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 not to accept the command reply, but there are some
827 command replies that the client should accept. Example of a such
828 command reply is reply to SILC_COMMAND_CMODE command that the server
829 uses to distribute the channel mode on all clients on the channel
830 when the mode has changed.
832 It is expected that some of the commands may be miss-used by clients
833 resulting various problems on the server side. Every implementation
834 should assure that commands may not be executed more than once, say,
835 in two (2) seconds. This should be sufficient to prevent the miss-use
838 SILC commands are described in section 5 SILC Commands.
844 Packets are naturally the most important part of the protocol and the
845 packets are what actually makes the protocol. Packets in SILC network
846 are always encrypted using, usually, the shared secret session key
847 or some other key, for example, channel key, when encrypting channel
848 messages. The SILC Packet Protocol is a wide protocol and is described
849 in [SILC2]. This document does not define or describe details of
855 3.8 Packet Encryption
857 All packets passed in SILC network must be encrypted. This section
858 defines how packets must be encrypted in the SILC network. The detailed
859 description of the actual encryption process of the packets are
860 described in [SILC2].
862 Client and its server shares secret symmetric session key which is
863 established by the SILC Key Exchange Protocol, described in [SILC3].
864 Every packet sent from client to server, with exception of packets for
865 channels, are encrypted with this session key.
867 Channels has their own key that are shared by every client on the channel.
868 However, the channel keys are cell specific thus one cell does not know
869 the channel key of the other cell, even if that key is for same channel.
870 Channel key is also known by the routers and all servers that has clients
871 on the channel. However, channels may have channel private keys that
872 are entirely local setting for client. All clients on the channel must
873 know the channel private key before hand to be able to talk on the
874 channel. In this case, no server or router knows the key for channel.
876 Server shares secret symmetric session key with router which is
877 established by the SILC Key Exchange Protocol. Every packet passed from
878 server to router, with exception of packets for channels, are encrypted
879 with the shared session key. Same way, router server shares secret
880 symmetric key with its primary route. However, every packet passed
881 from router to other router, including packets for channels, are
882 encrypted with the shared session key. Every router connection has
883 their own session keys.
887 3.8.1 Determination of the Source and the Destination
889 The source and the destination of the packet needs to be determined
890 to be able to route the packets to correct receiver. This information
891 is available in the SILC Packet Header which is included in all packets
892 sent in SILC network. The SILC Packet Header is described in [SILC2].
894 The header is always encrypted with the session key who is next receiver
895 of the packet along the route. The receiver of the packet, for example
896 a router along the route, is able to determine the sender and the
897 destination of the packet by decrypting the SILC Packet Header and
898 checking the ID's attached to the header. The ID's in the header will
899 tell to where the packet needs to be sent and where it is coming from.
901 The header in the packet does not change during the routing of the
902 packet. The original sender, for example client, assembles the packet
903 and the packet header and server or router between the sender and the
904 receiver must not change the packet header.
906 Note that the packet and the packet header may be encrypted with
907 different keys. For example, packets to channels are encrypted with
908 the channel key, however, the header is encrypted with the session key
909 as described above. However, the header and the packet may be encrypted
910 with same key. This is case, for example, with command packets.
914 3.8.2 Client To Client
916 Process of message delivery and encryption from client to another
917 client is as follows.
919 Example: Private message from client to another client on different
920 servers. Clients do not share private message delivery
921 keys; normal session keys are used.
923 o Client 1. sends encrypted packet to its server. The packet is
924 encrypted with the session key shared between client and its
927 o Server determines the destination of the packet and decrypts
928 the packet. Server encrypts the packet with session key shared
929 between the server and its router, and sends the packet to the
932 o Router determines the destination of the packet and decrypts
933 the packet. Router encrypts the packet with session key
934 shared between the router and the destination server, and sends
935 the packet to the server.
937 o Server determines the client to which the packet is destined
938 to and decrypts the packet. Server encrypts the packet with
939 session key shared between the server and the destination client,
940 and sends the packet to the client.
942 o Client 2. decrypts the packet.
945 Example: Private message from client to another client on different
946 servers. Clients has established secret shared private
947 message delivery key with each other and that is used in
948 the message encryption.
950 o Client 1. sends encrypted packet to its server. The packet is
951 encrypted with the private message delivery key shared between
954 o Server determines the destination of the packet and sends the
955 packet to the router.
957 o Router determines the destination of the packet and sends the
958 packet to the server.
960 o Server determines the client to which the packet is destined
961 to and sends the packet to the client.
963 o Client 2. decrypts the packet with the secret shared key.
966 If clients share secret key with each other the private message
967 delivery is much simpler since servers and routers between the
968 clients do not need to decrypt and re-encrypt the packet.
970 The process for clients on same server is much simpler as there are
971 no need to send the packet to the router. The process for clients
972 on different cells is same as above except that the packet is routed
973 outside the cell. The router of the destination cell routes the
974 packet to the destination same way as described above.
978 3.8.3 Client To Channel
980 Process of message delivery from client on channel to all the clients
983 Example: Channel of four users; two on same server, other two on
984 different cells. Client sends message to the channel.
986 o Client 1. encrypts the packet with channel key and sends the
987 packet to its server.
989 o Server determines local clients on the channel and sends the
990 packet to the Client on the same server. Server then sends
991 the packet to its router for further routing.
993 o Router determines local clients on the channel, if found
994 sends packet to the local clients. Router determines global
995 clients on the channel and sends the packet to its primary
996 router or fastest route.
998 o (Other router(s) do the same thing and sends the packet to
1001 o Server determines local clients on the channel and sends the
1002 packet to the client.
1004 o All clients receiving the packet decrypts the packet.
1008 3.8.4 Server To Server
1010 Server to server packet delivery and encryption is described in above
1011 examples. Router to router packet delivery is analogous to server to
1012 server. However, some packets, such as channel packets, are processed
1013 differently. These cases are described later in this document and
1014 more in detail in [SILC2].
1018 3.9 Key Exchange And Authentication
1020 Key exchange is done always when for example client connects to server
1021 but also when server and router and router and router connects to each
1022 other. The purpose of key exchange protocol is to provide secure key
1023 material to be used in the communication. The key material is used to
1024 derive various security parameters used to secure SILC packets. The
1025 SILC Key Exchange protocol is described in detail in [SILC3].
1027 Authentication is done after key exchange protocol has been successfully
1028 completed. The purpose of authentication is to authenticate for example
1029 client connecting to the server. However, Usually clients are accepted
1030 to connect to server without explicit authentication. Servers are
1031 required use authentication protocol when connecting. The authentication
1032 may be based on passphrase (pre-shared-secret) or public key. The
1033 connection authentication protocol is described in detail in [SILC3].
1039 This section defines all the allowed algorithms that can be used in
1040 the SILC protocol. This includes mandatory cipher, mandatory public
1041 key algorithm and MAC algorithms.
1047 Cipher is the encryption algorithm that is used to protect the data
1048 in the SILC packets. See [SILC2] of the actual encryption process and
1049 definition of how it must be done. SILC has a mandatory algorithm that
1050 must be supported in order to be compliant with this protocol.
1052 Following ciphers are defined in SILC protocol:
1055 aes-cbc AES in CBC mode (mandatory)
1056 twofish-cbc Twofish in CBC mode (optional)
1057 blowfish-cbc Blowfish in CBC mode (optional)
1058 rc6-cbc RC6 in CBC mode (optional)
1059 rc5-cbc RC5 in CBC mode (optional)
1060 mars-cbc Mars in CBC mode (optional)
1061 none No encryption (optional)
1065 All algorithms must use minimum of 128 bit key, by default. Several
1066 algorithms, however, supports longer keys and it is recommended to use
1067 longer keys if they are available.
1069 Algorithm none does not perform any encryption process at all and
1070 thus is not recommended to be used. It is recommended that no client
1071 or server implementation would accept none algorithms except in special
1074 Additional ciphers may be defined to be used in SILC by using the
1075 same name format as above.
1079 3.10.2 Public Key Algorithms
1081 Public keys are used in SILC to authenticate entities in SILC network
1082 and to perform other tasks related to public key cryptography. The
1083 public keys are also used in the SILC Key Exchange protocol [SILC3].
1085 Following public key algorithms are defined in SILC protocol:
1092 Both of the algorithms are described in [Scheneir] and [Menezes].
1094 Additional public key algorithms may be defined to be used in SILC.
1098 3.10.3 MAC Algorithms
1100 Data integrity is protected by computing a message authentication code
1101 (MAC) of the packet data. See [SILC2] for details how to compute the
1104 Following MAC algorithms are defined in SILC protocol:
1107 hmac-sha1 HMAC-SHA1, length = 20 (mandatory)
1108 hmac-md5 HMAC-MD5, length = 16 (optional)
1109 none No MAC (optional)
1112 The none MAC is not recommended to be used as the packet is not
1113 authenticated when MAC is not computed. It is recommended that no
1114 client or server would accept none MAC except in special debugging
1117 The HMAC algorithm is described in [HMAC] and hash algorithms that
1118 are used as part of the HMACs are described in [Scheneir] and in
1121 Additional MAC algorithms may be defined to be used in SILC.
1125 3.10.4 Compression Algorithms
1127 SILC protocol supports compression that may be applied to unencrypted
1128 data. It is recommended to use compression on slow links as it may
1129 significantly speed up the data transmission. By default, SILC does not
1130 use compression which is the mode that must be supported by all SILC
1133 Following compression algorithms are defined:
1136 none No compression (mandatory)
1137 zlib GNU ZLIB (LZ77) compression (optional)
1140 Additional compression algorithms may be defined to be used in SILC.
1144 3.11 SILC Public Key
1146 This section defines the type and format of the SILC public key. All
1147 implementations must support this public key type. See [SILC3] for
1148 other optional public key and certificate types allowed in SILC
1149 protocol. Public keys in SILC may be used to authenticate entities
1150 and to perform other tasks related to public key cryptography.
1152 The format of the SILC Public Key is as follows:
1158 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
1159 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1160 | Public Key Length |
1161 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1162 | Algorithm Name Length | |
1163 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1167 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1168 | Identifier Length | |
1169 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1173 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1177 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1181 Figure 5: SILC Public Key
1185 o Public Key Length (4 bytes) - Indicates the full length
1186 of the public key, not including this field.
1188 o Algorithm Name Length (2 bytes) - Indicates the length
1189 of the Algorithm Length field, not including this field.
1191 o Algorithm name (variable length) - Indicates the name
1192 of the public key algorithm that the key is. See the
1193 section 3.10.2 Public Key Algorithms for defined names.
1195 o Identifier Length (2 bytes) - Indicates the length of
1196 the Identifier field, not including this field.
1198 o Identifier (variable length) - Indicates the identifier
1199 of the public key. This data can be used to identify
1200 the owner of the key. The identifier is of following
1204 HN Host name or IP address
1211 Examples of an identifier:
1213 `UN=priikone, HN=poseidon.pspt.fi, E=priikone@poseidon.pspt.fi'
1215 `UN=sam, HN=dummy.fi, RN=Sammy Sam, O=Company XYZ, C=Finland'
1217 At least user name (UN) and host name (HN) must be provided as
1218 identifier. The fields are separated by commas (`,'). If
1219 comma is in the identifier string it must be written as `\\,',
1220 for example, `O=Company XYZ\\, Inc.'.
1222 o Public Data (variable length) - Includes the actual
1223 public data of the public key.
1225 The format of this field for RSA algorithm is
1234 The format of this field for DSS algorithm is
1246 The variable length fields are multiple precession
1247 integers encoded as strings in both examples.
1249 Other algorithms must define their own type of this
1250 field if they are used.
1253 All fields in the public key are in MSB (most significant byte first)
1258 3.12 SILC Version Detection
1260 The version detection of both client and server is performed at the
1261 connection phase while executing the SILC Key Exchange protocol. The
1262 version identifier is exchanged between initiator and responder. The
1263 version identifier is of following format:
1266 SILC-<protocol version>-<software version>
1269 The version strings are of following format:
1272 protocol version = <major>.<minor>
1273 software version = <major>[.<minor>[.<build>]]
1276 Protocol version may provide both major and minor version. Currently
1277 implementations must set the protocol version and accept the protocol
1278 version as SILC-1.0-<sotware version>.
1280 Software version may provide major, minor and build version. The
1281 software version may be freely set and accepted.
1284 Thus, the version string could be, for example:
1294 This section describes various SILC procedures such as how the
1295 connections are created and registered, how channels are created and
1296 so on. The section describes the procedures only generally as details
1297 are described in [SILC2] and [SILC3].
1301 4.1 Creating Client Connection
1303 This section describes the procedure when client connects to SILC server.
1304 When client connects to server the server must perform IP address lookup
1305 and reverse IP address lookup to assure that the origin host really is
1306 who it claims to be. Client, host, connecting to server must have
1307 both valid IP address and fully qualified domain name (FQDN).
1309 After that client and server performs SILC Key Exchange protocol which
1310 will provide the key material used later in the communication. The
1311 key exchange protocol must be completed successfully before the connection
1312 registration may continue. The SILC Key Exchange protocol is described
1315 Typical server implementation would keep a list of connections that it
1316 allows to connect to the server. The implementation would check, for
1317 example, the connecting client's IP address from the connection list
1318 before the SILC Key Exchange protocol has been started. Reason for
1319 this is that if the host is not allowed to connect to the server there
1320 is no reason to perform a key exchange protocol.
1322 After successful key exchange protocol the client and server performs
1323 connection authentication protocol. The purpose of the protocol is to
1324 authenticate the client connecting to the server. Flexible
1325 implementation could also accept the client to connect to the server
1326 without explicit authentication. However, if authentication is
1327 desired for a specific client it may be based on passphrase or
1328 public key authentication. If authentication fails the connection
1329 must be terminated. The connection authentication protocol is described
1332 After successful key exchange and authentication protocol the client
1333 registers itself by sending SILC_PACKET_NEW_CLIENT packet to the
1334 server. This packet includes various information about the client
1335 that the server uses to create the client. Server creates the client
1336 and sends SILC_PACKET_NEW_ID to the client which includes the created
1337 Client ID that the client must start using after that. After that
1338 all SILC packets from the client must have the Client ID as the
1339 Source ID in the SILC Packet Header, described in [SILC2].
1341 Client must also get the server's Server ID that is to be used as
1342 Destination ID in the SILC Packet Header when communicating with
1343 the server (for example when sending commands to the server). The
1344 ID may be resolved in two ways. Client can take the ID from an
1345 previously received packet from server that must include the ID,
1346 or to send SILC_COMMAND_INFO command and receive the Server ID as
1349 Server may choose not to use the information received in the
1350 SILC_PACKET_NEW_CLIENT packet. For example, if public key or
1351 certificate were used in the authentication, server may use those
1352 informations rather than what it received from client. This is suitable
1353 way to get the true information about client if it is available.
1355 The nickname of client is initially set to the username sent in the
1356 SILC_PACKET_NEW_CLIENT packet. User should set the nickname to more
1357 suitable by sending SILC_COMMAND_NICK command. However, this is not
1358 required as part of registration process.
1360 Server must also distribute the information about newly registered
1361 client to its router (or if the server is router, to all routers in
1362 the SILC network). More information about this in [SILC2].
1366 4.2 Creating Server Connection
1368 This section descibres the procedure when server connects to its
1369 router (or when router connects to other router, the cases are
1370 equivalent). The procedure is very much alike when client connects
1371 to the server thus it is not repeated here.
1373 One difference is that server must perform connection authentication
1374 protocol with proper authentication. Proper authentication is based
1375 on passphrase or public key authentication.
1377 After server and router has successfully performed the key exchange
1378 and connection authentication protocol, the server register itself
1379 to the router by sending SILC_PACKET_NEW_SERVER packet. This packet
1380 includes the server's Server ID that it has created by itself and
1381 other relevant information about the server.
1383 After router has received the SILC_PACKET_NEW_SERVER packet it
1384 distributes the information about newly registered server to all routers
1385 in the SILC network. More information about this in [SILC2].
1387 As client needed to resolve the destination ID this must be done by the
1388 server that connected to the router, as well. The way to resolve it is
1389 to get the ID from previously received packet. Server must also start
1390 using its own Server ID as Source ID in SILC Packet Header and the
1391 router's Server ID as Destination when communicating with the router.
1393 If the server has already connected clients and locally created
1394 channels the server must distribute these informations to the router.
1395 The distribution is done by sending packet SILC_PACKET_NEW_CHANNEL.
1396 See [SILC2] for more information on this.
1400 4.3 Joining to a Channel
1402 This section describes the procedure when client joins to a channel.
1403 Client may join to channel by sending command SILC_COMMAND_JOIN to the
1404 server. If the receiver receiving join command is normal server the
1405 server must check its local list whether this channel already exists
1406 locally. This would indicate that some client connected to the server
1407 has already joined to the channel. If this is case the client is
1408 joined to the client, new channel key is created and information about
1409 newly joined channel is sent to the router. The new channel key is
1410 also distributed to the router and to all clients on the channel.
1412 If the channel does not exist in the local list the command must be
1413 forwarded to the router which will then perform the actual joining
1414 procedure. When server receives the reply to the command from the
1415 router it must be distributed to the client who sent the command
1416 originally. Server will also receive the channel key from the server
1417 that it must distribute to the client who originally requested the
1418 join command. The server must also save the channel key.
1420 If the receiver of the join command is router it must first check its
1421 local list whether anyone in the cell has already joined to the channel.
1422 If this is the case the client is joined to the channel and reply is
1423 sent to the client. If the command was sent by server the command reply
1424 is sent to the server who sent it. Then the router must also create
1425 new channel key and distribute it to all clients on the channel and
1426 all servers that has clients on the channel.
1428 If the channel does not exist on the router's local list it must
1429 check the global list whether the channel exists at all. If it does
1430 the client is joined to the channel as described previously. If
1431 the channel does not exist the channel is created and the client
1432 is joined to the channel. The channel key is also created and
1433 distributed as previously described. The client joining to the created
1434 channel is made automatically channel founder and both channel founder
1435 and channel operator privileges is set for the client.
1437 When the router joins the client to the channel it must send
1438 information about newly joined client to all routers in the SILC
1439 network. Also, if the channel was created in the process, information
1440 about newly created channel must also be distributed to all routers.
1441 The distribution of newly created channel is done by sending packet
1442 SILC_PACKET_NEW_CHANNEL.
1444 It is important to note that new channel key is created always when
1445 new client joins to channel, whether the channel has existed previously
1446 or not. This way the new client on the channel is not able to decrypt
1447 any of the old traffic on the channel. Client who receives the reply to
1448 the join command must start using the received Channel ID in the channel
1449 message communication thereafter. However, client must not start
1450 communicating on the channel before it has received the packet
1451 SILC_PACKET_CHANNEL_KEY.
1453 If client wants to know the other clients currently on the channel
1454 the client must send SILC_COMMAND_NAMES command to receive a list of
1455 channel users. Server implementation, however, may send command reply
1456 packet to SILC_COMMAND_NAMES command after client has joined to the
1457 channel even if the client has not sent the command. Server should also
1458 send SILC_NOTIFY_TYPE_JOIN to all clients on the channel about a new
1459 client on the channel.
1463 4.4 Channel Key Generation
1465 Channel keys are created by router who creates the channel by taking
1466 enough randomness from cryptographically strong random number generator.
1467 The key is generated always when channel is created, when new client
1468 joins a channel and after the key has expired. Key could expire for
1471 The key must also be re-generated whenever some client leaves a channel.
1472 In this case the key is created from scratch by taking enough randomness
1473 from the random number generator. After that the key is distributed to
1474 all clients on the channel. However, channel keys are cell specific thus
1475 the key is created only on the cell where the client, who left the
1476 channel, exists. While the server or router is creating the new channel
1477 key, no other client may join to the channel. Messages that are sent
1478 while creating the new key are still processed with the old key. After
1479 server has sent the SILC_PACKET_CHANNEL_KEY packet must client start
1480 using the new key. If server creates the new key the server must also
1481 send the new key to its router. See [SILC2] on more information about
1482 how channel messages must be encrypted and decrypted when router is
1487 4.5 Private Message Sending and Reception
1489 Private messages are sent point to point. Client explicitly destines
1490 a private message to specific client that is delivered to only to that
1491 client. No other client may receive the private message. The receiver
1492 of the private message is destined in the SILC Packet Header as any
1493 other packet as well.
1495 If the sender of a private message does not know the receiver's Client
1496 ID, it must resolve it from server. There are two ways to resolve the
1497 client ID from server; it is recommended that client implementations
1498 send SILC_COMMAND_IDENTIFY command to receive the Client ID. Client
1499 may also send SILC_COMMAND_WHOIS command to receive the Client ID.
1500 If the sender has received earlier a private message from the receiver
1501 it should have cached the Client ID from the SILC Packet Header.
1503 Receiver of a private message should not explicitly trust the nickname
1504 that it receives in the Private Message Payload, described in [SILC2].
1505 Implementations could resolve the nickname from server, as described
1506 previously, and compare the received Client ID and the SILC Packet
1507 Header's Client ID. The nickname in the payload is merely provided
1508 to be displayed for end user.
1510 See [SILC2] for description of private message encryption and decryption
1515 4.6 Private Message Key Generation
1517 Private message may be protected by key generated by client. The key
1518 may be generated and sent to the other client by sending packet
1519 SILC_PACKET_PRIVATE_MESSAGE_KEY which travels through the network
1520 and is secured by session keys. After that the private message key
1521 is used in the private message communication between those clients.
1522 See more information about how this works technically in [SILC2].
1524 Other choice is to entirely use keys that are not sent through
1525 the SILC network at all. This significantly adds security. This key
1526 would be pre-shared-key that is known by both of the clients. Both
1527 agree about using the key and starts sending packets that indicate
1528 that the private message is secured using private message key. This
1529 is the technical aspect mentioned previously that is described
1532 If the private message keys are not set to be used, which is the
1533 case by default in SILC, the private messages are secured by using
1534 normal session keys established by SILC Key Exchange protocol.
1540 4.7 Channel Message Sending and Reception
1542 Channel messages are delivered to group of users. The group forms a
1543 channel and all clients on the channel receives messages sent to the
1546 Channel messages are destined to channel by specifying the Channel ID
1547 as Destination ID in the SILC Packet Header. The server must then
1548 distribute the message to all clients on the channel by sending the
1549 channel message destined explicitly to a client on the channel.
1551 See [SILC2] for description of channel message encryption and decryption
1556 4.8 Session Key Regeneration
1558 Session keys should be regenerated periodically, say, once in an hour.
1559 The re-key process is started by sending SILC_PACKET_REKEY packet to
1560 other end, to indicate that re-key must be performed.
1562 If perfect forward secrecy (PFS) flag was selected in the SILC Key
1563 Exchange protocol [SILC3] the re-key must cause new key exchange with
1564 SKE protocol. In this case the protocol is secured with the old key
1565 and the protocol results to new key material. See [SILC3] for more
1566 information. After the SILC_PACKET_REKEY packet is sent the sender
1567 will perform the SKE protocol.
1569 If PFS flag was not set, which is the default case, then re-key is done
1570 without executing SKE protocol. In this case, the new key is created by
1571 hashing the old key with hash function selected earlier in the SKE
1572 protocol. If the digest length of the hash function is too short for the
1573 key, then the key is distributed as described in section Processing the
1574 Key Material in [SILC3]. After both parties has regenerated the session
1575 key, both send SILC_PACKET_REKEY_DONE packet to each other. These packets
1576 are still secured with the old key. After these packets, following
1577 packets must be protected with the new key.
1581 4.9 Command Sending and Reception
1583 Client usually sends the commands in the SILC network. In this case
1584 the client simply sends the command packet to server and the server
1585 processes it and replies with command reply packet.
1587 However, if the server is not able to process the command, it is usually
1588 sent to the server's router. This is case for example with commands such
1589 as, SILC_COMMAND_JOIN and SILC_COMMAND_WHOIS commands. However, there
1590 are other commands as well. For example, if client sends the WHOIS
1591 command requesting specific information about some client the server must
1592 send the WHOIS command to router so that all clients in SILC network
1593 are searched. The router, on the other hand, sends the WHOIS command
1594 to further to receive the exact information about the requested client.
1595 The WHOIS command travels all the way to the server who owns the client
1596 and it replies with command reply packet. Finally, the server who
1597 sent the command receives the command reply and it must be able to
1598 determine which client sent the original command. The server then
1599 sends command reply to the client. Implementations should have some
1600 kind of cache to handle, for example, WHOIS information. Servers
1601 and routers along the route could all cache the information for faster
1602 referencing in the future.
1604 The commands sent by server may be sent hop by hop until someone is able
1605 to process the command. However, it is preferred to destine the command
1606 as precisely as it is possible. In this case, other routers en route
1607 must route the command packet by checking the true sender and true
1608 destination of the packet. However, servers and routers must not route
1609 command reply packets to clients coming from other server. Client
1610 must not accept command reply packet originated from anyone else but
1611 from its own server.
1618 5.1 SILC Commands Syntax
1620 This section briefly describes the syntax of the command notions
1621 in this document. Every field in command is separated from each
1622 other by whitespaces (` ') indicating that each field is independent
1623 argument and each argument must have own Command Argument Payload.
1624 The number of maximum arguments are defined with each command
1625 separately. The Command Argument Payload is described in [SILC2].
1627 Every command defines specific number for each argument. Currently,
1628 they are defined in ascending order; first argument has number one
1629 (1), second has number two (2) and so on. This number is set into the
1630 Argument Type field in the Command Argument Payload. This makes it
1631 possible to send the arguments in free order as the number must be
1632 used to identify the type of the argument. This makes is it also
1633 possible to have multiple optional arguments in commands and in
1634 command replies. The number of argument is marked in parentheses
1635 before the actual argument.
1640 Example: Arguments: (1) <nickname> (2) <username@host>
1644 Every command replies with Status Payload. This payload tells the
1645 sender of the command whether the command was completed successfully or
1646 whether there was an error. If error occured the payload includes the
1647 error type. In the next section the Status Payload is not described
1648 as it is common to all commands and has been described here. Commands
1649 may reply with other arguments as well. These arguments are command
1650 specific and are described in the next section.
1659 Arguments: (1) <nickname>[@<server>] (2) <message>
1662 The command has maximum of 3 arguments. However, only first
1663 and second arguments are mandatory.
1665 First argument <nickname> is mandatory but may have optional
1666 <nickname@server> format as well. Second argument is mandatory
1667 <message> argument. Third argument is optional <count> argument.
1669 The numbers in parentheses are the argument specific numbers
1670 that specify the type of the argument in Command Argument Payload.
1671 The receiver always knows that, say, argument number two (2) is
1672 <message> argument, regardless of the ordering of the arguments in
1673 the Command Payload.
1675 Reply messages to the command:
1678 Arguments: (1) <Status Payload> (2) [<channel list>]
1679 (3) <idle time> (4) [<away message>]
1681 This command may reply with maximum of 4 arguments. However,
1682 only the first and third arguments are mandatory. The numbers
1683 in the parentheses have the same meaning as in the upper
1684 command sending specification.
1686 Every command reply with <Status Payload>, it is mandatory
1687 argument for all command replies and for this reason it is not
1688 described in the command reply descriptions.
1695 SILC_STATUS_ERR_TOO_MANY_TARGETS
1696 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
1697 SILC_STATUS_ERR_NO_SUCH_NICK
1699 Every command reply also defines set of status message that it
1700 may return inside the <Status Payload>. All status messages
1701 are defined in the section 5.3 SILC Command Status Types.
1704 Every command that has some kind of ID as argument (for example
1705 <Client ID>) are actually ID Payloads, defined in [SILC2] that includes
1706 the type of the ID, length of the ID and the actual ID data. This
1707 way variable length ID's can be sent as arguments.
1711 5.2 SILC Commands List
1713 This section lists all SILC commands, however, it is expected that a
1714 implementation and especially client implementation has many more
1715 commands that has only local affect. These commands are official
1716 SILC commands that has both client and server sides and cannot be
1717 characterized as local commands.
1719 List of all defined commands in SILC follows.
1724 None. This is reserved command and must not be sent.
1727 1 SILC_COMMAND_WHOIS
1730 Arguments: (1) <nickname>[@<server>] (2) [<Client ID>]
1733 Whois command is used to query various information about specific
1734 user. The user maybe requested by their nickname and server name.
1735 The query may find multiple matching users as there are no unique
1736 nicknames in the SILC. The <count> option maybe given to narrow
1737 down the number of accepted results. If this is not defined there
1738 are no limit of accepted results. The query may also be narrowed
1739 down by defining the server name of the nickname.
1741 It is also possible to search the user by Client ID. If <Client ID>
1742 is provided server must use it as the search value instead of
1745 To prevent miss-use of this service wildcards in the nickname
1746 or in the servername are not permitted. It is not allowed
1747 to request all users on some server. The WHOIS requests must
1748 be based on specific nickname request.
1750 The WHOIS request must be always forwarded to router by server
1751 so that all users are searched. However, the server still must
1752 search its locally connected clients. The server must send
1753 this command to the server who owns the requested client. That
1754 server must reply to the command.
1756 Reply messages to the command:
1759 Arguments: (1) <Status Payload> (2) <Client ID>
1760 (3) <nickname>[@<server>] (4) <username@host>
1761 (5) <real name> (6) [<channel list>]
1764 This command may reply with several command reply messages to
1765 form a list of results. In this case the status payload will
1766 include STATUS_LIST_START status in the first reply and
1767 STATUS_LIST_END in the last reply to indicate the end of the
1768 list. If there are only one reply the status is set to normal
1771 The command replies include the Client ID of the nickname,
1772 nickname and servername, username and hostname and users real
1773 name. Client should process these replies only after the last
1774 reply has been received with the STATUS_LIST_END status. If the
1775 <count> option were defined in the query there will be only
1776 <count> many replies from the server.
1781 SILC_STATUS_LIST_START
1782 SILC_STATUS_LIST_END
1783 SILC_STATUS_ERR_NO_SUCH_NICK
1784 SILC_STATUS_ERR_WILDCARDS
1785 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
1786 SILC_STATUS_ERR_TOO_MANY_PARAMS
1791 2 SILC_COMMAND_WHOWAS
1794 Arguments: (1) <nickname>[@<server>] (2) [<count>]
1796 Whowas. This command is used to query history information about
1797 specific user. The user maybe requested by their nickname and
1798 server name. The query may find multiple matching users as there
1799 are no unique nicknames in the SILC. The <count> option maybe
1800 given to narrow down the number of accepted results. If this
1801 is not defined there are no limit of accepted results. The query
1802 may also be narrowed down by defining the server name of the
1805 To prevent miss-use of this service wildcards in the nickname
1806 or in the servername are not permitted. The WHOWAS requests must
1807 be based on specific nickname request.
1809 The WHOWAS request must be always forwarded to router by server
1810 so that all users are searched. However, the server still must
1811 search its locally connected clients.
1813 Reply messages to the command:
1816 Arguments: (1) <Status Payload> (2) <nickname>[@<server>]
1819 This command may reply with several command reply messages to form
1820 a list of results. In this case the status payload will include
1821 STATUS_LIST_START status in the first reply and STATUS_LIST_END in
1822 the last reply to indicate the end of the list. If there are only
1823 one reply the status is set to normal STATUS_OK.
1825 The command replies with nickname and username and hostname.
1826 Every server must keep history for some period of time of its
1827 locally connected clients.
1832 SILC_STATUS_LIST_START
1833 SILC_STATUS_LIST_END
1834 SILC_STATUS_ERR_NO_SUCH_NICK
1835 SILC_STATUS_ERR_WILDCARDS
1836 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
1837 SILC_STATUS_ERR_TOO_MANY_PARAMS
1840 3 SILC_COMMAND_IDENTIFY
1843 Arguments: (1) <nickname>[@<server>] (2) [<Client ID>]
1846 Identify. Identify command is almost analogous to WHOIS command,
1847 except that it does not return as much information. Only relevant
1848 information such as Client ID is returned. This is usually used
1849 to get the Client ID of a client used in the communication with
1852 The query may find multiple matching users as there are no unique
1853 nicknames in the SILC. The <count> option maybe given to narrow
1854 down the number of accepted results. If this is not defined there
1855 are no limit of accepted results. The query may also be narrowed
1856 down by defining the server name of the nickname.
1858 It is also possible to search the user by Client ID. If <Client ID>
1859 is provided server must use it as the search value instead of
1862 To prevent miss-use of this service wildcards in the nickname
1863 or in the servername are not permitted. It is not allowed
1864 to request all users on some server. The IDENTIFY requests must
1865 be based on specific nickname request.
1867 Implementations may not want to give interface access to this
1868 command as it is hardly a command that would be used a end user.
1869 However, it must be implemented as it is used with private message
1872 The IDENTIFY must be always forwarded to router by server so that
1873 all users are searched. However, server must still search its
1874 locally connected clients.
1876 Reply messages to the command:
1879 Arguments: (1) <Status Payload> (2) <Client ID>
1880 (3) [<nickname>[@<server>]] (4) [<username@host>]
1882 This command may reply with several command reply messages to form
1883 a list of results. In this case the status payload will include
1884 STATUS_LIST_START status in the first reply and STATUS_LIST_END in
1885 the last reply to indicate the end of the list. If there are only
1886 one reply the status is set to normal STATUS_OK.
1888 The command replies with Client ID of the nickname and if more
1889 information is available it may reply with nickname and username
1890 and hostname. If the <count> option were defined in the query
1891 there will be only <count> many replies from the server.
1896 SILC_STATUS_LIST_START
1897 SILC_STATUS_LIST_END
1898 SILC_STATUS_ERR_NO_SUCH_NICK
1899 SILC_STATUS_ERR_WILDCARDS
1900 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
1901 SILC_STATUS_ERR_TOO_MANY_PARAMS
1907 Arguments: (1) <nickname>
1909 Set/change nickname. This command is used to set nickname for
1910 user. There is no limit of the length of the nickname in SILC.
1911 Nickname must not include any spaces (` '), non-printable
1912 characters, commas (`,') and any wildcard characters. Note:
1913 nicknames in SILC are case-sensitive which must be taken into
1914 account when searching clients by nickname.
1916 Reply messages to the command:
1919 Arguments: (1) <Status Payload> (2) <New ID Payload>
1921 This command is replied always with New ID Payload that is
1922 generated by the server every time user changes their nickname.
1923 Client receiving this payload must start using the received
1924 Client ID as its current valid Client ID. The New ID Payload
1925 is described in [SILC2].
1930 SILC_STATUS_ERR_WILDCARDS
1931 SILC_STATUS_ERR_NICKNAME_IN_USE
1932 SILC_STATUS_ERR_BAD_NICKNAME
1933 SILC_STATUS_ERR_NOT_REGISTERED
1934 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
1935 SILC_STATUS_ERR_TOO_MANY_PARAMS
1945 Arguments: (1) [<Channel ID>] [<server>]
1947 The list command is used to list channels and their topics on
1948 current server. If the <Channel ID> parameter is used, only the
1949 status of that channel is displayed. Secret channels are not
1950 listed at all. Private channels are listed with status indicating
1951 that the channel is private.
1953 If the <server> argument is specified the specified server's
1954 channels are listed. In this case the command must be sent to
1955 the server who owns the channel that was requested.
1957 Reply messages to the command:
1960 Arguments: (1) <Status Payload> (2) <Channel ID>
1961 (3) <channel> (4) <topic>
1963 This command may reply with several command reply messages to form
1964 a list of results. In this case the status payload will include
1965 STATUS_LIST_START status in the first reply and STATUS_LIST_END in
1966 the last reply to indicate the end of the list. If there are only
1967 one reply the status is set to normal STATUS_OK.
1969 This command replies with Channel ID, name and the topic of the
1970 channel. If the channel is private channel the <topic> includes
1976 SILC_STATUS_LIST_START
1977 SILC_STATUS_LIST_END
1978 SILC_STATUS_ERR_WILDCARDS
1979 SILC_STATUS_ERR_NOT_REGISTERED
1980 SILC_STATUS_ERR_TOO_MANY_PARAMS
1981 SILC_STATUS_ERR_NO_SUCH_CHANNEL
1982 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
1983 SILC_STATUS_ERR_NO_SUCH_SERVER
1986 6 SILC_COMMAND_TOPIC
1989 Arguments: (1) <Channel ID> (2) [<topic>]]
1991 This command is used to change or view the topic of a channel.
1992 The topic for channel <Channel ID> is returned if there is no
1993 <topic> given. If the <topic> parameter is present, the topic
1994 for that channel will be changed, if the channel modes permit
1997 Reply messages to the command:
2000 Arguments: (1) <Status Payload> (2) <Channel ID>
2003 The command may reply with the topic of the channel if it is
2009 SILC_STATUS_ERR_NOT_ON_CHANNEL
2010 SILC_STATUS_ERR_WILDCARDS
2011 SILC_STATUS_ERR_NOT_REGISTERED
2012 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2013 SILC_STATUS_ERR_NO_SUCH_CHANNEL
2014 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
2015 SILC_STATUS_ERR_NO_CHANNEL_ID
2016 SILC_STATUS_ERR_BAD_CHANNEL_ID
2017 SILC_STATUS_ERR_TOO_MANY_PARAMS
2018 SILC_STATUS_ERR_NO_CHANNEL_PRIV
2021 7 SILC_COMMAND_INVITE
2024 Arguments: (1) <Client ID> (2) <Channel ID>
2026 This command is used to invite other clients to join to the
2027 channel. The <Client ID> argument is the target client's ID that
2028 is being invited. The <Channel ID> is the Channel ID of the
2029 requested channel. The sender of this command must be on the
2030 channel. This command must fail if the requested channel does
2031 not exist, the requested client is already on the channel or if
2032 the channel is invite only channel and the caller of this command
2033 does not have at least channel operator privileges.
2035 Reply messages to the command:
2038 Arguments: (1) <Status Payload>
2040 This command replies only with Status Payload.
2045 SILC_STATUS_ERR_NOT_REGISTERED
2046 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2047 SILC_STATUS_ERR_TOO_MANY_PARAMS
2048 SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
2049 SILC_STATUS_ERR_NO_CLIENT_ID
2050 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
2051 SILC_STATUS_ERR_NO_CHANNEL_ID
2052 SILC_STATUS_ERR_NOT_ON_CHANNEL
2053 SILC_STATUS_ERR_USER_ON_CHANNEL
2059 Arguments: (1) [<quit message>]
2061 This command is used by client to end SILC session. The server
2062 must close the connection to a client which sends this command.
2063 if <quit message> is given it will be sent to other clients on
2064 channel if the client is on channel when quitting.
2066 Reply messages to the command:
2068 This command does not reply anything.
2074 Arguments: (1) <Client ID> (2) [<comment>]
2076 This command is used by SILC operators to remove a client from
2077 SILC network. The removing has temporary effects and client may
2078 reconnect to SILC network. The <Client ID> is the client to be
2079 removed from SILC. The <comment> argument may be provided to
2080 give to the removed client some information why it was removed
2083 Reply messages to the command:
2086 Arguments: (1) <Status Payload>
2088 This command replies only with Status Payload.
2093 SILC_STATUS_ERR_WILDCARDS
2094 SILC_STATUS_ERR_NOT_REGISTERED
2095 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2096 SILC_STATUS_ERR_TOO_MANY_PARAMS
2097 SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
2098 SILC_STATUS_ERR_NO_CLIENT_ID
2101 10 SILC_COMMAND_INFO
2104 Arguments: (1) [<server>]
2106 This command is used to fetch various information about a server.
2107 If <server> argument is specified the command must be sent to
2108 the requested server.
2110 Reply messages to the command:
2113 Arguments: (1) <Status Payload> (2) <Server ID>
2116 This command replies with the Server ID of the server and a
2117 string which tells the information about the server.
2122 SILC_STATUS_ERR_WILDCARDS
2123 SILC_STATUS_ERR_NOT_REGISTERED
2124 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2125 SILC_STATUS_ERR_TOO_MANY_PARAMS
2126 SILC_STATUS_ERR_NO_SUCH_SERVER
2129 11 SILC_COMMAND_CONNECT
2132 Arguments: (1) <Server ID>
2133 (2) [<remote server/router>[ <port>]]
2135 This command is used by operators to force a server to try to
2136 establish a new connection to another router (if the connecting
2137 server is normal server) or server (if the connecting server is
2138 router server). Operator may specify the server/router to be
2139 connected by setting <remote server> argument. The separator
2140 between <remote server address> and <port> is whitespace (` ').
2142 Reply messages to the command:
2145 Arguments: (1) <Status Payload>
2147 This command replies only with Status Payload.
2154 SILC_STATUS_ERR_WILDCARDS
2155 SILC_STATUS_ERR_NOT_REGISTERED
2156 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2157 SILC_STATUS_ERR_TOO_MANY_PARAMS
2158 SILC_STATUS_ERR_NO_SUCH_SERVER_ID
2159 SILC_STATUS_ERR_NO_SERVER_PRIV
2160 SILC_STATUS_ERR_NO_ROUTER_PRIV
2163 12 SILC_COMMAND_PING
2166 Arguments: (1) <Server ID>
2168 This command is used by client and server to test the communication
2169 channel to its server if one suspects that the communication is not
2170 working correctly. The <Server ID> is the ID of the server the
2171 sender is connected to.
2173 Reply messages to the command:
2176 Arguments: (1) <Status Payload>
2178 This command replies only with Status Payload. Server returns
2179 SILC_STATUS_OK in Status Payload if pinging was successful.
2186 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2187 SILC_STATUS_ERR_TOO_MANY_PARAMS
2188 SILC_STATUS_ERR_NO_SERVER_ID
2189 SILC_STATUS_ERR_NO_SUCH_SERVER
2190 SILC_STATUS_ERR_NOT_REGISTERED
2193 13 SILC_COMMAND_OPER
2196 Arguments: (1) <username> (2) <authentication data>
2198 This command is used by normal client to obtain server operator
2199 privileges on some server or router. Note that router operator
2200 has router privileges that supersedes the server operator
2201 privileges and this does not obtain those privileges. Client
2202 must use SILCOPER command to obtain router level privileges.
2204 The <username> is the username set in the server configurations
2205 as operator. The <authentication data> is the data that the
2206 client is authenticated against. It may be passphrase prompted
2207 for user on client's screen or it may be public key
2208 authentication data (data signed with private key), or
2211 Reply messages to the command:
2214 Arguments: (1) <Status Payload>
2216 This command replies only with Status Payload.
2221 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2222 SILC_STATUS_ERR_TOO_MANY_PARAMS
2223 SILC_STATUS_ERR_NOT_REGISTERED
2224 SILC_STATUS_ERR_BAD_PASSWORD
2225 SILC_STATUS_ERR_AUTH_FAILED
2231 14 SILC_COMMAND_JOIN
2234 Arguments: (1) <channel> (2) [<passphrase>]
2237 Join to channel/create new channel. This command is used to
2238 join to a channel. If the channel does not exist the channel is
2239 created. If server is normal server this command must be forwarded
2240 to router who will create the channel. The channel may be protected
2241 with passphrase. If this is the case the passphrase must be sent
2242 along the join command.
2244 The name of the <channel> must not include any spaces (` '),
2245 non-printable characters, commas (`,') or any wildcard characters.
2247 Cipher to be used to secure the traffic on the channel may be
2248 requested by sending the name of the requested <cipher>. This
2249 is used only if the channel does not exist and is created. If
2250 the channel already exists the cipher set previously for the
2251 channel will be used to secure the traffic.
2253 The server must check whether the user is allowed to join to
2254 the requested channel. Various modes set to the channel affect
2255 the ability of the user to join the channel. These conditions
2258 o The user must be invited to the channel if the channel
2259 is invite-only channel.
2261 o The Client ID/nickname/username/hostname must not match
2264 o The correct passphrase must be provided if passphrase
2265 is set to the channel.
2267 o The user count limit, if set, must not be reached.
2269 Reply messages to the command:
2272 Arguments: (1) <Status Payload> (2) <channel>
2273 (3) <Channel ID> (4) <channel mode mask>
2274 (5) [<ban mask>] (6) [<invite list>]
2277 This command replies with the channel name requested by the
2278 client, channel ID of the channel and topic of the channel
2279 if it exists. It also replies with the channel mode mask
2280 which tells all the modes set on the channel. If the
2281 channel is created the mode mask is zero (0). If ban mask
2282 and/or invite list is set they are sent as well.
2284 Client must not start transmitting to the channel even after
2285 server has replied to this command. Client is permitted to
2286 start transmitting on channel after server has sent packet
2287 SILC_PACKET_CHANNEL_KEY to the client.
2292 SILC_STATUS_ERR_WILDCARDS
2293 SILC_STATUS_ERR_NOT_REGISTERED
2294 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2295 SILC_STATUS_ERR_TOO_MANY_PARAMS
2296 SILC_STATUS_ERR_BAD_PASSWORD
2297 SILC_STATUS_ERR_CHANNEL_IS_FULL
2298 SILC_STATUS_ERR_NOT_INVITED
2299 SILC_STATUS_ERR_BANNED_FROM_CHANNEL
2300 SILC_STATUS_ERR_BAD_CHANNEL
2301 SILC_STATUS_ERR_USER_ON_CHANNEL
2304 15 SILC_COMMAND_MOTD
2307 Arguments: (1) <server>
2309 This command is used to query the Message of the Day of the server.
2311 Reply messages to the command:
2314 Arguments: (1) <Status Payload> (2) [<motd>]
2316 This command replies with the motd message if it exists.
2321 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2322 SILC_STATUS_ERR_TOO_MANY_PARAMS
2323 SILC_STATUS_ERR_NOT_REGISTERED
2324 SILC_STATUS_ERR_NO_SUCH_SERVER
2327 16 SILC_COMMAND_UMODE
2330 Arguments: (1) <Client ID> (2) <client mode mask>
2332 This command is used by client to set/unset modes for itself.
2333 However, there are some modes that the client may not set itself,
2334 but they will be set by server. However, client may unset any
2335 mode. Modes may be masked together ORing them thus having
2336 several modes set. Client must keep its client mode mask
2337 locally so that the mode setting/unsetting would work without
2338 problems. Client may change only its own modes.
2340 Following client modes are defined:
2342 0x0000 SILC_UMODE_NONE
2344 No specific mode for client. This is the initial
2345 setting when new client is created. The client is
2349 0x0001 SILC_UMODE_SERVER_OPERATOR
2351 Marks the user as server operator. Client cannot
2352 set this mode itself. Server sets this mode to the
2353 client when client attains the server operator
2354 privileges by SILC_COMMAND_OPER command. Client
2355 may unset the mode itself.
2358 0x0002 SILC_UMODE_ROUTER_OPERATOR
2360 Marks the user as router (SILC) operator. Client
2361 cannot this mode itself. Router sets this mode to
2362 the client when client attains the router operator
2363 privileges by SILC_COMMAND_SILCOPER command. Client
2364 may unset the mode itself.
2366 Reply messages to the command:
2369 Arguments: (1) <Status Payload> (2) <client mode mask>
2371 This command replies with the changed client mode mask that
2372 the client is required to keep locally.
2378 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2379 SILC_STATUS_ERR_TOO_MANY_PARAMS
2380 SILC_STATUS_ERR_NOT_REGISTERED
2381 SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
2382 SILC_STATUS_ERR_BAD_CLIENT_ID
2383 SILC_STATUS_ERR_NOT_YOU
2384 SILC_STATUS_ERR_UNKNOWN_MODE
2385 SILC_STATUS_ERR_NO_RECIPIENT
2386 SILC_STATUS_ERR_NO_CLIENT_ID
2389 17 SILC_COMMAND_CMODE
2392 Arguments: (1) <Channel ID> (2) <channel mode mask>
2393 (3) [<user limit>] (4) [<passphrase>]
2394 (5) [<ban mask>] (6) [<invite list>]
2395 (7) [<Client ID>] (8) [<cipher>[:<key len>]]
2397 This command is used by client to set or change channel flags on
2398 a channel. Channel has several modes that set various properties
2399 of a channel. Modes may be masked together by ORing them thus
2400 having several modes set. The <Channel ID> is the ID of the
2401 target channel. The client changing channel mode must be on
2402 the same channel and poses sufficient privileges to be able to
2405 Following channel modes are defined:
2407 0x0000 SILC_CMODE_NONE
2409 No specific mode on channel. This is the default when
2410 channel is created. This means that channel is just plain
2414 0x0001 SILC_CMODE_PRIVATE
2416 Channel is private channel. Private channels are shown
2417 in the channel list listed with SILC_COMMAND_LIST command
2418 with indication that the channel is private. Also,
2419 client on private channel will no be detected to be on
2420 the channel as the channel is not shown in the client's
2421 currently joined channel list. Channel founder and
2422 channel operator may set/unset this mode.
2424 Typical implementation would use [+|-]p on user interface
2425 to set/unset this mode.
2428 0x0002 SILC_CMODE_SECRET
2430 Channel is secret channel. Secret channels are not shown
2431 in the list listed with SILC_COMMAND_LIST command. Secret
2432 channels can be considered to be invisible channels.
2433 Channel founder and channel operator may set/unset this
2436 Typical implementation would use [+|-]s on user interface
2437 to set/unset this mode.
2440 0x0004 SILC_CMODE_PRIVKEY
2442 Channel uses private channel key to protect the traffic
2443 on the channel. When this mode is set the client will be
2444 responsible to set the key it wants to use to encrypt and
2445 decrypt the traffic on channel. Server generated channel
2446 keys are not used at all. This mode provides additional
2447 security as clients on channel may agree to use private
2448 channel key that even servers do not know. Naturally,
2449 this requires that every client on the channel knows
2450 the key before hand (it is considered to be pre-shared-
2451 key). This specification does not define how the private
2452 channel key is set as it is entirely local setting on
2455 As it is local setting it is possible to have several
2456 private channel keys on one channel. In this case several
2457 clients can talk on same channel but only those clients
2458 that share the key with the message sender will be able
2459 to hear the talking. Client should not display those
2460 message for the end user that it is not able to decrypt
2461 when this mode is set.
2463 Only channel founder may set/unset this mode. If this
2464 mode is unset the server will distribute new channel
2465 key to all clients on the channel which will be used
2468 Typical implementation would use [+|-]k on user interface
2469 to set/unset this mode.
2472 0x0008 SILC_CMODE_INVITE
2474 Channel is invite only channel. Client may join to this
2475 channel only if it is invited to the channel. Channel
2476 founder and channel operator may set/unset this mode.
2478 Typical implementation would use [+|-]i on user interface
2479 to set/unset this mode.
2482 0x0010 SILC_CMODE_TOPIC
2484 The topic of the channel may only be set by client that
2485 is channel founder or channel operator. Normal clients
2486 on channel will not be able to set topic when this mode
2487 is set. Channel founder and channel operator may set/
2490 Typical implementation would use [+|-]t on user interface
2491 to set/unset this mode.
2494 0x0020 SILC_CMODE_ULIMIT
2496 User limit has been set to the channel. New clients
2497 may not join to the channel when the limit set is
2498 reached. Channel founder and channel operator may set/
2499 unset the limit. The <user limit> argument is the
2500 number of limited users.
2502 Typical implementation would use [+|-]l on user interface
2503 to set/unset this mode.
2506 0x0040 SILC_CMODE_PASSPHRASE
2508 Passphrase has been set to the channel. Client may
2509 join to the channel only if it is able to provide the
2510 correct passphrase. Setting passphrases to channel
2511 is entirely safe as all commands are protected in the
2512 SILC network. Only channel founder may set/unset
2513 the passphrase. The <passphrase> argument is the
2516 Typical implementation would use [+|-]a on user interface
2517 to set/unset this mode.
2520 0x0080 SILC_CMODE_BAN
2522 Ban mask has been set to the channel. The ban mask
2523 may be used to ban specific clients to join the channel.
2524 The <ban mask> argument is the set ban mask. When
2525 unsetting a ban mask the mask must be provided as
2526 argument. Channel founder and channel operator may
2527 set/unset this mode. Channel founder may not be
2528 added to the ban list.
2530 Typical implementation would use [+|-]b on user interface
2531 to set/unset this mode.
2534 0x0100 SILC_CMODE_INVITE
2536 Invite list has been set to the channel. The invite list
2537 can be used to mark the clients that is able to join
2538 channel without being invited when the channel is set to
2539 be invite-only channel. The <invite list> argument is the
2540 set invite mask. When unsetting entry from the invite list
2541 the entry must be provided as argument. Channel founder and
2542 channel operator may set/unset this mode.
2544 Typical implementation would use [+|-]I on user interface
2545 to set/unset this mode.
2548 0x0200 SILC_CMODE_OPERATOR
2550 Sets channel operator privileges on the channel for a
2551 client on the channel. The <Client ID> argument is the
2552 target client on the channel. Channel founder and
2553 channel operator may set/unset (promote/demote) this
2556 Typical implementation would use [+|-]o on user interface
2557 to set/unset this mode.
2560 0x0400 SILC_CMODE_CIPHER
2562 Sets specific cipher to be used to protect channel
2563 traffic. The <cipher> argument is the requested cipher.
2564 When set or unset the server must re-generate new
2565 channel key. If <key len> argument is specified with
2566 <cipher> argument the new key is generated of <key len>
2569 Typical implementation would use [+|-]c on user interface
2570 to set/unset this mode.
2573 To make the mode system work, client must keep the channel mode
2574 mask locally so that the mode setting and unsetting would work
2575 without problems. The client receives the initial channel mode
2576 mask when it joins to the channel. When the mode changes on
2577 channel the server distributes the changed channel mode mask to
2578 all clients on the channel by sending SILC_COMMAND_CMODE command
2582 Reply messages to the command:
2585 Arguments: (1) <Status Payload> (2) <channel mode mask>
2587 This command replies with the changed channel mode mask that
2588 client is required to keep locally. The same mask is also
2589 sent to all clients on channel by sending additional command
2595 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2596 SILC_STATUS_ERR_TOO_MANY_PARAMS
2597 SILC_STATUS_ERR_NOT_REGISTERED
2598 SILC_STATUS_ERR_NOT_ON_CHANNEL
2599 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
2600 SILC_STATUS_ERR_BAD_CHANNEL_ID
2601 SILC_STATUS_ERR_NO_CHANNEL_ID
2602 SILC_STATUS_ERR_NO_CHANNEL_PRIV
2603 SILC_STATUS_ERR_UNKNOWN_MODE
2604 SILC_STATUS_ERR_NO_CLIENT_ID
2609 18 SILC_COMMAND_KICK
2612 Arguments: (1) <channel> (2) <Client ID>
2615 This command is used by channel operators to remove a client from
2616 channel. The <channel> argument is the channel the client to be
2617 removed is on currently. Note that the "kicker" must be on the same
2618 channel. If <comment> is provided it will be sent to the removed
2621 Reply messages to the command:
2624 Arguments: (1) <Status Payload>
2626 This command replies only with Status Payload.
2631 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2632 SILC_STATUS_ERR_TOO_MANY_PARAMS
2633 SILC_STATUS_ERR_NOT_REGISTERED
2634 SILC_STATUS_ERR_NO_SUCH_CHANNEL
2635 SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
2636 SILC_STATUS_ERR_NO_CHANNEL_PRIV
2637 SILC_STATUS_ERR_NO_CLIENT_ID
2640 19 SILC_COMMAND_RESTART
2645 This command may only be used by server operator to force a
2646 server to restart itself.
2648 Reply messages to the command:
2651 Arguments: (1) <Status Payload>
2653 This command replies only with Status Payload.
2658 SILC_STATUS_ERR_NOT_REGISTERED
2659 SILC_STATUS_ERR_NO_SERVER_PRIV
2665 20 SILC_COMMAND_CLOSE
2668 Arguments: (1) <Server ID>
2670 This command is used only by operator to close connection to a
2671 remote site. The <Server ID> argument is the ID of the remote
2672 site and must be valid.
2674 Reply messages to the command:
2677 Arguments: (1) <Status Payload>
2679 This command replies only with Status Payload.
2684 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2685 SILC_STATUS_ERR_TOO_MANY_PARAMS
2686 SILC_STATUS_ERR_NOT_REGISTERED
2687 SILC_STATUS_ERR_NO_SUCH_SERVER
2688 SILC_STATUS_ERR_NO_SERVER_PRIV
2689 SILC_STATUS_ERR_NO_SUCH_SERVER_ID
2697 This command is used only by operator to shutdown the server.
2698 All connections to the server will be closed and the server is
2701 Reply messages to the command:
2706 Arguments: (1) <Status Payload>
2708 This command replies only with Status Payload.
2713 SILC_STATUS_ERR_NOT_REGISTERED
2714 SILC_STATUS_ERR_NO_SERVER_PRIV
2717 22 SILC_COMMAND_SILCOPER
2720 Arguments: (1) <username> (2) <authentication data>
2722 This command is used by normal client to obtain router operator
2723 privileges (also known as SILC operator) on some router. Note
2724 that router operator has router privileges that supersedes the
2725 server operator privileges.
2727 The <username> is the username set in the server configurations
2728 as operator. The <authentication data> is the data that the
2729 client is authenticated against. It may be passphrase prompted
2730 for user on client's screen or it may be public key
2731 authentication data (data signed with private key), or
2734 Difference between router operator and server operator is that
2735 router operator is able to handle cell level properties while
2736 server operator (even on router server) is able to handle only
2737 local properties, such as, local connections and normal server
2740 Reply messages to the command:
2743 Arguments: (1) <Status Payload>
2745 This command replies only with Status Payload.
2750 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2751 SILC_STATUS_ERR_TOO_MANY_PARAMS
2752 SILC_STATUS_ERR_NOT_REGISTERED
2753 SILC_STATUS_ERR_BAD_PASSWORD
2754 SILC_STATUS_ERR_AUTH_FAILED
2757 23 SILC_COMMAND_LEAVE
2760 Arguments: (1) <Channel ID>
2762 This command is used by client to leave a channel the client is
2763 joined to. After a client has leaved the channel the server
2764 must create new key for the channel and distribute to all clients
2765 still currently on the channel.
2767 Reply messages to the command:
2770 Arguments: (1) <Status Payload>
2772 This command replies only with Status Payload.
2777 SILC_STATUS_ERR_NOT_REGISTERED
2778 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2779 SILC_STATUS_ERR_TOO_MANY_PARAMS
2780 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
2781 SILC_STATUS_ERR_BAD_CHANNEL_ID
2782 SILC_STATUS_ERR_NO_CHANNEL_ID
2785 24 SILC_COMMAND_NAMES
2788 Arguments: (1) <Channel ID>
2790 This command is used to list user names currently on the requested
2791 channel; argument <Channel ID>. The server must resolve the
2792 user names and send a comma (`,') separated list of user names
2793 on the channel. Server or router may resolve the names by sending
2794 SILC_COMMAND_WHOIS commands.
2796 If the requested channel is a private or secret channel, this
2797 command must not send the list of users, as private and secret
2798 channels cannot be seen by outside. In this case the returned
2799 name list may include a indication that the server could not
2800 resolve the names of the users on the channel.
2802 Reply messages to the command:
2805 Arguments: (1) <Status Payload> (2) <Channel ID>
2806 (3) <name list> (4) <Client ID list>
2808 This command replies with the Channel ID of the requested channel,
2809 comma separated list of users on the channel and Client ID list
2810 of the users on the list. The Client ID list has Client ID's
2811 of all users in the list. First Client ID in the list must be
2812 the Client ID of the first user in <name list>. The Client ID
2813 List is formed by adding Client ID's each after each. Note that
2814 the Client ID list is binary data.
2819 SILC_STATUS_ERR_NOT_REGISTERED
2820 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2821 SILC_STATUS_ERR_TOO_MANY_PARAMS
2822 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
2823 SILC_STATUS_ERR_BAD_CHANNEL_ID
2824 SILC_STATUS_ERR_NO_CHANNEL_ID
2825 SILC_STATUS_ERR_NOT_ON_CHANNEL
2830 Currently undefined commands.
2835 These commands are reserved for private use and will not be defined
2839 255 SILC_COMMAND_MAX
2841 Reserved command. This must not be sent.
2846 5.3 SILC Command Status Types
2849 5.3.1 SILC Command Status Payload
2851 Command Status Payload is sent in command reply messages to indicate
2852 the status of the command. The payload is one of argument in the
2853 command thus this is the data area in Command Argument Payload described
2854 in [SILC2]. The payload is only 2 bytes of length. Following diagram
2855 represents the Command Status Payload (field is always in MSB order).
2864 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
2865 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2867 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2871 Figure 6: SILC Command Status Payload
2875 o Status Message (2 bytes) - Indicates the status message.
2876 All Status messages are described in the next section.
2881 5.3.2 SILC Command Status List
2883 Command Status messages are returned in the command reply messages
2884 to indicate whether the command were executed without errors. If error
2885 has occured the status tells which error occured. Status payload only
2886 sends numeric reply about the status. Receiver of the payload must
2887 convert the numeric values into human readable error messages. The
2888 list of status messages below has an example human readable error
2889 messages that client may display for the user.
2891 List of all defined command status messages following.
2894 Generic status messages:
2898 Ok status. Everything went Ok. The status payload maybe
2899 safely ignored in this case.
2901 1 SILC_STATUS_LIST_START
2903 Start of the list. There will be several command replies and
2904 this reply is the start of the list.
2906 2 SILC_STATUS_LIST_ITEM
2908 Item in the list. This is one of the item in the list but not the
2911 3 SILC_STATUS_LIST_END
2913 End of the list. There were several command replies and this
2914 reply is the last of the list. There won't be other replies
2915 belonging to this list after this one.
2919 Currently undefined and has been reserved for the future.
2922 Error status message:
2924 10 SILC_STATUS_ERR_NO_SUCH_NICK
2926 "No such nickname". Requested nickname does not exist.
2928 11 SILC_STATUS_ERR_NO_SUCH_CHANNEL
2930 "No such channel". Requested channel name does not exist.
2932 12 SILC_STATUS_ERR_NO_SUCH_SERVER
2934 "No such server". Requested server name does not exist.
2936 13 SILC_STATUS_ERR_TOO_MANY_TARGETS
2938 "Duplicate recipients. No message delivered". Message were
2939 tried to be sent to recipient which has several occurrences in
2942 14 SILC_STATUS_ERR_NO_RECIPIENT
2944 "No recipient given". Command required recipient which was
2947 15 SILC_STATUS_ERR_UNKNOWN_COMMAND
2949 "Unknown command". Command sent to server is unknown by the
2952 16 SILC_STATUS_ERR_WILDCARDS
2954 "Wildcards cannot be used". Wildcards were provided but they
2957 17 SILC_STATUS_ERR_NO_CLIENT_ID
2959 "No Client ID given". Client ID were expected as command
2960 parameter but were not found.
2962 18 SILC_STATUS_ERR_NO_CHANNEL_ID
2964 "No Channel ID given". Channel ID were expected as command
2965 parameter but were not found.
2967 19 SILC_STATUS_ERR_NO_SERVER_ID
2969 "No Serve ID given". Server ID were expected as command
2970 parameter but were not found.
2972 20 SILC_STATUS_ERR_BAD_CLIENT_ID
2974 "Bad Client ID". Client ID provided were erroneous.
2976 21 SILC_STATUS_ERR_BAD_CHANNEL_ID
2978 "Bad Channel ID". Channel ID provided were erroneous.
2980 22 SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
2982 "No such Client ID". Client ID provided does not exist.
2984 23 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
2986 "No such Channel ID". Channel ID provided does not exist.
2988 24 SILC_STATUS_ERR_NICKNAME_IN_USE
2990 "Nickname already exists". Nickname created could not be
2991 registered because number of same nicknames were already set to
2992 maximum. This is not expected to happen in real life but is
2995 25 SILC_STATUS_ERR_NOT_ON_CHANNEL
2997 "You are not on that channel". The command were specified for
2998 client user is not currently on.
3000 26 SILC_STATUS_ERR_USER_ON_CHANNEL
3002 "User already on channel". User were invited on channel they
3005 27 SILC_STATUS_ERR_NOT_REGISTERED
3007 "You have not registered". User executed command that requires
3008 the client to be registered on the server before it may be
3011 28 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
3013 "Not enough parameters". Command requires more parameters
3016 29 SILC_STATUS_ERR_TOO_MANY_PARAMS
3018 "Too many parameters". Too many parameters were provided
3021 30 SILC_STATUS_ERR_PERM_DENIED
3023 "Your host is not among the privileged". The client tried to
3024 register on server that does not allow this host to connect.
3026 31 SILC_STATUS_ERR_BANNED_FROM_SERVER
3028 "You are banned from this server". The client tried to register
3029 on server that has explicitly denied this host to connect.
3031 32 SILC_STATUS_ERR_BAD_PASSWORD
3033 "Cannot join channel. Incorrect password". Password provided for
3034 channel were not accepted.
3036 33 SILC_STATUS_ERR_CHANNEL_IS_FULL
3038 "Cannot join channel. Channel is full". The channel is full
3039 and client cannot be joined to it.
3041 34 SILC_STATUS_ERR_NOT_INVITED
3043 "Cannot join channel. You have not been invited". The channel
3044 is invite only channel and client has not been invited.
3046 35 SILC_STATUS_ERR_BANNED_FROM_CHANNEL
3048 "Cannot join channel. You have been banned". The client has
3049 been banned from the channel.
3051 36 SILC_STATUS_ERR_UNKNOWN_MODE
3053 "Unknown mode". Mode provided by the client were unknown to
3056 37 SILC_STATUS_ERR_NOT_YOU
3058 "Cannot change mode for other users". User tried to change
3059 someone else's mode.
3061 38 SILC_STATUS_ERR_NO_CHANNEL_PRIV
3063 "Permission denied. You are not channel operator". Command may
3064 be executed only by channel operator.
3066 39 SILC_STATUS_ERR_NO_SERVER_PRIV
3068 "Permission denied. You are not server operator". Command may
3069 be executed only by server operator.
3071 40 SILC_STATUS_ERR_NO_ROUTER_PRIV
3073 "Permission denied. You are not SILC operator". Command may be
3074 executed only by router (SILC) operator.
3076 41 SILC_STATUS_ERR_BAD_NICKNAME
3078 "Bad nickname". Nickname requested contained illegal characters
3081 42 SILC_STATUS_ERR_BAD_CHANNEL
3083 "Bad channel name". Channel requested contained illegal characters
3086 43 SILC_STATUS_ERR_AUTH_FAILED
3088 "Authentication failed". The authentication data sent as
3089 argument were wrong and thus authentication failed.
3094 6 Security Considerations
3096 Security is central to the design of this protocol, and these security
3097 considerations permeate the specification.
3103 [SILC2] Riikonen, P., "SILC Packet Protocol", Internet Draft,
3106 [SILC3] Riikonen, P., "SILC Key Exchange and Authentication
3107 Protocols", Internet Draft, June 2000.
3109 [IRC] Oikarinen, J., and Reed D., "Internet Relay Chat Protocol",
3112 [SSH-TRANS] Ylonen, T., et al, "SSH Transport Layer Protocol",
3115 [PGP] Callas, J., et al, "OpenPGP Message Format", RFC 2440,
3118 [SPKI] Ellison C., et al, "SPKI Certificate Theory", RFC 2693,
3121 [PKIX-Part1] Housley, R., et al, "Internet X.509 Public Key
3122 Infrastructure, Certificate and CRL Profile", RFC 2459,
3125 [Schneier] Schneier, B., "Applied Cryptography Second Edition",
3126 John Wiley & Sons, New York, NY, 1996.
3128 [Menezes] Menezes, A., et al, "Handbook of Applied Cryptography",
3131 [OAKLEY] Orman, H., "The OAKLEY Key Determination Protocol",
3132 RFC 2412, November 1998.
3134 [ISAKMP] Maughan D., et al, "Internet Security Association and
3135 Key Management Protocol (ISAKMP)", RFC 2408, November
3138 [IKE] Harkins D., and Carrel D., "The Internet Key Exchange
3139 (IKE)", RFC 2409, November 1998.
3141 [HMAC] Krawczyk, H., "HMAC: Keyed-Hashing for Message
3142 Authentication", RFC 2104, February 1997.
3155 EMail: priikone@poseidon.pspt.fi
3157 This Internet-Draft expires 6 Jun 2001