8 .ds RF FORMFEED[Page %]
17 Network Working Group P. Riikonen
19 draft-riikonen-silc-spec-00.txt 28 June 2000
25 Secure Internet Live Conferencing (SILC),
26 Protocol Specification
27 <draft-riikonen-silc-spec-00.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 3 SILC Specification ............................................ 7
82 3.1 Client .................................................... 7
83 3.1.1 Client ID ........................................... 8
84 3.2 Server .................................................... 9
85 3.2.1 Server's Local ID List .............................. 9
86 3.2.2 Server ID ........................................... 10
87 3.2.3 SILC Server Ports ................................... 11
88 3.3 Router .................................................... 11
89 3.3.1 Router's Local ID List .............................. 11
90 3.3.2 Router's Global ID List ............................. 12
91 3.3.3 Router's Server ID .................................. 13
92 3.4 Channels .................................................. 13
93 3.4.1 Channel ID .......................................... 14
94 3.5 Operators ................................................. 14
95 3.6 SILC Commands ............................................. 15
96 3.7 SILC Packets .............................................. 15
97 3.8 Packet Encryption ......................................... 16
98 3.8.1 Determination of the Source and the Destination ..... 16
99 3.8.2 Client To Client .................................... 17
100 3.8.3 Client To Channel ................................... 18
101 3.8.4 Server To Server .................................... 19
102 3.9 Key Exchange And Authentication ........................... 19
103 3.10 Algorithms ............................................... 19
104 3.10.1 Ciphers ............................................ 19
105 3.10.2 Public Key Algorithms .............................. 20
106 3.10.3 MAC Algorithms ..................................... 20
107 3.10.4 Compression Algorithms ............................. 21
108 3.11 SILC Public Key .......................................... 21
109 4 SILC Procedures ............................................... 24
110 4.1 Creating Client Connection ................................ 24
111 4.2 Creating Server Connection ................................ 25
112 4.3 Joining to a Channel ...................................... 26
113 4.4 Channel Key Generation .................................... 27
114 4.5 Private Message Sending and Reception ..................... 27
115 4.6 Private Message Key Generation ............................ 28
116 4.7 Channel Message Sending and Reception ..................... 29
117 4.8 Session Key Regeneration .................................. 29
118 4.9 Command Sending and Reception ............................. 29
119 5 SILC Commands ................................................. 30
120 5.1 SILC Commands Syntax ...................................... 30
121 5.2 SILC Commands List ........................................ 32
122 5.3 SILC Command Status Types ................................. 53
123 5.3.1 SILC Command Status Payload ......................... 53
124 5.3.2 SILC Command Status List ............................ 54
125 6 Security Considerations ....................................... 59
126 7 References .................................................... 59
127 8 Author's Address .............................................. 60
134 Figure 1: SILC Network Topology
135 Figure 2: Communication Inside cell
136 Figure 3: Communication Between Cells
137 Figure 4: SILC Public Key
138 Figure 5: SILC Command Status Payload
144 This document describes a Secure Internet Live Conferencing (SILC)
145 protocol which provides secure conferencing services over insecure
146 network channel. SILC is IRC [IRC] like protocol, however, it is
147 not equivalent to IRC and does not support IRC.
149 Strong cryptographic methods are used to protect SILC packets inside
150 SILC network. Two other Internet Drafts relates very closely to this
151 memo; SILC Packet Protocol [SILC2] and SILC Key Exchange and
152 Authentication Protocols [SILC3].
154 The protocol uses extensively packets as conferencing protocol
155 requires message and command sending. The SILC Packet Protocol is
156 described in [SILC2] and should be read to fully comprehend this
157 document and protocol. [SILC2] also describes the packet encryption
158 and decryption in detail.
160 The security of SILC protocol and for any security protocol for that
161 matter is based on strong and secure key exchange protocol. The SILC
162 Key Exchange protocol is described in [SILC3] along with connection
163 authentication protocol and should be read to fully comprehend this
164 document and protocol.
166 The SILC protocol has been developed to work on TCP/IP network
167 protocol, although it could be made to work on other network protocols
168 with only minor changes. However, it is recommended that TCP/IP
169 protocol is used under SILC protocol. Typical implementation would
170 be made in client-server model.
176 This section describes various SILC protocol concepts that forms the
177 actual protocol, and in the end, the actual SILC network. The mission
178 of the protocol is to deliver messages from clients to other clients
179 through routers and servers in secure manner. The messages may also
180 be delivered from one client to many clients forming a group, also
183 This section does not focus to security issues, instead basic network
184 concepts are introduced to make the topology of the SILC network
189 2.1 SILC Network Topology
191 SILC network is a cellular network as opposed to tree style network
192 topology. The rationale for this is to have servers that can perform
193 specific kind of tasks what other servers cannot perform. This leads
194 to two kinds of servers; normal SILC servers and SILC routers.
196 A difference between normal server and router server is that routers
197 knows everything about everything in the network. They also do the
198 actual routing of the messages to the correct receiver. Normal servers
199 knows only about local information and nothing about global information.
200 This makes the network faster as there are less servers that needs to
201 keep global information up to date at all time.
203 This, on the other hand, leads to cellular like network, where routers
204 are in the centrum on the cell and servers are connected to the router.
206 Following diagram represents SILC network topology.
226 ---- ---- ---- ---- ---- ----
227 | S8 | S5 | S4 | | S7 | S5 | S6 |
228 ----- ---- ----- ----- ---- -----
229 | S7 | S/R1 | S2 | --- | S8 | S/R2 | S4 |
230 ---- ------ ---- ---- ------ ----
231 | S6 | S3 | S1 | | S1 | S3 | S2 | ---- ----
232 ---- ---- ---- ---- ---- ---- | S3 | S1 |
233 Cell 1. \\ Cell 2. | \\____ ----- -----
235 ---- ---- ---- ---- ---- ---- ---- ------
236 | S7 | S4 | S2 | | S1 | S3 | S2 | | S2 | S5 |
237 ----- ---- ----- ----- ---- ----- ---- ----
238 | S6 | S/R3 | S1 | --- | S4 | S/R5 | S5 | Cell 4.
239 ---- ------ ---- ---- ------ ----
240 | S8 | S5 | S3 | | S6 | S7 | S8 | ... etc ...
241 ---- ---- ---- ---- ---- ----
246 Figure 1: SILC Network Topology
249 A cell is formed when a server or servers connect to one router. In
250 SILC network normal server cannot directly connect to other normal
251 server. Normal server may only connect to SILC router which then
252 routes the messages to the other servers in the cell. Router servers
253 on the other hand may connect to other routers to form the actual SILC
254 network, as seen in above figure. However, router is also normal SILC
255 server; clients may connect to it the same way as to normal SILC
256 servers. Normal server also cannot have active connections to more
257 than one router. Normal server cannot be connected to two different
258 cells. Router servers, on the other hand, may have as many router to
259 router connections as needed.
261 There are many issues in this network topology that needs to be careful
262 about. Issues like the size of the cells, the number of the routers in
263 the SILC network and the capacity requirements of the routers. These
264 issues should be discussed in the Internet Community and additional
265 documents on the issue will be written.
269 2.2 Communication Inside a Cell
271 It is always guaranteed that inside a cell message is delivered to the
272 recipient with at most two server hops. Client who is connected to
273 server in the cell and is talking on channel to other client connected
274 to other server in the same cell, will have its messages delivered from
275 its local server first to the router of the cell, and from the router
276 to the other server in the cell. Following diagram represents this
291 Figure 2: Communication Inside cell
294 Example: Client 1. connected to Server 1. message sent to
295 Client 4. connected to Server 2. travels from Server 1.
296 first to Router which routes the message to Server 2.
297 which then sends it to the Client 4. All the other
298 servers in the cell will not see the routed message.
301 If client is connected directly to the router, as router is also normal
302 SILC server, the messages inside the cell are always delivered only with
303 one server hop. If clients communicating with each other are connected
304 to the same server, no router interaction is needed. This is the optimal
305 situation of message delivery in the SILC network.
309 2.3 Communication in the Network
311 If the message is destined to server that does not belong to local cell
312 the message is routed to the router server to which the destination
313 server belongs, if the local router is connected to destination router.
314 If there is no direct connection to the destination router, the local
315 router routes the message to its primary route. Following diagram
316 represents message sending between cells.
321 1 --- S1 S4 --- 5 S2 --- 1
322 S/R - - - - - - - - S/R
332 Figure 3: Communication Between Cells
335 Example: Client 5. connected to Server 4. in Cell 1. message sent
336 to Client 2. connected to Server 1. in Cell 2. travels
337 from Server 4. to Router which routes the message to
338 Router in Cell 2, which then routes the message to
339 Server 1. All the other servers and routers in the
340 network will not see the routed message.
343 The optimal case of message delivery from client point of view is
344 when clients are connected directly to the routers and the messages
345 are delivered from one router to the other router.
349 2.4 Channel Communication
351 Messages may be sent to group of clients as well. Sending messages to
352 many clients works the same way as sending messages point to point, from
353 message delivery point of view. Security issues are another matter
354 which are not discussed in this section.
356 Router server handles the message routing to multiple recipients. If
357 any recipient is not in the same cell as the sender the messages are
360 Server distributes the channel message to its local clients who are
361 joined to the channel. Also, router distributes the message to its
362 local clients on the channel.
366 3. SILC Specification
368 This section describes the SILC protocol. However, [SILC2] and
369 [SILC3] describes other important protocols that are part of this SILC
370 specification and must be read.
376 A client is a piece of software connecting to SILC server. SILC client
377 cannot be SILC server. Purpose of clients is to provide the user
378 interface of the SILC services for end user. Clients are distinguished
379 from other clients by unique Client ID. Client ID is a 128 bit ID that
380 is used in the communication in the SILC network. The client ID is
381 based on the nickname selected by the user. User uses logical nicknames
382 in communication which are then mapped to the corresponding Client ID.
383 Client ID's are low level identifications and must not be seen by the
386 Clients provide other information about the end user as well. Information
387 such as the nickname of the user, username and the hostname of the end
388 user and user's real name. See section 3.2 Server for information of
389 the requirements of keeping this information.
391 The nickname selected by the user is not unique in the SILC network.
392 There can be 2^8 same nicknames for one IP address. As for comparison to
393 IRC [IRC] where nicknames are unique this is a fundamental difference
394 between SILC and IRC. This causes the server names to be used along
395 with the nicknames to identify specific users when sending messages.
396 This feature of SILC makes IRC style nickname-wars obsolete as no one
397 owns their nickname; there can always be someone else with the same
398 nickname. Another difference is that there are no limit of the length
399 of the nickname in the SILC.
405 Client ID is used to identify users in the SILC network. The Client ID
406 is unique to the extent that there can be 2^128 different Client ID's.
407 Collisions are not expected to happen. The Client ID is defined as
411 128 bit Client ID based on IPv4 addresses:
413 32 bit ServerID IP address (bits 1-32)
415 88 bit Truncated MD5 hash value of the nickname
417 o Server ID IP address - Indicates the server where this
418 client is coming from. The IP address hence equals the
419 server IP address where to the client has connected.
421 o Random number - Random number to further unify the
422 Client ID. This makes it possible to have 2^8 same
423 nicknames from the same server IP address.
425 o MD5 hash - MD5 hash value of the nickname is truncated
426 taking 88 bits from the start of the hash value. This
427 hash value is used to search the user's Client ID from
431 Collisions could occur when more than 2^8 clients using same nickname
432 from the same server IP address is connected to the SILC network.
433 Server must be able to handle this situation by refusing to accept
434 anymore of that nickname.
436 Another possible collision may happen with the truncated hash value of
437 the nickname. It could be possible to have same truncated hash value for
438 two different nicknames. However, this is not expected to happen nor
439 cause any problems if it would occur. Nicknames are usually logical and
440 it is unlikely to have two distinct logical nicknames produce same
441 truncated hash value.
447 Servers are the most important parts of the SILC network. They form the
448 basis of the SILC, providing a point to which clients may connect to.
449 There are two kinds of servers in SILC; normal servers and router servers.
450 This section focuses on the normal server and router server is described
451 in the section 3.3 Router.
453 Normal servers may not directly connect to other normal server. Normal
454 servers may only directly connect to router server. If the message sent
455 by the client is destined outside the local server it is always sent to
456 the router server for further routing. Server may only have one active
457 connection to router on same port. Normal server may not connect to other
458 cell's router except in situations where its cell's router is unavailable.
460 Servers and routers in the SILC network are considered to be trusted.
461 With out a doubt, servers that are set to work on ports above 1023 are
462 not considered to be trusted. Also, the service provider acts important
463 role in the server's trustworthy.
467 3.2.1 Server's Local ID List
469 Normal server keeps various information about the clients and their end
470 users connected to it. Every normal server must keep list of all locally
471 connected clients, Client ID's, nicknames, usernames and hostnames and
472 user's real name. Normal servers only keeps local information and it
473 does not keep any global information. Hence, normal servers knows only
474 about their locally connected clients. This makes servers efficient as
475 they don't have to worry about global clients. Server is also responsible
476 of creating the Client ID's for their clients.
478 Normal server also keeps information about locally created channels and
488 Hence, local list for normal server includes:
491 server list - Router connection
499 client list - All clients in server
507 channel list - All channels in server
510 o Client ID's on channel
511 o Client ID modes on channel
520 Servers are distinguished from other servers by unique 64 bit Server ID.
521 The Server ID is used in the SILC to route messages to correct servers.
522 Server ID's also provide information for Client ID's, see section 3.1.1
523 Client ID. Server ID is defined as follows.
526 64 bit Server ID based on IPv4 addresses:
528 32 bit IP address of the server
532 o IP address of the server - This is the real IP address of
535 o Port - This is the port the server is binded to.
537 o Random number - This is used to further unify the Server ID.
540 Collisions are not expected to happen in any conditions. The Server ID
541 is always created by the server itself and server is resposible of
542 distributing it to the router.
546 3.2.3 SILC Server Ports
548 SILC uses currently TCP port 334 on SILC network. However, this is not
549 official port assigned for SILC. Official port has been requested by
552 If there are needs to create new SILC networks in the future the port
553 numbers must be officially assigned by the IANA. Most convenience case
554 would be to assign port numbers upwards from 334.
556 Server on network above privileged ports (>1023) should not be trusted
557 as they could have been set up by untrusted party.
563 Router server in SILC network is responsible for keeping the cell together
564 and routing messages to other servers and to other routers. Router server
565 is also a normal server thus clients may connect to it as it would be
566 just normal SILC server.
568 However, router servers has a lot of important tasks that normal servers
569 do not have. Router server knows everything about everything in the SILC.
570 They know all clients currently on SILC, all servers and routers and all
571 channels in SILC. Routers are the only servers in SILC that care about
572 global information and keeping them up to date at all time. And, this
573 is what they must do.
577 3.3.1 Router's Local ID List
579 Router server as well must keep local list of connected clients and
580 locally created channels. However, this list is extended to include all
581 the informations of the entire cell, not just the server itself as for
584 However, on router this list is a lot smaller since routers do not keep
585 information about user's nickname, username and hostname and real name
586 since these are not needed by the router. Router keeps only information
593 Hence, local list for router includes:
596 server list - All servers in the cell
603 client list - All clients in the cell
606 channel list - All channels in the cell
608 o Client ID's on channel
609 o Client ID modes on channel
614 Note that locally connected clients and other information include all the
615 same information as defined in section section 3.2.1 Server's Local ID
620 3.3.2 Router's Global ID List
622 Router server must also keep global list. Normal servers do not have
623 global list as they know only about local information. Global list
624 includes all the clients on SILC, their Client ID's, all created channels
625 and their Channel ID's and all servers and routers on SILC and their
626 Server ID's. That is said, global list is for global information and the
627 list must not include the local information already on the router's local
630 Note that the global list does not include information like nicknames,
631 usernames and hostnames or user's real names. Router does not keep
632 these informations as they are not needed by the router. This
633 information is available from the client's server which maybe queried
636 Hence, global list includes:
639 server list - All servers in SILC
645 client list - All clients in SILC
648 channel list - All channels in SILC
650 o Client ID's on channel
651 o Client ID modes on channel
656 3.3.3 Router's Server ID
658 Router's Server ID's are equivalent to normal Server ID's. As routers
659 are normal servers as well same types of ID's applies for routers as well.
660 Thus, see section 3.2.2 Server ID. Server ID's for routers are always
661 created by the remote router where the router is connected to.
667 A channel is a named group of one or more clients which will all receive
668 messages addressed to that channel. The channel is created when first
669 client requests JOIN command to the channel, and the channel ceases to
670 exist when the last client leaves it. When channel exists, any client
671 can reference it using the name of the channel.
673 Channel names are unique although the real uniqueness comes from 64 bit
674 Channel ID that unifies each channel. However, channel names are still
675 unique and no two global channels with same name may exist. Channel name
676 is a string which begins with `#' character. There is no limit on the
677 length of the channel name. Channel names may not contain any spaces
678 (` '), any non-printable ASCII characters, commas (`,') and wildcard
681 Channels can have operators that can administrate the channel and
682 operate all of its modes. Following operators on channel exist on SILC
686 o Channel founder - When channel is created the joining client becomes
687 channel founder. Channel founder is channel operator with some more
688 privileges. Basically, channel founder can fully operate the channel
689 and all of its modes. The privileges are limited only to the particular
690 channel. There can be only one channel founder per channel. Channel
691 founder supersedes channel operator's privileges.
693 Channel founder privileges cannot be removed by any other operator on
694 channel. When channel founder leaves the channel there is no channel
695 founder on the channel. Channel founder also cannot be removed by
696 force from the channel.
698 o Channel operator - When client joins to channel that has not existed
699 previously it will become automatically channel operator (and channel
700 founder discussed above). Channel operator is able administrate the
701 channel, set some modes on channel, remove a badly behaving client from
702 the channel and promote other clients to become channel operator.
703 The privileges are limited only to the particular channel.
705 Normal channel user may be promoted (opped) to channel operator
706 gaining channel operator privileges. Channel founder or other channel
707 operator may also demote (deop) channel operator to normal channel
715 Channels are distinguished from other channels by unique Channel ID.
716 The Channel ID is a 64 bit ID and collisions are not expected to happen
717 in any conditions. Channel names are just for logical use of channels.
718 The Channel ID is created by the server where the channel is created.
719 The Channel ID is defined as follows.
722 64 bit Channel ID based on IPv4 addresses:
724 32 bit Router's Server ID IP address (bits 1-32)
725 16 bit Router's Server ID port (bits 33-48)
728 o Router's Server ID IP address - Indicates the IP address of
729 the router of the cell where this channel is created. This is
730 taken from the router's Server ID. This way SILC router knows
731 where this channel resides in the SILC network.
733 o Router's Server ID port - Indicates the port of the channel on
734 the server. This is taken from the router's Server ID.
736 o Random number - To further unify the Channel ID. This makes
737 sure that there are no collisions. This also means that
738 in a cell there can be 2^16 channels.
745 Operators are normal users with extra privileges to their server or
746 router. Usually these people are SILC server and router administrators
747 that take care of their own server and clients on them. The purpose of
748 operators is to administrate the SILC server or router. However, even
749 an operator with highest privileges is not able to enter invite-only
750 channel, to gain access to the contents of a encrypted and authenticated
751 packets traveling in the SILC network or to gain channel operator
752 privileges on public channels without being promoted. They have the
753 same privileges as everyone else except they are able to administrate
754 their server or router.
760 Commands are very important part on SILC network especially for client
761 which uses commands to operate on the SILC network. Commands are used
762 to set nickname, join to channel, change modes and many other things.
764 Client usually sends the commands and server replies by sending a reply
765 packet to the command. Server may also send commands usually to serve
766 the original client's request. However, server may not send command
767 to client and there are some commands that server must not send.
769 Note that the command reply is usually sent only after client has sent
770 the command request but server is allowed to send command reply packet
771 to client even if client has not requested the command. Client may,
772 however, choose not to accept the command reply, but there are some
773 command replies that the client should accept. Example of a such
774 command reply is reply to SILC_COMMAND_CMODE command that the server
775 uses to distribute the channel mode on all clients on the channel
776 when the mode has changed.
778 It is expected that some of the commands may be miss-used by clients
779 resulting various problems on the server side. Every implementation
780 should assure that commands may not be executed more than once, say,
781 in two (2) seconds. This should be sufficient to prevent the miss-use
784 SILC commands are described in section 5 SILC Commands.
790 Packets are naturally the most important part of the protocol and the
791 packets are what actually makes the protocol. Packets in SILC network
792 are always encrypted using, usually, the shared secret session key
793 or some other key, for example, channel key, when encrypting channel
794 messages. The SILC Packet Protocol is a wide protocol and is described
795 in [SILC2]. This document does not define or describe details of
802 3.8 Packet Encryption
804 All packets passed in SILC network must be encrypted. This section
805 defines how packets must be encrypted in the SILC network. The detailed
806 description of the actual encryption process of the packets are
807 described in [SILC2].
809 Client and its server shares secret symmetric session key which is
810 established by the SILC Key Exchange Protocol, described in [SILC3].
811 Every packet sent from client to server, with exception of packets for
812 channels, are encrypted with this session key.
814 Channels has their own key that are shared by every client on the channel.
815 However, the channel keys are cell specific thus one cell does not know
816 the channel key of the other cell, even if that key is for same channel.
817 Channel key is also known by the routers and all servers that has clients
818 on the channel. However, channels may have channel private keys that
819 are entirely local setting for client. All clients on the channel must
820 know the channel private key before hand to be able to talk on the
821 channel. In this case, no server or router knows the key for channel.
823 Server shares secret symmetric session key with router which is
824 established by the SILC Key Exchange Protocol. Every packet passed from
825 server to router, with exception of packets for channels, are encrypted
826 with the shared session key. Same way, router server shares secret
827 symmetric key with its primary route. However, every packet passed
828 from router to other router, including packets for channels, are
829 encrypted with the shared session key. Every router connection has
830 their own session keys.
834 3.8.1 Determination of the Source and the Destination
836 The source and the destination of the packet needs to be determined
837 to be able to route the packets to correct receiver. This information
838 is available in the SILC Packet Header which is included in all packets
839 sent in SILC network. The SILC Packet Header is described in [SILC2].
841 The header is always encrypted with the session key who is next receiver
842 of the packet along the route. The receiver of the packet, for example
843 a router along the route, is able to determine the sender and the
844 destination of the packet by decrypting the SILC Packet Header and
845 checking the ID's attached to the header. The ID's in the header will
846 tell to where the packet needs to be sent and where it is coming from.
848 The header in the packet does not change during the routing of the
849 packet. The original sender, for example client, assembles the packet
850 and the packet header and server or router between the sender and the
851 receiver must not change the packet header.
853 Note that the packet and the packet header may be encrypted with
854 different keys. For example, packets to channels are encrypted with
855 the channel key, however, the header is encrypted with the session key
856 as described above. However, the header and the packet may be encrypted
857 with same key. This is case, for example, with command packets.
861 3.8.2 Client To Client
863 Process of message delivery and encryption from client to another
864 client is as follows.
866 Example: Private message from client to another client on different
867 servers. Clients do not share private message delivery
868 keys; normal session keys are used.
870 o Client 1. sends encrypted packet to its server. The packet is
871 encrypted with the session key shared between client and its
874 o Server determines the destination of the packet and decrypts
875 the packet. Server encrypts the packet with session key shared
876 between the server and its router, and sends the packet to the
879 o Router determines the destination of the packet and decrypts
880 the packet. Router encrypts the packet with session key
881 shared between the router and the destination server, and sends
882 the packet to the server.
884 o Server determines the client to which the packet is destined
885 to and decrypts the packet. Server encrypts the packet with
886 session key shared between the server and the destination client,
887 and sends the packet to the client.
889 o Client 2. decrypts the packet.
892 Example: Private message from client to another client on different
893 servers. Clients has established secret shared private
894 message delivery key with each other and that is used in
895 the message encryption.
897 o Client 1. sends encrypted packet to its server. The packet is
898 encrypted with the private message delivery key shared between
901 o Server determines the destination of the packet and sends the
902 packet to the router.
904 o Router determines the destination of the packet and sends the
905 packet to the server.
907 o Server determines the client to which the packet is destined
908 to and sends the packet to the client.
910 o Client 2. decrypts the packet with the secret shared key.
913 If clients share secret key with each other the private message
914 delivery is much simpler since servers and routers between the
915 clients do not need to decrypt and re-encrypt the packet.
917 The process for clients on same server is much simpler as there are
918 no need to send the packet to the router. The process for clients
919 on different cells is same as above except that the packet is routed
920 outside the cell. The router of the destination cell routes the
921 packet to the destination same way as described above.
925 3.8.3 Client To Channel
927 Process of message delivery from client on channel to all the clients
930 Example: Channel of four users; two on same server, other two on
931 different cells. Client sends message to the channel.
933 o Client 1. encrypts the packet with channel key and sends the
934 packet to its server.
936 o Server determines local clients on the channel and sends the
937 packet to the Client on the same server. Server then sends
938 the packet to its router for further routing.
940 o Router determines local clients on the channel, if found
941 sends packet to the local clients. Router determines global
942 clients on the channel and sends the packet to its primary
943 router or fastest route.
945 o (Other router(s) do the same thing and sends the packet to
948 o Server determines local clients on the channel and sends the
949 packet to the client.
951 o All clients receiving the packet decrypts the packet.
955 3.8.4 Server To Server
957 Server to server packet delivery and encryption is described in above
958 examples. Router to router packet delivery is analogous to server to
959 server. However, some packets, such as channel packets, are processed
960 differently. These cases are described later in this document and
961 more in detail in [SILC2].
965 3.9 Key Exchange And Authentication
967 Key exchange is done always when for example client connects to server
968 but also when server and router and router and router connects to each
969 other. The purpose of key exchange protocol is to provide secure key
970 material to be used in the communication. The key material is used to
971 derive various security parameters used to secure SILC packets. The
972 SILC Key Exchange protocol is described in detail in [SILC3].
974 Authentication is done after key exchange protocol has been successfully
975 completed. The purpose of authentication is to authenticate for example
976 client connecting to the server. However, Usually clients are accepted
977 to connect to server without explicit authentication. Servers are
978 required use authentication protocol when connecting. The authentication
979 may be based on passphrase (pre-shared-secret) or public key. The
980 connection authentication protocol is described in detail in [SILC3].
986 This section defines all the allowed algorithms that can be used in
987 the SILC protocol. This includes mandatory cipher, mandatory public
988 key algorithm and MAC algorithms.
994 Cipher is the encryption algorithm that is used to protect the data
995 in the SILC packets. See [SILC2] of the actual encryption process and
996 definition of how it must be done. SILC has a mandatory algorithm that
997 must be supported in order to be compliant with this protocol.
1004 Following ciphers are defined in SILC protocol:
1007 blowfish-cbc Blowfish in CBC mode (mandatory)
1008 twofish-cbc Twofish in CBC mode (optional)
1009 rc6-cbc RC6 in CBC mode (optional)
1010 rc5-cbc RC5 in CBC mode (optional)
1011 mars-cbc Mars in CBC mode (optional)
1012 none No encryption (optional)
1016 All algorithms must use minimum of 128 bit key, by default. Several
1017 algorithms, however, supports longer keys and it is recommended to use
1018 longer keys if they are available.
1020 Algorithm none does not perform any encryption process at all and
1021 thus is not recommended to be used. It is recommended that no client
1022 or server implementation would accept none algorithms except in special
1025 Additional ciphers may be defined to be used in SILC by using the
1026 same name format as above.
1030 3.10.2 Public Key Algorithms
1032 Public keys are used in SILC to authenticate entities in SILC network
1033 and to perform other tasks related to public key cryptography. The
1034 public keys are also used in the SILC Key Exchange protocol [SILC3].
1036 Following public key algorithms are defined in SILC protocol:
1043 Both of the algorithms are described in [Scheneir] and [Menezes].
1045 Additional public key algorithms may be defined to be used in SILC.
1049 3.10.3 MAC Algorithms
1051 Data integrity is protected by computing a message authentication code
1052 (MAC) of the packet data. See [SILC2] for details how to compute the
1059 Following MAC algorithms are defined in SILC protocol:
1062 hmac-sha1 HMAC-SHA1, length = 20 (mandatory)
1063 hmac-md5 HMAC-MD5, length = 16 (optional)
1064 none No MAC (optional)
1067 The none MAC is not recommended to be used as the packet is not
1068 authenticated when MAC is not computed. It is recommended that no
1069 client or server would accept none MAC except in special debugging
1072 The HMAC algorithm is described in [HMAC] and hash algorithms that
1073 are used as part of the HMACs are described in [Scheneir] and in
1076 Additional MAC algorithms may be defined to be used in SILC.
1080 3.10.4 Compression Algorithms
1082 SILC protocol supports compression that may be applied to unencrypted
1083 data. It is recommended to use compression on slow links as it may
1084 significantly speed up the data transmission. By default, SILC does not
1085 use compression which is the mode that must be supported by all SILC
1088 Following compression algorithms are defined:
1091 none No compression (mandatory)
1092 zlib GBU ZLIB (LZ77) compression (optional)
1095 Additional compression algorithms may be defined to be used in SILC.
1099 3.11 SILC Public Key
1101 This section defines the type and format of the SILC public key. All
1102 implementations must support this public key type. See [SILC3] for
1103 other optional public key and certificate types allowed in SILC
1104 protocol. Public keys in SILC may be used to authenticate entities
1105 and to perform other tasks related to public key cryptography.
1107 The format of the SILC Public Key is as follows:
1118 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
1119 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1120 | Public Key Length |
1121 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1122 | Algorithm Name Length | |
1123 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1127 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1128 | Identifier Length | |
1129 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1133 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1137 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1141 Figure 4: SILC Public Key
1145 o Public Key Length (4 bytes) - Indicates the full length
1146 of the public key, not including this field.
1148 o Algorithm Name Length (2 bytes) - Indicates the length
1149 of the Algorithm Length field, not including this field.
1151 o Algorithm name (variable length) - Indicates the name
1152 of the public key algorithm that the key is. See the
1153 section 3.10.2 Public Key Algorithms for defined names.
1155 o Identifier Length (2 bytes) - Indicates the length of
1156 the Identifier field, not including this field.
1158 o Identifier (variable length) - Indicates the identifier
1159 of the public key. This data can be used to identify
1160 the owner of the key. The identifier is of following
1164 HN Host name or IP address
1171 Examples of an identifier:
1173 `UN=priikone, HN=poseidon.pspt.fi, E=priikone@poseidon.pspt.fi'
1175 `UN=sam, HN=dummy.fi, RN=Sammy Sam, O=Company XYZ, C=Finland'
1177 At least user name (UN) and host name (HN) must be provided as
1178 identifier. The fields are separated by commas (`,'). If
1179 comma is in the identifier string it must be written as `\\,',
1180 for example, `O=Company XYZ\\, Inc.'.
1182 o Public Data (variable length) - Includes the actual
1183 public data of the public key.
1185 The format of this field for RSA algorithm is
1194 The format of this field for DSS algorithm is
1206 The variable length fields are multiple precession
1207 integers encoded as strings in both examples.
1209 Other algorithms must define their own type of this
1210 field if they are used.
1213 All fields in the public key are in MSB (most significant byte first)
1220 This section describes various SILC procedures such as how the
1221 connections are created and registered, how channels are created and
1222 so on. The section describes the procedures only generally as details
1223 are described in [SILC2] and [SILC3].
1227 4.1 Creating Client Connection
1229 This section descibres the procedure when client connects to SILC server.
1230 When client connects to server the server must perform IP address lookup
1231 and reverse IP address lookup to assure that the origin host really is
1232 who it claims to be. Client, host, connecting to server must have
1233 both valid IP address and fully qualified domain name (FQDN).
1235 After that client and server performs SILC Key Exchange protocol which
1236 will provide the key material used later in the communication. The
1237 key exchange protocol must be completed successfully before the connection
1238 registration may continue. The SILC Key Exchange protocol is described
1241 Typical server implementation would keep a list of connections that it
1242 allows to connect to the server. The implementation would check, for
1243 example, the connecting client's IP address from the connection list
1244 before the SILC Key Exchange protocol has been started. Reason for
1245 this is that if the host is not allowed to connect to the server there
1246 is no reason to perform a key exchange protocol.
1248 After successful key exchange protocol the client and server performs
1249 connection authentication protocol. The purpose of the protocol is to
1250 authenticate the client connecting to the server. Flexible
1251 implementation could also accept the client to connect to the server
1252 without explicit authentication. However, if authentication is
1253 desired for a specific client it may be based on passphrase or
1254 public key authentication. If authentication fails the connection
1255 must be terminated. The connection authentication protocol is described
1258 After successful key exchange and authentication protocol the client
1259 registers itself by sending SILC_PACKET_NEW_CLIENT packet to the
1260 server. This packet includes various information about the client
1261 that the server uses to create the client. Server creates the client
1262 and sends SILC_PACKET_NEW_ID to the client which includes the created
1263 Client ID that the client must start using after that. After that
1264 all SILC packets from the client must have the Client ID as the
1265 Source ID in the SILC Packet Header, described in [SILC2].
1267 Client must also get the server's Server ID that is to be used as
1268 Destination ID in the SILC Packet Header when communicating with
1269 the server (for example when sending commands to the server). The
1270 ID may be resolved in two ways. Client can take the ID from an
1271 previously received packet from server that must include the ID,
1272 or to send SILC_COMMAND_INFO command and receive the Server ID as
1275 Server may choose not to use the information received in the
1276 SILC_PACKET_NEW_CLIENT packet. For example, if public key or
1277 certificate were used in the authentication, server may use those
1278 informations rather than what it received from client. This is suitable
1279 way to get the true information about client if it is available.
1281 The nickname of client is initially set to the username sent in the
1282 SILC_PACKET_NEW_CLIENT packet. User should set the nickname to more
1283 suitable by sending SILC_COMMAND_NICK command. However, this is not
1284 required as part of registration process.
1286 Server must also distribute the information about newly registered
1287 client to its router (or if the server is router, to all routers in
1288 the SILC network). More information about this in [SILC2].
1292 4.2 Creating Server Connection
1294 This section descibres the procedure when server connects to its
1295 router (or when router connects to other router, the cases are
1296 equivalent). The procedure is very much alike when client connects
1297 to the server thus it is not repeated here.
1299 One difference is that server must perform connection authentication
1300 protocol with proper authentication. Proper authentication is based
1301 on passphrase or public key authentication.
1303 After server and router has successfully performed the key exchange
1304 and connection authentication protocol, the server register itself
1305 to the router by sending SILC_PACKET_NEW_SERVER packet. This packet
1306 includes the server's Server ID that it has created by itself and
1307 other relevant information about the server.
1309 After router has received the SILC_PACKET_NEW_SERVER packet it
1310 distributes the information about newly registered server to all routers
1311 in the SILC network. More information about this in [SILC2].
1313 As client needed to resolve the destination ID this must be done by the
1314 server that connected to the router, as well. The way to resolve it is
1315 to get the ID from previously received packet. Server must also start
1316 using its own Server ID as Source ID in SILC Packet Header and the
1317 router's Server ID as Destination when communicating with the router.
1319 If the server has already connected clients and locally created
1320 channels the server must distribute these informations to the router.
1321 The distribution is done by sending packet SILC_PACKET_NEW_CHANNEL.
1322 See [SILC2] for more information on this.
1326 4.3 Joining to a Channel
1328 This section describes the procedure when client joins to a channel.
1329 Client may join to channel by sending command SILC_COMMAND_JOIN to the
1330 server. If the receiver receiving join command is normal server the
1331 server must check its local list whether this channel already exists
1332 locally. This would indicate that some client connected to the server
1333 has already joined to the channel. If this is case the client is
1334 joined to the client, new channel key is created and information about
1335 newly joined channel is sent to the router. The new channel key is
1336 also distributed to the router and to all clients on the channel.
1338 If the channel does not exist in the local list the command must be
1339 sent to the router which will then perform the actual joining
1340 procedure. When server receives the reply to the command from the
1341 router it must be distributed to the client who sent the command
1342 originally. Server will also receive the channel key from the server
1343 that it must distribute to the client who originally requested the
1344 join command. The server must also save the channel key.
1346 If the receiver of the join command is router it must first check its
1347 local list whether anyone in the cell has already joined to the channel.
1348 If this is the case the client is joined to the channel and reply is
1349 sent to the client. If the command was sent by server the command reply
1350 is sent to the server who sent it. Then the router must also create
1351 new channel key and distribute it to all clients on the channel and
1352 all servers that has clients on the channel.
1354 If the channel does not exist on the router's local list it must
1355 check the global list whether the channel exists at all. If it does
1356 the client is joined to the channel as described previously. If
1357 the channel does not exist the channel is created and the client
1358 is joined to the channel. The channel key is also created and
1359 distributed as previously described. The client joining to the created
1360 channel is made automatically channel founder and both channel founder
1361 and channel operator privileges is set for the client.
1363 When the router joins the client to the channel it must send
1364 information about newly joined client to all routers in the SILC
1365 network. Also, if the channel was created in the process, information
1366 about newly created channel must also be distributed to all routers.
1367 The distribution of newly created channel is done by sending packet
1368 SILC_PACKET_NEW_CHANNEL.
1370 It is important to note that new channel key is created always when
1371 new client joins to channel, whether the channel has existed previously
1372 or not. This way the new client on the channel is not able to decrypt
1373 any of the old traffic on the channel.
1375 Client who receives the reply to the join command must start using
1376 the received Channel ID in the channel message communication thereafter.
1377 However, client must not start communicating on the channel before
1378 it has received the packet SILC_PACKET_CHANNEL_KEY.
1380 If client wants to know the other clients currently on the channel
1381 the client must send SILC_COMMAND_NAMES command to receive a list of
1382 channel users. Server implementation, however, may send command reply
1383 packet to SILC_COMMAND_NAMES command after client has joined to the
1384 channel even if the client has not sent the command.
1388 4.4 Channel Key Generation
1390 Channel keys are created by router who creates the channel by taking
1391 enough randomness from cryptographically strong random number generator.
1392 The key is generated always when channel is created, when new client
1393 joins a channel and after the key has expired. Key could expire for
1396 The key must also be re-generated whenever some client leaves a channel.
1397 In this case the key is created from scratch by taking enough randomness
1398 from the random number generator. After that the key is distributed to
1399 all clients on the channel. However, channel keys are cell specific thus
1400 the key is created only on the cell where the client, who leaved the
1401 channel, exists. While the server or router is creating the new channel
1402 key, no other client may join to the channel. Messages that are sent
1403 while creating the new key are still processed with the old key. After
1404 server has sent the SILC_PACKET_CHANNEL_KEY packet must client start
1405 using the new key. If server creates the new key the server must also
1406 send the new key to its router. See [SILC2] on more information about
1407 how channel messages must be encrypted and decrypted when router is
1412 4.5 Private Message Sending and Reception
1414 Private messages are sent point to point. Client explicitly destines
1415 a private message to specific client that is delivered to only to that
1416 client. No other client may receive the private message. The receiver
1417 of the private message is destined in the SILC Packet Header as any
1418 other packet as well.
1420 If the sender of a private message does not know the receiver's Client
1421 ID, it must resolve it from server. There are two ways to resolve the
1422 client ID from server; it is recommended that client ipmlementations
1423 send SILC_COMMAND_IDENTIFY command to receive the Client ID. Client
1424 may also send SILC_COMMAND_WHOIS command to receive the Client ID.
1425 If the sender has received earlier a private message from the receiver
1426 it should have cached the Client ID from the SILC Packet Header.
1428 Receiver of a private message should not explicitly trust the nickname
1429 that it receives in the Private Message Payload, described in [SILC2].
1430 Implementations could resolve the nickname from server, as described
1431 previously, and compare the received Client ID and the SILC Packet
1432 Header's Client ID. The nickname in the payload is merely provided
1433 to be displayed for end user.
1435 See [SILC2] for describtion of private message encryption and decryption
1440 4.6 Private Message Key Generation
1442 Private message may be protected by key generated by client. The key
1443 may be generated and sent to the other client by sending packet
1444 SILC_PACKET_PRIVATE_MESSAGE_KEY which travels through the network
1445 and is secured by session keys. After that the private message key
1446 is used in the private message communication between those clients.
1447 See more information about how this works technically in [SILC2].
1449 Other choice is to entirely use keys that are not sent through
1450 the SILC network at all. This significantly adds security. This key
1451 would be pre-shared-key that is known by both of the clients. Both
1452 agree about using the key and starts sending packets that indicate
1453 that the private message is secured using private message key. This
1454 is the technical aspect mentioned previously that is described
1457 If the private message keys are not set to be used, which is the
1458 case by default in SILC, the private messages are secured by using
1459 normal session keys established by SILC Key Exchange protocol.
1465 4.7 Channel Message Sending and Reception
1467 Channel messages are delivered to group of users. The group forms a
1468 channel and all clients on the channel receives messages sent to the
1471 Channel messages are destined to channel by specifying the Channel ID
1472 as Destination ID in the SILC Packet Header. The server must then
1473 distribute the message to all clients on the channel by sending the
1474 channel message destined explicitly to a client on the channel.
1476 See [SILC2] for describtion of channel message encryption and decryption
1481 4.8 Session Key Regeneration
1483 Session keys should be regenerated peridiocally, say, once in an hour.
1484 The re-key process is started by sending SILC_PACKET_REKEY packet to
1485 other end, to indicate that re-key must be performed.
1487 If perfect forward secrecy (PFS) flag was selected in the SILC Key
1488 Exchange protocol [SILC3] the re-key must cause new key exchange with
1489 SKE protocol. In this case the protocol is secured with the old key
1490 and the protocol results to new key material. See [SILC3] for more
1491 information. After the SILC_PACKET_REKEY packet is sent the sender
1492 will perform the SKE protocol.
1494 If PFS flag was not set, which is the default case, then re-key is done
1495 without executing SKE protocol. In this case, the new key is created by
1496 hashing the old key with hash function selected earlier in the SKE
1497 protocol. If the digest length of the hash function is too short for the
1498 key, then the key is distributed as described in section Processing the
1499 Key Material in [SILC3]. After both parties has regenerated the session
1500 key, both send SILC_PACKET_REKEY_DONE packet to each other. These packets
1501 are still secured with the old key. After these packets, following
1502 packets must be protected with the new key.
1506 4.9 Command Sending and Reception
1508 Client usually sends the commands in the SILC network. In this case
1509 the client simply sends the command packet to server and the server
1510 processes it and replies with command reply packet.
1512 However, if the server is not able to process the command, it is usually
1513 sent to the server's router. This is case for example with commands such
1514 as, SILC_COMMAND_JOIN and SILC_COMMAND_WHOIS commands. However, there
1515 are other commands as well. For example, if client sends the WHOIS
1516 command requesting specific information about some client the server must
1517 send the WHOIS command to router so that all clients in SILC network
1518 are searched. The router, on the other hand, sends the WHOIS command
1519 to further to receive the exact information about the requested client.
1520 The WHOIS command travels all the way to the server who owns the client
1521 and it replies with command reply packet. Finally, the server who
1522 sent the command receives the command reply and it must be able to
1523 determine which client sent the original command. The server then
1524 sends command reply to the client. Implementations should have some
1525 kind of cache to handle, for example, WHOIS information. Servers
1526 and routers along the route could all cache the information for faster
1527 referencing in the future.
1529 The commands sent by server may be sent hop by hop until someone is able
1530 to process the command. However, it is preferred to destine the command
1531 as precisely as it is possible. In this case, other routers en route
1532 must route the command packet by checking the true sender and true
1533 destination of the packet. However, servers and routers must not route
1534 command reply packets to clients coming from other server. Client
1535 must not accept command reply packet originated from anyone else but
1536 from its own server.
1543 5.1 SILC Commands Syntax
1545 This section briefly describes the syntax of the command notions
1546 in this document. Every field in command is separated from each
1547 other by whitespaces (` ') indicating that each field is independent
1548 argument and each argument must have own Command Argument Payload.
1549 The number of maximum arguments are defined with each command
1550 separately. The Command Argument Payload is described in [SILC2].
1552 Every command defines specific number for each argument. Currently,
1553 they are defined in ascending order; first argument has number one
1554 (1), second has number two (2) and so on. This number is set into the
1555 Argument Type field in the Command Argument Payload. This makes it
1556 possible to send the arguments in free order as the number must be
1557 used to identify the type of the argument. This makes is it also
1558 possible to have multiple optional arguments in commands and in
1559 command replies. The number of argument is marked in parentheses
1560 before the actual argument.
1567 Example: Arguments: (1) <nickname> (2) <username@host>
1571 Every command replies with Status Payload. This payload tells the
1572 sender of the command whether the command was completed succefully or
1573 whether there was an error. If error occured the payload includes the
1574 error type. In the next section the Status Payload is not described
1575 as it is common to all commands and has been described here. Commands
1576 may reply with other arguments as well. These arguments are command
1577 specific and are described in the next section.
1586 Arguments: (1) <nickname>[@<server>] (2) <message>
1589 The command has maximum of 3 arguments. However, only first
1590 and second arguments are mandatory.
1592 First argument <nickname> is mandatory but may have optional
1593 <nickname@server> format as well. Second argument is mandatory
1594 <message> argument. Third argument is optional <count> argument.
1596 The numbers in parentheses are the argument specific numbers
1597 that specify the type of the argument in Command Argument Payload.
1598 The receiver always knows that, say, argument number two (2) is
1599 <message> argument, regardles of the ordering of the arguments in
1600 the Command Payload.
1602 Reply messages to the command:
1605 Arguments: (1) <Status Payload> (2) [<channel list>]
1606 (3) <idle time> (4) [<away message>]
1608 This command may reply with maximum of 4 arguments. However,
1609 only the first and third arguments are mandatory. The numbers
1610 in the parentheses have the same meaning as in the upper
1611 command sending specification.
1613 Every command reply with <Status Payload>, it is mandatory
1614 argument for all command replies and for this reason it is not
1615 described in the command reply descriptions.
1622 SILC_STATUS_ERR_TOO_MANY_TARGETS
1623 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
1624 SILC_STATUS_ERR_NO_SUCH_NICK
1626 Every command reply also defines set of status message that it
1627 may return inside the <Status Payload>. All status messages
1628 are defined in the section 5.3 SILC Command Status Types.
1633 5.2 SILC Commands List
1635 This section lists all SILC commands, however, it is expected that a
1636 implementation and especially client implementation has many more
1637 commands that has only local affect. These commands are official
1638 SILC commands that has both client and server sides and cannot be
1639 characterized as local commands.
1641 List of all defined commands in SILC follows.
1646 None. This is reserved command and must not be sent.
1649 2 SILC_COMMAND_WHOIS
1652 Arguments: (1) <nickname>[@<server>] (2) [<count>]
1654 Whois. Whois command is used to query various information about
1655 specific user. The user maybe requested by their nickname and
1656 server name. The query may find multiple matching users as
1657 there are no unique nicknames in the SILC. The <count> option
1658 maybe given to narrow down the number of accepted results. If
1659 this is not defined there are no limit of accepted results.
1660 The query may also be narrowed down by defining the server name
1663 To prevent miss-use of this service wildcards in the nickname
1664 or in the servername are not permitted. It is not allowed
1665 to request all users on some server. The WHOIS requests must
1666 be based on specific nickname request.
1668 The WHOIS request must be always forwarded to router by server
1669 so that all users are searched. However, the server still must
1670 search its locally connected clients. The server must send
1671 this command to the server who owns the requested client. That
1672 server must reply to the command.
1674 Reply messages to the command:
1677 Arguments: (1) <Status Payload> (2) <Client ID>
1678 (3) <nickname>[@<server>] (4) <username@host>
1679 (5) <real name> (6) [<channel list>]
1682 This command may reply with several command reply messages to
1683 form a list of results. In this case the status payload will
1684 include STATUS_LIST_START status in the first reply and
1685 STATUS_LIST_END in the last reply to indicate the end of the
1686 list. If there are only one reply the status is set to normal
1689 The command replies include the Client ID of the nickname,
1690 nickname and servername, username and hostnamea and users real
1691 name. Client should process these replies only after the last
1692 reply has been received with the STATUS_LIST_END status. If the
1693 <count> option were defined in the query there will be only
1694 <count> many replies from the server.
1699 SILC_STATUS_LIST_START
1700 SILC_STATUS_LIST_END
1701 SILC_STATUS_ERR_NO_SUCH_NICK
1702 SILC_STATUS_ERR_WILDCARDS
1703 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
1704 SILC_STATUS_ERR_TOO_MANY_PARAMS
1707 3 SILC_COMMAND_WHOWAS
1710 Arguments: (1) <nickname>[@<server>] (2) [<count>]
1712 Whowas. This command is used to query history information about
1713 specific user. The user maybe requested by their nickname and
1714 server name. The query may find multiple matching users as there
1715 are no unique nicknames in the SILC. The <count> option maybe
1716 given to narrow down the number of accepted results. If this
1717 is not defined there are no limit of accepted results. The query
1718 may also be narrowed down by defining the server name of the
1721 To prevent miss-use of this service wildcards in the nickname
1722 or in the servername are not permitted. The WHOWAS requests must
1723 be based on specific nickname request.
1725 The WHOWAS request must be always forwarded to router by server
1726 so that all users are searched. However, the server still must
1727 search its locally connected clients.
1729 Reply messages to the command:
1732 Arguments: (1) <Status Payload> (2) <nickname>[@<server>]
1735 This command may reply with several command reply messages to form
1736 a list of results. In this case the status payload will include
1737 STATUS_LIST_START status in the first reply and STATUS_LIST_END in
1738 the last reply to indicate the end of the list. If there are only
1739 one reply the status is set to normal STATUS_OK.
1741 The command replies with nickname and username and hostname.
1742 Every server must keep history for some period of time of its
1743 locally connected clients.
1748 SILC_STATUS_LIST_START
1749 SILC_STATUS_LIST_END
1750 SILC_STATUS_ERR_NO_SUCH_NICK
1751 SILC_STATUS_ERR_WILDCARDS
1752 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
1753 SILC_STATUS_ERR_TOO_MANY_PARAMS
1756 4 SILC_COMMAND_IDENTIFY
1759 Arguments: (1) <nickname>[@<server>] (2) [<count>]
1761 Identify. Identify command is almost analogous to WHOIS command,
1762 except that it does not return as much information. Only relevant
1763 information such as Client ID is returned. This is usually used
1764 to get the Client ID of a client used in the communication with
1767 The query may find multiple matching users as there are no unique
1768 nicknames in the SILC. The <count> option maybe given to narrow
1769 down the number of accepted results. If this is not defined there
1770 are no limit of accepted results. The query may also be narrowed
1771 down by defining the server name of the nickname.
1773 To prevent miss-use of this service wildcards in the nickname
1774 or in the servername are not permitted. It is not allowed
1775 to request all users on some server. The IDENTIFY requests must
1776 be based on specific nickname request.
1778 Implementations may not want to give interface access to this
1779 commands as it is hardly a command that would be used a end user.
1780 However, it must be implemented as it is used with private message
1783 The IDENTIFY must be always forwarded to router by server so that
1784 all users are searched. However, server must still search its
1785 locally connected clients.
1787 Reply messages to the command:
1790 Arguments: (1) <Status Payload> (2) <Client ID>
1791 (3) [<nickname>[@<server>]] (4) [<username@host>]
1793 This command may reply with several command reply messages to form
1794 a list of results. In this case the status payload will include
1795 STATUS_LIST_START status in the first reply and STATUS_LIST_END in
1796 the last reply to indicate the end of the list. If there are only
1797 one reply the status is set to normal STATUS_OK.
1799 The command replies with Client ID of the nickname and if more
1800 information is available it may reply with nickname and username
1801 and hostname. If the <count> option were defined in the query
1802 there will be only <count> many replies from the server.
1807 SILC_STATUS_LIST_START
1808 SILC_STATUS_LIST_END
1809 SILC_STATUS_ERR_NO_SUCH_NICK
1810 SILC_STATUS_ERR_WILDCARDS
1811 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
1812 SILC_STATUS_ERR_TOO_MANY_PARAMS
1818 Arguments: (1) <nickname>
1820 Set/change nickname. This command is used to set nickname for
1821 user. There is no limit of the length of the nickname in SILC.
1822 Nickname must not include any spaces (` '), non-printable
1823 characters, commas (`,') and any wildcard characters. Note:
1824 nicknames in SILC are case-sensitive which must be taken into
1825 account when searching clients by nickname.
1827 Reply messages to the command:
1830 Arguments: (1) <Status Payload> (2) <New ID Payload>
1832 This command is replied always with New ID Payload that is
1833 generated by the server every time user changes their nickname.
1834 Client receiving this payload must start using the received
1835 Client ID as its current valid Client ID. The New ID Payload
1836 is described in [SILC2].
1841 SILC_STATUS_ERR_WILDCARDS
1842 SILC_STATUS_ERR_NICKNAME_IN_USE
1843 SILC_STATUS_ERR_BAD_NICKNAME
1844 SILC_STATUS_ERR_NOT_REGISTERED
1845 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
1846 SILC_STATUS_ERR_TOO_MANY_PARAMS
1852 Arguments: (1) [<Channel ID>] [<server>]
1854 The list command is used to list channels and their topics on
1855 current server. If the <Channel ID> parameter is used, only the
1856 status of that channel is displayed. Secret channels are not
1857 listed at all. Private channels are listed with status indicating
1858 that the channel is private.
1860 If the <server> argument is specified the specified server's
1861 channels are listed. In this case the command must be sent to
1862 the server who owns the channel that was requested.
1864 Reply messages to the command:
1867 Arguments: (1) <Status Payload> (2) <channel>
1870 This command may reply with several command reply messages to form
1871 a list of results. In this case the status payload will include
1872 STATUS_LIST_START status in the first reply and STATUS_LIST_END in
1873 the last reply to indicate the end of the list. If there are only
1874 one reply the status is set to normal STATUS_OK.
1876 This command replies with channel name and the topic of the
1877 channel. If the channel is private channel the <topic> includes
1883 SILC_STATUS_LIST_START
1884 SILC_STATUS_LIST_END
1885 SILC_STATUS_ERR_WILDCARDS
1886 SILC_STATUS_ERR_NOT_REGISTERED
1887 SILC_STATUS_ERR_TOO_MANY_PARAMS
1888 SILC_STATUS_ERR_NO_SUCH_CHANNEL
1889 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
1890 SILC_STATUS_ERR_NO_SUCH_SERVER
1893 7 SILC_COMMAND_TOPIC
1896 Arguments: (1) <Channel ID> (2) [<server>]]
1898 This command is used to change or view the topic of a channel.
1899 The topic for channel <Channel ID> is returned if there is no
1900 <topic> given. If the <topic> parameter is present, the topic
1901 for that channel will be changed, if the channel modes permit
1904 Reply messages to the command:
1907 Arguments: (1) <Status Payload> (2) [<topic>]
1909 The command may reply with the topic of the channel if it is
1915 SILC_STATUS_ERR_NOT_ON_CHANNEL
1916 SILC_STATUS_ERR_WILDCARDS
1917 SILC_STATUS_ERR_NOT_REGISTERED
1918 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
1919 SILC_STATUS_ERR_NO_SUCH_CHANNEL
1920 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
1921 SILC_STATUS_ERR_NO_CHANNEL_ID
1922 SILC_STATUS_ERR_BAD_CHANNEL_ID
1923 SILC_STATUS_ERR_TOO_MANY_PARAMS
1924 SILC_STATUS_ERR_NO_CHANNEL_PRIV
1927 8 SILC_COMMAND_INVITE
1930 Arguments: (1) <Client ID> (2) <channel>
1932 This command is used to invite other clients to join to the
1933 channel. There is no requirement that the channel the target
1934 client is being invited to must exist or be a valid channel.
1935 The <Client ID> argument is the target client's ID that is being
1938 Reply messages to the command:
1942 Arguments: (1) <Status Payload>
1944 This command replies only with Status Payload.
1949 SILC_STATUS_ERR_NOT_ON_CHANNEL
1950 SILC_STATUS_ERR_WILDCARDS
1951 SILC_STATUS_ERR_NOT_REGISTERED
1952 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
1953 SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
1954 SILC_STATUS_ERR_TOO_MANY_PARAMS
1955 SILC_STATUS_ERR_NO_RECIPIENT
1956 SILC_STATUS_ERR_USER_ON_CHANNEL
1957 SILC_STATUS_ERR_NO_CLIENT_ID
1963 Arguments: (1) [<quit message>]
1965 This command is used by client to end SILC session. The server
1966 must close the connection to a client which sends this command.
1967 if <quit message> is given it will be sent to other clients on
1968 channel if the client is on channel when quitting.
1970 Reply messages to the command:
1972 This command does not reply anything.
1975 10 SILC_COMMAND_KILL
1978 Arguments: (1) <Client ID> (2) [<comment>]
1980 This command is used by SILC operators to remove a client from
1981 SILC network. The removing has temporary effects and client may
1982 reconnect to SILC network. The <Client ID> is the client to be
1983 removed from SILC. The <comment> argument may be provided to
1984 give to the removed client some information why it was removed
1987 Reply messages to the command:
1990 Arguments: (1) <Status Payload>
1992 This command replies only with Status Payload.
1997 SILC_STATUS_ERR_WILDCARDS
1998 SILC_STATUS_ERR_NOT_REGISTERED
1999 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2000 SILC_STATUS_ERR_TOO_MANY_PARAMS
2001 SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
2002 SILC_STATUS_ERR_NO_CLIENT_ID
2008 11 SILC_COMMAND_INFO
2011 Arguments: (1) [<server>]
2013 This command is used to fetch various information about a server.
2014 If <server> argument is specified the command must be sent to
2015 the requested server.
2017 Reply messages to the command:
2020 Arguments: (1) <Status Payload> (2) <Server ID>
2023 This command replies with the Server ID of the server and a
2024 string which tells the information about the server.
2029 SILC_STATUS_ERR_WILDCARDS
2030 SILC_STATUS_ERR_NOT_REGISTERED
2031 SILC_STATUS_ERR_TOO_MANY_PARAMS
2032 SILC_STATUS_ERR_NO_SUCH_SERVER_ID
2033 SILC_STATUS_ERR_NO_SUCH_SERVER
2036 12 SILC_COMMAND_CONNECT
2039 Arguments: (1) <Server ID>
2040 (2) [<remote server/router>[:<port>]]
2042 This command is used by operators to force a server to try to
2043 establish a new connection to another router (if the connecting
2044 server is normal server) or server (if the conneceting server is
2045 router server). Operator may specify the server/router to be
2046 connected by setting <remote server> argument.
2048 Reply messages to the command:
2051 Arguments: (1) <Status Payload>
2053 This command replies only with Status Payload.
2060 SILC_STATUS_ERR_WILDCARDS
2061 SILC_STATUS_ERR_NOT_REGISTERED
2062 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2063 SILC_STATUS_ERR_TOO_MANY_PARAMS
2064 SILC_STATUS_ERR_NO_SUCH_SERVER_ID
2065 SILC_STATUS_ERR_NO_SERVER_PRIV
2066 SILC_STATUS_ERR_NO_ROUTER_PRIV
2069 13 SILC_COMMAND_PING
2072 Arguments: (1) <Server ID>
2074 This command is used by clients to test the communication
2075 channel to its server if client suspects that the communication
2076 is not working correctly. The <Server ID> is the ID of the
2077 server the client is connected to.
2079 Reply messages to the command:
2082 Arguments: (1) <Status Payload>
2084 This command replies only with Status Payload. Server returns
2085 SILC_STATUS_OK in Status Payload if pinging was successful.
2090 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2091 SILC_STATUS_ERR_TOO_MANY_PARAMS
2092 SILC_STATUS_ERR_NO_SUCH_SERVER_ID
2093 SILC_STATUS_ERR_NOT_REGISTERED
2096 14 SILC_COMMAND_OPER
2099 Arguments: (1) <username> (2) <authentication data>
2101 This command is used by normal client to obtain server operator
2102 privileges on some server or router. Note that router operator
2103 has router privileges that supersedes the server operator
2104 privileges and this does not obtain those privileges. Client
2105 must use SILCOPER command to obtain router level privileges.
2107 The <username> is the username set in the server configurations
2108 as operator. The <authentication data> is the data that the
2109 client is authenticated against. It may be passphrase prompted
2110 for user on client's screen or it may be public key
2111 authentication data (data signed with private key), or
2114 Reply messages to the command:
2117 Arguments: (1) <Status Payload>
2119 This command replies only with Status Payload.
2124 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2125 SILC_STATUS_ERR_TOO_MANY_PARAMS
2126 SILC_STATUS_ERR_NOT_REGISTERED
2127 SILC_STATUS_ERR_BAD_PASSWORD
2128 SILC_STATUS_ERR_AUTH_FAILED
2131 15 SILC_COMMAND_JOIN
2134 Arguments: (1) <channel> (2) [<passphrase>]
2137 Join to channel/create new channel. This command is used to
2138 join to a channel. If the channel does not exist the channel is
2139 created on the server receiving the join request. The channel
2140 may be protected with passphrase. If this is the case the
2141 passphrase must be sent along the join command.
2143 The name of the <channel> must not include any spaces (` '),
2144 non-printable characters, commas (`,') or any wildcard characters.
2146 Cipher to be used to secure the traffic on the channel may be
2147 requested by sending the name of the requested <cipher>. This
2148 is used only if the channel does not exist and is created. If
2149 the channel already exists the cipher set previously for the
2150 channel will be used to secure the traffic.
2152 The server must check whether the user is allowed to join to
2153 the requested channel. Various modes set to the channel affect
2154 the ability of the user to join the channel. These conditions
2157 o The user must be invited to the channel if the channel
2158 is invite-only channel.
2160 o The Client ID/nickname/username/hostname must not match
2163 o The correct passphrase must be provided if passphrase
2164 is set to the channel.
2166 o The user count limit, if set, must not be reached.
2168 Reply messages to the command:
2171 Arguments: (1) <Status Payload> (2) <channel>
2172 (3) <Channel ID> (4) <channel mode mask>
2175 This command replies with the channel name requested by the
2176 client, channel ID of the channel and topic of the channel
2177 if it exists. It also replies with the channel mode mask
2178 which tells all the modes set on the channel. If the
2179 channel is created the mode mask is zero (0).
2181 Client must not start transmitting to the channel even after
2182 server has replied to this command. Client is permitted to
2183 start transmitting on channel after server has sent packet
2184 SILC_PACKET_CHANNEL_KEY to the client.
2189 SILC_STATUS_ERR_WILDCARDS
2190 SILC_STATUS_ERR_NOT_REGISTERED
2191 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2192 SILC_STATUS_ERR_TOO_MANY_PARAMS
2193 SILC_STATUS_ERR_BAD_PASSWORD
2194 SILC_STATUS_ERR_CHANNEL_IS_FULL
2195 SILC_STATUS_ERR_NOT_INVITED
2196 SILC_STATUS_ERR_BANNED_FROM_CHANNEL
2197 SILC_STATUS_ERR_BAD_CHANNEL
2198 SILC_STATUS_ERR_USER_ON_CHANNEL
2201 16 SILC_COMMAND_MOTD
2204 Arguments: (1) <server>
2206 This command is used to query the Message of the Day of a server.
2208 Reply messages to the command:
2211 Arguments: (1) <Status Payload> (2) [<motd>]
2213 This command replies with the motd message if it exists.
2218 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2219 SILC_STATUS_ERR_TOO_MANY_PARAMS
2220 SILC_STATUS_ERR_NOT_REGISTERED
2221 SILC_STATUS_ERR_NO_SUCH_SERVER
2224 17 SILC_COMMAND_UMODE
2227 Arguments: (1) <Client ID> (2) <client mode mask>
2229 This command is used by client to set/unset modes for itself.
2230 However, there are some modes that the client may not set itself,
2231 but they will be set by server. However, client may unset any
2232 mode. Modes may be masked together ORing them thus having
2233 several modes set. Client must keep its client mode mask
2234 locally so that the mode setting/unsetting would work without
2235 problems. Client may change only its own modes.
2237 Following client modes are defined:
2239 0x0000 SILC_UMODE_NONE
2241 No specific mode for client. This is the initial
2242 setting when new client is created. The client is
2246 0x0001 SILC_UMODE_SERVER_OPERATOR
2248 Marks the user as server operator. Client cannot
2249 set this mode itself. Server sets this mode to the
2250 client when client attains the server operator
2251 privileges by SILC_COMMAND_OPER command. Client
2252 may unset the mode itself.
2255 0x0002 SILC_UMODE_ROUTER_OPERATOR
2257 Marks the user as router (SILC) operator. Client
2258 cannot this mode itself. Router sets this mode to
2259 the client when client attains the router operator
2260 privileges by SILC_COMMAND_SILCOPER command. Client
2261 may unset the mode itself.
2263 Reply messages to the command:
2266 Arguments: (1) <Status Payload> (2) <client mode mask>
2268 This command replies with the changed client mode mask that
2269 the client is required to keep locally.
2275 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2276 SILC_STATUS_ERR_TOO_MANY_PARAMS
2277 SILC_STATUS_ERR_NOT_REGISTERED
2278 SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
2279 SILC_STATUS_ERR_BAD_CLIENT_ID
2280 SILC_STATUS_ERR_NOT_YOU
2281 SILC_STATUS_ERR_UNKNOWN_MODE
2282 SILC_STATUS_ERR_NO_RECIPIENT
2283 SILC_STATUS_ERR_NO_CLIENT_ID
2286 18 SILC_COMMAND_CMODE
2289 Arguments: (1) <Channel ID> (2) <channel mode mask>
2290 (3) [<user limit>] (4) [<passphrase>]
2291 (5) [<Client ID>] (6) [<cipher>[:<key len>]]
2293 This command is used by client to set or change channel flags on
2294 a channel. Channel has several modes that set various properties
2295 of a channel. Modes may be masked together by ORing them thus
2296 having several modes set. The <Channel ID> is the ID of the
2297 target channel. The client changing channel mode must be on
2298 the same channel and poses sufficient privileges to be able to
2301 Following channel modes are defined:
2303 0x0000 SILC_CMODE_NONE
2305 No specific mode on channel. This is the default when
2306 channel is created. This means that channel is just plain
2310 0x0001 SILC_CMODE_PRIVATE
2312 Channel is private channel. Private channels are shown
2313 in the channel list listed with SILC_COMMAND_LIST command
2314 with indicatioin that the channel is private. Also,
2315 client on private channel will no be detected to be on
2316 the channel as the channel is not shown in the client's
2317 currently joined channel list. Channel founder and
2318 channel operator may set/unset this mode.
2320 Typical implementation would use [+|-]p on user interface
2321 to set/unset this mode.
2324 0x0002 SILC_CMODE_SECRET
2326 Channel is secret channel. Secret channels are not shown
2327 in the list listed with SILC_COMMAND_LIST command. Secret
2328 channels can be considered to be invisible channels.
2329 Channel founder and channel operator may set/unset this
2332 Typical implementation would use [+|-]s on user interface
2333 to set/unset this mode.
2336 0x0004 SILC_CMODE_PRIVKEY
2338 Channel uses private channel key to protect the traffic
2339 on the channel. When this mode is set the client will be
2340 responsible to set the key it wants to use to encrypt and
2341 decrypt the traffic on channel. Server generated channel
2342 keys are not used at all. This mode provides additional
2343 security as clients on channel may agree to use private
2344 channel key that even servers do not know. Naturally,
2345 this requires that every client on the channel knows
2346 the key before hand (it is considered to be pre-shared-
2347 key). This specification does not define how the private
2348 channel key is set as it is entirely local setting on
2351 As it is local setting it is possible to have several
2352 private channel keys on one channel. In this case several
2353 clients can talk on same channel but only those clients
2354 that share the key with the message sender will be able
2355 to hear the talking. Client should not display those
2356 message for the end user that it is not able to decrypt
2357 when this mode is set.
2359 Only channel founder may set/unset this mode. If this
2360 mode is unset the server will distribute new channel
2361 key to all clients on the channel which will be used
2364 Typical implementation would use [+|-]k on user interface
2365 to set/unset this mode.
2368 0x0008 SILC_CMODE_INVITE
2370 Channel is invite only channel. Client may join to this
2371 channel only if it is invited to the channel. Channel
2372 founder and channel operator may set/unset this mode.
2374 Typical implementation would use [+|-]i on user interface
2375 to set/unset this mode.
2378 0x0010 SILC_CMODE_TOPIC
2380 The topic of the channel may only be set by client that
2381 is channel founder or channel operator. Normal clients
2382 on channel will not be able to set topic when this mode
2383 is set. Channel founder and channel operator may set/
2386 Typical implementation would use [+|-]t on user interface
2387 to set/unset this mode.
2390 0x0020 SILC_CMODE_ULIMIT
2392 User limit has been set to the channel. New clients
2393 may not join to the channel when the limit set is
2394 reached. Channel founder and channel operator may set/
2395 unset the limit. The <user limit> argument is the
2396 number of limited users.
2398 Typical implementation would use [+|-]l on user interface
2399 to set/unset this mode.
2402 0x0040 SILC_CMODE_PASSPHRASE
2404 Passphrase has been set to the channel. Client may
2405 join to the channel only if it is able to provide the
2406 correct passphrase. Setting passphrases to channel
2407 is entirely safe as all commands are protected in the
2408 SILC network. Only channel founder may set/unset
2409 the passphrase. The <passphrase> argument is the
2412 Typical implementation would use [+|-]a on user interface
2413 to set/unset this mode.
2416 0x0080 SILC_CMODE_BAN
2418 Ban mask has been set to the channel. The ban mask
2419 may be used to ban specific clients to join the channel.
2420 The <ban mask> argument is the set ban mask. When
2421 unsetting a ban mask the mask must be provided as
2422 argument. Channel founder and channel operator may
2423 set/unset this mode. Channel founder may not be
2424 added to the ban list.
2426 Typical implementation would use [+|-]b on user interface
2427 to set/unset this mode.
2430 0x0100 SILC_CMODE_OPERATOR
2432 Sets channel operator privileges on the channel for a
2433 client on the channel. The <Client ID> argument is the
2434 target client on the channel. Channel founder and
2435 channel operator may set/unset (promote/demote) this
2438 Typical implementation would use [+|-]o on user interface
2439 to set/unset this mode.
2442 0x0200 SILC_CMODE_CIPHER
2444 Sets specific cipher to be used to protect channel
2445 traffic. The <cipher> argument is the requested cipher.
2446 When set or unset the server must re-generate new
2447 channel key. If <key len> argument is specified with
2448 <cipher> argument the new key is generated of <key len>
2451 Typical implementation would use [+|-]c on user interface
2452 to set/unset this mode.
2455 To make the mode system work, client must keep the channel mode
2456 mask locally so that the mode setting and unsetting would work
2457 without problems. The client receives the initial channel mode
2458 mask when it joins to the channel. When the mode changes on
2459 channel the server distributes the changed channel mode mask to
2460 all clients on the channel by sending SILC_COMMAND_CMODE command
2464 Reply messages to the command:
2467 Arguments: (1) <Status Payload> (2) <channel mode mask>
2469 This command replies with the changed channel mode mask that
2470 client is required to keep locally. The same mask is also
2471 sent to all clients on channel by sending additional command
2477 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2478 SILC_STATUS_ERR_TOO_MANY_PARAMS
2479 SILC_STATUS_ERR_NOT_REGISTERED
2480 SILC_STATUS_ERR_NOT_ON_CHANNEL
2481 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
2482 SILC_STATUS_ERR_BAD_CHANNEL_ID
2483 SILC_STATUS_ERR_NO_CHANNEL_ID
2484 SILC_STATUS_ERR_NO_CHANNEL_PRIV
2485 SILC_STATUS_ERR_UNKNOWN_MODE
2486 SILC_STATUS_ERR_NO_CLIENT_ID
2491 19 SILC_COMMAND_KICK
2494 Arguments: (1) <channel> (2) <Client ID>
2497 This command is used by channel operators to remove a client from
2498 channel. The <channel> argument is the channel the client to be
2499 removed is on currently. Note that the "kicker" must be on the same
2500 channel. If <comment> is provided it will be sent to the removed
2503 Reply messages to the command:
2506 Arguments: (1) <Status Payload>
2508 This command replies only with Status Payload.
2513 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2514 SILC_STATUS_ERR_TOO_MANY_PARAMS
2515 SILC_STATUS_ERR_NOT_REGISTERED
2516 SILC_STATUS_ERR_NO_SUCH_CHANNEL
2517 SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
2518 SILC_STATUS_ERR_NO_CHANNEL_PRIV
2519 SILC_STATUS_ERR_NO_CLIENT_ID
2522 20 SILC_COMMAND_RESTART
2527 This command may only be used by server operator to force a
2528 server to restart itself.
2530 Reply messages to the command:
2533 Arguments: (1) <Status Payload>
2535 This command replies only with Status Payload.
2542 SILC_STATUS_ERR_NOT_REGISTERED
2543 SILC_STATUS_ERR_NO_SERVER_PRIV
2546 21 SILC_COMMAND_CLOSE
2549 Arguments: (1) <Server ID>
2551 This command is used only by operator to close connection to a
2552 remote site. The <Server ID> argument is the ID of the remote
2553 site and must be valid.
2555 Reply messages to the command:
2558 Arguments: (1) <Status Payload>
2560 This command replies only with Status Payload.
2567 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2568 SILC_STATUS_ERR_TOO_MANY_PARAMS
2569 SILC_STATUS_ERR_NOT_REGISTERED
2570 SILC_STATUS_ERR_NO_SUCH_SERVER
2571 SILC_STATUS_ERR_NO_SERVER_PRIV
2572 SILC_STATUS_ERR_NO_SUCH_SERVER_ID
2580 This command is used only by operator to shutdown the server.
2581 All connections to the server will be closed and the server is
2584 Reply messages to the command:
2589 Arguments: (1) <Status Payload>
2591 This command replies only with Status Payload.
2596 SILC_STATUS_ERR_NOT_REGISTERED
2597 SILC_STATUS_ERR_NO_SERVER_PRIV
2600 23 SILC_COMMAND_SILCOPER
2603 Arguments: (1) <username> (2) <authentication data>
2605 This command is used by normal client to obtain router operator
2606 privileges (also known as SILC operator) on some router. Note
2607 that router operator has router privileges that supersedes the
2608 server operator privileges.
2610 The <username> is the username set in the server configurations
2611 as operator. The <authentication data> is the data that the
2612 client is authenticated against. It may be passphrase prompted
2613 for user on client's screen or it may be public key
2614 authentication data (data signed with private key), or
2617 Difference between router operator and server operator is that
2618 router operator is able to handle cell level properties while
2619 server operator (even on router server) is able to handle only
2620 local properties, such as, local connections and normal server
2623 Reply messages to the command:
2626 Arguments: (1) <Status Payload>
2628 This command replies only with Status Payload.
2633 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2634 SILC_STATUS_ERR_TOO_MANY_PARAMS
2635 SILC_STATUS_ERR_NOT_REGISTERED
2636 SILC_STATUS_ERR_BAD_PASSWORD
2637 SILC_STATUS_ERR_AUTH_FAILED
2640 24 SILC_COMMAND_LEAVE
2643 Arguments: (1) <Channel ID>
2645 This command is used by client to leave a channel the client is
2646 joined to. After a client has leaved the channel the server
2647 must create new key for the channel and distribute to all clients
2648 still currently on the channel.
2650 Reply messages to the command:
2653 Arguments: (1) <Status Payload>
2655 This command replies only with Status Payload.
2660 SILC_STATUS_ERR_NOT_REGISTERED
2661 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2662 SILC_STATUS_ERR_TOO_MANY_PARAMS
2663 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
2664 SILC_STATUS_ERR_BAD_CHANNEL_ID
2665 SILC_STATUS_ERR_NO_CHANNEL_ID
2668 25 SILC_COMMAND_NAMES
2671 Arguments: (1) <Channel ID>
2673 This command is used to list user names currently on the requested
2674 channel; argument <Channel ID>. The server must resolve the
2675 user names and send a comma (`,') separated list of user names
2676 on the channel. Server or router may resolve the names by sending
2677 SILC_COMMAND_WHOIS commands.
2679 If the requested channel is a private or secret channel, this
2680 command must not send the list of users, as private and secret
2681 channels cannot be seen by outside. In this case the returned
2682 name list may include a indication that the server could not
2683 resolve the names of the users on the channel.
2685 Reply messages to the command:
2688 Arguments: (1) <Status Payload> (2) <name list>
2690 This command replies with the comma separated list of users on
2696 SILC_STATUS_ERR_NOT_REGISTERED
2697 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2698 SILC_STATUS_ERR_TOO_MANY_PARAMS
2699 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
2700 SILC_STATUS_ERR_BAD_CHANNEL_ID
2701 SILC_STATUS_ERR_NO_CHANNEL_ID
2702 SILC_STATUS_ERR_NOT_ON_CHANNEL
2707 Currently undefined commands.
2710 255 SILC_COMMAND_MAX
2712 Reserved command. This must not be sent.
2717 5.3 SILC Command Status Types
2720 5.3.1 SILC Command Status Payload
2722 Command Status Payload is sent in command reply messages to indicate
2723 the status of the command. The payload is one of argument in the
2724 command thus this is the data area in Command Argument Payload described
2725 in [SILC2]. The payload is only 2 bytes of length. Following diagram
2726 represents the Command Status Payload (field is always in MSB order).
2732 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
2733 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2735 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2739 Figure 5: SILC Command Status Payload
2743 o Status Message (2 bytes) - Indicates the status message.
2744 All Status messages are described in the next section.
2749 5.3.2 SILC Command Status List
2751 Command Status messages are returned in the command reply messages
2752 to indicate whether the command were executed without errors. If error
2753 has occured the status tells which error occured. Status payload only
2754 sends numeric reply about the status. Receiver of the payload must
2755 convert the numeric values into human readable error messages. The
2756 list of status messages below has an example human readable error
2757 messages that client may display for the user.
2759 List of all defined command status messages following.
2762 Generic status messages:
2766 Ok status. Everything went Ok. The status payload maybe
2767 safely ignored in this case.
2769 1 SILC_STATUS_LIST_START
2771 Start of the list. There will be several command replies and
2772 this reply is the start of the list.
2774 2 SILC_STATUS_LIST_END
2776 End of the list. There were several command replies and this
2777 reply is the last of the list. There won't be other replies
2778 beloning to this list after this one.
2782 Currently undefined and has been reserved for the future.
2785 Error status message:
2787 10 SILC_STATUS_ERR_NO_SUCH_NICK
2789 "No such nickname". Requested nickname does not exist.
2791 11 SILC_STATUS_ERR_NO_SUCH_CHANNEL
2793 "No such channel". Requested channel name does not exist.
2795 12 SILC_STATUS_ERR_NO_SUCH_SERVER
2797 "No such server". Requested server name does not exist.
2799 13 SILC_STATUS_ERR_TOO_MANY_TARGETS
2801 "Duplicate recipients. No message delivered". Message were
2802 tried to be sent to recipient which has several occurrences in
2805 14 SILC_STATUS_ERR_NO_RECIPIENT
2807 "No recipient given". Command required recipient which was
2810 15 SILC_STATUS_ERR_UNKNOWN_COMMAND
2812 "Unknown command". Command sent to server is unknown by the
2815 16 SILC_STATUS_ERR_WILDCARDS
2817 "Wildcards cannot be used". Wildcards were provided but they
2820 17 SILC_STATUS_ERR_NO_CLIENT_ID
2822 "No Client ID given". Client ID were expected as command
2823 parameter but were not found.
2825 18 SILC_STATUS_ERR_NO_CHANNEL_ID
2827 "No Channel ID given". Channel ID were expected as command
2828 parameter but were not found.
2830 19 SILC_STATUS_ERR_BAD_CLIENT_ID
2832 "Bad Client ID". Client ID provided were erroneous.
2834 20 SILC_STATUS_ERR_BAD_CHANNEL_ID
2836 "Bad Channel ID". Channel ID provided were erroneous.
2838 21 SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
2840 "No such Client ID". Client ID provided does not exist.
2843 22 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
2845 "No such Channel ID". Channel ID provided does not exist.
2847 23 SILC_STATUS_ERR_NICKNAME_IN_USE
2849 "Nickname already exists". Nickname created could not be
2850 registered because number of same nicknames were already set to
2851 maximum. This is not expected to happen in real life but is
2854 24 SILC_STATUS_ERR_NOT_ON_CHANNEL
2856 "You are not on that channel". The command were specified for
2857 client user is not currently on.
2859 25 SILC_STATUS_ERR_USER_ON_CHANNEL
2861 "User already on channel". User were invited on channel they
2864 26 SILC_STATUS_ERR_NOT_REGISTERED
2866 "You have not registered". User executed command that requires
2867 the client to be registered on the server before it may be
2870 27 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2872 "Not enough parameters". Command requires more parameters
2875 28 SILC_STATUS_ERR_TOO_MANY_PARAMS
2877 "Too many parameters". Too many parameters were provided
2880 29 SILC_STATUS_ERR_PERM_DENIED
2882 "Your host is not among the privileged". The client tried to
2883 register on server that does not allow this host to connect.
2885 30 SILC_STATUS_ERR_BANNED_FROM_SERVER
2887 "You are banned from this server". The client tried to register
2888 on server that has explicitly denied this host to connect.
2892 31 SILC_STATUS_ERR_BAD_PASSWORD
2894 "Cannot join channel. Incorrect password". Password provided for
2895 channel were not accepted.
2897 32 SILC_STATUS_ERR_CHANNEL_IS_FULL
2899 "Cannot join channel. Channel is full". The channel is full
2900 and client cannot be joined to it.
2902 33 SILC_STATUS_ERR_NOT_INVITED
2904 "Cannot join channel. You have not been invited". The channel
2905 is invite only channel and client has not been invited.
2907 34 SILC_STATUS_ERR_BANNED_FROM_CHANNEL
2909 "Cannot join channel. You have been banned". The client has
2910 been banned from the channel.
2912 35 SILC_STATUS_ERR_UNKNOWN_MODE
2914 "Unknown mode". Mode provided by the client were unknown to
2917 36 SILC_STATUS_ERR_NOT_YOU
2919 "Cannot change mode for other users". User tried to change
2920 someone else's mode.
2922 37 SILC_STATUS_ERR_NO_CHANNEL_PRIV
2924 "Permission denied. You are not channel operator". Command may
2925 be executed only by channel operator.
2927 38 SILC_STATUS_ERR_NO_SERVER_PRIV
2929 "Permission denied. You are not server operator". Command may
2930 be executed only by server operator.
2932 39 SILC_STATUS_ERR_NO_ROUTER_PRIV
2934 "Permission denied. You are not SILC operator". Command may be
2935 executed only by router (SILC) operator.
2937 40 SILC_STATUS_ERR_BAD_NICKNAME
2939 "Bad nickname". Nickname requested contained illegal characters
2942 41 SILC_STATUS_ERR_BAD_CHANNEL
2944 "Bad channel name". Channel requested contained illegal characters
2947 42 SILC_STATUS_ERR_AUTH_FAILED
2949 "Authentication failed". The authentication data sent as
2950 argument were wrong and thus authentication failed.
2955 6 Security Considerations
2957 Security is central to the design of this protocol, and these security
2958 considerations permeate the specification.
2967 [SILC2] Riikonen, P., "SILC Packet Protocol", Internet Draft,
2970 [SILC3] Riikonen, P., "SILC Key Exchange and Authentication
2971 Protocols", Internet Draft, June 2000.
2973 [IRC] Oikarinen, J., and Reed D., "Internet Relay Chat Protocol",
2976 [SSH-TRANS] Ylonen, T., et al, "SSH Transport Layer Protocol",
2979 [PGP] Callas, J., et al, "OpenPGP Message Format", RFC 2440,
2982 [SPKI] Ellison C., et al, "SPKI Certificate Theory", RFC 2693,
2985 [PKIX-Part1] Housley, R., et al, "Internet X.509 Public Key
2986 Infrastructure, Certificate and CRL Profile", RFC 2459,
2989 [Schneier] Schneier, B., "Applied Cryptography Second Edition",
2990 John Wiley & Sons, New York, NY, 1996.
2992 [Menezes] Menezes, A., et al, "Handbook of Applied Cryptography",
2995 [OAKLEY] Orman, H., "The OAKLEY Key Determination Protocol",
2996 RFC 2412, November 1998.
2998 [ISAKMP] Maughan D., et al, "Internet Security Association and
2999 Key Management Protocol (ISAKMP)", RFC 2408, November
3002 [IKE] Harkins D., and Carrel D., "The Internet Key Exhange
3003 (IKE)", RFC 2409, November 1998.
3005 [HMAC] Krawczyk, H., "HMAC: Keyed-Hashing for Message
3006 Authentication", RFC 2104, February 1997.
3019 EMail: priikone@poseidon.pspt.fi
3021 This Internet-Draft expires 28 Jan 2001