7 Network Working Group P. Riikonen
9 draft-riikonen-silc-spec-00.txt 28 June 2000
13 Secure Internet Live Conferencing (SILC),
14 Protocol Specification
18 This document is an Internet-Draft. Internet-Drafts are working
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35 The distribution of this memo is unlimited.
40 This memo describes a Secure Internet Live Conferencing (SILC)
41 protocol which provides secure conferencing services over insecure
42 network channel. SILC is IRC [IRC] like protocol, however, it is
43 not equivalent to IRC and does not support IRC. Strong cryptographic
44 methods are used to protect SILC packets inside SILC network. Two
45 other Internet Drafts relates very closely to this memo; SILC Packet
46 Protocol [SILC2] and SILC Key Exchange and Authentication Protocols
60 Internet Draft Secure Internet Live Conferencing 28 June 2000
65 1 Introduction .................................................. 3
66 2 SILC Concepts ................................................. 3
67 2.1 SILC Network Topology ..................................... 4
68 2.2 Communication Inside a Cell ............................... 5
69 2.3 Communication in the Network .............................. 6
70 2.4 Channel Communication ..................................... 7
71 3 SILC Specification ............................................ 7
72 3.1 Client .................................................... 7
73 3.1.1 Client ID ........................................... 8
74 3.2 Server .................................................... 8
75 3.2.1 Server's Local ID List .............................. 9
76 3.2.2 Server ID ........................................... 10
77 3.2.3 SILC Server Ports ................................... 10
78 3.3 Router .................................................... 11
79 3.3.1 Router's Local ID List .............................. 11
80 3.3.2 Router's Global ID List ............................. 12
81 3.3.3 Router's Server ID .................................. 12
82 3.4 Channels .................................................. 12
83 3.4.1 Channel ID .......................................... 13
84 3.5 Operators ................................................. 14
85 3.6 SILC Commands ............................................. 14
86 3.7 SILC Packets .............................................. 15
87 3.8 Packet Encryption ......................................... 15
88 3.8.1 Determination of the Source and the Destination ..... 16
89 3.8.2 Client To Client .................................... 16
90 3.8.3 Client To Channel ................................... 17
91 3.8.4 Server To Server .................................... 18
92 3.9 Key Exchange And Authentication ........................... 18
93 3.10 Algorithms ............................................... 19
94 3.10.1 Ciphers ............................................ 19
95 3.10.2 Public Key Algorithms .............................. 20
96 3.10.3 MAC Algorithms ..................................... 20
97 3.10.4 Compression Algorithms ............................. 20
98 3.11 SILC Public Key .......................................... 21
99 4 SILC Procedures ............................................... 23
100 4.1 Creating Client Connection ................................ 23
101 4.2 Creating Server Connection ................................ 24
102 4.3 Joining to a Channel ...................................... 25
103 4.4 Channel Key Generation .................................... 26
104 4.5 Private Message Sending and Reception ..................... 27
105 4.6 Private Message Key Generation ............................ 27
106 4.7 Channel Message Sending and Reception ..................... 28
107 4.8 Session Key Regeneration .................................. 28
108 4.9 Command Sending and Reception ............................. 29
109 5 SILC Commands ................................................. 29
110 5.1 SILC Commands Syntax ...................................... 29
116 Internet Draft Secure Internet Live Conferencing 28 June 2000
119 5.2 SILC Commands List ........................................ 31
120 5.3 SILC Command Status Types ................................. 54
121 5.3.1 SILC Command Status Payload ......................... 54
122 5.3.2 SILC Command Status List ............................ 54
123 6 Security Considerations ....................................... 58
124 7 References .................................................... 59
125 8 Author's Address .............................................. 60
130 Figure 1: SILC Network Topology
131 Figure 2: Communication Inside cell
132 Figure 3: Communication Between Cells
133 Figure 4: SILC Public Key
134 Figure 5: SILC Command Status Payload
139 This document describes a Secure Internet Live Conferencing (SILC)
140 protocol which provides secure conferencing services over insecure
141 network channel. SILC is IRC [IRC] like protocol, however, it is
142 not equivalent to IRC and does not support IRC. Strong cryptographic
143 methods are used to protect SILC packets inside SILC network. Two
144 other Internet Drafts relates very closely to this memo; SILC Packet
145 Protocol [SILC2] and SILC Key Exchange and Authentication Protocols
148 The protocol uses extensively packets as conferencing protocol
149 requires message and command sending. The SILC Packet Protocol is
150 described in [SILC2] and should be read to fully comprehend this
151 document and protocol. [SILC2] also describes the packet encryption
152 and decryption in detail.
154 The security of SILC protocol and for any security protocol for that
155 matter is based on strong and secure key exchange protocol. The SILC
156 Key Exchange protocol is described in [SILC3] along with connection
157 authentication protocol and should be read to fully comprehend this
158 document and protocol.
160 The SILC protocol has been developed to work on TCP/IP network
161 protocol, although it could be made to work on other network protocols
162 with only minor changes. However, it is recommended that TCP/IP
163 protocol is used under SILC protocol. Typical implementation would
164 be made in client-server model.
172 Internet Draft Secure Internet Live Conferencing 28 June 2000
177 This section describes various SILC protocol concepts that forms the
178 actual protocol, and in the end, the actual SILC network. The mission
179 of the protocol is to deliver messages from clients to other clients
180 through routers and servers in secure manner. The messages may also
181 be delivered from one client to many clients forming a group, also
184 This section does not focus to security issues, instead basic network
185 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.
195 A difference between normal server and router server is that routers
196 knows everything about everything in the network. They also do the
197 actual routing of the messages to the correct receiver. Normal servers
198 knows only about local information and nothing about global information.
199 This makes the network faster as there are less servers that needs to
200 keep global information up to date at all time.
202 This, on the other hand, leads to cellular like network, where routers
203 are in the centrum on the cell and servers are connected to the router.
204 Following diagram represents SILC network topology.
207 ---- ---- ---- ---- ---- ----
208 | S8 | S5 | S4 | | S7 | S5 | S6 |
209 ----- ---- ----- ----- ---- -----
210 | S7 | S/R1 | S2 | --- | S8 | S/R2 | S4 |
211 ---- ------ ---- ---- ------ ----
212 | S6 | S3 | S1 | | S1 | S3 | S2 | ---- ----
213 ---- ---- ---- ---- ---- ---- | S3 | S1 |
214 Cell 1. \ Cell 2. | \____ ----- -----
216 ---- ---- ---- ---- ---- ---- ---- ------
217 | S7 | S4 | S2 | | S1 | S3 | S2 | | S2 | S5 |
218 ----- ---- ----- ----- ---- ----- ---- ----
219 | S6 | S/R3 | S1 | --- | S4 | S/R5 | S5 | Cell 4.
220 ---- ------ ---- ---- ------ ----
221 | S8 | S5 | S3 | | S6 | S7 | S8 | ... etc ...
222 ---- ---- ---- ---- ---- ----
228 Internet Draft Secure Internet Live Conferencing 28 June 2000
233 Figure 1: SILC Network Topology
236 A cell is formed when a server or servers connect to one router. In
237 SILC network normal server cannot directly connect to other normal
238 server. Normal server may only connect to SILC router which then
239 routes the messages to the other servers in the cell. Router servers
240 on the other hand may connect to other routers to form the actual SILC
241 network, as seen in above figure. However, router is also normal SILC
242 server; clients may connect to it the same way as to normal SILC
243 servers. Normal server also cannot have active connections to more
244 than one router. Normal server cannot be connected to two different
245 cells. Router servers, on the other hand, may have as many router to
246 router connections as needed.
248 There are many issues in this network topology that needs to be careful
249 about. Issues like the size of the cells, the number of the routers in
250 the SILC network and the capacity requirements of the routers. These
251 issues should be discussed in the Internet Community and additional
252 documents on the issue will be written.
255 2.2 Communication Inside a Cell
257 It is always guaranteed that inside a cell message is delivered to the
258 recipient with at most two server hops. Client who is connected to
259 server in the cell and is talking on channel to other client connected
260 to other server in the same cell, will have its messages delivered from
261 its local server first to the router of the cell, and from the router
262 to the other server in the cell. Following diagram represents this
273 Figure 2: Communication Inside cell
276 Example: Client 1. connected to Server 1. message sent to
277 Client 4. connected to Server 2. travels from Server 1.
278 first to Router which routes the message to Server 2.
284 Internet Draft Secure Internet Live Conferencing 28 June 2000
287 which then sends it to the Client 4. All the other
288 servers in the cell will not see the routed message.
291 If client is connected directly to the router, as router is also normal
292 SILC server, the messages inside the cell are always delivered only with
293 one server hop. If clients communicating with each other are connected
294 to the same server, no router interaction is needed. This is the optimal
295 situation of message delivery in the SILC network.
298 2.3 Communication in the Network
300 If the message is destined to server that does not belong to local cell
301 the message is routed to the router server to which the destination
302 server belongs, if the local router is connected to destination router.
303 If there is no direct connection to the destination router, the local
304 router routes the message to its primary route. Following diagram
305 represents message sending between cells.
308 1 --- S1 S4 --- 5 S2 --- 1
309 S/R - - - - - - - - S/R
317 Figure 3: Communication Between Cells
320 Example: Client 5. connected to Server 4. in Cell 1. message sent
321 to Client 2. connected to Server 1. in Cell 2. travels
322 from Server 4. to Router which routes the message to
323 Router in Cell 2, which then routes the message to
324 Server 1. All the other servers and routers in the
325 network will not see the routed message.
328 The optimal case of message delivery from client point of view is
329 when clients are connected directly to the routers and the messages
330 are delivered from one router to the other router.
340 Internet Draft Secure Internet Live Conferencing 28 June 2000
343 2.4 Channel Communication
345 Messages may be sent to group of clients as well. Sending messages to
346 many clients works the same way as sending messages point to point, from
347 message delivery point of view. Security issues are another matter
348 which are not discussed in this section.
350 Router server handles the message routing to multiple recipients. If
351 any recipient is not in the same cell as the sender the messages are
354 Server distributes the channel message to its local clients who are
355 joined to the channel. Also, router distributes the message to its
356 local clients on the channel.
359 3. SILC Specification
361 This section describes the SILC protocol. However, [SILC2] and
362 [SILC3] describes other important protocols that are part of this SILC
363 specification and must be read.
368 A client is a piece of software connecting to SILC server. SILC client
369 cannot be SILC server. Purpose of clients is to provide the user
370 interface of the SILC services for end user. Clients are distinguished
371 from other clients by unique Client ID. Client ID is a 128 bit ID that
372 is used in the communication in the SILC network. The client ID is
373 based on the nickname selected by the user. User uses logical nicknames
374 in communication which are then mapped to the corresponding Client ID.
375 Client ID's are low level identifications and must not be seen by the
378 Clients provide other information about the end user as well. Information
379 such as the nickname of the user, username and the hostname of the end
380 user and user's real name. See section 3.2 Server for information of
381 the requirements of keeping this information.
383 The nickname selected by the user is not unique in the SILC network.
384 There can be 2^8 same nicknames for one IP address. As for comparison to
385 IRC [IRC] where nicknames are unique this is a fundamental difference
386 between SILC and IRC. This causes the server names to be used along
387 with the nicknames to identify specific users when sending messages.
388 This feature of SILC makes IRC style nickname-wars obsolete as no one
389 owns their nickname; there can always be someone else with the same
390 nickname. Another difference is that there are no limit of the length
396 Internet Draft Secure Internet Live Conferencing 28 June 2000
399 of the nickname in the SILC.
404 Client ID is used to identify users in the SILC network. The Client ID
405 is unique to the extent that there can be 2^128 different Client ID's.
406 Collisions are not expected to happen. The Client ID is defined as
409 128 bit Client ID based on IPv4 addresses:
411 32 bit ServerID IP address (bits 1-32)
413 88 bit Truncated MD5 hash value of the nickname
415 o Server ID IP address - Indicates the server where this
416 client is coming from. The IP address hence equals the
417 server IP address where to the client has connected.
419 o Random number - Random number to further unify the
420 Client ID. This makes it possible to have 2^8 same
421 nicknames from the same server IP address.
423 o MD5 hash - MD5 hash value of the nickname is truncated
424 taking 88 bits from the start of the hash value. This
425 hash value is used to search the user's Client ID from
428 Collisions could occur when more than 2^8 clients using same nickname
429 from the same server IP address is connected to the SILC network.
430 Server must be able to handle this situation by refusing to accept
431 anymore of that nickname.
433 Another possible collision may happen with the truncated hash value of
434 the nickname. It could be possible to have same truncated hash value for
435 two different nicknames. However, this is not expected to happen nor
436 cause any problems if it would occur. Nicknames are usually logical and
437 it is unlikely to have two distinct logical nicknames produce same
438 truncated hash value.
443 Servers are the most important parts of the SILC network. They form the
444 basis of the SILC, providing a point to which clients may connect to.
445 There are two kinds of servers in SILC; normal servers and router servers.
446 This section focuses on the normal server and router server is described
452 Internet Draft Secure Internet Live Conferencing 28 June 2000
455 in the section 3.3 Router.
457 Normal servers may not directly connect to other normal server. Normal
458 servers may only directly connect to router server. If the message sent
459 by the client is destined outside the local server it is always sent to
460 the router server for further routing. Server may only have one active
461 connection to router on same port. Normal server may not connect to other
462 cell's router except in situations where its cell's router is unavailable.
464 Servers and routers in the SILC network are considered to be trusted.
465 With out a doubt, servers that are set to work on ports above 1023 are
466 not considered to be trusted. Also, the service provider acts important
467 role in the server's trustworthy.
470 3.2.1 Server's Local ID List
472 Normal server keeps various information about the clients and their end
473 users connected to it. Every normal server must keep list of all locally
474 connected clients, Client ID's, nicknames, usernames and hostnames and
475 user's real name. Normal servers only keeps local information and it
476 does not keep any global information. Hence, normal servers knows only
477 about their locally connected clients. This makes servers efficient as
478 they don't have to worry about global clients. Server is also responsible
479 of creating the Client ID's for their clients.
481 Normal server also keeps information about locally created channels and
484 Hence, local list for normal server includes:
486 server list - Router connection
494 client list - All clients in server
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511 channel list - All channels in server
514 o Client ID's on channel
515 o Client ID modes on channel
522 Servers are distinguished from other servers by unique 64 bit Server ID.
523 The Server ID is used in the SILC to route messages to correct servers.
524 Server ID's also provide information for Client ID's, see section 3.1.1
525 Client ID. Server ID is defined as follows.
527 64 bit Server ID based on IPv4 addresses:
529 32 bit IP address of the server
533 o IP address of the server - This is the real IP address of
536 o Port - This is the port the server is binded to.
538 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.
545 3.2.3 SILC Server Ports
547 SILC uses currently TCP port 334 on SILC network. However, this is not
548 official port assigned for SILC. Official port has been requested by
551 If there are needs to create new SILC networks in the future the port
552 numbers must be officially assigned by the IANA. Most convenience case
553 would be to assign port numbers upwards from 334.
555 Server on network above privileged ports (>1023) should not be trusted
556 as they could have been set up by untrusted party.
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569 Router server in SILC network is responsible for keeping the cell together
570 and routing messages to other servers and to other routers. Router server
571 is also a normal server thus clients may connect to it as it would be
572 just normal SILC server.
574 However, router servers has a lot of important tasks that normal servers
575 do not have. Router server knows everything about everything in the SILC.
576 They know all clients currently on SILC, all servers and routers and all
577 channels in SILC. Routers are the only servers in SILC that care about
578 global information and keeping them up to date at all time. And, this
579 is what they must do.
582 3.3.1 Router's Local ID List
584 Router server as well must keep local list of connected clients and
585 locally created channels. However, this list is extended to include all
586 the informations of the entire cell, not just the server itself as for
589 However, on router this list is a lot smaller since routers do not keep
590 information about user's nickname, username and hostname and real name
591 since these are not needed by the router. Router keeps only information
594 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
613 Note that locally connected clients and other information include all the
614 same information as defined in section section 3.2.1 Server's Local ID
620 Internet Draft Secure Internet Live Conferencing 28 June 2000
626 3.3.2 Router's Global ID List
628 Router server must also keep global list. Normal servers do not have
629 global list as they know only about local information. Global list
630 includes all the clients on SILC, their Client ID's, all created channels
631 and their Channel ID's and all servers and routers on SILC and their
632 Server ID's. That is said, global list is for global information and the
633 list must not include the local information already on the router's local
636 Note that the global list does not include information like nicknames,
637 usernames and hostnames or user's real names. Router does not keep
638 these informations as they are not needed by the router. This
639 information is available from the client's server which maybe queried
642 Hence, global list includes:
644 server list - All servers in SILC
649 client list - All clients in SILC
652 channel list - All channels in SILC
654 o Client ID's on channel
655 o Client ID modes on channel
658 3.3.3 Router's Server ID
660 Router's Server ID's are equivalent to normal Server ID's. As routers
661 are normal servers as well same types of ID's applies for routers as well.
662 Thus, see section 3.2.2 Server ID. Server ID's for routers are always
663 created by the remote router where the router is connected to.
668 A channel is a named group of one or more clients which will all receive
669 messages addressed to that channel. The channel is created when first
670 client requests JOIN command to the channel, and the channel ceases to
676 Internet Draft Secure Internet Live Conferencing 28 June 2000
679 exist when the last client leaves it. When channel exists, any client
680 can reference it using the name of the channel.
682 Channel names are unique although the real uniqueness comes from 64 bit
683 Channel ID that unifies each channel. However, channel names are still
684 unique and no two global channels with same name may exist. Channel name
685 is a string which begins with `#' character. There is no limit on the
686 length of the channel name. Channel names may not contain any spaces
687 (` '), any non-printable ASCII characters, commas (`,') and wildcard
690 Channels can have operators that can administrate the channel and
691 operate all of its modes. Following operators on channel exist on SILC
694 o Channel founder - When channel is created the joining client becomes
695 channel founder. Channel founder is channel operator with some more
696 privileges. Basically, channel founder can fully operate the channel
697 and all of its modes. The privileges are limited only to the particular
698 channel. There can be only one channel founder per channel. Channel
699 founder supersedes channel operator's privileges.
701 Channel founder privileges cannot be removed by any other operator on
702 channel. When channel founder leaves the channel there is no channel
703 founder on the channel. Channel founder also cannot be removed by
704 force from the channel.
706 o Channel operator - When client joins to channel that has not existed
707 previously it will become automatically channel operator (and channel
708 founder discussed above). Channel operator is able administrate the
709 channel, set some modes on channel, remove a badly behaving client from
710 the channel and promote other clients to become channel operator.
711 The privileges are limited only to the particular channel.
713 Normal channel user may be promoted (opped) to channel operator
714 gaining channel operator privileges. Channel founder or other channel
715 operator may also demote (deop) channel operator to normal channel
721 Channels are distinguished from other channels by unique Channel ID.
722 The Channel ID is a 64 bit ID and collisions are not expected to happen
723 in any conditions. Channel names are just for logical use of channels.
724 The Channel ID is created by the server where the channel is created.
725 The Channel ID is defined as follows.
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735 64 bit Channel ID based on IPv4 addresses:
737 32 bit Router's Server ID IP address (bits 1-32)
738 16 bit Router's Server ID port (bits 33-48)
741 o Router's Server ID IP address - Indicates the IP address of
742 the router of the cell where this channel is created. This is
743 taken from the router's Server ID. This way SILC router knows
744 where this channel resides in the SILC network.
746 o Router's Server ID port - Indicates the port of the channel on
747 the server. This is taken from the router's Server ID.
749 o Random number - To further unify the Channel ID. This makes
750 sure that there are no collisions. This also means that
751 in a cell there can be 2^16 channels.
756 Operators are normal users with extra privileges to their server or
757 router. Usually these people are SILC server and router administrators
758 that take care of their own server and clients on them. The purpose of
759 operators is to administrate the SILC server or router. However, even
760 an operator with highest privileges is not able to enter invite-only
761 channel, to gain access to the contents of a encrypted and authenticated
762 packets traveling in the SILC network or to gain channel operator
763 privileges on public channels without being promoted. They have the
764 same privileges as everyone else except they are able to administrate
765 their server or router.
770 Commands are very important part on SILC network especially for client
771 which uses commands to operate on the SILC network. Commands are used
772 to set nickname, join to channel, change modes and many other things.
774 Client usually sends the commands and server replies by sending a reply
775 packet to the command. Server may also send commands usually to serve
776 the original client's request. However, server may not send command
777 to client and there are some commands that server must not send.
779 Note that the command reply is usually sent only after client has sent
780 the command request but server is allowed to send command reply packet
781 to client even if client has not requested the command. Client may,
782 however, choose not to accept the command reply, but there are some
788 Internet Draft Secure Internet Live Conferencing 28 June 2000
791 command replies that the client should accept. Example of a such
792 command reply is reply to SILC_COMMAND_CMODE command that the server
793 uses to distribute the channel mode on all clients on the channel
794 when the mode has changed.
796 It is expected that some of the commands may be miss-used by clients
797 resulting various problems on the server side. Every implementation
798 should assure that commands may not be executed more than once, say,
799 in two (2) seconds. This should be sufficient to prevent the miss-use
802 SILC commands are described in section 5 SILC Commands.
807 Packets are naturally the most important part of the protocol and the
808 packets are what actually makes the protocol. Packets in SILC network
809 are always encrypted using, usually, the shared secret session key
810 or some other key, for example, channel key, when encrypting channel
811 messages. The SILC Packet Protocol is a wide protocol and is described
812 in [SILC2]. This document does not define or describe details of
816 3.8 Packet Encryption
818 All packets passed in SILC network must be encrypted. This section
819 defines how packets must be encrypted in the SILC network. The detailed
820 description of the actual encryption process of the packets are
821 described in [SILC2].
823 Client and its server shares secret symmetric session key which is
824 established by the SILC Key Exchange Protocol, described in [SILC3].
825 Every packet sent from client to server, with exception of packets for
826 channels, are encrypted with this session key.
828 Channels has their own key that are shared by every client on the channel.
829 However, the channel keys are cell specific thus one cell does not know
830 the channel key of the other cell, even if that key is for same channel.
831 Channel key is also known by the routers and all servers that has clients
832 on the channel. However, channels may have channel private keys that
833 are entirely local setting for client. All clients on the channel must
834 know the channel private key before hand to be able to talk on the
835 channel. In this case, no server or router knows the key for channel.
837 Server shares secret symmetric session key with router which is
838 established by the SILC Key Exchange Protocol. Every packet passed from
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847 server to router, with exception of packets for channels, are encrypted
848 with the shared session key. Same way, router server shares secret
849 symmetric key with its primary route. However, every packet passed
850 from router to other router, including packets for channels, are
851 encrypted with the shared session key. Every router connection has
852 their own session keys.
855 3.8.1 Determination of the Source and the Destination
857 The source and the destination of the packet needs to be determined
858 to be able to route the packets to correct receiver. This information
859 is available in the SILC Packet Header which is included in all packets
860 sent in SILC network. The SILC Packet Header is described in [SILC2].
862 The header is always encrypted with the session key who is next receiver
863 of the packet along the route. The receiver of the packet, for example
864 a router along the route, is able to determine the sender and the
865 destination of the packet by decrypting the SILC Packet Header and
866 checking the ID's attached to the header. The ID's in the header will
867 tell to where the packet needs to be sent and where it is coming from.
869 The header in the packet does not change during the routing of the
870 packet. The original sender, for example client, assembles the packet
871 and the packet header and server or router between the sender and the
872 receiver must not change the packet header.
874 Note that the packet and the packet header may be encrypted with
875 different keys. For example, packets to channels are encrypted with
876 the channel key, however, the header is encrypted with the session key
877 as described above. However, the header and the packet may be encrypted
878 with same key. This is case, for example, with command packets.
881 3.8.2 Client To Client
883 Process of message delivery and encryption from client to another
884 client is as follows.
886 Example: Private message from client to another client on different
887 servers. Clients do not share private message delivery
888 keys; normal session keys are used.
890 o Client 1. sends encrypted packet to its server. The packet is
891 encrypted with the session key shared between client and its
894 o Server determines the destination of the packet and decrypts
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903 the packet. Server encrypts the packet with session key shared
904 between the server and its router, and sends the packet to the
907 o Router determines the destination of the packet and decrypts
908 the packet. Router encrypts the packet with session key
909 shared between the router and the destination server, and sends
910 the packet to the server.
912 o Server determines the client to which the packet is destined
913 to and decrypts the packet. Server encrypts the packet with
914 session key shared between the server and the destination client,
915 and sends the packet to the client.
917 o Client 2. decrypts the packet.
920 Example: Private message from client to another client on different
921 servers. Clients has established secret shared private
922 message delivery key with each other and that is used in
923 the message encryption.
925 o Client 1. sends encrypted packet to its server. The packet is
926 encrypted with the private message delivery key shared between
929 o Server determines the destination of the packet and sends the
930 packet to the router.
932 o Router determines the destination of the packet and sends the
933 packet to the server.
935 o Server determines the client to which the packet is destined
936 to and sends the packet to the client.
938 o Client 2. decrypts the packet with the secret shared key.
941 If clients share secret key with each other the private message
942 delivery is much simpler since servers and routers between the
943 clients do not need to decrypt and re-encrypt the packet.
945 The process for clients on same server is much simpler as there are
946 no need to send the packet to the router. The process for clients
947 on different cells is same as above except that the packet is routed
948 outside the cell. The router of the destination cell routes the
949 packet to the destination same way as described above.
956 Internet Draft Secure Internet Live Conferencing 28 June 2000
959 3.8.3 Client To Channel
961 Process of message delivery from client on channel to all the clients
964 Example: Channel of four users; two on same server, other two on
965 different cells. Client sends message to the channel.
967 o Client 1. encrypts the packet with channel key and sends the
968 packet to its server.
970 o Server determines local clients on the channel and sends the
971 packet to the Client on the same server. Server then sends
972 the packet to its router for further routing.
974 o Router determines local clients on the channel, if found
975 sends packet to the local clients. Router determines global
976 clients on the channel and sends the packet to its primary
977 router or fastest route.
979 o (Other router(s) do the same thing and sends the packet to
982 o Server determines local clients on the channel and sends the
983 packet to the client.
985 o All clients receiving the packet decrypts the packet.
988 3.8.4 Server To Server
990 Server to server packet delivery and encryption is described in above
991 examples. Router to router packet delivery is analogous to server to
992 server. However, some packets, such as channel packets, are processed
993 differently. These cases are described later in this document and
994 more in detail in [SILC2].
997 3.9 Key Exchange And Authentication
999 Key exchange is done always when for example client connects to server
1000 but also when server and router and router and router connects to each
1001 other. The purpose of key exchange protocol is to provide secure key
1002 material to be used in the communication. The key material is used to
1003 derive various security parameters used to secure SILC packets. The
1004 SILC Key Exchange protocol is described in detail in [SILC3].
1006 Authentication is done after key exchange protocol has been successfully
1012 Internet Draft Secure Internet Live Conferencing 28 June 2000
1015 completed. The purpose of authentication is to authenticate for example
1016 client connecting to the server. However, Usually clients are accepted
1017 to connect to server without explicit authentication. Servers are
1018 required use authentication protocol when connecting. The authentication
1019 may be based on passphrase (pre-shared-secret) or public key. The
1020 connection authentication protocol is described in detail in [SILC3].
1025 This section defines all the allowed algorithms that can be used in
1026 the SILC protocol. This includes mandatory cipher, mandatory public
1027 key algorithm and MAC algorithms.
1032 Cipher is the encryption algorithm that is used to protect the data
1033 in the SILC packets. See [SILC2] of the actual encryption process and
1034 definition of how it must be done. SILC has a mandatory algorithm that
1035 must be supported in order to be compliant with this protocol.
1037 Following ciphers are defined in SILC protocol:
1039 blowfish-cbc Blowfish in CBC mode (mandatory)
1040 twofish-cbc Twofish in CBC mode (optional)
1041 rc6-cbc RC6 in CBC mode (optional)
1042 rc5-cbc RC5 in CBC mode (optional)
1043 mars-cbc Mars in CBC mode (optional)
1044 none No encryption (optional)
1047 All algorithms must use minimum of 128 bit key, by default. Several
1048 algorithms, however, supports longer keys and it is recommended to use
1049 longer keys if they are available.
1051 Algorithm none does not perform any encryption process at all and
1052 thus is not recommended to be used. It is recommended that no client
1053 or server implementation would accept none algorithms except in special
1056 Additional ciphers may be defined to be used in SILC by using the
1057 same name format as above.
1068 Internet Draft Secure Internet Live Conferencing 28 June 2000
1071 3.10.2 Public Key Algorithms
1073 Public keys are used in SILC to authenticate entities in SILC network
1074 and to perform other tasks related to public key cryptography. The
1075 public keys are also used in the SILC Key Exchange protocol [SILC3].
1077 Following public key algorithms are defined in SILC protocol:
1082 Both of the algorithms are described in [Scheneir] and [Menezes].
1084 Additional public key algorithms may be defined to be used in SILC.
1087 3.10.3 MAC Algorithms
1089 Data integrity is protected by computing a message authentication code
1090 (MAC) of the packet data. See [SILC2] for details how to compute the
1093 Following MAC algorithms are defined in SILC protocol:
1095 hmac-sha1 HMAC-SHA1, length = 20 (mandatory)
1096 hmac-md5 HMAC-MD5, length = 16 (optional)
1097 none No MAC (optional)
1099 The none MAC is not recommended to be used as the packet is not
1100 authenticated when MAC is not computed. It is recommended that no
1101 client or server would accept none MAC except in special debugging
1104 The HMAC algorithm is described in [HMAC] and hash algorithms that
1105 are used as part of the HMACs are described in [Scheneir] and in
1108 Additional MAC algorithms may be defined to be used in SILC.
1111 3.10.4 Compression Algorithms
1113 SILC protocol supports compression that may be applied to unencrypted
1114 data. It is recommended to use compression on slow links as it may
1115 significantly speed up the data transmission. By default, SILC does not
1116 use compression which is the mode that must be supported by all SILC
1124 Internet Draft Secure Internet Live Conferencing 28 June 2000
1127 Following compression algorithms are defined:
1129 none No compression (mandatory)
1130 zlib GBU ZLIB (LZ77) compression (optional)
1132 Additional compression algorithms may be defined to be used in SILC.
1135 3.11 SILC Public Key
1137 This section defines the type and format of the SILC public key. All
1138 implementations must support this public key type. See [SILC3] for
1139 other optional public key and certificate types allowed in SILC
1140 protocol. Public keys in SILC may be used to authenticate entities
1141 and to perform other tasks related to public key cryptography.
1143 The format of the SILC Public Key is as follows:
1147 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
1148 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1149 | Public Key Length |
1150 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1151 | Algorithm Name Length | |
1152 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1156 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1157 | Identifier Length | |
1158 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1162 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1166 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1168 Figure 4: SILC Public Key
1171 o Public Key Length (4 bytes) - Indicates the full length
1172 of the public key, not including this field.
1174 o Algorithm Name Length (2 bytes) - Indicates the length
1180 Internet Draft Secure Internet Live Conferencing 28 June 2000
1183 of the Algorithm Length field, not including this field.
1185 o Algorithm name (variable length) - Indicates the name
1186 of the public key algorithm that the key is. See the
1187 section 3.10.2 Public Key Algorithms for defined names.
1189 o Identifier Length (2 bytes) - Indicates the length of
1190 the Identifier field, not including this field.
1192 o Identifier (variable length) - Indicates the identifier
1193 of the public key. This data can be used to identify
1194 the owner of the key. The identifier is of following
1198 HN Host name or IP address
1205 Examples of an identifier:
1207 `UN=priikone, HN=poseidon.pspt.fi, E=priikone@poseidon.pspt.fi'
1209 `UN=sam, HN=dummy.fi, RN=Sammy Sam, O=Company XYZ, C=Finland'
1211 At least user name (UN) and host name (HN) must be provided as
1212 identifier. The fields are separated by commas (`,'). If
1213 comma is in the identifier string it must be written as `\,',
1214 for example, `O=Company XYZ\, Inc.'.
1216 o Public Data (variable length) - Includes the actual
1217 public data of the public key.
1219 The format of this field for RSA algorithm is
1228 The format of this field for DSS algorithm is
1236 Internet Draft Secure Internet Live Conferencing 28 June 2000
1248 The variable length fields are multiple precession
1249 integers encoded as strings in both examples.
1251 Other algorithms must define their own type of this
1252 field if they are used.
1254 All fields in the public key are in MSB (most significant byte first)
1260 This section describes various SILC procedures such as how the
1261 connections are created and registered, how channels are created and
1262 so on. The section describes the procedures only generally as details
1263 are described in [SILC2] and [SILC3].
1266 4.1 Creating Client Connection
1268 This section descibres the procedure when client connects to SILC server.
1269 When client connects to server the server must perform IP address lookup
1270 and reverse IP address lookup to assure that the origin host really is
1271 who it claims to be. Client, host, connecting to server must have
1272 both valid IP address and fully qualified domain name (FQDN).
1274 After that client and server performs SILC Key Exchange protocol which
1275 will provide the key material used later in the communication. The
1276 key exchange protocol must be completed successfully before the connection
1277 registration may continue. The SILC Key Exchange protocol is described
1280 Typical server implementation would keep a list of connections that it
1281 allows to connect to the server. The implementation would check, for
1282 example, the connecting client's IP address from the connection list
1283 before the SILC Key Exchange protocol has been started. Reason for
1284 this is that if the host is not allowed to connect to the server there
1285 is no reason to perform a key exchange protocol.
1292 Internet Draft Secure Internet Live Conferencing 28 June 2000
1295 After successful key exchange protocol the client and server performs
1296 connection authentication protocol. The purpose of the protocol is to
1297 authenticate the client connecting to the server. Flexible
1298 implementation could also accept the client to connect to the server
1299 without explicit authentication. However, if authentication is
1300 desired for a specific client it may be based on passphrase or
1301 public key authentication. If authentication fails the connection
1302 must be terminated. The connection authentication protocol is described
1305 After successful key exchange and authentication protocol the client
1306 registers itself by sending SILC_PACKET_NEW_CLIENT packet to the
1307 server. This packet includes various information about the client
1308 that the server uses to create the client. Server creates the client
1309 and sends SILC_PACKET_NEW_ID to the client which includes the created
1310 Client ID that the client must start using after that. After that
1311 all SILC packets from the client must have the Client ID as the
1312 Source ID in the SILC Packet Header, described in [SILC2].
1314 Client must also get the server's Server ID that is to be used as
1315 Destination ID in the SILC Packet Header when communicating with
1316 the server (for example when sending commands to the server). The
1317 ID may be resolved in two ways. Client can take the ID from an
1318 previously received packet from server that must include the ID,
1319 or to send SILC_COMMAND_INFO command and receive the Server ID as
1322 Server may choose not to use the information received in the
1323 SILC_PACKET_NEW_CLIENT packet. For example, if public key or
1324 certificate were used in the authentication, server may use those
1325 informations rather than what it received from client. This is suitable
1326 way to get the true information about client if it is available.
1328 The nickname of client is initially set to the username sent in the
1329 SILC_PACKET_NEW_CLIENT packet. User should set the nickname to more
1330 suitable by sending SILC_COMMAND_NICK command. However, this is not
1331 required as part of registration process.
1333 Server must also distribute the information about newly registered
1334 client to its router (or if the server is router, to all routers in
1335 the SILC network). More information about this in [SILC2].
1338 4.2 Creating Server Connection
1340 This section descibres the procedure when server connects to its
1341 router (or when router connects to other router, the cases are
1342 equivalent). The procedure is very much alike when client connects
1348 Internet Draft Secure Internet Live Conferencing 28 June 2000
1351 to the server thus it is not repeated here.
1353 One difference is that server must perform connection authentication
1354 protocol with proper authentication. Proper authentication is based
1355 on passphrase or public key authentication.
1357 After server and router has successfully performed the key exchange
1358 and connection authentication protocol, the server register itself
1359 to the router by sending SILC_PACKET_NEW_SERVER packet. This packet
1360 includes the server's Server ID that it has created by itself and
1361 other relevant information about the server.
1363 After router has received the SILC_PACKET_NEW_SERVER packet it
1364 distributes the information about newly registered server to all routers
1365 in the SILC network. More information about this in [SILC2].
1367 As client needed to resolve the destination ID this must be done by the
1368 server that connected to the router, as well. The way to resolve it is
1369 to get the ID from previously received packet. Server must also start
1370 using its own Server ID as Source ID in SILC Packet Header and the
1371 router's Server ID as Destination when communicating with the router.
1373 If the server has already connected clients and locally created
1374 channels the server must distribute these informations to the router.
1375 The distribution is done by sending packet SILC_PACKET_NEW_CHANNEL.
1376 See [SILC2] for more information on this.
1379 4.3 Joining to a Channel
1381 This section describes the procedure when client joins to a channel.
1382 Client may join to channel by sending command SILC_COMMAND_JOIN to the
1383 server. If the receiver receiving join command is normal server the
1384 server must check its local list whether this channel already exists
1385 locally. This would indicate that some client connected to the server
1386 has already joined to the channel. If this is case the client is
1387 joined to the client, new channel key is created and information about
1388 newly joined channel is sent to the router. The new channel key is
1389 also distributed to the router and to all clients on the channel.
1391 If the channel does not exist in the local list the command must be
1392 sent to the router which will then perform the actual joining
1393 procedure. When server receives the reply to the command from the
1394 router it must be distributed to the client who sent the command
1395 originally. Server will also receive the channel key from the server
1396 that it must distribute to the client who originally requested the
1397 join command. The server must also save the channel key.
1404 Internet Draft Secure Internet Live Conferencing 28 June 2000
1407 If the receiver of the join command is router it must first check its
1408 local list whether anyone in the cell has already joined to the channel.
1409 If this is the case the client is joined to the channel and reply is
1410 sent to the client. If the command was sent by server the command reply
1411 is sent to the server who sent it. Then the router must also create
1412 new channel key and distribute it to all clients on the channel and
1413 all servers that has clients on the channel.
1415 If the channel does not exist on the router's local list it must
1416 check the global list whether the channel exists at all. If it does
1417 the client is joined to the channel as described previously. If
1418 the channel does not exist the channel is created and the client
1419 is joined to the channel. The channel key is also created and
1420 distributed as previously described. The client joining to the created
1421 channel is made automatically channel founder and both channel founder
1422 and channel operator privileges is set for the client.
1424 When the router joins the client to the channel it must send
1425 information about newly joined client to all routers in the SILC
1426 network. Also, if the channel was created in the process, information
1427 about newly created channel must also be distributed to all routers.
1428 The distribution of newly created channel is done by sending packet
1429 SILC_PACKET_NEW_CHANNEL.
1431 It is important to note that new channel key is created always when
1432 new client joins to channel, whether the channel has existed previously
1433 or not. This way the new client on the channel is not able to decrypt
1434 any of the old traffic on the channel.
1436 Client who receives the reply to the join command must start using
1437 the received Channel ID in the channel message communication thereafter.
1438 However, client must not start communicating on the channel before
1439 it has received the packet SILC_PACKET_CHANNEL_KEY.
1441 If client wants to know the other clients currently on the channel
1442 the client must send SILC_COMMAND_NAMES command to receive a list of
1443 channel users. Server implementation, however, may send command reply
1444 packet to SILC_COMMAND_NAMES command after client has joined to the
1445 channel even if the client has not sent the command.
1448 4.4 Channel Key Generation
1450 Channel keys are created by router who creates the channel by taking
1451 enough randomness from cryptographically strong random number generator.
1452 The key is generated always when channel is created, when new client
1453 joins a channel and after the key has expired. Key could expire for
1460 Internet Draft Secure Internet Live Conferencing 28 June 2000
1463 The key must also be re-generated whenever some client leaves a channel.
1464 In this case the key is created from scratch by taking enough randomness
1465 from the random number generator. After that the key is distributed to
1466 all clients on the channel. However, channel keys are cell specific thus
1467 the key is created only on the cell where the client, who leaved the
1468 channel, exists. While the server or router is creating the new channel
1469 key, no other client may join to the channel. Messages that are sent
1470 while creating the new key are still processed with the old key. After
1471 server has sent the SILC_PACKET_CHANNEL_KEY packet must client start
1472 using the new key. If server creates the new key the server must also
1473 send the new key to its router. See [SILC2] on more information about
1474 how channel messages must be encrypted and decrypted when router is
1478 4.5 Private Message Sending and Reception
1480 Private messages are sent point to point. Client explicitly destines
1481 a private message to specific client that is delivered to only to that
1482 client. No other client may receive the private message. The receiver
1483 of the private message is destined in the SILC Packet Header as any
1484 other packet as well.
1486 If the sender of a private message does not know the receiver's Client
1487 ID, it must resolve it from server. There are two ways to resolve the
1488 client ID from server; it is recommended that client ipmlementations
1489 send SILC_COMMAND_IDENTIFY command to receive the Client ID. Client
1490 may also send SILC_COMMAND_WHOIS command to receive the Client ID.
1491 If the sender has received earlier a private message from the receiver
1492 it should have cached the Client ID from the SILC Packet Header.
1494 Receiver of a private message should not explicitly trust the nickname
1495 that it receives in the Private Message Payload, described in [SILC2].
1496 Implementations could resolve the nickname from server, as described
1497 previously, and compare the received Client ID and the SILC Packet
1498 Header's Client ID. The nickname in the payload is merely provided
1499 to be displayed for end user.
1501 See [SILC2] for describtion of private message encryption and decryption
1505 4.6 Private Message Key Generation
1507 Private message may be protected by key generated by client. The key
1508 may be generated and sent to the other client by sending packet
1509 SILC_PACKET_PRIVATE_MESSAGE_KEY which travels through the network
1510 and is secured by session keys. After that the private message key
1516 Internet Draft Secure Internet Live Conferencing 28 June 2000
1519 is used in the private message communication between those clients.
1520 See more information about how this works technically in [SILC2].
1522 Other choice is to entirely use keys that are not sent through
1523 the SILC network at all. This significantly adds security. This key
1524 would be pre-shared-key that is known by both of the clients. Both
1525 agree about using the key and starts sending packets that indicate
1526 that the private message is secured using private message key. This
1527 is the technical aspect mentioned previously that is described
1530 If the private message keys are not set to be used, which is the
1531 case by default in SILC, the private messages are secured by using
1532 normal session keys established by SILC Key Exchange protocol.
1535 4.7 Channel Message Sending and Reception
1537 Channel messages are delivered to group of users. The group forms a
1538 channel and all clients on the channel receives messages sent to the
1541 Channel messages are destined to channel by specifying the Channel ID
1542 as Destination ID in the SILC Packet Header. The server must then
1543 distribute the message to all clients on the channel by sending the
1544 channel message destined explicitly to a client on the channel.
1546 See [SILC2] for describtion of channel message encryption and decryption
1550 4.8 Session Key Regeneration
1552 Session keys should be regenerated peridiocally, say, once in an hour.
1553 The re-key process is started by sending SILC_PACKET_REKEY packet to
1554 other end, to indicate that re-key must be performed.
1556 If perfect forward secrecy (PFS) flag was selected in the SILC Key
1557 Exchange protocol [SILC3] the re-key must cause new key exchange with
1558 SKE protocol. In this case the protocol is secured with the old key
1559 and the protocol results to new key material. See [SILC3] for more
1560 information. After the SILC_PACKET_REKEY packet is sent the sender
1561 will perform the SKE protocol.
1563 If PFS flag was not set, which is the default case, then re-key is done
1564 without executing SKE protocol. In this case, the new key is created by
1565 hashing the old key with hash function selected earlier in the SKE
1566 protocol. If the digest length of the hash function is too short for the
1572 Internet Draft Secure Internet Live Conferencing 28 June 2000
1575 key, then the key is distributed as described in section Processing the
1576 Key Material in [SILC3]. After both parties has regenerated the session
1577 key, both send SILC_PACKET_REKEY_DONE packet to each other. These packets
1578 are still secured with the old key. After these packets, following
1579 packets must be protected with the new key.
1582 4.9 Command Sending and Reception
1584 Client usually sends the commands in the SILC network. In this case
1585 the client simply sends the command packet to server and the server
1586 processes it and replies with command reply packet.
1588 However, if the server is not able to process the command, it is usually
1589 sent to the server's router. This is case for example with commands such
1590 as, SILC_COMMAND_JOIN and SILC_COMMAND_WHOIS commands. However, there
1591 are other commands as well. For example, if client sends the WHOIS
1592 command requesting specific information about some client the server must
1593 send the WHOIS command to router so that all clients in SILC network
1594 are searched. The router, on the other hand, sends the WHOIS command
1595 to further to receive the exact information about the requested client.
1596 The WHOIS command travels all the way to the server who owns the client
1597 and it replies with command reply packet. Finally, the server who
1598 sent the command receives the command reply and it must be able to
1599 determine which client sent the original command. The server then
1600 sends command reply to the client. Implementations should have some
1601 kind of cache to handle, for example, WHOIS information. Servers
1602 and routers along the route could all cache the information for faster
1603 referencing in the future.
1605 The commands sent by server may be sent hop by hop until someone is able
1606 to process the command. However, it is preferred to destine the command
1607 as precisely as it is possible. In this case, other routers en route
1608 must route the command packet by checking the true sender and true
1609 destination of the packet. However, servers and routers must not route
1610 command reply packets to clients coming from other server. Client
1611 must not accept command reply packet originated from anyone else but
1612 from its own server.
1617 5.1 SILC Commands Syntax
1619 This section briefly describes the syntax of the command notions
1620 in this document. Every field in command is separated from each
1621 other by whitespaces (` ') indicating that each field is independent
1622 argument and each argument must have own Command Argument Payload.
1628 Internet Draft Secure Internet Live Conferencing 28 June 2000
1631 The number of maximum arguments are defined with each command
1632 separately. The Command Argument Payload is described in [SILC2].
1634 Every command defines specific number for each argument. Currently,
1635 they are defined in ascending order; first argument has number one
1636 (1), second has number two (2) and so on. This number is set into the
1637 Argument Type field in the Command Argument Payload. This makes it
1638 possible to send the arguments in free order as the number must be
1639 used to identify the type of the argument. This makes is it also
1640 possible to have multiple optional arguments in commands and in
1641 command replies. The number of argument is marked in parentheses
1642 before the actual argument.
1644 Example: Arguments: (1) <nickname> (2) <username@host>
1647 Every command replies with Status Payload. This payload tells the
1648 sender of the command whether the command was completed succefully or
1649 whether there was an error. If error occured the payload includes the
1650 error type. In the next section the Status Payload is not described
1651 as it is common to all commands and has been described here. Commands
1652 may reply with other arguments as well. These arguments are command
1653 specific and are described in the next section.
1660 Arguments: (1) <nickname>[@<server>] (2) <message>
1663 The command has maximum of 3 arguments. However, only first
1664 and second arguments are mandatory.
1666 First argument <nickname> is mandatory but may have optional
1667 <nickname@server> format as well. Second argument is mandatory
1668 <message> argument. Third argument is optional <count> argument.
1670 The numbers in parentheses are the argument specific numbers
1671 that specify the type of the argument in Command Argument Payload.
1672 The receiver always knows that, say, argument number two (2) is
1673 <message> argument, regardles of the ordering of the arguments in
1674 the Command Payload.
1684 Internet Draft Secure Internet Live Conferencing 28 June 2000
1687 Reply messages to the command:
1690 Arguments: (1) <Status Payload> (2) [<channel list>]
1691 (3) <idle time> (4) [<away message>]
1693 This command may reply with maximum of 4 arguments. However,
1694 only the first and third arguments are mandatory. The numbers
1695 in the parentheses have the same meaning as in the upper
1696 command sending specification.
1698 Every command reply with <Status Payload>, it is mandatory
1699 argument for all command replies and for this reason it is not
1700 described in the command reply descriptions.
1705 SILC_STATUS_ERR_TOO_MANY_TARGETS
1706 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
1707 SILC_STATUS_ERR_NO_SUCH_NICK
1709 Every command reply also defines set of status message that it
1710 may return inside the <Status Payload>. All status messages
1711 are defined in the section 5.3 SILC Command Status Types.
1714 5.2 SILC Commands List
1716 This section lists all SILC commands, however, it is expected that a
1717 implementation and especially client implementation has many more
1718 commands that has only local affect. These commands are official
1719 SILC commands that has both client and server sides and cannot be
1720 characterized as local commands.
1722 List of all defined commands in SILC follows.
1726 None. This is reserved command and must not be sent.
1729 2 SILC_COMMAND_WHOIS
1732 Arguments: (1) <nickname>[@<server>] (2) [<count>]
1734 Whois. Whois command is used to query various information about
1740 Internet Draft Secure Internet Live Conferencing 28 June 2000
1743 specific user. The user maybe requested by their nickname and
1744 server name. The query may find multiple matching users as
1745 there are no unique nicknames in the SILC. The <count> option
1746 maybe given to narrow down the number of accepted results. If
1747 this is not defined there are no limit of accepted results.
1748 The query may also be narrowed down by defining the server name
1751 To prevent miss-use of this service wildcards in the nickname
1752 or in the servername are not permitted. It is not allowed
1753 to request all users on some server. The WHOIS requests must
1754 be based on specific nickname request.
1756 The WHOIS request must be always forwarded to router by server
1757 so that all users are searched. However, the server still must
1758 search its locally connected clients. The server must send
1759 this command to the server who owns the requested client. That
1760 server must reply to the command.
1762 Reply messages to the command:
1765 Arguments: (1) <Status Payload> (2) <Client ID>
1766 (3) <nickname>[@<server>] (4) <username@host>
1767 (5) <real name> (6) [<channel list>]
1770 This command may reply with several command reply messages to
1771 form a list of results. In this case the status payload will
1772 include STATUS_LIST_START status in the first reply and
1773 STATUS_LIST_END in the last reply to indicate the end of the
1774 list. If there are only one reply the status is set to normal
1777 The command replies include the Client ID of the nickname,
1778 nickname and servername, username and hostnamea and users real
1779 name. Client should process these replies only after the last
1780 reply has been received with the STATUS_LIST_END status. If the
1781 <count> option were defined in the query there will be only
1782 <count> many replies from the server.
1787 SILC_STATUS_LIST_START
1788 SILC_STATUS_LIST_END
1789 SILC_STATUS_ERR_NO_SUCH_NICK
1790 SILC_STATUS_ERR_WILDCARDS
1796 Internet Draft Secure Internet Live Conferencing 28 June 2000
1799 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
1800 SILC_STATUS_ERR_TOO_MANY_PARAMS
1803 3 SILC_COMMAND_WHOWAS
1806 Arguments: (1) <nickname>[@<server>] (2) [<count>]
1808 Whowas. This command is used to query history information about
1809 specific user. The user maybe requested by their nickname and
1810 server name. The query may find multiple matching users as there
1811 are no unique nicknames in the SILC. The <count> option maybe
1812 given to narrow down the number of accepted results. If this
1813 is not defined there are no limit of accepted results. The query
1814 may also be narrowed down by defining the server name of the
1817 To prevent miss-use of this service wildcards in the nickname
1818 or in the servername are not permitted. The WHOWAS requests must
1819 be based on specific nickname request.
1821 The WHOWAS request must be always forwarded to router by server
1822 so that all users are searched. However, the server still must
1823 search its locally connected clients.
1825 Reply messages to the command:
1828 Arguments: (1) <Status Payload> (2) <nickname>[@<server>]
1831 This command may reply with several command reply messages to form
1832 a list of results. In this case the status payload will include
1833 STATUS_LIST_START status in the first reply and STATUS_LIST_END in
1834 the last reply to indicate the end of the list. If there are only
1835 one reply the status is set to normal STATUS_OK.
1837 The command replies with nickname and username and hostname.
1838 Every server must keep history for some period of time of its
1839 locally connected clients.
1844 SILC_STATUS_LIST_START
1845 SILC_STATUS_LIST_END
1846 SILC_STATUS_ERR_NO_SUCH_NICK
1852 Internet Draft Secure Internet Live Conferencing 28 June 2000
1855 SILC_STATUS_ERR_WILDCARDS
1856 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
1857 SILC_STATUS_ERR_TOO_MANY_PARAMS
1860 4 SILC_COMMAND_IDENTIFY
1863 Arguments: (1) <nickname>[@<server>] (2) [<count>]
1865 Identify. Identify command is almost analogous to WHOIS command,
1866 except that it does not return as much information. Only relevant
1867 information such as Client ID is returned. This is usually used
1868 to get the Client ID of a client used in the communication with
1871 The query may find multiple matching users as there are no unique
1872 nicknames in the SILC. The <count> option maybe given to narrow
1873 down the number of accepted results. If this is not defined there
1874 are no limit of accepted results. The query may also be narrowed
1875 down by defining the server name of the nickname.
1877 To prevent miss-use of this service wildcards in the nickname
1878 or in the servername are not permitted. It is not allowed
1879 to request all users on some server. The IDENTIFY requests must
1880 be based on specific nickname request.
1882 Implementations may not want to give interface access to this
1883 commands as it is hardly a command that would be used a end user.
1884 However, it must be implemented as it is used with private message
1887 The IDENTIFY must be always forwarded to router by server so that
1888 all users are searched. However, server must still search its
1889 locally connected clients.
1891 Reply messages to the command:
1894 Arguments: (1) <Status Payload> (2) <Client ID>
1895 (3) [<nickname>[@<server>]] (4) [<username@host>]
1897 This command may reply with several command reply messages to form
1898 a list of results. In this case the status payload will include
1899 STATUS_LIST_START status in the first reply and STATUS_LIST_END in
1900 the last reply to indicate the end of the list. If there are only
1901 one reply the status is set to normal STATUS_OK.
1908 Internet Draft Secure Internet Live Conferencing 28 June 2000
1911 The command replies with Client ID of the nickname and if more
1912 information is available it may reply with nickname and username
1913 and hostname. If the <count> option were defined in the query
1914 there will be only <count> many replies from the server.
1919 SILC_STATUS_LIST_START
1920 SILC_STATUS_LIST_END
1921 SILC_STATUS_ERR_NO_SUCH_NICK
1922 SILC_STATUS_ERR_WILDCARDS
1923 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
1924 SILC_STATUS_ERR_TOO_MANY_PARAMS
1930 Arguments: (1) <nickname>
1932 Set/change nickname. This command is used to set nickname for
1933 user. There is no limit of the length of the nickname in SILC.
1934 Nickname must not include any spaces (` '), non-printable
1935 characters, commas (`,') and any wildcard characters. Note:
1936 nicknames in SILC are case-sensitive which must be taken into
1937 account when searching clients by nickname.
1939 Reply messages to the command:
1942 Arguments: (1) <Status Payload> (2) <New ID Payload>
1944 This command is replied always with New ID Payload that is
1945 generated by the server every time user changes their nickname.
1946 Client receiving this payload must start using the received
1947 Client ID as its current valid Client ID. The New ID Payload
1948 is described in [SILC2].
1953 SILC_STATUS_ERR_WILDCARDS
1954 SILC_STATUS_ERR_NICKNAME_IN_USE
1955 SILC_STATUS_ERR_BAD_NICKNAME
1956 SILC_STATUS_ERR_NOT_REGISTERED
1957 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
1958 SILC_STATUS_ERR_TOO_MANY_PARAMS
1964 Internet Draft Secure Internet Live Conferencing 28 June 2000
1970 Arguments: (1) [<Channel ID>] [<server>]
1972 The list command is used to list channels and their topics on
1973 current server. If the <Channel ID> parameter is used, only the
1974 status of that channel is displayed. Secret channels are not
1975 listed at all. Private channels are listed with status indicating
1976 that the channel is private.
1978 If the <server> argument is specified the specified server's
1979 channels are listed. In this case the command must be sent to
1980 the server who owns the channel that was requested.
1982 Reply messages to the command:
1985 Arguments: (1) <Status Payload> (2) <channel>
1988 This command may reply with several command reply messages to form
1989 a list of results. In this case the status payload will include
1990 STATUS_LIST_START status in the first reply and STATUS_LIST_END in
1991 the last reply to indicate the end of the list. If there are only
1992 one reply the status is set to normal STATUS_OK.
1994 This command replies with channel name and the topic of the
1995 channel. If the channel is private channel the <topic> includes
2001 SILC_STATUS_LIST_START
2002 SILC_STATUS_LIST_END
2003 SILC_STATUS_ERR_WILDCARDS
2004 SILC_STATUS_ERR_NOT_REGISTERED
2005 SILC_STATUS_ERR_TOO_MANY_PARAMS
2006 SILC_STATUS_ERR_NO_SUCH_CHANNEL
2007 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
2008 SILC_STATUS_ERR_NO_SUCH_SERVER
2020 Internet Draft Secure Internet Live Conferencing 28 June 2000
2023 7 SILC_COMMAND_TOPIC
2026 Arguments: (1) <Channel ID> (2) [<server>]]
2028 This command is used to change or view the topic of a channel.
2029 The topic for channel <Channel ID> is returned if there is no
2030 <topic> given. If the <topic> parameter is present, the topic
2031 for that channel will be changed, if the channel modes permit
2034 Reply messages to the command:
2037 Arguments: (1) <Status Payload> (2) [<topic>]
2039 The command may reply with the topic of the channel if it is
2045 SILC_STATUS_ERR_NOT_ON_CHANNEL
2046 SILC_STATUS_ERR_WILDCARDS
2047 SILC_STATUS_ERR_NOT_REGISTERED
2048 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2049 SILC_STATUS_ERR_NO_SUCH_CHANNEL
2050 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
2051 SILC_STATUS_ERR_NO_CHANNEL_ID
2052 SILC_STATUS_ERR_BAD_CHANNEL_ID
2053 SILC_STATUS_ERR_TOO_MANY_PARAMS
2054 SILC_STATUS_ERR_NO_CHANNEL_PRIV
2057 8 SILC_COMMAND_INVITE
2060 Arguments: (1) <Client ID> (2) <channel>
2062 This command is used to invite other clients to join to the
2063 channel. There is no requirement that the channel the target
2064 client is being invited to must exist or be a valid channel.
2065 The <Client ID> argument is the target client's ID that is being
2068 Reply messages to the command:
2076 Internet Draft Secure Internet Live Conferencing 28 June 2000
2080 Arguments: (1) <Status Payload>
2082 This command replies only with Status Payload.
2087 SILC_STATUS_ERR_NOT_ON_CHANNEL
2088 SILC_STATUS_ERR_WILDCARDS
2089 SILC_STATUS_ERR_NOT_REGISTERED
2090 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2091 SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
2092 SILC_STATUS_ERR_TOO_MANY_PARAMS
2093 SILC_STATUS_ERR_NO_RECIPIENT
2094 SILC_STATUS_ERR_USER_ON_CHANNEL
2095 SILC_STATUS_ERR_NO_CLIENT_ID
2101 Arguments: (1) [<quit message>]
2103 This command is used by client to end SILC session. The server
2104 must close the connection to a client which sends this command.
2105 if <quit message> is given it will be sent to other clients on
2106 channel if the client is on channel when quitting.
2108 Reply messages to the command:
2110 This command does not reply anything.
2113 10 SILC_COMMAND_KILL
2116 Arguments: (1) <Client ID> (2) [<comment>]
2118 This command is used by SILC operators to remove a client from
2119 SILC network. The removing has temporary effects and client may
2120 reconnect to SILC network. The <Client ID> is the client to be
2121 removed from SILC. The <comment> argument may be provided to
2122 give to the removed client some information why it was removed
2125 Reply messages to the command:
2132 Internet Draft Secure Internet Live Conferencing 28 June 2000
2136 Arguments: (1) <Status Payload>
2138 This command replies only with Status Payload.
2143 SILC_STATUS_ERR_WILDCARDS
2144 SILC_STATUS_ERR_NOT_REGISTERED
2145 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2146 SILC_STATUS_ERR_TOO_MANY_PARAMS
2147 SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
2148 SILC_STATUS_ERR_NO_CLIENT_ID
2151 11 SILC_COMMAND_INFO
2154 Arguments: (1) [<server>]
2156 This command is used to fetch various information about a server.
2157 If <server> argument is specified the command must be sent to
2158 the requested server.
2160 Reply messages to the command:
2163 Arguments: (1) <Status Payload> (2) <Server ID>
2166 This command replies with the Server ID of the server and a
2167 string which tells the information about the server.
2172 SILC_STATUS_ERR_WILDCARDS
2173 SILC_STATUS_ERR_NOT_REGISTERED
2174 SILC_STATUS_ERR_TOO_MANY_PARAMS
2175 SILC_STATUS_ERR_NO_SUCH_SERVER_ID
2176 SILC_STATUS_ERR_NO_SUCH_SERVER
2188 Internet Draft Secure Internet Live Conferencing 28 June 2000
2191 12 SILC_COMMAND_CONNECT
2194 Arguments: (1) <Server ID>
2195 (2) [<remote server/router>[:<port>]]
2197 This command is used by operators to force a server to try to
2198 establish a new connection to another router (if the connecting
2199 server is normal server) or server (if the conneceting server is
2200 router server). Operator may specify the server/router to be
2201 connected by setting <remote server> argument.
2203 Reply messages to the command:
2206 Arguments: (1) <Status Payload>
2208 This command replies only with Status Payload.
2213 SILC_STATUS_ERR_WILDCARDS
2214 SILC_STATUS_ERR_NOT_REGISTERED
2215 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2216 SILC_STATUS_ERR_TOO_MANY_PARAMS
2217 SILC_STATUS_ERR_NO_SUCH_SERVER_ID
2218 SILC_STATUS_ERR_NO_SERVER_PRIV
2219 SILC_STATUS_ERR_NO_ROUTER_PRIV
2222 13 SILC_COMMAND_PING
2225 Arguments: (1) <Server ID>
2227 This command is used by clients to test the communication
2228 channel to its server if client suspects that the communication
2229 is not working correctly. The <Server ID> is the ID of the
2230 server the client is connected to.
2232 Reply messages to the command:
2235 Arguments: (1) <Status Payload>
2237 This command replies only with Status Payload. Server returns
2238 SILC_STATUS_OK in Status Payload if pinging was successful.
2244 Internet Draft Secure Internet Live Conferencing 28 June 2000
2250 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2251 SILC_STATUS_ERR_TOO_MANY_PARAMS
2252 SILC_STATUS_ERR_NO_SUCH_SERVER_ID
2253 SILC_STATUS_ERR_NOT_REGISTERED
2256 14 SILC_COMMAND_OPER
2259 Arguments: (1) <username> (2) <authentication data>
2261 This command is used by normal client to obtain server operator
2262 privileges on some server or router. Note that router operator
2263 has router privileges that supersedes the server operator
2264 privileges and this does not obtain those privileges. Client
2265 must use SILCOPER command to obtain router level privileges.
2267 The <username> is the username set in the server configurations
2268 as operator. The <authentication data> is the data that the
2269 client is authenticated against. It may be passphrase prompted
2270 for user on client's screen or it may be public key
2271 authentication data (data signed with private key), or
2274 Reply messages to the command:
2277 Arguments: (1) <Status Payload>
2279 This command replies only with Status Payload.
2284 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2285 SILC_STATUS_ERR_TOO_MANY_PARAMS
2286 SILC_STATUS_ERR_NOT_REGISTERED
2287 SILC_STATUS_ERR_BAD_PASSWORD
2288 SILC_STATUS_ERR_AUTH_FAILED
2300 Internet Draft Secure Internet Live Conferencing 28 June 2000
2303 15 SILC_COMMAND_JOIN
2306 Arguments: (1) <channel> (2) [<passphrase>]
2309 Join to channel/create new channel. This command is used to
2310 join to a channel. If the channel does not exist the channel is
2311 created on the server receiving the join request. The channel
2312 may be protected with passphrase. If this is the case the
2313 passphrase must be sent along the join command.
2315 The name of the <channel> must not include any spaces (` '),
2316 non-printable characters, commas (`,') or any wildcard characters.
2318 Cipher to be used to secure the traffic on the channel may be
2319 requested by sending the name of the requested <cipher>. This
2320 is used only if the channel does not exist and is created. If
2321 the channel already exists the cipher set previously for the
2322 channel will be used to secure the traffic.
2324 The server must check whether the user is allowed to join to
2325 the requested channel. Various modes set to the channel affect
2326 the ability of the user to join the channel. These conditions
2329 o The user must be invited to the channel if the channel
2330 is invite-only channel.
2332 o The Client ID/nickname/username/hostname must not match
2335 o The correct passphrase must be provided if passphrase
2336 is set to the channel.
2338 o The user count limit, if set, must not be reached.
2340 Reply messages to the command:
2343 Arguments: (1) <Status Payload> (2) <channel>
2344 (3) <Channel ID> (4) <channel mode mask>
2347 This command replies with the channel name requested by the
2348 client, channel ID of the channel and topic of the channel
2349 if it exists. It also replies with the channel mode mask
2350 which tells all the modes set on the channel. If the
2356 Internet Draft Secure Internet Live Conferencing 28 June 2000
2359 channel is created the mode mask is zero (0).
2361 Client must not start transmitting to the channel even after
2362 server has replied to this command. Client is permitted to
2363 start transmitting on channel after server has sent packet
2364 SILC_PACKET_CHANNEL_KEY to the client.
2369 SILC_STATUS_ERR_WILDCARDS
2370 SILC_STATUS_ERR_NOT_REGISTERED
2371 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2372 SILC_STATUS_ERR_TOO_MANY_PARAMS
2373 SILC_STATUS_ERR_BAD_PASSWORD
2374 SILC_STATUS_ERR_CHANNEL_IS_FULL
2375 SILC_STATUS_ERR_NOT_INVITED
2376 SILC_STATUS_ERR_BANNED_FROM_CHANNEL
2377 SILC_STATUS_ERR_BAD_CHANNEL
2378 SILC_STATUS_ERR_USER_ON_CHANNEL
2381 16 SILC_COMMAND_MOTD
2384 Arguments: (1) <server>
2386 This command is used to query the Message of the Day of a server.
2388 Reply messages to the command:
2391 Arguments: (1) <Status Payload> (2) [<motd>]
2393 This command replies with the motd message if it exists.
2398 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2399 SILC_STATUS_ERR_TOO_MANY_PARAMS
2400 SILC_STATUS_ERR_NOT_REGISTERED
2401 SILC_STATUS_ERR_NO_SUCH_SERVER
2412 Internet Draft Secure Internet Live Conferencing 28 June 2000
2415 17 SILC_COMMAND_UMODE
2418 Arguments: (1) <Client ID> (2) <client mode mask>
2420 This command is used by client to set/unset modes for itself.
2421 However, there are some modes that the client may not set itself,
2422 but they will be set by server. However, client may unset any
2423 mode. Modes may be masked together ORing them thus having
2424 several modes set. Client must keep its client mode mask
2425 locally so that the mode setting/unsetting would work without
2426 problems. Client may change only its own modes.
2428 Following client modes are defined:
2430 0x0000 SILC_UMODE_NONE
2432 No specific mode for client. This is the initial
2433 setting when new client is created. The client is
2437 0x0001 SILC_UMODE_SERVER_OPERATOR
2439 Marks the user as server operator. Client cannot
2440 set this mode itself. Server sets this mode to the
2441 client when client attains the server operator
2442 privileges by SILC_COMMAND_OPER command. Client
2443 may unset the mode itself.
2446 0x0002 SILC_UMODE_ROUTER_OPERATOR
2448 Marks the user as router (SILC) operator. Client
2449 cannot this mode itself. Router sets this mode to
2450 the client when client attains the router operator
2451 privileges by SILC_COMMAND_SILCOPER command. Client
2452 may unset the mode itself.
2454 Reply messages to the command:
2457 Arguments: (1) <Status Payload> (2) <client mode mask>
2459 This command replies with the changed client mode mask that
2460 the client is required to keep locally.
2468 Internet Draft Secure Internet Live Conferencing 28 June 2000
2474 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2475 SILC_STATUS_ERR_TOO_MANY_PARAMS
2476 SILC_STATUS_ERR_NOT_REGISTERED
2477 SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
2478 SILC_STATUS_ERR_BAD_CLIENT_ID
2479 SILC_STATUS_ERR_NOT_YOU
2480 SILC_STATUS_ERR_UNKNOWN_MODE
2481 SILC_STATUS_ERR_NO_RECIPIENT
2482 SILC_STATUS_ERR_NO_CLIENT_ID
2485 18 SILC_COMMAND_CMODE
2488 Arguments: (1) <Channel ID> (2) <channel mode mask>
2489 (3) [<user limit>] (4) [<passphrase>]
2490 (5) [<Client ID>] (6) [<cipher>[:<key len>]]
2492 This command is used by client to set or change channel flags on
2493 a channel. Channel has several modes that set various properties
2494 of a channel. Modes may be masked together by ORing them thus
2495 having several modes set. The <Channel ID> is the ID of the
2496 target channel. The client changing channel mode must be on
2497 the same channel and poses sufficient privileges to be able to
2500 Following channel modes are defined:
2502 0x0000 SILC_CMODE_NONE
2504 No specific mode on channel. This is the default when
2505 channel is created. This means that channel is just plain
2509 0x0001 SILC_CMODE_PRIVATE
2511 Channel is private channel. Private channels are shown
2512 in the channel list listed with SILC_COMMAND_LIST command
2513 with indicatioin that the channel is private. Also,
2514 client on private channel will no be detected to be on
2515 the channel as the channel is not shown in the client's
2516 currently joined channel list. Channel founder and
2517 channel operator may set/unset this mode.
2524 Internet Draft Secure Internet Live Conferencing 28 June 2000
2527 Typical implementation would use [+|-]p on user interface
2528 to set/unset this mode.
2531 0x0002 SILC_CMODE_SECRET
2533 Channel is secret channel. Secret channels are not shown
2534 in the list listed with SILC_COMMAND_LIST command. Secret
2535 channels can be considered to be invisible channels.
2536 Channel founder and channel operator may set/unset this
2539 Typical implementation would use [+|-]s on user interface
2540 to set/unset this mode.
2543 0x0004 SILC_CMODE_PRIVKEY
2545 Channel uses private channel key to protect the traffic
2546 on the channel. When this mode is set the client will be
2547 responsible to set the key it wants to use to encrypt and
2548 decrypt the traffic on channel. Server generated channel
2549 keys are not used at all. This mode provides additional
2550 security as clients on channel may agree to use private
2551 channel key that even servers do not know. Naturally,
2552 this requires that every client on the channel knows
2553 the key before hand (it is considered to be pre-shared-
2554 key). This specification does not define how the private
2555 channel key is set as it is entirely local setting on
2558 As it is local setting it is possible to have several
2559 private channel keys on one channel. In this case several
2560 clients can talk on same channel but only those clients
2561 that share the key with the message sender will be able
2562 to hear the talking. Client should not display those
2563 message for the end user that it is not able to decrypt
2564 when this mode is set.
2566 Only channel founder may set/unset this mode. If this
2567 mode is unset the server will distribute new channel
2568 key to all clients on the channel which will be used
2571 Typical implementation would use [+|-]k on user interface
2572 to set/unset this mode.
2580 Internet Draft Secure Internet Live Conferencing 28 June 2000
2583 0x0008 SILC_CMODE_INVITE
2585 Channel is invite only channel. Client may join to this
2586 channel only if it is invited to the channel. Channel
2587 founder and channel operator may set/unset this mode.
2589 Typical implementation would use [+|-]i on user interface
2590 to set/unset this mode.
2593 0x0010 SILC_CMODE_TOPIC
2595 The topic of the channel may only be set by client that
2596 is channel founder or channel operator. Normal clients
2597 on channel will not be able to set topic when this mode
2598 is set. Channel founder and channel operator may set/
2601 Typical implementation would use [+|-]t on user interface
2602 to set/unset this mode.
2605 0x0020 SILC_CMODE_ULIMIT
2607 User limit has been set to the channel. New clients
2608 may not join to the channel when the limit set is
2609 reached. Channel founder and channel operator may set/
2610 unset the limit. The <user limit> argument is the
2611 number of limited users.
2613 Typical implementation would use [+|-]l on user interface
2614 to set/unset this mode.
2617 0x0040 SILC_CMODE_PASSPHRASE
2619 Passphrase has been set to the channel. Client may
2620 join to the channel only if it is able to provide the
2621 correct passphrase. Setting passphrases to channel
2622 is entirely safe as all commands are protected in the
2623 SILC network. Only channel founder may set/unset
2624 the passphrase. The <passphrase> argument is the
2627 Typical implementation would use [+|-]a on user interface
2628 to set/unset this mode.
2636 Internet Draft Secure Internet Live Conferencing 28 June 2000
2639 0x0080 SILC_CMODE_BAN
2641 Ban mask has been set to the channel. The ban mask
2642 may be used to ban specific clients to join the channel.
2643 The <ban mask> argument is the set ban mask. When
2644 unsetting a ban mask the mask must be provided as
2645 argument. Channel founder and channel operator may
2646 set/unset this mode. Channel founder may not be
2647 added to the ban list.
2649 Typical implementation would use [+|-]b on user interface
2650 to set/unset this mode.
2653 0x0100 SILC_CMODE_OPERATOR
2655 Sets channel operator privileges on the channel for a
2656 client on the channel. The <Client ID> argument is the
2657 target client on the channel. Channel founder and
2658 channel operator may set/unset (promote/demote) this
2661 Typical implementation would use [+|-]o on user interface
2662 to set/unset this mode.
2665 0x0200 SILC_CMODE_CIPHER
2667 Sets specific cipher to be used to protect channel
2668 traffic. The <cipher> argument is the requested cipher.
2669 When set or unset the server must re-generate new
2670 channel key. If <key len> argument is specified with
2671 <cipher> argument the new key is generated of <key len>
2674 Typical implementation would use [+|-]c on user interface
2675 to set/unset this mode.
2678 To make the mode system work, client must keep the channel mode
2679 mask locally so that the mode setting and unsetting would work
2680 without problems. The client receives the initial channel mode
2681 mask when it joins to the channel. When the mode changes on
2682 channel the server distributes the changed channel mode mask to
2683 all clients on the channel by sending SILC_COMMAND_CMODE command
2692 Internet Draft Secure Internet Live Conferencing 28 June 2000
2695 Reply messages to the command:
2698 Arguments: (1) <Status Payload> (2) <channel mode mask>
2700 This command replies with the changed channel mode mask that
2701 client is required to keep locally. The same mask is also
2702 sent to all clients on channel by sending additional command
2708 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2709 SILC_STATUS_ERR_TOO_MANY_PARAMS
2710 SILC_STATUS_ERR_NOT_REGISTERED
2711 SILC_STATUS_ERR_NOT_ON_CHANNEL
2712 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
2713 SILC_STATUS_ERR_BAD_CHANNEL_ID
2714 SILC_STATUS_ERR_NO_CHANNEL_ID
2715 SILC_STATUS_ERR_NO_CHANNEL_PRIV
2716 SILC_STATUS_ERR_UNKNOWN_MODE
2717 SILC_STATUS_ERR_NO_CLIENT_ID
2720 19 SILC_COMMAND_KICK
2723 Arguments: (1) <channel> (2) <Client ID>
2726 This command is used by channel operators to remove a client from
2727 channel. The <channel> argument is the channel the client to be
2728 removed is on currently. Note that the "kicker" must be on the same
2729 channel. If <comment> is provided it will be sent to the removed
2732 Reply messages to the command:
2735 Arguments: (1) <Status Payload>
2737 This command replies only with Status Payload.
2742 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2748 Internet Draft Secure Internet Live Conferencing 28 June 2000
2751 SILC_STATUS_ERR_TOO_MANY_PARAMS
2752 SILC_STATUS_ERR_NOT_REGISTERED
2753 SILC_STATUS_ERR_NO_SUCH_CHANNEL
2754 SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
2755 SILC_STATUS_ERR_NO_CHANNEL_PRIV
2756 SILC_STATUS_ERR_NO_CLIENT_ID
2759 20 SILC_COMMAND_RESTART
2764 This command may only be used by server operator to force a
2765 server to restart itself.
2767 Reply messages to the command:
2770 Arguments: (1) <Status Payload>
2772 This command replies only with Status Payload.
2777 SILC_STATUS_ERR_NOT_REGISTERED
2778 SILC_STATUS_ERR_NO_SERVER_PRIV
2781 21 SILC_COMMAND_CLOSE
2784 Arguments: (1) <Server ID>
2786 This command is used only by operator to close connection to a
2787 remote site. The <Server ID> argument is the ID of the remote
2788 site and must be valid.
2790 Reply messages to the command:
2793 Arguments: (1) <Status Payload>
2795 This command replies only with Status Payload.
2804 Internet Draft Secure Internet Live Conferencing 28 June 2000
2810 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2811 SILC_STATUS_ERR_TOO_MANY_PARAMS
2812 SILC_STATUS_ERR_NOT_REGISTERED
2813 SILC_STATUS_ERR_NO_SUCH_SERVER
2814 SILC_STATUS_ERR_NO_SERVER_PRIV
2815 SILC_STATUS_ERR_NO_SUCH_SERVER_ID
2823 This command is used only by operator to shutdown the server.
2824 All connections to the server will be closed and the server is
2827 Reply messages to the command:
2830 Arguments: (1) <Status Payload>
2832 This command replies only with Status Payload.
2837 SILC_STATUS_ERR_NOT_REGISTERED
2838 SILC_STATUS_ERR_NO_SERVER_PRIV
2841 23 SILC_COMMAND_SILCOPER
2844 Arguments: (1) <username> (2) <authentication data>
2846 This command is used by normal client to obtain router operator
2847 privileges (also known as SILC operator) on some router. Note
2848 that router operator has router privileges that supersedes the
2849 server operator privileges.
2851 The <username> is the username set in the server configurations
2852 as operator. The <authentication data> is the data that the
2853 client is authenticated against. It may be passphrase prompted
2854 for user on client's screen or it may be public key
2860 Internet Draft Secure Internet Live Conferencing 28 June 2000
2863 authentication data (data signed with private key), or
2866 Difference between router operator and server operator is that
2867 router operator is able to handle cell level properties while
2868 server operator (even on router server) is able to handle only
2869 local properties, such as, local connections and normal server
2872 Reply messages to the command:
2875 Arguments: (1) <Status Payload>
2877 This command replies only with Status Payload.
2882 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2883 SILC_STATUS_ERR_TOO_MANY_PARAMS
2884 SILC_STATUS_ERR_NOT_REGISTERED
2885 SILC_STATUS_ERR_BAD_PASSWORD
2886 SILC_STATUS_ERR_AUTH_FAILED
2889 24 SILC_COMMAND_LEAVE
2892 Arguments: (1) <Channel ID>
2894 This command is used by client to leave a channel the client is
2895 joined to. After a client has leaved the channel the server
2896 must create new key for the channel and distribute to all clients
2897 still currently on the channel.
2899 Reply messages to the command:
2902 Arguments: (1) <Status Payload>
2904 This command replies only with Status Payload.
2909 SILC_STATUS_ERR_NOT_REGISTERED
2910 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2916 Internet Draft Secure Internet Live Conferencing 28 June 2000
2919 SILC_STATUS_ERR_TOO_MANY_PARAMS
2920 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
2921 SILC_STATUS_ERR_BAD_CHANNEL_ID
2922 SILC_STATUS_ERR_NO_CHANNEL_ID
2925 25 SILC_COMMAND_NAMES
2928 Arguments: (1) <Channel ID>
2930 This command is used to list user names currently on the requested
2931 channel; argument <Channel ID>. The server must resolve the
2932 user names and send a comma (`,') separated list of user names
2933 on the channel. Server or router may resolve the names by sending
2934 SILC_COMMAND_WHOIS commands.
2936 If the requested channel is a private or secret channel, this
2937 command must not send the list of users, as private and secret
2938 channels cannot be seen by outside. In this case the returned
2939 name list may include a indication that the server could not
2940 resolve the names of the users on the channel.
2942 Reply messages to the command:
2945 Arguments: (1) <Status Payload> (2) <name list>
2947 This command replies with the comma separated list of users on
2953 SILC_STATUS_ERR_NOT_REGISTERED
2954 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
2955 SILC_STATUS_ERR_TOO_MANY_PARAMS
2956 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
2957 SILC_STATUS_ERR_BAD_CHANNEL_ID
2958 SILC_STATUS_ERR_NO_CHANNEL_ID
2959 SILC_STATUS_ERR_NOT_ON_CHANNEL
2964 Currently undefined commands.
2972 Internet Draft Secure Internet Live Conferencing 28 June 2000
2975 255 SILC_COMMAND_MAX
2977 Reserved command. This must not be sent.
2980 5.3 SILC Command Status Types
2982 5.3.1 SILC Command Status Payload
2984 Command Status Payload is sent in command reply messages to indicate
2985 the status of the command. The payload is one of argument in the
2986 command thus this is the data area in Command Argument Payload described
2987 in [SILC2]. The payload is only 2 bytes of length. Following diagram
2988 represents the Command Status Payload (field is always in MSB order).
2992 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
2993 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2995 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2997 Figure 5: SILC Command Status Payload
3000 o Status Message (2 bytes) - Indicates the status message.
3001 All Status messages are described in the next section.
3004 5.3.2 SILC Command Status List
3006 Command Status messages are returned in the command reply messages
3007 to indicate whether the command were executed without errors. If error
3008 has occured the status tells which error occured. Status payload only
3009 sends numeric reply about the status. Receiver of the payload must
3010 convert the numeric values into human readable error messages. The
3011 list of status messages below has an example human readable error
3012 messages that client may display for the user.
3014 List of all defined command status messages following.
3016 Generic status messages:
3020 Ok status. Everything went Ok. The status payload maybe
3021 safely ignored in this case.
3028 Internet Draft Secure Internet Live Conferencing 28 June 2000
3031 1 SILC_STATUS_LIST_START
3033 Start of the list. There will be several command replies and
3034 this reply is the start of the list.
3036 2 SILC_STATUS_LIST_END
3038 End of the list. There were several command replies and this
3039 reply is the last of the list. There won't be other replies
3040 beloning to this list after this one.
3044 Currently undefined and has been reserved for the future.
3047 Error status message:
3049 10 SILC_STATUS_ERR_NO_SUCH_NICK
3051 "No such nickname". Requested nickname does not exist.
3053 11 SILC_STATUS_ERR_NO_SUCH_CHANNEL
3055 "No such channel". Requested channel name does not exist.
3057 12 SILC_STATUS_ERR_NO_SUCH_SERVER
3059 "No such server". Requested server name does not exist.
3061 13 SILC_STATUS_ERR_TOO_MANY_TARGETS
3063 "Duplicate recipients. No message delivered". Message were
3064 tried to be sent to recipient which has several occurrences in
3067 14 SILC_STATUS_ERR_NO_RECIPIENT
3069 "No recipient given". Command required recipient which was
3072 15 SILC_STATUS_ERR_UNKNOWN_COMMAND
3074 "Unknown command". Command sent to server is unknown by the
3084 Internet Draft Secure Internet Live Conferencing 28 June 2000
3087 16 SILC_STATUS_ERR_WILDCARDS
3089 "Wildcards cannot be used". Wildcards were provided but they
3092 17 SILC_STATUS_ERR_NO_CLIENT_ID
3094 "No Client ID given". Client ID were expected as command
3095 parameter but were not found.
3097 18 SILC_STATUS_ERR_NO_CHANNEL_ID
3099 "No Channel ID given". Channel ID were expected as command
3100 parameter but were not found.
3102 19 SILC_STATUS_ERR_BAD_CLIENT_ID
3104 "Bad Client ID". Client ID provided were erroneous.
3106 20 SILC_STATUS_ERR_BAD_CHANNEL_ID
3108 "Bad Channel ID". Channel ID provided were erroneous.
3110 21 SILC_STATUS_ERR_NO_SUCH_CLIENT_ID
3112 "No such Client ID". Client ID provided does not exist.
3115 22 SILC_STATUS_ERR_NO_SUCH_CHANNEL_ID
3117 "No such Channel ID". Channel ID provided does not exist.
3119 23 SILC_STATUS_ERR_NICKNAME_IN_USE
3121 "Nickname already exists". Nickname created could not be
3122 registered because number of same nicknames were already set to
3123 maximum. This is not expected to happen in real life but is
3126 24 SILC_STATUS_ERR_NOT_ON_CHANNEL
3128 "You are not on that channel". The command were specified for
3129 client user is not currently on.
3131 25 SILC_STATUS_ERR_USER_ON_CHANNEL
3133 "User already on channel". User were invited on channel they
3140 Internet Draft Secure Internet Live Conferencing 28 June 2000
3143 26 SILC_STATUS_ERR_NOT_REGISTERED
3145 "You have not registered". User executed command that requires
3146 the client to be registered on the server before it may be
3149 27 SILC_STATUS_ERR_NOT_ENOUGH_PARAMS
3151 "Not enough parameters". Command requires more parameters
3154 28 SILC_STATUS_ERR_TOO_MANY_PARAMS
3156 "Too many parameters". Too many parameters were provided
3159 29 SILC_STATUS_ERR_PERM_DENIED
3161 "Your host is not among the privileged". The client tried to
3162 register on server that does not allow this host to connect.
3164 30 SILC_STATUS_ERR_BANNED_FROM_SERVER
3166 "You are banned from this server". The client tried to register
3167 on server that has explicitly denied this host to connect.
3169 31 SILC_STATUS_ERR_BAD_PASSWORD
3171 "Cannot join channel. Incorrect password". Password provided for
3172 channel were not accepted.
3174 32 SILC_STATUS_ERR_CHANNEL_IS_FULL
3176 "Cannot join channel. Channel is full". The channel is full
3177 and client cannot be joined to it.
3179 33 SILC_STATUS_ERR_NOT_INVITED
3181 "Cannot join channel. You have not been invited". The channel
3182 is invite only channel and client has not been invited.
3184 34 SILC_STATUS_ERR_BANNED_FROM_CHANNEL
3186 "Cannot join channel. You have been banned". The client has
3187 been banned from the channel.
3196 Internet Draft Secure Internet Live Conferencing 28 June 2000
3199 35 SILC_STATUS_ERR_UNKNOWN_MODE
3201 "Unknown mode". Mode provided by the client were unknown to
3204 36 SILC_STATUS_ERR_NOT_YOU
3206 "Cannot change mode for other users". User tried to change
3207 someone else's mode.
3209 37 SILC_STATUS_ERR_NO_CHANNEL_PRIV
3211 "Permission denied. You are not channel operator". Command may
3212 be executed only by channel operator.
3214 38 SILC_STATUS_ERR_NO_SERVER_PRIV
3216 "Permission denied. You are not server operator". Command may
3217 be executed only by server operator.
3219 39 SILC_STATUS_ERR_NO_ROUTER_PRIV
3221 "Permission denied. You are not SILC operator". Command may be
3222 executed only by router (SILC) operator.
3224 40 SILC_STATUS_ERR_BAD_NICKNAME
3226 "Bad nickname". Nickname requested contained illegal characters
3229 41 SILC_STATUS_ERR_BAD_CHANNEL
3231 "Bad channel name". Channel requested contained illegal characters
3234 42 SILC_STATUS_ERR_AUTH_FAILED
3236 "Authentication failed". The authentication data sent as
3237 argument were wrong and thus authentication failed.
3240 6 Security Considerations
3242 Security is central to the design of this protocol, and these security
3243 considerations permeate the specification.
3252 Internet Draft Secure Internet Live Conferencing 28 June 2000
3257 [SILC2] Riikonen, P., "SILC Packet Protocol", Internet Draft,
3260 [SILC3] Riikonen, P., "SILC Key Exchange and Authentication
3261 Protocols", Internet Draft, June 2000.
3263 [IRC] Oikarinen, J., and Reed D., "Internet Relay Chat Protocol",
3266 [SSH-TRANS] Ylonen, T., et al, "SSH Transport Layer Protocol",
3269 [PGP] Callas, J., et al, "OpenPGP Message Format", RFC 2440,
3272 [SPKI] Ellison C., et al, "SPKI Certificate Theory", RFC 2693,
3275 [PKIX-Part1] Housley, R., et al, "Internet X.509 Public Key
3276 Infrastructure, Certificate and CRL Profile", RFC 2459,
3279 [Schneier] Schneier, B., "Applied Cryptography Second Edition",
3280 John Wiley & Sons, New York, NY, 1996.
3282 [Menezes] Menezes, A., et al, "Handbook of Applied Cryptography",
3285 [OAKLEY] Orman, H., "The OAKLEY Key Determination Protocol",
3286 RFC 2412, November 1998.
3288 [ISAKMP] Maughan D., et al, "Internet Security Association and
3289 Key Management Protocol (ISAKMP)", RFC 2408, November
3292 [IKE] Harkins D., and Carrel D., "The Internet Key Exhange
3293 (IKE)", RFC 2409, November 1998.
3295 [HMAC] Krawczyk, H., "HMAC: Keyed-Hashing for Message
3296 Authentication", RFC 2104, February 1997.
3308 Internet Draft Secure Internet Live Conferencing 28 June 2000
3318 EMail: priikone@poseidon.pspt.fi