8 .ds RF FORMFEED[Page %]
17 Network Working Group P. Riikonen
19 draft-riikonen-silc-pp-05.txt XXX
26 <draft-riikonen-silc-pp-05.txt>
31 This document is an Internet-Draft and is in full conformance with
32 all provisions of Section 10 of RFC 2026. Internet-Drafts are
33 working documents of the Internet Engineering Task Force (IETF), its
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37 Internet-Drafts are draft documents valid for a maximum of six months
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39 time. It is inappropriate to use Internet-Drafts as reference
40 material or to cite them other than as "work in progress."
42 The list of current Internet-Drafts can be accessed at
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45 The list of Internet-Draft Shadow Directories can be accessed at
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48 The distribution of this memo is unlimited.
54 This memo describes a Packet Protocol used in the Secure Internet Live
55 Conferencing (SILC) protocol, specified in the Secure Internet Live
56 Conferencing, Protocol Specification Internet Draft [SILC1]. This
57 protocol describes the packet types and packet payloads which defines
58 the contents of the packets. The protocol provides secure binary packet
59 protocol that assures that the contents of the packets are secured and
73 1 Introduction .................................................. 3
74 1.1 Requirements Terminology .................................. 4
75 2 SILC Packet Protocol .......................................... 4
76 2.1 SILC Packet ............................................... 4
77 2.2 SILC Packet Header ........................................ 5
78 2.3 SILC Packet Types ......................................... 8
79 2.3.1 SILC Packet Payloads ................................ 17
80 2.3.2 Generic payloads .................................... 17
81 2.3.2.1 ID Payload .................................. 17
82 2.3.2.2 Argument Payload ............................ 18
83 2.3.2.3 Channel Payload ............................. 19
84 2.3.2.4 Public Key Payload .......................... 20
85 2.3.2.5 Message Payload ............................. 20
86 2.3.3 Disconnect Payload .................................. 20
87 2.3.4 Success Payload ..................................... 21
88 2.3.5 Failure Payload ..................................... 22
89 2.3.6 Reject Payload ...................................... 22
90 2.3.7 Notify Payload ...................................... 23
91 2.3.8 Error Payload ....................................... 31
92 2.3.9 Channel Message Payload ............................. 31
93 2.3.10 Channel Key Payload ................................ 35
94 2.3.11 Private Message Payload ............................ 36
95 2.3.12 Private Message Key Payload ........................ 38
96 2.3.13 Command Payload .................................... 39
97 2.3.14 Command Reply Payload .............................. 40
98 2.3.15 Connection Auth Request Payload .................... 40
99 2.3.16 New ID Payload ..................................... 42
100 2.3.17 New Client Payload ................................. 42
101 2.3.18 New Server Payload ................................. 43
102 2.3.19 New Channel Payload ................................ 44
103 2.3.20 Key Agreement Payload .............................. 45
104 2.3.21 Resume Router Payload .............................. 46
105 2.3.22 File Transfer Payload .............................. 46
106 2.3.23 Resume Client Payload .............................. 48
107 2.4 SILC ID Types ............................................. 49
108 2.5 Packet Encryption And Decryption .......................... 49
109 2.5.1 Normal Packet Encryption And Decryption ............. 50
110 2.5.2 Channel Message Encryption And Decryption ........... 50
111 2.5.3 Private Message Encryption And Decryption ........... 51
112 2.6 Packet MAC Generation ..................................... 52
113 2.7 Packet Padding Generation ................................. 52
114 2.8 Packet Compression ........................................ 53
115 2.9 Packet Sending ............................................ 53
116 2.10 Packet Reception ......................................... 54
117 2.11 Packet Routing ........................................... 54
118 2.12 Packet Broadcasting ...................................... 55
119 3 Security Considerations ....................................... 56
120 4 References .................................................... 56
121 5 Author's Address .............................................. 58
127 Figure 1: Typical SILC Packet
128 Figure 2: SILC Packet Header
130 Figure 4: Argument Payload
131 Figure 5: Channel Payload
132 Figure 6: Public Key Payload
133 Figure 7: Message Payload
134 Figure 8: Disconnect Payload
135 Figure 9: Success Payload
136 Figure 10: Failure Payload
137 Figure 11: Reject Payload
138 Figure 12: Notify Payload
139 Figure 13: Error Payload
140 Figure 14: Channel Key Payload
141 Figure 15: Private Message Key Payload
142 Figure 16: Command Payload
143 Figure 17: Connection Auth Request Payload
144 Figure 18: New Client Payload
145 Figure 19: New Server Payload
146 Figure 20: Key Agreement Payload
147 Figure 21: Resume Router Payload
148 Figure 22: File Transfer Payload
149 Figure 23: Resume Client Payload
155 This document describes a Packet Protocol used in the Secure Internet
156 Live Conferencing (SILC) protocol specified in the Secure Internet Live
157 Conferencing, Protocol Specification Internet Draft [SILC1]. This
158 protocol describes the packet types and packet payloads which defines
159 the contents of the packets. The protocol provides secure binary packet
160 protocol that assures that the contents of the packets are secured and
161 authenticated. The packet protocol is designed to be compact to avoid
162 unnecessary overhead as much as possible. This makes the SILC suitable
163 also in environment of low bandwidth requirements such as mobile networks.
164 All packet payloads can also be compressed to further reduce the size
167 The basis of SILC protocol relies in the SILC packets and it is with
168 out a doubt the most important part of the protocol. It is also probably
169 the most complicated part of the protocol. Packets are used all the
170 time in the SILC network to send messages, commands and other information.
171 All packets in SILC network are always encrypted and their integrity
172 is assured by computed MACs. The protocol defines several packet types
173 and packet payloads. Each packet type usually has a specific packet
174 payload that actually defines the contents of the packet. Each packet
175 also includes a default SILC Packet Header that provides sufficient
176 information about the origin of the packet and destination of the
181 1.1 Requirements Terminology
183 The keywords MUST, MUST NOT, REQUIRED, SHOULD, SHOULD NOT, RECOMMENDED,
184 MAY, and OPTIONAL, when they appear in this document, are to be
185 interpreted as described in [RFC2119].
189 2 SILC Packet Protocol
194 SILC packets deliver messages from sender to receiver securely by
195 encrypting important fields of the packet. The packet consists of
196 default SILC Packet Header, Padding, Packet Payload data, and, packet
199 The following diagram illustrates typical SILC packet.
204 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
205 | n bytes | 1 - n bytes | n bytes | n bytes
206 | SILC Header | Padding | Data Payload | MAC
207 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
211 Figure 1: Typical SILC Packet
214 SILC Header is always the first part of the packet and its purpose
215 is to provide information about the packet. It provides for example
216 the packet type, origin of the packet and the destination of the packet.
217 The header is variable in length. See the following section for
218 description of SILC Packet header. Packets without SILC header or
219 with malformed SILC header MUST be dropped.
221 Padding follows the packet header. The purpose of the padding is to
222 make the packet multiple by eight (8) or by the block size of the
223 cipher used in the encryption, which ever is larger. The maximum
224 length of padding is currently 128 bytes. The padding is always
225 encrypted. The padding is applied always, even if the packet is
226 not encrypted. See the section 2.7 Padding Generation for more
227 detailed information.
229 Data payload area follows padding and it is the actual data of the
230 packet. The packet data is the packet payloads defined in this
231 protocol. The data payload area is always encrypted.
233 The last part of SILC packet is the packet MAC that assures the
234 integrity of the packet. See the section 2.6 Packet MAC Generation
235 for more information. If compression is used the compsession is
236 always applied before encryption.
238 All fields in all packet payloads are always in MSB (most significant
243 2.2 SILC Packet Header
245 The SILC packet header is applied to all SILC packets and it is
246 variable in length. The purpose of SILC Packet header is to provide
247 detailed information about the packet. The receiver of the packet
248 uses the packet header to parse the packet and gain other relevant
249 parameters of the packet.
251 The following diagram represents the SILC packet header.
256 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
257 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
258 | Payload Length | Flags | Packet Type |
259 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
260 | Pad Length | RESERVED | Source ID Len | Dest ID Len |
261 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
267 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
273 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
277 Figure 2: SILC Packet Header
281 o Payload Length (2 bytes) - Is the length of the packet
282 not including the padding of the packet.
284 o Flags (1 byte) - Indicates flags to be used in packet
285 processing. Several flags may be set by ORing the flags
288 The following flags are reserved for this field:
293 In this case the field is ignored.
296 Private Message Key 0x01
298 Indicates that the packet must include private
299 message that is encrypted using private key set by
300 client. Servers does not know anything about this
301 key and this causes that the private message is
302 not handled by the server at all, it is just
303 passed along. See section 2.5.3 Private Message
304 Encryption And Decryption for more information.
309 Indicates that the packet consists of list of
310 packet payloads indicated by the Packet Type field.
311 The payloads are added one after the other. Note that
312 there are packet types that must not be used as
313 list. Parsing of list packet is done by calculating
314 the length of each payload and parsing them one by
320 Marks the packet to be broadcasted. Client cannot
321 send broadcast packet and normal server cannot send
322 broadcast packet. Only router server may send broadcast
323 packet. The router receiving of packet with this flag
324 set MUST send (broadcast) the packet to its primary
325 route. If router has several router connections the
326 packet may be sent only to the primary route. See
327 section 2.12 Packet Broadcasting for description of
333 Marks that the payload of the packet is compressed.
334 The sender of the packet marks this flag when it
335 compresses the payload, and any server or router
336 en route to the recipient MUST NOT unset this flag.
337 See section 2.8 Packet Compression for description of
345 o Packet Type (1 byte) - Is the type of the packet. Receiver
346 uses this field to parse the packet. See section 2.3
347 SILC Packets for list of defined packet types.
349 o Pad Length (1 byte) - Indicates the length of the padding
350 applied after the SILC Packet header. Maximum length for
351 padding is 128 bytes.
353 o RESERVED (1 byte) - Reserved field and must include a
356 o Source ID Length (1 byte) - Indicates the length of the
357 Source ID field in the header, not including this or any
360 o Destination ID Length (1 byte) - Indicates the length of the
361 Destination ID field in the header, not including this or
364 o Src ID Type (1 byte) - Indicates the type of ID in the
365 Source ID field. See section 2.4 SILC ID Types for
368 o Source ID (variable length) - The actual source ID that
369 indicates which is the original sender of the packet.
371 o Dst ID Type (1 byte) - Indicates the type of ID in the
372 Destination ID field. See section 2.4 SILC ID Types for
375 o Destination ID (variable length) - The actual destination
376 ID that indicates which is the end receiver of the packet.
381 2.3 SILC Packet Types
383 SILC packet types defines the contents of the packet and it is used by
384 the receiver to parse the packet. The packet type is 8 bits, as a one
385 byte, in length. The range for the packet types are from 0 - 255,
386 where 0 is never sent and 255 is currently reserved for future
387 extensions and MUST NOT be defined to any other purpose. Every SILC
388 specification compliant implementation SHOULD support all of these packet
391 The below list of the SILC Packet types includes reference to the packet
392 payload as well. Packet payloads are the actual packet, that is, the data
393 that the packet consists of. Each packet type defines packet payload
394 which usually may only be sent with the specific packet type.
396 Most of the packets are packets that must be destined directly to entity
397 that is connected to the sender. It is not allowed, for example, for
398 router to send disconnect packet to client that is not directly connected
399 to the router. However, there are some special packet types that may
400 be destined to some entity that the sender has not direct connection
401 with. These packets are for example private message packets, channel
402 message packets, command packets and some other packets that may be
403 broadcasted in the SILC network. If the packet is allowed to be sent to
404 indirectly connected entity it is mentioned separately in the packet
405 description (unless it is obvious as in private and channel message
406 packets). Other packets MUST NOT be sent or accepted, if sent, to
407 indirectly connected entities.
409 List of SILC Packet types are defined as follows.
414 This type is reserved and it is never sent.
417 1 SILC_PACKET_DISCONNECT
419 This packet is sent to disconnect the remote end. Reason of
420 the disconnection is sent inside the packet payload. Client
421 usually does not send this packet.
423 This packet MUST NOT be sent as list and the List flag MUST
426 Payload of the packet: See section 2.3.3 Disconnect Payload
429 2 SILC_PACKET_SUCCESS
431 This packet is sent upon successful execution of some protocol.
432 The status of the success is sent in the packet.
434 This packet MUST NOT be sent as list and the List flag MUST
437 Payload of the packet: See section 2.3.4 Success Payload
440 3 SILC_PACKET_FAILURE
442 This packet is sent upon failure of some protocol. The status
443 of the failure is sent in the packet.
445 This packet MUST NOT be sent as list and the List flag MUST
448 Payload of the packet: See section 2.3.5 Failure Payload
453 This packet MAY be sent upon rejection of some protocol.
454 The status of the rejection is sent in the packet.
456 This packet MUST NOT be sent as list and the List flag MUST
459 Payload of the packet: See section 2.3.6 Reject Payload
464 This packet is used to send notify message, usually from
465 server to client, although it MAY be sent from server to another
466 server as well. Client MUST NOT send this packet. Server MAY
467 send this packet to channel as well when the packet is
468 distributed to all clients on the channel.
470 Payload of the packet: See section 2.3.7 Notify Payload.
476 This packet is sent when an error occurs. Server MAY
477 send this packet. Client MUST NOT send this packet. The
478 client MAY entirely ignore the packet, however, server is
479 most likely to take action anyway. This packet MAY be sent
480 to entity that is indirectly connected to the sender.
482 This packet MUST NOT be sent as list and the List flag MUST
485 Payload of the packet: See section 2.3.8 Error Payload.
488 7 SILC_PACKET_CHANNEL_MESSAGE
490 This packet is used to send messages to channels. The packet
491 includes Channel ID of the channel and the actual message to
492 the channel. Messages sent to the channel are always protected
493 by channel specific keys. Channel Keys are distributed by
494 SILC_PACKET_CHANNEL_KEY packet.
496 This packet MUST NOT be sent as list and the List flag MUST
499 Payload of the packet: See section 2.3.9 Channel Message
503 8 SILC_PACKET_CHANNEL_KEY
505 This packet is used to distribute new key for particular
506 channel. Each channel has their own independent keys that
507 is used to protect the traffic on the channel. Only server
508 may send this packet. This packet MAY be sent to entity
509 that is indirectly connected to the sender.
511 This packet MUST NOT be sent as list and the List flag MUST
514 Payload of the packet: See section 2.3.10 Channel Key Payload
517 9 SILC_PACKET_PRIVATE_MESSAGE
519 This packet is used to send private messages from client
520 to another client. By default, private messages are protected
521 by session keys established by normal key exchange protocol.
522 However, it is possible to use specific key to protect private
523 messages. SILC_PACKET_PRIVATE_MESSAGE_KEY packet is used to
524 agree the key with the remote client. Pre-shared key MAY be
525 used as well if both of the client knows it, however, it needs
526 to be agreed outside SILC. See more of this in [SILC1].
528 This packet MUST NOT be sent as list and the List flag MUST
531 Payload of the packet: See section 2.3.11 Private Message
535 10 SILC_PACKET_PRIVATE_MESSAGE_KEY
537 This packet is used to agree about a key to be used to protect
538 the private messages between two clients. If this is not sent
539 the normal session key is used to protect the private messages
540 inside SILC network. Agreeing to use specific key to protect
541 private messages adds security, as no server between the two
542 clients will be able to decrypt the private message. However,
543 servers inside SILC network are considered to be trusted, thus
544 using normal session key to protect private messages does not
545 degrade security. Whether to agree to use specific keys by
546 default or to use normal session keys by default, is
547 implementation specific issue. See more of this in [SILC1].
549 This packet MUST NOT be sent as list and the List flag MUST
552 Payload of the packet: See section 2.3.12 Private Message
556 11 SILC_PACKET_COMMAND
558 This packet is used to send commands from client to server.
559 Server MAY send this packet to other servers as well. All
560 commands are listed in their own section SILC Command Types
561 in [SILC4]. The contents of this packet is command specific.
562 This packet MAY be sent to entity that is indirectly connected
565 This packet MUST NOT be sent as list and the List flag MUST
568 Payload of the packet: See section 2.3.13 Command Payload
571 12 SILC_PACKET_COMMAND_REPLY
573 This packet is sent as reply to the SILC_PACKET_COMMAND packet.
574 The contents of this packet is command specific. This packet
575 MAY be sent to entity that is indirectly connected to the
578 This packet MUST NOT be sent as list and the List flag MUST
581 Payload of the packet: See section 2.3.14 Command Reply
582 Payload and section 2.3.13 Command
588 13 SILC_PACKET_KEY_EXCHANGE
590 This packet is used to start SILC Key Exchange Protocol,
591 described in detail in [SILC3].
593 This packet MUST NOT be sent as list and the List flag MUST
596 Payload of the packet: Payload of this packet is described
597 in the section SILC Key Exchange
598 Protocol and its sub sections in
602 14 SILC_PACKET_KEY_EXCHANGE_1
604 This packet is used as part of the SILC Key Exchange Protocol.
606 This packet MUST NOT be sent as list and the List flag MUST
609 Payload of the packet: Payload of this packet is described
610 in the section SILC Key Exchange
611 Protocol and its sub sections in
615 15 SILC_PACKET_KEY_EXCHANGE_2
617 This packet is used as part of the SILC Key Exchange Protocol.
619 This packet MUST NOT be sent as list and the List flag MUST
622 Payload of the packet: Payload of this packet is described
623 in the section SILC Key Exchange
624 Protocol and its sub sections in
628 16 SILC_PACKET_CONNECTION_AUTH_REQUEST
630 This packet is used to request the authentication method to
631 be used in the SILC Connection Authentication Protocol. If
632 initiator of the protocol does not know the mandatory
633 authentication method this packet MAY be used to determine it.
635 The party receiving this payload MUST respond with the same
636 packet including the mandatory authentication method.
638 This packet MUST NOT be sent as list and the List flag MUST
641 Payload of the packet: See section 2.3.15 Connection Auth
647 17 SILC_PACKET_CONNECTION_AUTH
649 This packet is used to start and perform the SILC Connection
650 Authentication Protocol. This protocol is used to authenticate
651 the connecting party. The protocol is described in detail in
654 This packet MUST NOT be sent as list and the List flag MUST
657 Payload of the packet: Payload of this packet is described
658 in the section SILC Authentication
659 Protocol and it sub sections in [SILC].
662 18 SILC_PACKET_NEW_ID
664 This packet is used to distribute new ID's from server to
665 router and from router to all routers in the SILC network.
666 This is used when for example new client is registered to
667 SILC network. The newly created ID's of these operations are
668 distributed by this packet. Only server may send this packet,
669 however, client MUST be able to receive this packet. This
670 packet MAY be sent to entity that is indirectly connected
673 Payload of the packet: See section 2.3.16 New ID Payload
676 19 SILC_PACKET_NEW_CLIENT
678 This packet is used by client to register itself to the
679 SILC network. This is sent after key exchange and
680 authentication protocols has been completed. Client sends
681 various information about itself in this packet.
683 This packet MUST NOT be sent as list and the List flag MUST
686 Payload of the packet: See section 2.3.17 New Client Payload
689 20 SILC_PACKET_NEW_SERVER
691 This packet is used by server to register itself to the
692 SILC network. This is sent after key exchange and
693 authentication protocols has been completed. Server sends
694 this to the router it connected to, or, if router was
695 connecting, to the connected router. Server sends its
696 Server ID and other information in this packet. The client
697 MUST NOT send or receive this packet.
699 This packet MUST NOT be sent as list and the List flag MUST
702 Payload of the packet: See section 2.3.18 New Server Payload
705 21 SILC_PACKET_NEW_CHANNEL
707 This packet is used to notify routers about newly created
708 channel. Channels are always created by the router and it MUST
709 notify other routers about the created channel. Router sends
710 this packet to its primary route. Client MUST NOT send this
711 packet. This packet MAY be sent to entity that is indirectly
712 connected to the sender.
714 Payload of the packet: See section 2.3.19 New Channel Payload
719 This packet is used to indicate that re-key must be performed
720 for session keys. See section Session Key Regeneration in
721 [SILC1] for more information. This packet does not have
724 This packet MUST NOT be sent as list and the List flag MUST
728 23 SILC_PACKET_REKEY_DONE
730 This packet is used to indicate that re-key is performed and
731 new keys must be used hereafter.
733 This packet MUST NOT be sent as list and the List flag MUST
737 24 SILC_PACKET_HEARTBEAT
739 This packet is used by clients, servers and routers to keep the
740 connection alive. It is recommended that all servers implement
741 keepalive actions and perform it to both direction in a link.
742 This packet does not have a payload.
744 This packet MUST NOT be sent as list and the List flag MUST
748 25 SILC_PACKET_KEY_AGREEMENT
750 This packet is used by clients to request key negotiation
751 between another client in the SILC network. If the negotiation
752 is started it is performed using the SKE protocol. The result of
753 the negotiation, the secret key material, can be used for
754 example as private message key. The server and router MUST NOT
757 This packet MUST NOT be sent as list and the List flag MUST
760 Payload of the packet: See section 2.3.20 Key Agreement Payload
765 26 SILC_PACKET_RESUME_ROUTER
767 This packet is used during backup router protocol when the
768 original primary router of the cell comes back online and wishes
769 to resume the position as being the primary router of the cell.
771 Payload of the packet: See section 2.3.21 Resume Router Payload
776 This packet is used to perform an file transfer protocol in the
777 SILC session with some entity in the network. The packet is
778 multi purpose. The packet is used to tell other entity in the
779 network that the sender wishes to perform an file transfer
780 protocol. The packet is also used to actually tunnel the
781 file transfer protocol stream. The file transfer protocol
782 stream is always protected with the SILC packet.
784 This packet MUST NOT be sent as list and the List flag MUST
787 Payload of the packet: See section 2.3.22 File Transfer Payload
790 28 SILC_PACKET_RESUME_CLIENT
792 This packet is used to resume a client back to the network
793 after it has been detached. A client is able to detach from
794 the network but the client is still valid client in the network.
795 The client may then later resume its session back by sending
796 this packet to a server. Routers also use this packet to notify
797 other routers in the network that the detached client has resumed.
799 This packet MUST NOT be sent as list and the List flag MUST
802 Payload of the packet: See section 2.3.23 Resume Client Payload
807 Currently undefined commands.
812 These packet types are reserved for private use and they will
813 not be defined by this document.
818 This type is reserved for future extensions and currently it
824 2.3.1 SILC Packet Payloads
826 All payloads resides in the main data area of the SILC packet. However
827 all payloads MUST be at the start of the data area after the SILC
828 packet header and padding. All fields in the packet payload are always
829 encrypted, as they reside in the data area of the packet which is
832 Payloads described in this section are common payloads that MUST be
833 accepted anytime during SILC session. Most of the payloads may only
834 be sent with specific packet type which is defined in the description
837 There are a lot of other payloads in the SILC as well. However, they
838 are not common in the sense that they could be sent at any time.
839 These payloads are not described in this section. These are payloads
840 such as SILC Key Exchange payloads and so on. These are described
841 in [SILC1], [SILC3] and [SILC4].
845 2.3.2 Generic payloads
847 This section describes generic payloads that are not associated to any
848 specific packet type. They can be used for example inside some other
855 This payload can be used to send an ID. ID's are variable in length
856 thus this payload provides a way to send variable length ID's.
858 The following diagram represents the ID Payload.
868 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
869 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
870 | ID Type | ID Length |
871 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
875 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
883 o ID Type (2 bytes) - Indicates the type of the ID. See
884 section 2.4 SILC ID Types for list of defined ID types.
886 o ID Length (2 bytes) - Length of the ID Data area not
887 including the length of any other fields in the payload.
889 o ID Data (variable length) - The actual ID data.
894 2.3.2.2 Argument Payload
896 Argument Payload is used to set arguments for any packet payload that
897 needs and supports arguments, such as commands. Number of arguments
898 associated with a packet MUST be indicated by the packet payload which
899 needs the arguments. Argument Payloads MUST always reside right after
900 the packet payload needing the arguments. Incorrect amount of argument
901 payloads MUST cause rejection of the packet.
903 The following diagram represents the Argument Payload.
908 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
909 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
910 | Payload Length | Argument Type | |
911 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
915 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
919 Figure 4: Argument Payload
923 o Payload Length (2 bytes) - Length of the Argument Data
924 area not including the length of any other field in the
927 o Argument Type (1 byte) - Indicates the type of the argument.
928 Every argument can have a specific type that MUST be defined
929 by the packet payload needing the argument. For example
930 every command specify a number for each argument that may be
931 associated with the command. By using this number the receiver
932 of the packet knows what type of argument this is. If there is
933 no specific argument type this field is set to zero (0) value.
935 o Argument Data (variable length) - Argument data.
940 2.3.2.3 Channel Payload
942 Generic Channel Payload may be used to send information about channel,
943 its name, the Channel ID and a mode.
945 The following diagram represents the Channel Payload.
950 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
951 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
952 | Channel Name Length | |
953 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
957 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
958 | Channel ID Length | |
959 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
963 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
965 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
969 Figure 5: New Channel Payload
973 o Channel Name Length (2 bytes) - Length of the channel name
976 o Channel Name (variable length) - The name of the channel.
978 o Channel ID Length (2 bytes) - Length of the Channel ID field.
980 o Channel ID (variable length) - The Channel ID.
982 o Mode Mask (4 bytes) - A mode. This can be the mode of the
983 channel but it can also be the mode of the client on the
984 channel. The contents of this field is dependent of the
985 usage of this payload. The usage is defined separately
986 when this payload is used. This is a 32 bit MSB first value.
991 2.3.2.4 Public Key Payload
993 Generic Public Key Payload may be used to send different types of
994 public keys and certificates.
996 The following diagram represents the Public Key Payload.
1003 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
1004 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1005 | Public Key Length | Public Key Type |
1006 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1008 ~ Public Key (or certificate) ~
1010 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1014 Figure 6: Public Key Payload
1018 o Public Key Length (2 bytes) - The length of the Public Key
1019 (or certificate) field, not including any other field.
1021 o Public Key Type (2 bytes) - The public key (or certificate)
1022 type. This field indicates the type of the public key in
1023 the packet. See the [SILC3] for defined public key types.
1025 o Public Key (or certificate) (variable length) - The
1026 public key or certificate.
1031 2.3.2.5 Message Payload
1033 Generic Message Payload can be used to send message in SILC. It
1034 is used to send channel messages and private messages.
1036 The following diagram represents the Message Payload.
1038 (*) indicates that the field is not encrypted.
1043 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
1044 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1045 | Message Flags | Message Length |
1046 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1050 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1051 | Padding Length | |
1052 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1056 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1058 ~ Initial Vector * ~
1060 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1064 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1068 Figure 7: Message Payload
1072 o Message Flags (2 bytes) - Includes the Message Flags of the
1073 message. The flags can indicate a reason or purpose for
1074 the message. The following Message Flags are defined:
1076 0x0000 SILC_MESSAGE_FLAG_NONE
1078 No specific flags set.
1080 0x0001 SILC_MESSAGE_FLAG_AUTOREPLY
1082 This message is an automatic reply to an earlier
1085 0x0002 SILC_MESSAGE_FLAG_NOREPLY
1087 There should not be reply messages to this
1090 0x0004 SILC_MESSAGE_FLAG_ACTION
1092 The sender is performing an action and the message
1093 is the indication of the action.
1095 0x0008 SILC_MESSAGE_FLAG_NOTICE
1097 The message is for example an informational notice
1100 0x0010 SILC_MESSAGE_FLAG_REQUEST
1102 This is a generic request flag to send request
1103 messages. A separate document should define any
1104 payloads associated to this flag.
1106 0x0020 SILC_MESSAGE_FLAG_SIGNED
1108 This flag indicates that the message is signed
1109 with sender's private key and thus can be verified
1110 by the receiver using the sender's public key. A
1111 separate document should define the detailed procedure
1112 of the signing process and any associated payloads
1115 0x0040 SILC_MESSAGE_FLAG_REPLY
1117 This is a generic reply flag to send a reply to
1118 previously received request. A separate document
1119 should define any payloads associated to this flag.
1121 0x0080 SILC_MESSAGE_FLAG_DATA
1123 This is a generic data flag, indicating that the
1124 message includes some data which can be interpreted
1125 in a specific way. Using this flag any kind of data
1126 can be delivered inside message payload. A separate
1127 document should define how this flag is interpreted
1128 and define any associated payloads.
1130 0x0100 SILC_MESSAGE_FLAG_UTF8
1132 This flag indicates that the message is UTF-8 encoded
1133 textual message. When sending text messages this
1134 flag SHOULD be used. When this flag is used the text
1135 sent as message MUST be UTF-8 encoded.
1137 0x0200 - 0x0800 RESERVED
1139 Reserved for future flags.
1141 0x1000 - 0x8000 PRIVATE RANGE
1143 Private range for free use.
1145 o Message Length (2 bytes) - Indicates the length of the
1146 Message Data field in the payload, not including any
1149 o Message Data (variable length) - The actual message data.
1151 o Padding Length (2 bytes) - Indicates the length of the
1152 Padding field in the payload, not including any other
1155 o Padding (variable length) - If this payload is used as
1156 channel messages, the padding MUST be applied because
1157 this payload is encrypted separately from other parts
1158 of the packet. If this payload is used as private
1159 messages, the padding is present only when the payload
1160 is encrypted with private message key. If encrypted
1161 with session keys this field is not present and the
1162 Padding Length field includes a zero (0) value. The
1163 padding SHOULD be random data.
1165 o Initial Vector (variable length) - This field MUST be
1166 present when this payload is used as channel messages.
1168 When encrypting private messages with session keys this
1169 field MUST NOT be present. For private messages this
1170 field is present only when encrypting with a static
1171 private message key (pre-shared key). If randomly
1172 generated key material is used this field MUST NOT be
1173 present. Also, If Key Agreement (SKE) was used to
1174 negotiate fresh key material for private message key
1175 this field MUST NOT be present. See the section 4.6
1176 in [SILC1] for more information about IVs when
1177 encrypting private messages.
1179 This field includes the initial vector used in message
1180 encryption. It need to be used in the packet decryption
1181 as well. Contents of this field depends on the encryption
1182 algorithm and encryption mode. This field is not encrypted,
1183 is not included in padding calculation and its length
1184 equals to cipher's block size. This field is authenticated
1187 o MAC (variable length) - The MAC computed from the
1188 Message Flags, Message Length, Message Data, Padding Length,
1189 Padding and Initial Vector fields in that order. The MAC
1190 is computed after the payload is encrypted. This is so
1191 called Encrypt-Then-MAC order; first encrypt, then compute
1192 MAC from ciphertext. The MAC protects the integrity of
1193 the Message Payload. Also, when used as channel messages
1194 it is possible to have multiple private channel keys set,
1195 and receiver can use MAC to verify which of the keys must
1196 be used in decryption. This field is not encrypted.
1201 2.3.3 Disconnect Payload
1203 Disconnect payload is sent upon disconnection. The payload is simple;
1204 reason of disconnection is sent to the disconnected party.
1206 The payload may only be sent with SILC_PACKET_DISCONNECT packet. It
1207 MUST NOT be sent in any other packet type. The following diagram
1208 represents the Disconnect Payload.
1214 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
1215 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1219 ~ Disconnect Message ~
1221 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1225 Figure 8: Disconnect Payload
1228 o Status (1 byte) - Indicates the Status Type, defined in [SILC3]
1229 for the reason of disconnection.
1231 o Disconnect Message (variable length) - Human readable UTF-8
1232 encoded string indicating reason of the disconnection. This
1238 2.3.4 Success Payload
1240 Success payload is sent when some protocol execution is successfully
1241 completed. The payload is simple; indication of the success is sent.
1242 This may be any data, including binary or human readable data.
1247 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
1248 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1250 ~ Success Indication ~
1252 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1256 Figure 9: Success Payload
1260 o Success Indication (variable length) - Indication of
1261 the success. This may be for example some flag that
1262 indicates the protocol and the success status or human
1263 readable success message. The true length of this
1264 payload is available by calculating it from the SILC
1271 2.3.5 Failure Payload
1273 This is opposite of Success Payload. Indication of failure of
1274 some protocol is sent in the payload.
1280 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
1281 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1283 ~ Failure Indication ~
1285 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1289 Figure 10: Failure Payload
1293 o Failure Indication (variable length) - Indication of
1294 the failure. This may be for example some flag that
1295 indicates the protocol and the failure status or human
1296 readable failure message. The true length of this
1297 payload is available by calculating it from the SILC
1303 2.3.6 Reject Payload
1305 This payload is sent when some protocol is rejected to be executed.
1306 Other operations MAY send this as well that was rejected. The
1307 indication of the rejection is sent in the payload. The indication
1308 may be binary or human readable data.
1314 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
1315 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1317 ~ Reject Indication ~
1319 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1323 Figure 11: Reject Payload
1327 o Reject Indication (variable length) - Indication of
1328 the rejection. This maybe for example some flag that
1329 indicates the protocol and the rejection status or human
1330 readable rejection message. The true length of this
1331 payload is available by calculating it from the SILC
1337 2.3.7 Notify Payload
1339 Notify payload is used to send notify messages. The payload is usually
1340 sent from server to client, however, server MAY send it to another
1341 server as well. This payload MAY also be sent to a channel. Client
1342 MUST NOT send this payload. The receiver of this payload MAY ignore
1343 the contents of the payload, however, notify message SHOULD be audited.
1345 The payload may only be sent with SILC_PACKET_NOTIFY packet. It MUST
1346 not be sent in any other packet type. The following diagram represents
1355 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
1356 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1357 | Notify Type | Payload Length |
1358 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1364 Figure 12: Notify Payload
1368 o Notify Type (2 bytes) - Indicates the type of the notify
1371 o Payload Length (2 bytes) - Length of the entire Notify Payload
1372 including any associated Argument Payloads.
1374 o Argument Nums (1 byte) - Indicates the number of Argument
1375 Payloads associated to this payload. Notify types may define
1376 arguments to be send along the notify message.
1379 The following list of currently defined notify types. The format for
1380 notify arguments is same as in SILC commands described in [SILC4].
1381 Note that all ID's sent in arguments are sent inside ID Payload. Also
1382 note that all passphrases that may be sent inside arguments MUST be
1383 UTF-8 [RFC2279] encoded. Also note that all public keys or certificates
1384 sent in arguments are actually Public Key Payloads.
1388 0 SILC_NOTIFY_TYPE_NONE
1390 If no specific notify type apply for the notify message this type
1394 Arguments: (1) <message>
1396 The <message> is implementation specific free UTF-8 text string.
1397 Receiver MAY ignore this message.
1400 1 SILC_NOTIFY_TYPE_INVITE
1402 Sent when an client is invited to a channel. This is also sent
1403 when the invite list of the channel is changed. This notify type
1404 is sent between routers and if an client was invited, to the
1405 client as well. In this case the packet is destined to the client.
1408 Arguments: (1) <Channel ID> (2) <channel name>
1409 (3) [<sender Client ID>] (4) [<add | del>]
1412 The <Channel ID> is the channel. The <channel name> is the name
1413 of the channel and is provided because the client which receives
1414 this notify packet may not have a way to resolve the name of the
1415 channel from the <Channel ID>. The <sender Client ID> is the
1416 Client ID which invited the client to the channel. The <add | del>
1417 is an argument of size of 1 byte where 0x00 means adding a client
1418 to invite list, and 0x01 means deleting a client from invite list.
1419 The <invite list>, if present, indicates the information to be
1420 added to or removed from the invite list. The <invite list>
1421 format is defined in [SILC4] with SILC_COMMAND_INVITE command.
1422 When this notify is destined to a client the <add | del> and
1423 <invite list> MUST NOT be sent.
1426 2 SILC_NOTIFY_TYPE_JOIN
1428 Sent when client has joined to a channel. The server MUST
1429 distribute this type only to the local clients on the channel
1430 and then send it to its primary router. The router or server
1431 receiving the packet distributes this type to the local clients
1432 on the channel and broadcast it to the network.
1435 Arguments: (1) [<Client ID>] (2) <Channel ID>
1437 The <Client ID> is the client that joined to the channel indicated
1438 by the <Channel ID>.
1441 3 SILC_NOTIFY_TYPE_LEAVE
1443 Sent when client has left a channel. The server must distribute
1444 this type only to the local clients on the channel and then send
1445 it to its primary router. The router or server receiving the
1446 packet distributes this type to the local clients on the channel
1447 and broadcast it to the network.
1450 Arguments: (1) <Client ID>
1452 The <Client ID> is the client which left the channel.
1455 4 SILC_NOTIFY_TYPE_SIGNOFF
1457 Sent when client signoff from SILC network. The server MUST
1458 distribute this type only to the local clients on the channel and
1459 then send it to its primary router. The router or server receiving
1460 the packet distributes this type to the local clients on the
1461 channel and broadcast it to the network.
1464 Arguments: (1) <Client ID> (2) <message>
1466 The <Client ID> is the client which left SILC network. The
1467 <message> is free text string indicating the reason of the signoff.
1470 5 SILC_NOTIFY_TYPE_TOPIC_SET
1472 Sent when topic is set/changed on a channel. This type must be
1473 sent only to the clients which is joined on the channel which
1474 topic was set or changed.
1477 Arguments: (1) <ID Payload> (2) <topic>
1479 The <ID Payload> is the ID of the entity who set the topic. It
1480 usually is Client ID but it can be Server ID and Channel ID as well.
1485 6 SILC_NOTIFY_TYPE_NICK_CHANGE
1487 Sent when client changes nick on a channel. The server MUST
1488 distribute this type only to the local clients on the channel
1489 and then send it to its primary router. The router or server
1490 receiving the packet distributes this type to the local clients
1491 on the channel and broadcast it to the network.
1494 Arguments: (1) <Old Client ID> (2) <New Client ID>
1497 The <Old Client ID> is the old ID of the client which changed
1498 the nickname. The <New Client ID> is the new ID generated by
1499 the change of the nickname. The <nickname> is the new nickname.
1500 Note that it is possible to send this notify even if the nickname
1501 has not changed, but client ID has changed.
1504 7 SILC_NOTIFY_TYPE_CMODE_CHANGE
1506 Sent when channel mode has changed. This type MUST be sent only
1507 to the clients which is joined on the channel which mode was
1511 Arguments: (1) <ID Payload> (2) <mode mask>
1512 (3) [<cipher>] (4) <[hmac>]
1513 (5) [<passphrase>] (6) [<founder public key>]
1515 The <ID Payload> is the ID (usually Client ID but it can be
1516 Server ID as well when the router is enforcing channel mode
1517 change) of the entity which changed the mode. The <mode mask>
1518 is the new mode mask of the channel. The client can safely
1519 ignore the <cipher> argument since the SILC_PACKET_CHANNEL_KEY
1520 packet will force the new channel key change anyway. The <hmac>
1521 argument is important since the client is responsible of setting
1522 the new HMAC and the hmac key into use. The <passphrase> is
1523 the passphrase of the channel, if it was now set. The <founder
1524 public key> argument is sent when the founder mode on the
1525 channel was set. All routers and servers that receive the packet
1526 MUST save the founder's public key so that the founder can
1527 reclaim the channel founder rights back for the channel on any
1528 server in the network.
1533 8 SILC_NOTIFY_TYPE_CUMODE_CHANGE
1535 Sent when user mode on channel has changed. This type MUST be
1536 sent only to the clients which is joined on the channel where
1537 the target client is on.
1540 Arguments: (1) <ID Payload> (2) <mode mask>
1541 (3) <Target Client ID> (3) [<founder pubkey>]
1543 The <ID Payload> is the ID (usually Client ID but it can be
1544 Server ID as well when the router is enforcing user's mode
1545 change) of the entity which changed the mode. The <mode mask>
1546 is the new mode mask of the channel. The <Target Client ID>
1547 is the client which mode was changed. The <founder pubkey>
1548 is the public key of the channel founder and is sent only
1549 when first setting the channel founder mode using the
1550 SILC_COMMAND_CUMODE command, and when sending this notify.
1553 9 SILC_NOTIFY_TYPE_MOTD
1555 Sent when Message of the Day (motd) is sent to a client.
1558 Arguments: (1) <motd>
1560 The <motd> is the Message of the Day.
1563 10 SILC_NOTIFY_TYPE_CHANNEL_CHANGE
1565 Sent when channel's ID has changed for a reason or another.
1566 This is sent by normal server to the client. This can also be
1567 sent by router to other server to force the Channel ID change.
1568 The Channel ID MUST be changed to use the new one. When sent
1569 to clients, this type MUST be sent only to the clients which is
1570 joined on the channel.
1573 Arguments: (1) <Old Channel ID> (2) <New Channel ID>
1575 The <Old Channel ID> is the channel's old ID and the <New
1576 Channel ID> is the new one that MUST replace the old one.
1577 Server which receives this from router MUST re-announce the
1578 channel to the router by sending SILC_PACKET_NEW_CHANNEL packet
1579 with the new Channel ID.
1582 11 SILC_NOTIFY_TYPE_SERVER_SIGNOFF
1584 Sent when server quits SILC network. Those clients from this
1585 server that are on channels must be removed from the channel.
1588 Arguments: (1) <Server ID> (n) [<Client ID>] [...]
1590 The <Server ID> is the server's ID. The rest of the arguments
1591 are the Client ID's of the client's which are coming from this
1592 server and are thus quitting the SILC network also. If the
1593 maximum number of arguments are reached another
1594 SILC_NOTIFY_TYPE_SERVER_SIGNOFF notify packet MUST be sent.
1595 When this notify packet is sent between routers the Client ID's
1596 MAY be omitted. Server receiving the Client ID's in the payload
1597 may use them directly to remove the client.
1600 12 SILC_NOTIFY_TYPE_KICKED
1602 Sent when a client has been kicked from a channel. This is
1603 sent also to the client which was kicked from the channel.
1604 The client which was kicked from the channel MUST be removed
1605 from the channel. The client MUST also be removed from channel's
1606 invite list if it is explicitly added in the list. This notify
1607 type is always destined to the channel. The router or server
1608 receiving the packet distributes this type to the local clients
1609 on the channel and broadcast it to the network.
1612 Arguments: (1) <Client ID> (2) [<comment>]
1613 (3) <Kicker's Client ID>
1615 The <Client ID> is the client which was kicked from the channel.
1616 The kicker may have set the <comment> to indicate the reason for
1617 the kicking. The <Kicker's Client ID> is the kicker.
1620 13 SILC_NOTIFY_TYPE_KILLED
1622 Sent when a client has been killed from the network. This is sent
1623 also to the client which was killed from the network. The client
1624 which was killed from the network MUST be removed from the network.
1625 This notify type is destined directly to the client which was
1626 killed and to channel if the client is on any channel. The router
1627 or server receiving the packet distributes this type to the local
1628 clients on the channel and broadcast it to the network. The client
1629 MUST also be removed from joined channels invite list if it is
1630 explicitly added in the lists.
1633 Arguments: (1) <Client ID> (2) [<comment>]
1636 The <Client ID> is the client which was killed from the network.
1637 The killer may have set the <comment> to indicate the reason for
1638 the killing. The <Killer's ID> is the killer, which may be
1639 client but also router server.
1642 14 SILC_NOTIFY_TYPE_UMODE_CHANGE
1644 Sent when user's mode in the SILC changes. This type is sent
1645 only between routers as broadcast packet.
1648 Arguments: (1) <Client ID> (2) <mode mask>
1650 The <Client ID> is the client which mode was changed. The
1651 <mode mask> is the new mode mask.
1654 15 SILC_NOTIFY_TYPE_BAN
1656 Sent when the ban list of the channel is changed. This type is
1657 sent only between routers as broadcast packet.
1660 Arguments: (1) <Channel ID> (2) [<add | del>]
1663 The <Channel ID> is the channel which ban list was changed.
1664 The <add | del> is an argument of size of 1 byte where 0x00 means
1665 adding a client to ban list, and 0x01 means deleting a client
1666 from ban list. The <ban list> indicates the information to be
1667 added to or removed from the ban list. The <ban list> format
1668 format is defined in [SILC4] with SILC_COMMAND_BAN command.
1671 16 SILC_NOTIFY_TYPE_ERROR
1673 Sent when an error occurs during processing some SILC procedure.
1674 This is not used when error occurs during command processing, see
1675 [SILC3] for more information about commands and command replies.
1676 This type is sent directly to the sender of the packet whose packet
1677 caused the error. See [SILC1] for definition when this type
1681 Arguments: (1) <Status Type> (n) [...]
1683 The <Status Type> is the error type defined in [SILC3]. Note that
1684 same types are also used with command replies to indicate the
1685 status of a command. Both commands and this notify type share
1686 same status types. Rest of the arguments are status type
1687 dependent and are specified with those status types that can be
1688 sent currently inside this notify type in [SILC3]. The <Status
1689 Type> is of size of 1 byte.
1692 17 SILC_NOTIFY_TYPE_WATCH
1694 Sent to indicate change in a watched user. Client can set
1695 nicknames to be watched with SILC_COMMAND_WATCH command, and
1696 receive notifications when they login to network, signoff from
1697 the network or their user mode is changed. This notify type
1698 is used to deliver these notifications. The notify type is
1699 sent directly to the watching client.
1702 Arguments: (1) <Client ID> (2) [<nickname>]
1703 (3) <user mode> (4) [<Notify Type>]
1705 The <Client ID> is the user's Client ID which is being watched,
1706 and the <nickname> is its nickname. If the client just
1707 changed the nickname, then <nickname> is the new nickname, but
1708 the <Client ID> is the old client ID. The <user mode> is the
1709 user's current user mode. The <Notify Type> can be same as the
1710 Notify Payload's Notify Type, and is 16 bit MSB first order value.
1711 If provided it may indicate the notify that occurred for the
1712 client. If client logged in to the network the <Notify Type>
1713 MUST NOT be present.
1716 Notify types starting from 16384 are reserved for private notify
1719 Router server which receives SILC_NOTIFY_TYPE_SIGNOFF,
1720 SILC_NOTIFY_TYPE_SERVER_SIGNOFF, SILC_NOTIFY_TYPE_KILLED,
1721 SILC_NOTIFY_TYPE_NICK_CHANGE and SILC_NOTIFY_TYPE_UMODE_CHANGE
1722 MUST check whether someone in the local cell is watching the nickname
1723 the client has, and send the SILC_NOTIFY_TYPE_WATCH notify to the
1724 watcher, unless the client in case has the SILC_UMODE_REJECT_WATCHING
1725 user mode set. If the watcher client and the client that was
1726 watched is same the notify SHOULD NOT be sent.
1734 Error payload is sent upon error. Error may occur in various
1735 conditions when server sends this packet. Client MUST NOT send this
1736 payload but MUST be able to accept it. However, client MAY
1737 totally ignore the contents of the packet as server is going to
1738 take action on the error anyway. However, it is recommended
1739 that the client takes error packet seriously.
1745 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
1746 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1750 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1754 Figure 13: Error Payload
1758 o Error Message (variable length) - Human readable error
1759 message as UTF-8 string.
1764 2.3.9 Channel Message Payload
1766 Channel Message Payload is used to send message to channels, a group
1767 of users. These messages can only be sent if client has joined to
1768 some channel. Even though this packet is very common in SILC it
1769 is still special packet. Some special handling on sending and
1770 reception of channel message is required.
1772 Padding MUST be applied into this payload since the payload is
1773 encrypted separately from other parts of the packet with the
1774 channel specific key. Hence the requirement of the padding.
1775 The packet MUST be made multiple by eight (8) or by the block
1776 size of the cipher, which ever is larger.
1778 The SILC header in this packet is encrypted with the session key
1779 of the next receiver of the packet. Nothing else is encrypted
1780 with that key. Thus, the actual packet and padding to be
1781 encrypted with the session key is SILC Header plus padding to it
1782 to make it multiple by eight (8) or multiple by the block size
1783 of the cipher, which ever is larger.
1785 Receiver of the the channel message packet is able to determine
1786 the channel the message is destined to by checking the destination
1787 ID from the SILC Packet header which tells the destination channel.
1788 The original sender of the packet is also determined by checking
1789 the source ID from the header which tells the client which sent
1792 This packet use generic Message Payload as Channel Message Payload.
1793 See section 2.3.2.5 for generic Message Payload.
1797 2.3.10 Channel Key Payload
1799 All traffic in channels are protected by channel specific keys.
1800 Channel Key Payload is used to distribute channel keys to all
1801 clients on the particular channel. Channel keys are sent when
1802 the channel is created, when new user joins to the channel and
1803 whenever a user has left a channel. Server creates the new
1804 channel key and distributes it to the clients by encrypting this
1805 payload with the session key shared between the server and
1806 the client. After that, client starts using the key received
1807 in this payload to protect the traffic on the channel.
1809 The client which is joining to the channel receives its key in the
1810 SILC_COMMAND_JOIN command reply message thus it is not necessary to
1811 send this payload to the entity which sent the SILC_COMMAND_JOIN
1814 Channel keys are cell specific thus every router in the cell have
1815 to create a channel key and distribute it if any client in the
1816 cell has joined to a channel. Channel traffic between cell's
1817 are not encrypted using channel keys, they are encrypted using
1818 normal session keys between two routers. Inside a cell, all
1819 channel traffic is encrypted with the specified channel key.
1820 Channel key should expire periodically, say, in one hour, in
1821 which case new channel key is created and distributed.
1823 The payload may only be sent with SILC_PACKET_CHANNEL_KEY packet.
1824 It MUST NOT be sent in any other packet type. The following diagram
1825 represents the Channel Key Payload.
1831 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
1832 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1833 | Channel ID Length | |
1834 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1838 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1839 | Cipher Name Length | |
1840 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1844 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1845 | Channel Key Length | |
1846 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1850 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1854 Figure 14: Channel Key Payload
1859 o Channel ID Length (2 bytes) - Indicates the length of the
1860 Channel ID field in the payload, not including any other
1863 o Channel ID (variable length) - The Channel ID of the
1864 channel this key is meant for.
1866 o Cipher Name Length (2 bytes) - Indicates the length of the
1867 Cipher name field in the payload, not including any other
1870 o Cipher Name (variable length) - Name of the cipher used
1871 in the protection of channel traffic. This name is
1872 initially decided by the creator of the channel but it
1873 MAY change during the life time of the channel as well.
1875 o Channel Key Length (2 bytes) - Indicates the length of the
1876 Channel Key field in the payload, not including any other
1879 o Channel Key (variable length) - The actual channel key
1885 2.3.11 Private Message Payload
1887 Private Message Payload is used to send private message between
1888 two clients. The messages are sent only to the specified user
1889 and no other user inside SILC network is able to see the message.
1891 The message can be protected by the session key established by the
1892 SILC Key Exchange Protocol. However, it is also possible to agree
1893 to use a private key to protect just the private messages. It is
1894 for example possible to perform Key Agreement between two clients.
1895 See section 2.3.20 Key Agreement Payload how to perform key
1896 agreement. See also section 2.3.12 Private Message Key Payload
1897 for another way of using private keys with private messages. See
1898 [SILC1] section 4.6 for detailed description for private message
1899 key generation procedure.
1901 If normal session key is used to protect the message, every server
1902 between the sender client and the receiving client MUST decrypt the
1903 packet and always re-encrypt it with the session key of the next
1904 receiver of the packet. See section Client To Client in [SILC1].
1906 When private key is used to protect the message, servers between
1907 the sender and the receiver needs not to decrypt/re-encrypt the
1908 packet. Section Client To Client in [SILC1] gives example of this
1911 This packet use generic Message Payload as Private Message Payload.
1912 See section 2.3.2.5 for generic Message Payload.
1916 2.3.12 Private Message Key Payload
1918 This payload is optional and can be used to send private message
1919 key between two clients in the network. The packet is secured with
1920 normal session keys. By default private messages are encrypted
1921 with session keys, and with this payload it is possible to set
1922 private key for private message encryption between two clients.
1924 The receiver of this payload SHOULD verify for example from user
1925 whether user wants to receive private message key. Note that there
1926 are other, more secure ways of exchanging private message keys in
1927 the SILC network. Instead of sending this payload it is possible to
1928 negotiate the private message key with SKE protocol using the Key
1929 Agreement payload directly peer to peer, see section 2.3.20.
1931 This payload may only be sent by client to another client. Server
1932 MUST NOT send this payload at any time. After sending this payload
1933 the sender of private messages must set the Private Message Key
1934 flag into SILC Packet Header.
1936 The payload may only be sent with SILC_PACKET_PRIVATE_MESSAGE_KEY
1937 packet. It MUST NOT be sent in any other packet type. The following
1938 diagram represents the Private Message Key Payload.
1944 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
1945 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1946 | Private Message Key Length | |
1947 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1949 ~ Private Message Key ~
1951 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1952 | Cipher Name Length | |
1953 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1957 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1958 | HMAC Name Length | |
1959 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1963 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1967 Figure 15: Private Message Key Payload
1973 o Private Message Key Length (2 bytes) - Indicates the length
1974 of the Private Message Key field in the payload, not including
1977 o Private Message Key (variable length) - The actual private
1978 message key material.
1980 o Cipher Name Length (2 bytes) - Indicates the length of the
1981 Cipher Name field in the payload, not including any other
1984 o Cipher Name (variable length) - Name of the cipher to use
1985 in the private message encryption. If this field does not
1986 exist then the default cipher of the SILC protocol is used.
1987 See the [SILC1] for defined ciphers.
1989 o HMAC Name Length (2 bytes) - Indicates the length of the
1990 HMAC Name field in the payload, not including any other
1993 o HMAC Name (variable length) - Name of the HMAC to use
1994 in the private message MAC computation. If this field does
1995 not exist then the default HMAC of the SILC protocol is used.
1996 See the [SILC1] for defined HMACs.
2001 2.3.13 Command Payload
2003 Command Payload is used to send SILC commands from client to server.
2004 Also server MAY send commands to other servers. The following diagram
2005 represents the Command Payload.
2011 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
2012 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2013 | Payload Length | SILC Command | Arguments Num |
2014 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2015 | Command Identifier |
2016 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2020 Figure 16: Command Payload
2024 o Payload Length (2 bytes) - Length of the entire command
2025 payload including any command argument payloads associated
2028 o SILC Command (1 byte) - Indicates the SILC command. This MUST
2029 be set to non-zero value. If zero (0) value is found in this
2030 field the packet MUST be discarded.
2032 o Arguments Num (1 byte) - Indicates the number of arguments
2033 associated with the command. If there are no arguments this
2034 field is set to zero (0). The arguments MUST follow the
2035 command payload. See section 2.3.2.2 for definition of the
2038 o Command Identifier (2 bytes) - Identifies this command at the
2039 sender's end. The entity which replies to this command MUST
2040 set the value found from this field into the Command Payload
2041 used to send the reply to the sender. This way the sender
2042 can identify which command reply belongs to which originally
2043 sent command. What this field includes is implementation
2044 issue but it is RECOMMENDED that wrapping counter value is
2045 used in the field. Value zero (0) in this field means that
2046 no specific value is set.
2049 See [SILC4] for detailed description of different SILC commands,
2050 their arguments and their reply messages.
2056 2.3.14 Command Reply Payload
2058 Command Reply Payload is used to send replies to the commands. The
2059 Command Reply Payload is identical to the Command Payload thus see
2060 the upper section for the Command Payload specification.
2062 The entity which sends the reply packet MUST set the Command Identifier
2063 field in the reply packet's Command Payload to the value it received
2064 in the original command packet.
2066 See SILC Commands in [SILC4] for detailed description of different
2067 SILC commands, their arguments and their reply messages.
2071 2.3.15 Connection Auth Request Payload
2073 Client MAY send this payload to server to request the authentication
2074 method that must be used in authentication protocol. If client knows
2075 this information beforehand this payload is not necessary to be sent.
2076 Server performing authentication with another server MAY also send
2077 this payload to request the authentication method. If the connecting
2078 server already knows this information this payload is not necessary
2081 Server receiving this request MUST reply with same payload sending
2082 the mandatory authentication method. Algorithms that may be required
2083 to be used by the authentication method are the ones already
2084 established by the SILC Key Exchange protocol. See section Key
2085 Exchange Start Payload in [SILC3] for detailed information.
2087 The payload may only be sent with SILC_PACKET_CONNECTION_AUTH_REQUEST
2088 packet. It MUST NOT be sent in any other packet type. The following
2089 diagram represents the Connection Auth Request Payload.
2095 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
2096 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2097 | Connection Type | Authentication Method |
2098 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2102 Figure 17: Connection Auth Request Payload
2106 o Connection Type (2 bytes) - Indicates the type of the
2107 connection. The following connection types are defined:
2114 If any other type is found in this field the packet MUST be
2115 discarded and the authentication MUST be failed.
2117 o Authentication Method (2 bytes) - Indicates the authentication
2118 method to be used in the authentication protocol. The following
2119 authentication methods are defined:
2122 1 password (mandatory)
2123 2 public key (mandatory)
2125 If any other type is found in this field the packet MUST be
2126 discarded and the authentication MUST be failed. If this
2127 payload is sent as request to receive the mandatory
2128 authentication method this field MUST be set to zero (0),
2129 indicating that receiver should send the mandatory
2130 authentication method. The receiver sending this payload
2131 to the requesting party, MAY also set this field to zero (0)
2132 to indicate that authentication is not required. In this
2133 case authentication protocol still MUST be started but
2134 server is most likely to respond with SILC_PACKET_SUCCESS
2142 2.3.16 New ID Payload
2144 New ID Payload is a multipurpose payload. It is used to send newly
2145 created ID's from clients and servers. When client connects to server
2146 and registers itself to the server by sending SILC_PACKET_NEW_CLIENT
2147 packet, server replies with this packet by sending the created ID for
2148 the client. Server always creates the ID for the client.
2150 This payload is also used when server tells its router that new client
2151 has registered to the SILC network. In this case the server sends
2152 the Client ID of the client to the router. Similarly when router
2153 distributes information to other routers about the client in the SILC
2154 network this payload is used.
2156 Also, when server connects to router, router uses this payload to inform
2157 other routers about new server in the SILC network. However, every
2158 server (or router) creates their own ID's thus the ID distributed by
2159 this payload is not created by the distributor in this case. Servers
2160 create their own ID's. Server registers itself to the network by
2161 sending SILC_PACKET_NEW_SERVER to the router it connected to. The case
2162 is same when router connects to another router.
2164 However, this payload MUST NOT be used to send information about new
2165 channels. New channels are always distributed by sending the dedicated
2166 SILC_PACKET_NEW_CHANNEL packet.
2168 Thus, this payload is very important and used every time when some
2169 new entity is registered to the SILC network. Client MUST NOT send this
2170 payload. Both client and server (and router) MAY receive this payload.
2172 The packet use generic ID Payload as New ID Payload. See section
2173 2.3.2.1 for generic ID Payload.
2177 2.3.17 New Client Payload
2179 When client is connected to the server, keys has been exchanged and
2180 connection has been authenticated client MUST register itself to the
2181 server. Client's first packet after key exchange and authentication
2182 protocols must be SILC_PACKET_NEW_CLIENT. This payload tells server all
2183 the relevant information about the connected user. Server creates a new
2184 client ID for the client when received this payload and sends it to the
2185 client in New ID Payload.
2187 This payload sends username and real name of the user on the remote host
2188 which is connected to the SILC server with SILC client. The server
2189 creates the client ID according the information sent in this payload.
2190 The nickname of the user becomes the username sent in this payload.
2191 However, client should call NICK command after sending this payload to
2192 set the real nickname of the user which is then used to create new
2195 The payload may only be sent with SILC_PACKET_NEW_CLIENT packet. It
2196 MUST NOT be sent in any other packet type. The following diagram
2197 represents the New Client Payload.
2203 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
2204 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2205 | Username Length | |
2206 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
2210 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2211 | Real Name Length | |
2212 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
2216 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2220 Figure 18: New Client Payload
2224 o Username Length (2 bytes) - Length of the Username field.
2226 o Username (variable length) - The username of the user on
2227 the host where connecting to the SILC server.
2229 o Real Name Length (2 bytes) - Length of the Real Name field.
2231 o Real Name (variable length) - The real name of the user
2232 on the host where connecting to the SILC server.
2237 2.3.18 New Server Payload
2239 This payload is sent by server when it has completed successfully both
2240 key exchange and connection authentication protocols. The server
2241 MUST register itself to the SILC Network by sending this payload.
2242 The first packet after these key exchange and authentication protocols
2243 is SILC_PACKET_NEW_SERVER packet. The payload includes the Server ID
2244 of the server that it has created by itself. It also includes a
2245 name of the server that is associated to the Server ID.
2247 The payload may only be sent with SILC_PACKET_NEW_SERVER packet. It
2248 MUST NOT be sent in any other packet type. The following diagram
2249 represents the New Server Payload.
2256 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
2257 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2258 | Server ID Length | |
2259 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
2263 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2264 | Server Name Length | |
2265 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
2269 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2273 Figure 19: New Server Payload
2277 o Server ID Length (2 bytes) - Length of the Server ID Data
2280 o Server ID Data (variable length) - The actual Server ID
2283 o Server Name Length (2 bytes) - Length of the server name
2286 o Server Name (variable length) - The server name.
2291 2.3.19 New Channel Payload
2293 Information about newly created channel is broadcasted to all routers
2294 in the SILC network by sending this packet payload. Channels are
2295 created by router of the cell. Server never creates channels unless
2296 it is a standalone server and it does not have router connection,
2297 in this case server acts as router. Normal server send JOIN command
2298 to the router (after it has received JOIN command from client) which
2299 then processes the command and creates the channel. Client MUST NOT
2300 send this packet. Server may send this packet to a router when it is
2301 announcing its existing channels to the router after it has connected
2304 The packet use generic Channel Payload as New Channel Payload. See
2305 section 2.3.2.3 for generic Channel Payload. The Mode Mask field in the
2306 Channel Payload is the mode of the channel.
2310 2.3.20 Key Agreement Payload
2312 This payload is used by clients to request key negotiation between
2313 another client in the SILC Network. The key agreement protocol used
2314 is the SKE protocol. The result of the protocol, the secret key
2315 material, can be used for example as private message key between the
2316 two clients. This significantly adds security as the key agreement
2317 is performed outside the SILC network. The server and router MUST NOT
2320 The sender MAY tell the receiver of this payload the hostname and the
2321 port where the SKE protocol is running in the sender's end. The
2322 receiver MAY then initiate the SKE negotiation with the sender. The
2323 sender MAY also optionally not to include the hostname and the port
2324 of its SKE protocol. In this case the receiver MAY reply to the
2325 request by sending the same payload filled with the receiver's hostname
2326 and the port where the SKE protocol is running. The sender MAY then
2327 initiate the SKE negotiation with the receiver.
2329 This payload may be sent with SILC_PACKET_KEY_AGREEMENT and
2330 SILC_PACKET_FTP packet types. It MUST NOT be sent in any other packet
2331 types. The following diagram represents the Key Agreement Payload.
2337 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
2338 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2339 | Hostname Length | |
2340 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
2344 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2346 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2350 Figure 20: Key Agreement Payload
2354 o Hostname Length (2 bytes) - Indicates the length of the
2357 o Hostname (variable length) - The hostname or IP address where
2358 the SKE protocol is running. The sender MAY fill this field
2359 when sending the payload. If the receiver sends this payload
2360 as reply to the request it MUST fill this field.
2362 o Port (4 bytes) - The port where the SKE protocol is bound.
2363 The sender MAY fill this field when sending the payload. If
2364 the receiver sends this payload as reply to the request it
2365 MUST fill this field. This is a 32 bit MSB first order value.
2369 After the key material has been received from the SKE protocol it is
2370 processed as the [SILC3] describes. If the key material is used as
2371 channel private key then the Sending Encryption Key, as defined in
2372 [SILC3] is used as the channel private key. Other key material must
2373 be discarded. The [SILC1] in section 4.6 defines the way to use the
2374 key material if it is intended to be used as private message keys.
2375 Any other use for the key material is undefined.
2379 2.3.21 Resume Router Payload
2381 The payload may only be sent with SILC_PACKET_RESUME_ROUTER packet. It
2382 MUST NOT be sent in any other packet type. The Following diagram
2383 represents the Resume Router Payload.
2389 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
2390 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2391 | Type | Session ID |
2392 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2396 Figure 21: Resume Router Payload
2400 o Type (1 byte) - Indicates the type of the backup resume
2401 protocol packet. The type values are defined in [SILC1].
2403 o Session ID (1 bytes) - Indicates the session ID for the
2404 backup resume protocol. The sender of the packet sets this
2405 value and the receiver MUST set the same value in subsequent
2411 2.3.22 File Transfer Payload
2413 File Transfer Payload is used to perform file transfer protocol
2414 between two entities in the network. The actual file transfer
2415 protocol is always encapsulated inside the SILC Packet. The actual
2416 data stream is also sent peer to peer outside SILC network.
2418 When an entity, usually a client wishes to perform file transfer
2419 protocol with another client in the network, they perform Key Agreement
2420 protocol as described in the section 2.3.20 Key Agreement Payload and
2421 in [SILC3], inside File Transfer Payload. After the Key Agreement
2422 protocol has been performed the subsequent packets in the data stream
2423 will be protected using the new key material. The actual file transfer
2424 protocol is also initialized in this stage. All file transfer protocol
2425 packets are always encapsulated in the File Transfer Payload and
2426 protected with the negotiated key material.
2428 The payload may only be sent with SILC_PACKET_FTP packet. It MUST NOT
2429 be sent in any other packet type. The following diagram represents the
2430 File Transfer Payload.
2435 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
2436 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2442 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2446 Figure 22: File Transfer Payload
2450 o Type (1 byte) - Indicates the type of the file transfer
2451 protocol. The following file transfer protocols has been
2454 1 Secure File Transfer Protocol (SFTP) (mandatory)
2456 If zero (0) value or any unsupported file transfer protocol
2457 type is found in this field the packet must be discarded.
2458 The currently mandatory file transfer protocol is SFTP.
2459 The SFTP protocol is defined in [SFTP].
2461 o Data (variable length) - Arbitrary file transfer data. The
2462 contents and encoding of this field is dependent of the usage
2463 of this payload and the type of the file transfer protocol.
2464 When this payload is used to perform the Key Agreement
2465 protocol, this field include the Key Agreement Payload,
2466 as defined in the section 2.3.20 Key Agreement Payload.
2467 When this payload is used to send the actual file transfer
2468 protocol data, the encoding is defined in the corresponding
2469 file transfer protocol.
2474 2.3.23 Resume Client Payload
2476 This payload is used by client to resume its detached session in the
2477 SILC Network. A client is able to detach itself from the network by
2478 sending SILC_COMMAND_DETACH command to its server. The network
2479 connection to the client is lost but the client remains as valid
2480 client in the network. The client is able to resume the session back
2481 by sending this packet and including the old Client ID, and an
2482 Authentication Payload [SILC1] which the server uses to verify with
2483 the detached client's public key. This also implies that the
2484 mandatory authentication method is public key authentication.
2486 Server or router that receives this from the client also sends this,
2487 without the Authentication Payload, to routers in the network so that
2488 they know the detached client has resumed. Refer to the [SILC1] for
2489 detailed description how the detaching and resuming procedure is
2492 The payload may only be sent with SILC_PACKET_RESUME CLIENT packet. It
2493 MUST NOT be sent in any other packet type. The following diagram
2494 represents the Resume Client Payload.
2499 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
2500 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2501 | Client ID Length | |
2502 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
2506 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2508 ~ Authentication Payload ~
2510 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2514 Figure 23: Resume Client Payload
2518 o Client ID Length (1 byte) - The length of the Client ID
2519 field not including any other field.
2521 o Client ID (variable length) - The detached client's Client
2522 ID. The client that sends this payload must know the Client
2525 o Authentication Payload (variable length) - The authentication
2526 payload that the server will verify with the detached client's
2527 public key. If the server doesn't know the public key, it must
2528 retrieve it for example with SILC_COMMAND_GETKEY command.
2536 ID's are extensively used in the SILC network to associate different
2537 entities. The following ID's has been defined to be used in the SILC
2543 This is used when other ID type is available at the time.
2547 Server ID to associate servers. See the format of
2552 Client ID to associate clients. See the format of
2557 Channel ID to associate channels. See the format of
2561 When encoding different IDs into the ID Payload, all fields are always
2562 in MSB first order. The IP address, port, and/or the random number
2563 are encoded in the MSB first order.
2567 2.5 Packet Encryption And Decryption
2569 SILC packets are encrypted almost entirely. Only small part of SILC
2570 header is not encrypted as described in section 5.2 SILC Packet Header.
2571 The SILC Packet header is the first part of a packet to be encrypted
2572 and it is always encrypted with the key of the next receiver of the
2573 packet. The data payload area of the packet is always entirely
2574 encrypted and it is usually encrypted with the next receiver's key.
2575 However, there are some special packet types and packet payloads
2576 that require special encryption process. These special cases are
2577 described in the next sections. First is described the normal packet
2582 2.5.1 Normal Packet Encryption And Decryption
2584 Normal SILC packets are encrypted with the session key of the next
2585 receiver of the packet. The entire SILC Packet header and the packet
2586 data payload is is also encrypted with the same key. Padding of the
2587 packet is also encrypted always with the session key, also in special
2588 cases. Computed MAC of the packet must not be encrypted.
2590 Decryption process in these cases are straightforward. The receiver
2591 of the packet MUST first decrypt the SILC Packet header, or some parts
2592 of it, usually first 16 bytes of it. Then the receiver checks the
2593 packet type from the decrypted part of the header and can determine
2594 how the rest of the packet must be decrypted. If the packet type is
2595 any of the special cases described in the following sections the packet
2596 decryption is special. If the packet type is not among those special
2597 packet types rest of the packet can be decrypted with the same key.
2599 With out a doubt, this sort of decryption processing causes some
2600 overhead to packet decryption, but never the less, is required.
2604 2.5.2 Channel Message Encryption And Decryption
2606 Channel Messages (Channel Message Payload) are always encrypted with
2607 the channel specific key. However, the SILC Packet header is not
2608 encrypted with that key. As in normal case, the header is encrypted
2609 with the key of the next receiver of the packet, who ever that might
2610 be. Note that in this case the encrypted data area is not touched
2611 at all; it MUST NOT be re-encrypted with the session key.
2613 Receiver of a channel message, who ever that is, is REQUIRED to decrypt
2614 the SILC Packet header to be able to even recognize the packet to be as
2615 channel message. This is same procedure as for normal SILC packets.
2616 As the receiver founds the packet to be channel message, rest of the
2617 packet processing is special. Rest of the SILC Packet header is
2618 decrypted with the same session key along with the padding of the
2619 packet. After that the packet is protected with the channel specific
2620 key and thus can be decrypted only if the receiver is the client on
2621 the channel. See section 2.7 Packet Padding Generation for more
2622 information about padding on special packets.
2624 If the receiver of the channel message is router which is routing the
2625 message to another router then it MUST decrypt the Channel Message
2626 payload. Between routers (that is, between cells) channel messages
2627 are protected with session keys shared between the routers. This
2628 causes another special packet processing for channel messages. If
2629 the channel message is received from another router then the entire
2630 packet, including Channel Message payload, MUST be encrypted with the
2631 session key shared between the routers. In this case the packet
2632 decryption process is as with normal SILC packets. Hence, if the
2633 router is sending channel message to another router the Channel
2634 Message payload MUST have been decrypted and MUST be re-encrypted
2635 with the session key shared between the another router. In this
2636 case the packet encryption is as with any normal SILC packet.
2638 It must be noted that this is only when the channel messages are sent
2639 from router to another router. In all other cases the channel
2640 message encryption and decryption is as described above. This
2641 different processing of channel messages with router to router
2642 connection is because channel keys are cell specific. All cells have
2643 their own channel keys thus the channel message traveling from one
2644 cell to another MUST be protected as it would be any normal SILC
2647 If the SILC_CMODE_PRIVKEY channel mode has been set for the channel
2648 then the router cannot decrypt the packet as it does not know the
2649 private key. In this case the entire packet MUST be encrypted with
2650 the session key and sent to the router. The router receiving the
2651 packet MUST check the channel mode and decrypt the packet accordingly.
2655 2.5.3 Private Message Encryption And Decryption
2657 By default, private message in SILC are protected by session keys.
2658 In this case the private message encryption and decryption process is
2659 equivalent to normal packet encryption and decryption.
2661 However, private messages MAY be protected with private message key
2662 which causes the packet to be special packet. The procedure in this
2663 case is very much alike to channel packets. The actual private message
2664 is encrypted with the private message key and other parts of the
2665 packet is encrypted with the session key. See 2.7 Packet Padding
2666 Generation for more information about padding on special packets.
2668 The difference from channel message processing is that server or router
2669 en route never decrypts the actual private message, as it does not
2670 have the key to do that. Thus, when sending packets between router
2671 the processing is same as in any other case as well; the packet's header
2672 and padding is protected by the session key and the data area is not
2675 The true receiver of the private message, client, that is, is able
2676 to decrypt the private message as it shares the key with the sender
2681 2.6 Packet MAC Generation
2683 Data integrity of a packet is protected by including a message
2684 authentication code (MAC) at the end of the packet. The MAC is computed
2685 from shared secret MAC key, that is established by the SILC Key Exchange
2686 protocol, from packet sequence number, and from the encrypted packet
2687 data. The MAC is always computed after packet is encrypted. This is
2688 so called Encrypt-Then-MAC order; packet is first encrypted, then MAC
2689 is computed from the encrypted data.
2691 The MAC is computed from entire packet. Every bit of data in the packet,
2692 including SILC Packet Header is used in the MAC computing. This way
2693 the entire packet becomes authenticated.
2695 Hence, packet's MAC generation is as follows:
2697 mac = MAC(key, sequence number | Encrypted SILC packet)
2699 The MAC key is negotiated during the SKE protocol. The sequence number
2700 is a 32 bit MSB first value starting from zero for first packet and
2701 increasing for subsequent packets, finally wrapping after 2^32 packets.
2702 The value is never reset, not even after rekey has been performed.
2703 However, rekey MUST be performed before the sequence number wraps
2704 and repeats from zero. Note that the sequence number is incremented only
2705 when MAC is computed for a packet. If packet is not encrypted and MAC is
2706 not computed then the sequence number is not incremented. Hence, the
2707 sequence number is zero for the very first encrypted packet.
2709 See [SILC1] for defined and allowed MAC algorithms.
2713 2.7 Packet Padding Generation
2715 Padding is needed in the packet because the packet is encrypted. It
2716 always MUST be multiple by eight (8) or multiple by the block size
2717 of the cipher, which ever is larger. The padding is always encrypted.
2719 For normal packets the padding is added after the SILC Packet Header
2720 and between the Data Payload area. The padding for normal packets
2721 may be calculated as follows:
2724 padding_length = 16 - (packet_length mod block_size)
2725 if (padding_length < 8)
2726 padding_length += block_size
2729 The `block_size' is the block size of the cipher. The maximum padding
2730 length is 128 bytes, and minimum is 8 bytes. For example, packets that
2731 include a passphrase or a password for authentication purposes SHOULD
2732 pad the packet up to the maximum padding length. The maximum padding
2733 is calculated as follows:
2736 padding_length = 128 - (packet_length mod block_size)
2739 For special packets the padding calculation is different as special
2740 packets may be encrypted differently. In these cases the encrypted
2741 data area MUST already be multiple by the block size thus in this case
2742 the padding is calculated only for SILC Packet Header, not for any
2743 other area of the packet. The same algorithm works in this case as
2744 well, except that the `packet length' is now the SILC Packet Header
2747 The padding MUST be random data, preferably, generated by
2748 cryptographically strong random number generator for each packet
2753 2.8 Packet Compression
2755 SILC Packets MAY be compressed. In this case the data payload area
2756 is compressed and all other areas of the packet MUST remain as they
2757 are. After compression is performed for the data area, the length
2758 field of Packet Header MUST be set to the compressed length of the
2761 The compression MUST always be applied before encryption. When
2762 the packet is received and decrypted the data area MUST be decompressed.
2763 Note that the true sender of the packet MUST apply the compression and
2764 the true receiver of the packet MUST apply the decompression. Any
2765 server or router en route SHOULD NOT decompress the packet.
2771 The sender of the packet MUST assemble the SILC Packet Header with
2772 correct values. It MUST set the Source ID of the header as its own
2773 ID, unless it is forwarding the packet. It MUST also set the Destination
2774 ID of the header to the true destination. If the destination is client
2775 it will be Client ID, if it is server it will be Server ID and if it is
2776 channel it will be Channel ID.
2778 If the sender wants to compress the packet it MUST apply the
2779 compression now. Sender MUST also compute the padding as described
2780 in above sections. Then sender MUST encrypt the packet as has been
2781 described in above sections according whether the packet is normal
2782 packet or special packet. Then sender MUST compute the MAC of the
2783 packet. The computed MAC MUST NOT be encrypted.
2787 2.10 Packet Reception
2789 On packet reception the receiver MUST check that all fields in the
2790 SILC Packet Header are valid. It MUST check the flags of the
2791 header and act accordingly. It MUST also check the MAC of the packet
2792 and if it is to be failed the packet MUST be discarded. Also if the
2793 header of the packet includes any bad fields the packet MUST be
2796 See above sections on the decryption process of the received packet.
2798 The receiver MUST also check that the ID's in the header are valid
2799 ID's. Unsupported ID types or malformed ID's MUST cause packet
2800 rejection. The padding on the reception is always ignored.
2802 The receiver MUST also check the packet type and start parsing the
2803 packet according to the type. However, note the above sections on
2804 special packet types and their parsing.
2810 Routers are the primary entities in the SILC network that takes care
2811 of packet routing. However, normal servers routes packets as well, for
2812 example, when they are routing channel message to the local clients.
2813 Routing is quite simple as every packet tells the true origin and the
2814 true destination of the packet.
2816 It is still RECOMMENDED for routers that has several routing connections
2817 to create route cache for those destinations that has faster route than
2818 the router's primary route. This information is available for the router
2819 when other router connects to the router. The connecting party then
2820 sends all of its locally connected clients, servers and channels. These
2821 informations helps to create the route cache. Also, when new channels
2822 are created to a cell its information is broadcasted to all routers
2823 in the network. Channel ID's are based on router's ID thus it is easy
2824 to create route cache based on these informations. If faster route for
2825 destination does not exist in router's route cache the packet MUST be
2826 routed to the primary route (default route).
2828 However, there are some issues when routing channel messages to group
2829 of users. Routers are responsible of routing the channel message to
2830 other routers, local servers and local clients as well. Routers MUST
2831 send the channel message to only one router in the network, preferably
2832 to the shortest route to reach the channel users. The message can be
2833 routed into either upstream or downstream. After the message is sent
2834 to a router in the network it MUST NOT be sent to any other router in
2835 either same route or other route. The message MUST NOT be routed to
2836 the router it came from.
2838 When routing for example private messages they should be routed to the
2839 shortest route always to reach the destination client as fast as possible.
2841 For server which receives a packet to be routed to its locally connected
2842 client the server MUST check whether the particular packet type is
2843 allowed to be routed to the client. Not all packets may be sent by
2844 some odd entity to client that is indirectly connected to the sender.
2845 See section 2.3 SILC Packet Types and paragraph about indirectly connected
2846 entities and sending packets to them. The section mentions the packets
2847 that may be sent to indirectly connected entities. It is clear that
2848 server cannot send, for example, disconnect packet to client that is not
2849 directly connected to the server.
2851 Routers form a ring in the SILC network. However, routers may have other
2852 direct connections to other routers in the network too. This can cause
2853 interesting routing problems in the network. Since the network is a ring,
2854 the packets usually should be routed into clock-wise direction, or if it
2855 cannot be used then always counter clock-wise (primary route) direction.
2856 Problems may arise when a faster direct route exists and router is routing
2857 a channel message. Currently channel messages must be routed either
2858 in upstream or downstream, they cannot be routed to other direct routes.
2859 The SILC protocol should have a shortest path discovery protocol, and some
2860 existing routing protocol, that can handle a ring network with other
2861 direct routes inside the ring (so called hybrid ring-mesh topology),
2862 MAY be defined to be used with the SILC protocol. Additional
2863 specifications MAY be written on the subject to permeate this
2868 2.12 Packet Broadcasting
2870 SILC packets MAY be broadcasted in SILC network. However, only router
2871 server may send or receive broadcast packets. Client and normal server
2872 MUST NOT send broadcast packets and they MUST ignore broadcast packets
2873 if they receive them. Broadcast packets are sent by setting Broadcast
2874 flag to the SILC packet header.
2876 Broadcasting packets means that the packet is sent to all routers in
2877 the SILC network, except to the router that sent the packet. The router
2878 receiving broadcast packet MUST send the packet to its primary route.
2879 The fact that SILC routers may have several router connections can
2880 cause problems, such as race conditions inside the SILC network, if
2881 care is not taken when broadcasting packets. Router MUST NOT send
2882 the broadcast packet to any other route except to its primary route.
2884 If the primary route of the router is the original sender of the packet
2885 the packet MUST NOT be sent to the primary route. This may happen
2886 if router has several router connections and some other router uses
2887 the router as its primary route.
2889 Routers use broadcast packets to broadcast for example information
2890 about newly registered clients, servers, channels etc. so that all the
2891 routers may keep these informations up to date.
2895 3 Security Considerations
2897 Security is central to the design of this protocol, and these security
2898 considerations permeate the specification. Common security considerations
2899 such as keeping private keys truly private and using adequate lengths for
2900 symmetric and asymmetric keys must be followed in order to maintain the
2901 security of this protocol.
2907 [SILC1] Riikonen, P., "Secure Internet Live Conferencing (SILC),
2908 Protocol Specification", Internet Draft, May 2002.
2910 [SILC3] Riikonen, P., "SILC Key Exchange and Authentication
2911 Protocols", Internet Draft, May 2002.
2913 [SILC4] Riikonen, P., "SILC Commands", Internet Draft, May 2002.
2915 [IRC] Oikarinen, J., and Reed D., "Internet Relay Chat Protocol",
2918 [IRC-ARCH] Kalt, C., "Internet Relay Chat: Architecture", RFC 2810,
2921 [IRC-CHAN] Kalt, C., "Internet Relay Chat: Channel Management", RFC
2924 [IRC-CLIENT] Kalt, C., "Internet Relay Chat: Client Protocol", RFC
2927 [IRC-SERVER] Kalt, C., "Internet Relay Chat: Server Protocol", RFC
2930 [SSH-TRANS] Ylonen, T., et al, "SSH Transport Layer Protocol",
2933 [PGP] Callas, J., et al, "OpenPGP Message Format", RFC 2440,
2936 [SPKI] Ellison C., et al, "SPKI Certificate Theory", RFC 2693,
2939 [PKIX-Part1] Housley, R., et al, "Internet X.509 Public Key
2940 Infrastructure, Certificate and CRL Profile", RFC 2459,
2943 [Schneier] Schneier, B., "Applied Cryptography Second Edition",
2944 John Wiley & Sons, New York, NY, 1996.
2946 [Menezes] Menezes, A., et al, "Handbook of Applied Cryptography",
2949 [OAKLEY] Orman, H., "The OAKLEY Key Determination Protocol",
2950 RFC 2412, November 1998.
2952 [ISAKMP] Maughan D., et al, "Internet Security Association and
2953 Key Management Protocol (ISAKMP)", RFC 2408, November
2956 [IKE] Harkins D., and Carrel D., "The Internet Key Exchange
2957 (IKE)", RFC 2409, November 1998.
2959 [HMAC] Krawczyk, H., "HMAC: Keyed-Hashing for Message
2960 Authentication", RFC 2104, February 1997.
2962 [PKCS1] Kalinski, B., and Staddon, J., "PKCS #1 RSA Cryptography
2963 Specifications, Version 2.0", RFC 2437, October 1998.
2965 [RFC2119] Bradner, S., "Key Words for use in RFCs to Indicate
2966 Requirement Levels", BCP 14, RFC 2119, March 1997.
2968 [SFTP] Ylonen T., and Lehtinen S., "Secure Shell File Transfer
2969 Protocol", Internet Draft, March 2001.
2971 [RFC2279] Yergeau, F., "UTF-8, a transformation format of ISO
2972 10646", RFC 2279, January 1998.
2979 Snellmaninkatu 34 A 15
2983 EMail: priikone@iki.fi
2985 This Internet-Draft expires 15 November 2002