS_ERR_TOO_MANY_PARAMS
2594 SILC_STATUS_ERR_NOT_REGISTERED
2595 SILC_STATUS_ERR_NOT_ON_CHANNEL
2596 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
2597 SILC_STATUS_ERR_BAD_CHANNEL_ID
2598 SILC_STATUS_ERR_NO_CHANNEL_ID
2599 SILC_STATUS_ERR_NO_CHANNEL_PRIV
2600 SILC_STATUS_ERR_UNKNOWN_MODE
2601 SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
2604 19 SILC_COMMAND_CUMODE
2607 Arguments: (1) <Channel ID> (2) <mode mask>
2610 This command is used by client to change channel user modes on
2611 channel. Users on channel may have some special modes and this
2612 command is used by channel operators to set or change these modes.
2613 The <Channel ID> is the ID of the target channel. The <mode mask>
2614 is OR'ed mask of modes. The <Client ID> is the target client.
2615 The client changing channel user modes must be on the same channel
2616 as the target client and poses sufficient privileges to be able to
2619 When the mode is changed SILC_NOTIFY_TYPE_CUMODE_CHANGE notify
2620 type is distributed to the channel.
2622 Following channel modes are defined:
2624 0x0000 SILC_CUMODE_NONE
2626 No specific mode. This is the normal situation for client.
2627 Also, this is the mode set when removing all modes from client.
2630 0x0001 SILC_CUMODE_FOUNDER
2632 The client is channel founder of the channel. This mode
2633 cannot be set by other client, it is set by the server when
2634 the channel was founded (created). The mode is provided
2635 because client may remove the founder rights from itself.
2638 0x0002 SILC_CUMODE_OPERATOR
2640 Sets channel operator privileges on the channel for a
2641 client on the channel. Channel founder and channel operator
2642 may set/unset (promote/demote) this mode.
2645 Reply messages to the command:
2648 Arguments: (1) <Status Payload> (2) <channel user mode mask>
2651 This command replies with the changed channel user mode mask that
2652 client is required to keep locally. The <Client ID> is the target
2658 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2659 SILC_STATUS_ERR_TOO_MANY_PARAMS
2660 SILC_STATUS_ERR_NOT_REGISTERED
2661 SILC_STATUS_ERR_NOT_ON_CHANNEL
2662 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
2663 SILC_STATUS_ERR_BAD_CHANNEL_ID
2664 SILC_STATUS_ERR_NO_CHANNEL_ID
2665 SILC_STATUS_ERR_NO_CHANNEL_PRIV
2666 SILC_STATUS_ERR_UNKNOWN_MODE
2667 SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
2670 19 SILC_COMMAND_KICK
2673 Arguments: (1) <channel> (2) <Client ID>
2676 This command is used by channel operators to remove a client from
2677 channel. The <channel> argument is the channel the client to be
2678 removed is on currently. Note that the "kicker" must be on the same
2679 channel. If <comment> is provided it will be sent to the removed
2682 Reply messages to the command:
2685 Arguments: (1) <Status Payload>
2687 This command replies only with Status Payload.
2692 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2693 SILC_STATUS_ERR_TOO_MANY_PARAMS
2694 SILC_STATUS_ERR_NOT_REGISTERED
2695 SILC_STATUS_ERR_NO_SUCH_CHANNEL
2696 SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
2697 SILC_STATUS_ERR_NO_CHANNEL_PRIV
2698 SILC_STATUS_ERR_NO_CLIENT_ID
2701 20 SILC_COMMAND_RESTART
2706 This command may only be used by server operator to force a
2707 server to restart itself.
2709 Reply messages to the command:
2712 Arguments: (1) <Status Payload>
2714 This command replies only with Status Payload.
2719 SILC_STATUS_ERR_NOT_REGISTERED
2720 SILC_STATUS_ERR_NO_SERVER_PRIV
2726 21 SILC_COMMAND_CLOSE
2729 Arguments: (1) <Server ID>
2731 This command is used only by operator to close connection to a
2732 remote site. The <Server ID> argument is the ID of the remote
2733 site and must be valid.
2735 Reply messages to the command:
2738 Arguments: (1) <Status Payload>
2740 This command replies only with Status Payload.
2745 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2746 SILC_STATUS_ERR_TOO_MANY_PARAMS
2747 SILC_STATUS_ERR_NOT_REGISTERED
2748 SILC_STATUS_ERR_NO_SUCH_SERVER
2749 SILC_STATUS_ERR_NO_SERVER_PRIV
2750 SILC_STATUS_ERR_NO_SUCH_SERVER_ID
2758 This command is used only by operator to shutdown the server.
2759 All connections to the server will be closed and the server is
2762 Reply messages to the command:
2767 Arguments: (1) <Status Payload>
2769 This command replies only with Status Payload.
2774 SILC_STATUS_ERR_NOT_REGISTERED
2775 SILC_STATUS_ERR_NO_SERVER_PRIV
2778 23 SILC_COMMAND_SILCOPER
2781 Arguments: (1) <username> (2) <authentication data>
2783 This command is used by normal client to obtain router operator
2784 privileges (also known as SILC operator) on some router. Note
2785 that router operator has router privileges that supersedes the
2786 server operator privileges.
2788 The <username> is the username set in the server configurations
2789 as operator. The <authentication data> is the data that the
2790 client is authenticated against. It may be passphrase prompted
2791 for user on client's screen or it may be public key
2792 authentication data (data signed with private key), or
2795 Difference between router operator and server operator is that
2796 router operator is able to handle cell level properties while
2797 server operator (even on router server) is able to handle only
2798 local properties, such as, local connections and normal server
2801 Reply messages to the command:
2804 Arguments: (1) <Status Payload>
2806 This command replies only with Status Payload.
2811 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2812 SILC_STATUS_ERR_TOO_MANY_PARAMS
2813 SILC_STATUS_ERR_NOT_REGISTERED
2814 SILC_STATUS_ERR_BAD_PASSWORD
2815 SILC_STATUS_ERR_AUTH_FAILED
2818 24 SILC_COMMAND_LEAVE
2821 Arguments: (1) <Channel ID>
2823 This command is used by client to leave a channel the client is
2824 joined to. After a client has leaved the channel the server
2825 must create new key for the channel and distribute to all clients
2826 still currently on the channel.
2828 Reply messages to the command:
2831 Arguments: (1) <Status Payload>
2833 This command replies only with Status Payload.
2838 SILC_STATUS_ERR_NOT_REGISTERED
2839 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2840 SILC_STATUS_ERR_TOO_MANY_PARAMS
2841 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
2842 SILC_STATUS_ERR_BAD_CHANNEL_ID
2843 SILC_STATUS_ERR_NO_CHANNEL_ID
2846 25 SILC_COMMAND_NAMES
2849 Arguments: (1) <Channel ID>
2851 This command is used to list user names currently on the requested
2852 channel; argument <Channel ID>. The server must resolve the
2853 user names and send a comma (`,') separated list of user names
2854 on the channel. Server or router may resolve the names by sending
2855 SILC_COMMAND_WHOIS commands.
2857 If the requested channel is a private or secret channel, this
2858 command must not send the list of users, as private and secret
2859 channels cannot be seen by outside. In this case the returned
2860 name list may include a indication that the server could not
2861 resolve the names of the users on the channel. Also, in this case
2862 Client ID's or client modes are not sent either.
2864 Reply messages to the command:
2867 Arguments: (1) <Status Payload> (2) <Channel ID>
2868 (3) <name list> (4) <Client ID list>
2869 (5) <client mode list>
2871 This command replies with the Channel ID of the requested channel,
2872 comma separated list of users on the channel and Client ID list
2873 of the users on the list. The Client ID list has Client ID's
2874 of all users in the list. First Client ID in the list must be
2875 the Client ID of the first user in <name list>. The <Client ID
2876 list> is formed by adding Client ID's each after each. Note that
2877 the Client ID list is binary data and the length of each ID must
2878 be snooped from the data. The <client mode list> is formed by
2879 adding client's user modes on the channel each after each (4 bytes
2885 SILC_STATUS_ERR_NOT_REGISTERED
2886 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2887 SILC_STATUS_ERR_TOO_MANY_PARAMS
2888 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
2889 SILC_STATUS_ERR_BAD_CHANNEL_ID
2890 SILC_STATUS_ERR_NO_CHANNEL_ID
2891 SILC_STATUS_ERR_NOT_ON_CHANNEL
2896 Currently undefined commands.
2901 These commands are reserved for private use and will not be defined
2905 255 SILC_COMMAND_MAX
2907 Reserved command. This must not be sent.
2912 5.3 SILC Command Status Types
2915 5.3.1 SILC Command Status Payload
2917 Command Status Payload is sent in command reply messages to indicate
2918 the status of the command. The payload is one of argument in the
2919 command thus this is the data area in Command Argument Payload described
2920 in [SILC2]. The payload is only 2 bytes of length. Following diagram
2921 represents the Command Status Payload (field is always in MSB order).
2930 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
2931 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2933 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2937 Figure 6: SILC Command Status Payload
2941 o Status Message (2 bytes) - Indicates the status message.
2942 All Status messages are described in the next section.
2947 5.3.2 SILC Command Status List
2949 Command Status messages are returned in the command reply messages
2950 to indicate whether the command were executed without errors. If error
2951 has occured the status tells which error occured. Status payload only
2952 sends numeric reply about the status. Receiver of the payload must
2953 convert the numeric values into human readable error messages. The
2954 list of status messages below has an example human readable error
2955 messages that client may display for the user.
2957 List of all defined command status messages following.
2960 Generic status messages:
2964 Ok status. Everything went Ok. The status payload maybe
2965 safely ignored in this case.
2967 1 SILC_STATUS_LIST_START
2969 Start of the list. There will be several command replies and
2970 this reply is the start of the list.
2972 2 SILC_STATUS_LIST_ITEM
2974 Item in the list. This is one of the item in the list but not the
2977 3 SILC_STATUS_LIST_END
2979 End of the list. There were several command replies and this
2980 reply is the last of the list. There won't be other replies
2981 belonging to this list after this one.
2985 Currently undefined and has been reserved for the future.
2988 Error status message:
2990 10 SILC_STATUS_ERR_NO_SUCH_NICK
2992 "No such nickname". Requested nickname does not exist.
2994 11 SILC_STATUS_ERR_NO_SUCH_CHANNEL
2996 "No such channel". Requested channel name does not exist.
2998 12 SILC_STATUS_ERR_NO_SUCH_SERVER
3000 "No such server". Requested server name does not exist.
3002 13 SILC_STATUS_ERR_TOO_MANY_TARGETS
3004 "Duplicate recipients. No message delivered". Message were
3005 tried to be sent to recipient which has several occurrences in
3008 14 SILC_STATUS_ERR_NO_RECIPIENT
3010 "No recipient given". Command required recipient which was
3013 15 SILC_STATUS_ERR_UNKNOWN_COMMAND
3015 "Unknown command". Command sent to server is unknown by the
3018 16 SILC_STATUS_ERR_WILDCARDS
3020 "Wildcards cannot be used". Wildcards were provided but they
3023 17 SILC_STATUS_ERR_NO_CLIENT_ID
3025 "No Client ID given". Client ID were expected as command
3026 parameter but were not found.
3028 18 SILC_STATUS_ERR_NO_CHANNEL_ID
3030 "No Channel ID given". Channel ID were expected as command
3031 parameter but were not found.
3033 19 SILC_STATUS_ERR_NO_SERVER_ID
3035 "No Serve ID given". Server ID were expected as command
3036 parameter but were not found.
3038 20 SILC_STATUS_ERR_BAD_CLIENT_ID
3040 "Bad Client ID". Client ID provided were erroneous.
3042 21 SILC_STATUS_ERR_BAD_CHANNEL_ID
3044 "Bad Channel ID". Channel ID provided were erroneous.
3046 22 SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
3048 "No such Client ID". Client ID provided does not exist.
3050 23 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
3052 "No such Channel ID". Channel ID provided does not exist.
3054 24 SILC_STATUS_ERR_NICKNAME_IN_USE
3056 "Nickname already exists". Nickname created could not be
3057 registered because number of same nicknames were already set to
3058 maximum. This is not expected to happen in real life but is
3061 25 SILC_STATUS_ERR_NOT_ON_CHANNEL
3063 "You are not on that channel". The command were specified for
3064 channel user is not currently on.
3066 26 SILC_STATUS_ERR_USER_NOT_ON_CHANNEL
3068 "They are not on channel". The requested target client is not
3069 on requested channel.
3071 27 SILC_STATUS_ERR_USER_ON_CHANNEL
3073 "User already on channel". User were invited on channel they
3076 28 SILC_STATUS_ERR_NOT_REGISTERED
3078 "You have not registered". User executed command that requires
3079 the client to be registered on the server before it may be
3082 29 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
3084 "Not enough parameters". Command requires more parameters
3087 30 SILC_STATUS_ERR_TOO_MANY_PARAMS
3089 "Too many parameters". Too many parameters were provided
3092 31 SILC_STATUS_ERR_PERM_DENIED
3094 "Your host is not among the privileged". The client tried to
3095 register on server that does not allow this host to connect.
3097 32 SILC_STATUS_ERR_BANNED_FROM_SERVER
3099 "You are banned from this server". The client tried to register
3100 on server that has explicitly denied this host to connect.
3102 33 SILC_STATUS_ERR_BAD_PASSWORD
3104 "Cannot join channel. Incorrect password". Password provided for
3105 channel were not accepted.
3107 34 SILC_STATUS_ERR_CHANNEL_IS_FULL
3109 "Cannot join channel. Channel is full". The channel is full
3110 and client cannot be joined to it.
3112 35 SILC_STATUS_ERR_NOT_INVITED
3114 "Cannot join channel. You have not been invited". The channel
3115 is invite only channel and client has not been invited.
3117 36 SILC_STATUS_ERR_BANNED_FROM_CHANNEL
3119 "Cannot join channel. You have been banned". The client has
3120 been banned from the channel.
3122 37 SILC_STATUS_ERR_UNKNOWN_MODE
3124 "Unknown mode". Mode provided by the client were unknown to
3127 38 SILC_STATUS_ERR_NOT_YOU
3129 "Cannot change mode for other users". User tried to change
3130 someone else's mode.
3132 39 SILC_STATUS_ERR_NO_CHANNEL_PRIV
3134 "Permission denied. You are not channel operator". Command may
3135 be executed only by channel operator.
3137 40 SILC_STATUS_ERR_NO_SERVER_PRIV
3139 "Permission denied. You are not server operator". Command may
3140 be executed only by server operator.
3142 41 SILC_STATUS_ERR_NO_ROUTER_PRIV
3144 "Permission denied. You are not SILC operator". Command may be
3145 executed only by router (SILC) operator.
3147 42 SILC_STATUS_ERR_BAD_NICKNAME
3149 "Bad nickname". Nickname requested contained illegal characters
3152 43 SILC_STATUS_ERR_BAD_CHANNEL
3154 "Bad channel name". Channel requested contained illegal characters
3157 44 SILC_STATUS_ERR_AUTH_FAILED
3159 "Authentication failed". The authentication data sent as
3160 argument were wrong and thus authentication failed.
3165 6 Security Considerations
3167 Security is central to the design of this protocol, and these security
3168 considerations permeate the specification. Common security considerations
3169 such as keeping private keys truly private and using adequate lengths for
3170 symmetric and asymmetric keys must be followed in order to maintain the
3171 security of this protocol.
3177 [SILC2] Riikonen, P., "SILC Packet Protocol", Internet Draft,
3180 [SILC3] Riikonen, P., "SILC Key Exchange and Authentication
3181 Protocols", Internet Draft, June 2000.
3183 [IRC] Oikarinen, J., and Reed D., "Internet Relay Chat Protocol",
3186 [SSH-TRANS] Ylonen, T., et al, "SSH Transport Layer Protocol",
3189 [PGP] Callas, J., et al, "OpenPGP Message Format", RFC 2440,
3192 [SPKI] Ellison C., et al, "SPKI Certificate Theory", RFC 2693,
3195 [PKIX-Part1] Housley, R., et al, "Internet X.509 Public Key
3196 Infrastructure, Certificate and CRL Profile", RFC 2459,
3199 [Schneier] Schneier, B., "Applied Cryptography Second Edition",
3200 John Wiley & Sons, New York, NY, 1996.
3202 [Menezes] Menezes, A., et al, "Handbook of Applied Cryptography",
3205 [OAKLEY] Orman, H., "The OAKLEY Key Determination Protocol",
3206 RFC 2412, November 1998.
3208 [ISAKMP] Maughan D., et al, "Internet Security Association and
3209 Key Management Protocol (ISAKMP)", RFC 2408, November
3212 [IKE] Harkins D., and Carrel D., "The Internet Key Exchange
3213 (IKE)", RFC 2409, November 1998.
3215 [HMAC] Krawczyk, H., "HMAC: Keyed-Hashing for Message
3216 Authentication", RFC 2104, February 1997.
3229 EMail: priikone@poseidon.pspt.fi
3231 This Internet-Draft expires 6 Jun 2001