8 .ds RF FORMFEED[Page %]
17 Network Working Group P. Riikonen
19 draft-riikonen-silc-pp-05.txt 15 May 2002
20 Expires: 15 November 2002
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
34 areas, and its working groups. Note that other groups may also
35 distribute working documents as Internet-Drafts.
37 Internet-Drafts are draft documents valid for a maximum of six months
38 and may be updated, replaced, or obsoleted by other documents at any
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
43 http://www.ietf.org/ietf/1id-abstracts.txt
45 The list of Internet-Draft Shadow Directories can be accessed at
46 http://www.ietf.org/shadow.html
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 2.3.3 Disconnect Payload .................................. 20
86 2.3.4 Success Payload ..................................... 21
87 2.3.5 Failure Payload ..................................... 22
88 2.3.6 Reject Payload ...................................... 22
89 2.3.7 Notify Payload ...................................... 23
90 2.3.8 Error Payload ....................................... 31
91 2.3.9 Channel Message Payload ............................. 31
92 2.3.10 Channel Key Payload ................................ 35
93 2.3.11 Private Message Payload ............................ 36
94 2.3.12 Private Message Key Payload ........................ 38
95 2.3.13 Command Payload .................................... 39
96 2.3.14 Command Reply Payload .............................. 40
97 2.3.15 Connection Auth Request Payload .................... 40
98 2.3.16 New ID Payload ..................................... 42
99 2.3.17 New Client Payload ................................. 42
100 2.3.18 New Server Payload ................................. 43
101 2.3.19 New Channel Payload ................................ 44
102 2.3.20 Key Agreement Payload .............................. 45
103 2.3.21 Resume Router Payload .............................. 46
104 2.3.22 File Transfer Payload .............................. 46
105 2.3.23 Resume Client Payload .............................. 48
106 2.4 SILC ID Types ............................................. 49
107 2.5 Packet Encryption And Decryption .......................... 49
108 2.5.1 Normal Packet Encryption And Decryption ............. 50
109 2.5.2 Channel Message Encryption And Decryption ........... 50
110 2.5.3 Private Message Encryption And Decryption ........... 51
111 2.6 Packet MAC Generation ..................................... 52
112 2.7 Packet Padding Generation ................................. 52
113 2.8 Packet Compression ........................................ 53
114 2.9 Packet Sending ............................................ 53
115 2.10 Packet Reception ......................................... 54
116 2.11 Packet Routing ........................................... 54
117 2.12 Packet Broadcasting ...................................... 55
118 3 Security Considerations ....................................... 56
119 4 References .................................................... 56
120 5 Author's Address .............................................. 58
126 Figure 1: Typical SILC Packet
127 Figure 2: SILC Packet Header
129 Figure 4: Argument Payload
130 Figure 5: Channel Payload
131 Figure 6: Public Key Payload
132 Figure 7: Disconnect Payload
133 Figure 8: Success Payload
134 Figure 9: Failure Payload
135 Figure 10: Reject Payload
136 Figure 11: Notify Payload
137 Figure 12: Error Payload
138 Figure 13: Channel Message Payload
139 Figure 14: Channel Key Payload
140 Figure 15: Private Message Payload
141 Figure 16: Private Message Key Payload
142 Figure 17: Command Payload
143 Figure 18: Connection Auth Request Payload
144 Figure 19: New Client Payload
145 Figure 20: New Server Payload
146 Figure 21: Key Agreement Payload
147 Figure 22: Resume Router Payload
148 Figure 23: File Transfer Payload
149 Figure 24: 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. The MAC is always computed from the packet
235 before the encryption is applied to the packet. If compression is used
236 in the packet the MAC is computed after the compression has been
237 applied. The compression, on the other hand, is always applied before
238 encryption. See more details in the section 2.6 Packet MAC Generation.
240 All fields in all packet payloads are always in MSB (most significant
245 2.2 SILC Packet Header
247 The SILC packet header is applied to all SILC packets and it is
248 variable in length. The purpose of SILC Packet header is to provide
249 detailed information about the packet. The receiver of the packet
250 uses the packet header to parse the packet and gain other relevant
251 parameters of the packet.
253 The following diagram represents the SILC packet header.
258 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
259 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
260 | Payload Length | Flags | Packet Type |
261 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
262 | Pad Length | RESERVED | Source ID Len | Dest ID Len |
263 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
269 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
275 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
279 Figure 2: SILC Packet Header
283 o Payload Length (2 bytes) - Is the length of the packet
284 not including the padding of the packet.
286 o Flags (1 byte) - Indicates flags to be used in packet
287 processing. Several flags may be set by ORing the flags
290 The following flags are reserved for this field:
295 In this case the field is ignored.
298 Private Message Key 0x01
300 Indicates that the packet must include private
301 message that is encrypted using private key set by
302 client. Servers does not know anything about this
303 key and this causes that the private message is
304 not handled by the server at all, it is just
305 passed along. See section 2.5.3 Private Message
306 Encryption And Decryption for more information.
311 Indicates that the packet consists of list of
312 packet payloads indicated by the Packet Type field.
313 The payloads are added one after the other. Note that
314 there are packet types that must not be used as
315 list. Parsing of list packet is done by calculating
316 the length of each payload and parsing them one by
322 Marks the packet to be broadcasted. Client cannot
323 send broadcast packet and normal server cannot send
324 broadcast packet. Only router server may send broadcast
325 packet. The router receiving of packet with this flag
326 set MUST send (broadcast) the packet to its primary
327 route. If router has several router connections the
328 packet may be sent only to the primary route. See
329 section 2.12 Packet Broadcasting for description of
335 Marks that the payload of the packet is compressed.
336 The sender of the packet marks this flag when it
337 compresses the payload, and any server or router
338 en route to the recipient MUST NOT unset this flag.
339 See section 2.8 Packet Compression for description of
347 o Packet Type (1 byte) - Is the type of the packet. Receiver
348 uses this field to parse the packet. See section 2.3
349 SILC Packets for list of defined packet types.
351 o Pad Length (1 byte) - Indicates the length of the padding
352 applied after the SILC Packet header. Maximum length for
353 padding is 128 bytes.
355 o RESERVED (1 byte) - Reserved field and must include a
358 o Source ID Length (1 byte) - Indicates the length of the
359 Source ID field in the header, not including this or any
362 o Destination ID Length (1 byte) - Indicates the length of the
363 Destination ID field in the header, not including this or
366 o Src ID Type (1 byte) - Indicates the type of ID in the
367 Source ID field. See section 2.4 SILC ID Types for
370 o Source ID (variable length) - The actual source ID that
371 indicates which is the original sender of the packet.
373 o Dst ID Type (1 byte) - Indicates the type of ID in the
374 Destination ID field. See section 2.4 SILC ID Types for
377 o Destination ID (variable length) - The actual destination
378 ID that indicates which is the end receiver of the packet.
383 2.3 SILC Packet Types
385 SILC packet types defines the contents of the packet and it is used by
386 the receiver to parse the packet. The packet type is 8 bits, as a one
387 byte, in length. The range for the packet types are from 0 - 255,
388 where 0 is never sent and 255 is currently reserved for future
389 extensions and MUST NOT be defined to any other purpose. Every SILC
390 specification compliant implementation SHOULD support all of these packet
393 The below list of the SILC Packet types includes reference to the packet
394 payload as well. Packet payloads are the actual packet, that is, the data
395 that the packet consists of. Each packet type defines packet payload
396 which usually may only be sent with the specific packet type.
398 Most of the packets are packets that must be destined directly to entity
399 that is connected to the sender. It is not allowed, for example, for
400 router to send disconnect packet to client that is not directly connected
401 to the router. However, there are some special packet types that may
402 be destined to some entity that the sender has not direct connection
403 with. These packets are for example private message packets, channel
404 message packets, command packets and some other packets that may be
405 broadcasted in the SILC network. If the packet is allowed to be sent to
406 indirectly connected entity it is mentioned separately in the packet
407 description (unless it is obvious as in private and channel message
408 packets). Other packets MUST NOT be sent or accepted, if sent, to
409 indirectly connected entities.
411 List of SILC Packet types are defined as follows.
416 This type is reserved and it is never sent.
419 1 SILC_PACKET_DISCONNECT
421 This packet is sent to disconnect the remote end. Reason of
422 the disconnection is sent inside the packet payload. Client
423 usually does not send this packet.
425 This packet MUST NOT be sent as list and the List flag MUST
428 Payload of the packet: See section 2.3.3 Disconnect Payload
431 2 SILC_PACKET_SUCCESS
433 This packet is sent upon successful execution of some protocol.
434 The status of the success is sent in the packet.
436 This packet MUST NOT be sent as list and the List flag MUST
439 Payload of the packet: See section 2.3.4 Success Payload
442 3 SILC_PACKET_FAILURE
444 This packet is sent upon failure of some protocol. The status
445 of the failure is sent in the packet.
447 This packet MUST NOT be sent as list and the List flag MUST
450 Payload of the packet: See section 2.3.5 Failure Payload
455 This packet MAY be sent upon rejection of some protocol.
456 The status of the rejection is sent in the packet.
458 This packet MUST NOT be sent as list and the List flag MUST
461 Payload of the packet: See section 2.3.6 Reject Payload
466 This packet is used to send notify message, usually from
467 server to client, although it MAY be sent from server to another
468 server as well. Client MUST NOT send this packet. Server MAY
469 send this packet to channel as well when the packet is
470 distributed to all clients on the channel.
472 Payload of the packet: See section 2.3.7 Notify Payload.
478 This packet is sent when an error occurs. Server MAY
479 send this packet. Client MUST NOT send this packet. The
480 client MAY entirely ignore the packet, however, server is
481 most likely to take action anyway. This packet MAY be sent
482 to entity that is indirectly connected to the sender.
484 This packet MUST NOT be sent as list and the List flag MUST
487 Payload of the packet: See section 2.3.8 Error Payload.
490 7 SILC_PACKET_CHANNEL_MESSAGE
492 This packet is used to send messages to channels. The packet
493 includes Channel ID of the channel and the actual message to
494 the channel. Messages sent to the channel are always protected
495 by channel specific keys. Channel Keys are distributed by
496 SILC_PACKET_CHANNEL_KEY packet.
498 This packet MUST NOT be sent as list and the List flag MUST
501 Payload of the packet: See section 2.3.9 Channel Message
505 8 SILC_PACKET_CHANNEL_KEY
507 This packet is used to distribute new key for particular
508 channel. Each channel has their own independent keys that
509 is used to protect the traffic on the channel. Only server
510 may send this packet. This packet MAY be sent to entity
511 that is indirectly connected to the sender.
513 This packet MUST NOT be sent as list and the List flag MUST
516 Payload of the packet: See section 2.3.10 Channel Key Payload
519 9 SILC_PACKET_PRIVATE_MESSAGE
521 This packet is used to send private messages from client
522 to another client. By default, private messages are protected
523 by session keys established by normal key exchange protocol.
524 However, it is possible to use specific key to protect private
525 messages. SILC_PACKET_PRIVATE_MESSAGE_KEY packet is used to
526 agree the key with the remote client. Pre-shared key MAY be
527 used as well if both of the client knows it, however, it needs
528 to be agreed outside SILC. See more of this in [SILC1].
530 This packet MUST NOT be sent as list and the List flag MUST
533 Payload of the packet: See section 2.3.11 Private Message
537 10 SILC_PACKET_PRIVATE_MESSAGE_KEY
539 This packet is used to agree about a key to be used to protect
540 the private messages between two clients. If this is not sent
541 the normal session key is used to protect the private messages
542 inside SILC network. Agreeing to use specific key to protect
543 private messages adds security, as no server between the two
544 clients will be able to decrypt the private message. However,
545 servers inside SILC network are considered to be trusted, thus
546 using normal session key to protect private messages does not
547 degrade security. Whether to agree to use specific keys by
548 default or to use normal session keys by default, is
549 implementation specific issue. See more of this in [SILC1].
551 This packet MUST NOT be sent as list and the List flag MUST
554 Payload of the packet: See section 2.3.12 Private Message
558 11 SILC_PACKET_COMMAND
560 This packet is used to send commands from client to server.
561 Server MAY send this packet to other servers as well. All
562 commands are listed in their own section SILC Command Types
563 in [SILC4]. The contents of this packet is command specific.
564 This packet MAY be sent to entity that is indirectly connected
567 This packet MUST NOT be sent as list and the List flag MUST
570 Payload of the packet: See section 2.3.13 Command Payload
573 12 SILC_PACKET_COMMAND_REPLY
575 This packet is sent as reply to the SILC_PACKET_COMMAND packet.
576 The contents of this packet is command specific. This packet
577 MAY be sent to entity that is indirectly connected to the
580 This packet MUST NOT be sent as list and the List flag MUST
583 Payload of the packet: See section 2.3.14 Command Reply
584 Payload and section 2.3.13 Command
590 13 SILC_PACKET_KEY_EXCHANGE
592 This packet is used to start SILC Key Exchange Protocol,
593 described in detail in [SILC3].
595 This packet MUST NOT be sent as list and the List flag MUST
598 Payload of the packet: Payload of this packet is described
599 in the section SILC Key Exchange
600 Protocol and its sub sections in
604 14 SILC_PACKET_KEY_EXCHANGE_1
606 This packet is used as part of the SILC Key Exchange Protocol.
608 This packet MUST NOT be sent as list and the List flag MUST
611 Payload of the packet: Payload of this packet is described
612 in the section SILC Key Exchange
613 Protocol and its sub sections in
617 15 SILC_PACKET_KEY_EXCHANGE_2
619 This packet is used as part of the SILC Key Exchange Protocol.
621 This packet MUST NOT be sent as list and the List flag MUST
624 Payload of the packet: Payload of this packet is described
625 in the section SILC Key Exchange
626 Protocol and its sub sections in
630 16 SILC_PACKET_CONNECTION_AUTH_REQUEST
632 This packet is used to request the authentication method to
633 be used in the SILC Connection Authentication Protocol. If
634 initiator of the protocol does not know the mandatory
635 authentication method this packet MAY be used to determine it.
637 The party receiving this payload MUST respond with the same
638 packet including the mandatory authentication method.
640 This packet MUST NOT be sent as list and the List flag MUST
643 Payload of the packet: See section 2.3.15 Connection Auth
649 17 SILC_PACKET_CONNECTION_AUTH
651 This packet is used to start and perform the SILC Connection
652 Authentication Protocol. This protocol is used to authenticate
653 the connecting party. The protocol is described in detail in
656 This packet MUST NOT be sent as list and the List flag MUST
659 Payload of the packet: Payload of this packet is described
660 in the section SILC Authentication
661 Protocol and it sub sections in [SILC].
664 18 SILC_PACKET_NEW_ID
666 This packet is used to distribute new ID's from server to
667 router and from router to all routers in the SILC network.
668 This is used when for example new client is registered to
669 SILC network. The newly created ID's of these operations are
670 distributed by this packet. Only server may send this packet,
671 however, client MUST be able to receive this packet. This
672 packet MAY be sent to entity that is indirectly connected
675 Payload of the packet: See section 2.3.16 New ID Payload
678 19 SILC_PACKET_NEW_CLIENT
680 This packet is used by client to register itself to the
681 SILC network. This is sent after key exchange and
682 authentication protocols has been completed. Client sends
683 various information about itself in this packet.
685 This packet MUST NOT be sent as list and the List flag MUST
688 Payload of the packet: See section 2.3.17 New Client Payload
691 20 SILC_PACKET_NEW_SERVER
693 This packet is used by server to register itself to the
694 SILC network. This is sent after key exchange and
695 authentication protocols has been completed. Server sends
696 this to the router it connected to, or, if router was
697 connecting, to the connected router. Server sends its
698 Server ID and other information in this packet. The client
699 MUST NOT send or receive this packet.
701 This packet MUST NOT be sent as list and the List flag MUST
704 Payload of the packet: See section 2.3.18 New Server Payload
707 21 SILC_PACKET_NEW_CHANNEL
709 This packet is used to notify routers about newly created
710 channel. Channels are always created by the router and it MUST
711 notify other routers about the created channel. Router sends
712 this packet to its primary route. Client MUST NOT send this
713 packet. This packet MAY be sent to entity that is indirectly
714 connected to the sender.
716 Payload of the packet: See section 2.3.19 New Channel Payload
721 This packet is used to indicate that re-key must be performed
722 for session keys. See section Session Key Regeneration in
723 [SILC1] for more information. This packet does not have
726 This packet MUST NOT be sent as list and the List flag MUST
730 23 SILC_PACKET_REKEY_DONE
732 This packet is used to indicate that re-key is performed and
733 new keys must be used hereafter.
735 This packet MUST NOT be sent as list and the List flag MUST
739 24 SILC_PACKET_HEARTBEAT
741 This packet is used by clients, servers and routers to keep the
742 connection alive. It is recommended that all servers implement
743 keepalive actions and perform it to both direction in a link.
744 This packet does not have a payload.
746 This packet MUST NOT be sent as list and the List flag MUST
750 25 SILC_PACKET_KEY_AGREEMENT
752 This packet is used by clients to request key negotiation
753 between another client in the SILC network. If the negotiation
754 is started it is performed using the SKE protocol. The result of
755 the negotiation, the secret key material, can be used for
756 example as private message key. The server and router MUST NOT
759 This packet MUST NOT be sent as list and the List flag MUST
762 Payload of the packet: See section 2.3.20 Key Agreement Payload
767 26 SILC_PACKET_RESUME_ROUTER
769 This packet is used during backup router protocol when the
770 original primary router of the cell comes back online and wishes
771 to resume the position as being the primary router of the cell.
773 Payload of the packet: See section 2.3.21 Resume Router Payload
778 This packet is used to perform an file transfer protocol in the
779 SILC session with some entity in the network. The packet is
780 multi purpose. The packet is used to tell other entity in the
781 network that the sender wishes to perform an file transfer
782 protocol. The packet is also used to actually tunnel the
783 file transfer protocol stream. The file transfer protocol
784 stream is always protected with the SILC packet.
786 This packet MUST NOT be sent as list and the List flag MUST
789 Payload of the packet: See section 2.3.22 File Transfer Payload
792 28 SILC_PACKET_RESUME_CLIENT
794 This packet is used to resume a client back to the network
795 after it has been detached. A client is able to detach from
796 the network but the client is still valid client in the network.
797 The client may then later resume its session back by sending
798 this packet to a server. Routers also use this packet to notify
799 other routers in the network that the detached client has resumed.
801 This packet MUST NOT be sent as list and the List flag MUST
804 Payload of the packet: See section 2.3.23 Resume Client Payload
809 Currently undefined commands.
814 These packet types are reserved for private use and they will
815 not be defined by this document.
820 This type is reserved for future extensions and currently it
826 2.3.1 SILC Packet Payloads
828 All payloads resides in the main data area of the SILC packet. However
829 all payloads MUST be at the start of the data area after the SILC
830 packet header and padding. All fields in the packet payload are always
831 encrypted, as they reside in the data area of the packet which is
834 Payloads described in this section are common payloads that MUST be
835 accepted anytime during SILC session. Most of the payloads may only
836 be sent with specific packet type which is defined in the description
839 There are a lot of other payloads in the SILC as well. However, they
840 are not common in the sense that they could be sent at any time.
841 These payloads are not described in this section. These are payloads
842 such as SILC Key Exchange payloads and so on. These are described
843 in [SILC1], [SILC3] and [SILC4].
847 2.3.2 Generic payloads
849 This section describes generic payloads that are not associated to any
850 specific packet type. They can be used for example inside some other
857 This payload can be used to send an ID. ID's are variable in length
858 thus this payload provides a way to send variable length ID's.
860 The following diagram represents the ID Payload.
870 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
871 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
872 | ID Type | ID Length |
873 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
877 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
885 o ID Type (2 bytes) - Indicates the type of the ID. See
886 section 2.4 SILC ID Types for list of defined ID types.
888 o ID Length (2 bytes) - Length of the ID Data area not
889 including the length of any other fields in the payload.
891 o ID Data (variable length) - The actual ID data.
896 2.3.2.2 Argument Payload
898 Argument Payload is used to set arguments for any packet payload that
899 needs and supports arguments, such as commands. Number of arguments
900 associated with a packet MUST be indicated by the packet payload which
901 needs the arguments. Argument Payloads MUST always reside right after
902 the packet payload needing the arguments. Incorrect amount of argument
903 payloads MUST cause rejection of the packet.
905 The following diagram represents the Argument Payload.
910 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
911 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
912 | Payload Length | Argument Type | |
913 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
917 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
921 Figure 4: Argument Payload
925 o Payload Length (2 bytes) - Length of the argument payload data
926 area not including the length of any other fields in the
929 o Argument Type (1 byte) - Indicates the type of the argument.
930 Every argument may have a specific type that MUST be defined
931 by the packet payload needing the argument. For example
932 every command specify a number for each argument that maybe
933 associated with the command. By using this number the receiver
934 of the packet knows what type of argument this is. If there is
935 no specific argument type this field is set to zero (0).
937 o Argument Data (variable length) - Argument data.
942 2.3.2.3 Channel Payload
944 Generic Channel Payload may be used to send information about channel,
945 its name, the Channel ID and a mode.
947 The following diagram represents the Channel Payload.
952 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
953 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
954 | Channel Name Length | |
955 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
959 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
960 | Channel ID Length | |
961 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
965 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
967 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
971 Figure 5: New Channel Payload
975 o Channel Name Length (2 bytes) - Length of the channel name
978 o Channel Name (variable length) - The name of the channel.
980 o Channel ID Length (2 bytes) - Length of the Channel ID field.
982 o Channel ID (variable length) - The Channel ID.
984 o Mode Mask (4 bytes) - A mode. This can be the mode of the
985 channel but it can also be the mode of the client on the
986 channel. The contents of this field is dependent of the
987 usage of this payload. The usage is defined separately
988 when this payload is used. This is a 32 bit MSB first value.
993 2.3.2.4 Public Key Payload
995 Generic Public Key Payload may be used to send different types of
996 public keys and certificates.
998 The following diagram represents the Public Key Payload.
1007 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
1008 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1009 | Public Key Length | Public Key Type |
1010 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1012 ~ Public Key of the party (or certificate) ~
1014 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1018 Figure 6: Public Key Payload
1022 o Public Key Length (2 bytes) - The length of the Public Key
1023 (or certificate) field, not including any other field.
1025 o Public Key Type (2 bytes) - The public key (or certificate)
1026 type. This field indicates the type of the public key in
1027 the packet. See the [SILC3] for defined public key types.
1029 o Public Key (or certificate) (variable length) - The
1030 public key or certificate.
1035 2.3.3 Disconnect Payload
1037 Disconnect payload is sent upon disconnection. The payload is simple;
1038 reason of disconnection is sent to the disconnected party.
1040 The payload may only be sent with SILC_PACKET_DISCONNECT packet. It
1041 MUST NOT be sent in any other packet type. The following diagram
1042 represents the Disconnect Payload.
1048 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
1049 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1053 ~ Disconnect Message ~
1055 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1059 Figure 7: Disconnect Payload
1062 o Status (1 byte) - Indicates the Status Type, defined in [SILC3]
1063 for the reason of disconnection.
1065 o Disconnect Message (variable length) - Human readable UTF-8
1066 encoded string indicating reason of the disconnection. This
1072 2.3.4 Success Payload
1074 Success payload is sent when some protocol execution is successfully
1075 completed. The payload is simple; indication of the success is sent.
1076 This may be any data, including binary or human readable data.
1081 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
1082 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1084 ~ Success Indication ~
1086 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1090 Figure 8: Success Payload
1094 o Success Indication (variable length) - Indication of
1095 the success. This may be for example some flag that
1096 indicates the protocol and the success status or human
1097 readable success message. The true length of this
1098 payload is available by calculating it from the SILC
1105 2.3.5 Failure Payload
1107 This is opposite of Success Payload. Indication of failure of
1108 some protocol is sent in the payload.
1114 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
1115 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1117 ~ Failure Indication ~
1119 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1123 Figure 9: Failure Payload
1127 o Failure Indication (variable length) - Indication of
1128 the failure. This may be for example some flag that
1129 indicates the protocol and the failure status or human
1130 readable failure message. The true length of this
1131 payload is available by calculating it from the SILC
1137 2.3.6 Reject Payload
1139 This payload is sent when some protocol is rejected to be executed.
1140 Other operations MAY send this as well that was rejected. The
1141 indication of the rejection is sent in the payload. The indication
1142 may be binary or human readable data.
1148 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
1149 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1151 ~ Reject Indication ~
1153 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1157 Figure 10: Reject Payload
1161 o Reject Indication (variable length) - Indication of
1162 the rejection. This maybe for example some flag that
1163 indicates the protocol and the rejection status or human
1164 readable rejection message. The true length of this
1165 payload is available by calculating it from the SILC
1171 2.3.7 Notify Payload
1173 Notify payload is used to send notify messages. The payload is usually
1174 sent from server to client, however, server MAY send it to another
1175 server as well. This payload MAY also be sent to a channel. Client
1176 MUST NOT send this payload. The receiver of this payload MAY ignore
1177 the contents of the payload, however, notify message SHOULD be audited.
1179 The payload may only be sent with SILC_PACKET_NOTIFY packet. It MUST
1180 not be sent in any other packet type. The following diagram represents
1189 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
1190 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1191 | Notify Type | Payload Length |
1192 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1198 Figure 11: Notify Payload
1202 o Notify Type (2 bytes) - Indicates the type of the notify
1205 o Payload Length (2 bytes) - Length of the entire Notify Payload
1206 including any associated Argument Payloads.
1208 o Argument Nums (2 bytes) - Indicates the number of Argument
1209 Payloads associated to this payload. Notify types may define
1210 arguments to be send along the notify message.
1213 The following list of currently defined notify types. The format for
1214 notify arguments is same as in SILC commands described in [SILC4].
1215 Note that all ID's sent in arguments are sent inside ID Payload. Also
1216 note that all passphrases that may be sent inside arguments MUST be
1217 UTF-8 [RFC2279] encoded.
1222 0 SILC_NOTIFY_TYPE_NONE
1224 If no specific notify type apply for the notify message this type
1228 Arguments: (1) <message>
1230 The <message> is implementation specific free text string.
1231 Receiver MAY ignore this message.
1234 1 SILC_NOTIFY_TYPE_INVITE
1236 Sent when an client is invited to a channel. This is also sent
1237 when the invite list of the channel is changed. This notify type
1238 is sent between routers and if an client was invited, to the
1239 client as well. In this case the packet is destined to the client.
1242 Arguments: (1) <Channel ID> (2) <channel name>
1243 (3) [<sender Client ID>] (4) [<adding client>]
1244 (5) [<removing client>]
1246 The <Channel ID> is the channel. The <channel name> is the name
1247 of the channel and is provided because the client which receives
1248 this notify packet may not have a way to resolve the name of the
1249 channel from the <Channel ID>. The <sender Client ID> is the
1250 Client ID which invited the client to the channel. The <adding
1251 client> and the <removing client> indicates the added or removed
1252 client from the channel's invite list. The format of the <adding
1253 client> and the <removing client> is defined in the [SILC4] with
1254 SILC_COMMAND_INVITE command.
1256 The <adding client> and <removing client> MUST NOT be sent when
1257 the packet is destined to a client.
1260 2 SILC_NOTIFY_TYPE_JOIN
1262 Sent when client has joined to a channel. The server MUST
1263 distribute this type only to the local clients on the channel
1264 and then send it to its primary router. The router or server
1265 receiving the packet distributes this type to the local clients
1266 on the channel and broadcast it to the network.
1269 Arguments: (1) [<Client ID>] (2) <Channel ID>
1271 The <Client ID> is the client that joined to the channel indicated
1272 by the <Channel ID>.
1275 3 SILC_NOTIFY_TYPE_LEAVE
1277 Sent when client has left a channel. The server must distribute
1278 this type only to the local clients on the channel and then send
1279 it to its primary router. The router or server receiving the
1280 packet distributes this type to the local clients on the channel
1281 and broadcast it to the network.
1284 Arguments: (1) <Client ID>
1286 The <Client ID> is the client which left the channel.
1289 4 SILC_NOTIFY_TYPE_SIGNOFF
1291 Sent when client signoff from SILC network. The server MUST
1292 distribute this type only to the local clients on the channel and
1293 then send it to its primary router. The router or server receiving
1294 the packet distributes this type to the local clients on the
1295 channel and broadcast it to the network.
1298 Arguments: (1) <Client ID> (2) <message>
1300 The <Client ID> is the client which left SILC network. The
1301 <message> is free text string indicating the reason of the signoff.
1304 5 SILC_NOTIFY_TYPE_TOPIC_SET
1306 Sent when topic is set/changed on a channel. This type must be
1307 sent only to the clients which is joined on the channel which
1308 topic was set or changed.
1311 Arguments: (1) <ID Payload> (2) <topic>
1313 The <ID Payload> is the ID of the entity who set the topic. It
1314 usually is Client ID but it can be Server ID and Channel ID as well.
1319 6 SILC_NOTIFY_TYPE_NICK_CHANGE
1321 Sent when client changes nick on a channel. The server MUST
1322 distribute this type only to the local clients on the channel
1323 and then send it to its primary router. The router or server
1324 receiving the packet distributes this type to the local clients
1325 on the channel and broadcast it to the network.
1328 Arguments: (1) <Old Client ID> (2) <New Client ID>
1331 The <Old Client ID> is the old ID of the client which changed
1332 the nickname. The <New Client ID> is the new ID generated by
1333 the change of the nickname. The <nickname> is the new nickname.
1334 Note that it is possible to send this notify even if the nickname
1335 has not changed, but client ID has changed.
1338 7 SILC_NOTIFY_TYPE_CMODE_CHANGE
1340 Sent when channel mode has changed. This type MUST be sent only
1341 to the clients which is joined on the channel which mode was
1345 Arguments: (1) <ID Payload> (2) <mode mask>
1346 (3) [<cipher>] (4) <[hmac>]
1347 (5) [<passphrase>] (6) [<founder public key>]
1349 The <ID Payload> is the ID (usually Client ID but it can be
1350 Server ID as well when the router is enforcing channel mode
1351 change) of the entity which changed the mode. The <mode mask>
1352 is the new mode mask of the channel. The client can safely
1353 ignore the <cipher> argument since the SILC_PACKET_CHANNEL_KEY
1354 packet will force the new channel key change anyway. The <hmac>
1355 argument is important since the client is responsible of setting
1356 the new HMAC and the hmac key into use. The <passphrase> is
1357 the passphrase of the channel, if it was now set. The <founder
1358 public key> argument is sent when the founder mode on the
1359 channel was set. All routers and servers that receive the packet
1360 MUST save the founder's public key so that the founder can
1361 reclaim the channel founder rights back for the channel on any
1362 server in the network.
1367 8 SILC_NOTIFY_TYPE_CUMODE_CHANGE
1369 Sent when user mode on channel has changed. This type MUST be
1370 sent only to the clients which is joined on the channel where
1371 the target client is on.
1374 Arguments: (1) <ID Payload> (2) <mode mask>
1375 (3) <Target Client ID> (3) [<founder pubkey>]
1377 The <ID Payload> is the ID (usually Client ID but it can be
1378 Server ID as well when the router is enforcing user's mode
1379 change) of the entity which changed the mode. The <mode mask>
1380 is the new mode mask of the channel. The <Target Client ID>
1381 is the client which mode was changed. The <founder pubkey>
1382 is the public key of the channel founder and is sent only
1383 when first setting the channel founder mode using the
1384 SILC_COMMAND_CUMODE command, and when sending this notify.
1387 9 SILC_NOTIFY_TYPE_MOTD
1389 Sent when Message of the Day (motd) is sent to a client.
1392 Arguments: (1) <motd>
1394 The <motd> is the Message of the Day.
1397 10 SILC_NOTIFY_TYPE_CHANNEL_CHANGE
1399 Sent when channel's ID has changed for a reason or another.
1400 This is sent by normal server to the client. This can also be
1401 sent by router to other server to force the Channel ID change.
1402 The Channel ID MUST be changed to use the new one. When sent
1403 to clients, this type MUST be sent only to the clients which is
1404 joined on the channel.
1407 Arguments: (1) <Old Channel ID> (2) <New Channel ID>
1409 The <Old Channel ID> is the channel's old ID and the <New
1410 Channel ID> is the new one that MUST replace the old one.
1411 Server which receives this from router MUST re-announce the
1412 channel to the router by sending SILC_PACKET_NEW_CHANNEL packet
1413 with the new Channel ID.
1416 11 SILC_NOTIFY_TYPE_SERVER_SIGNOFF
1418 Sent when server quits SILC network. Those clients from this
1419 server that are on channels must be removed from the channel.
1422 Arguments: (1) <Server ID> (n) [<Client ID>] [...]
1424 The <Server ID> is the server's ID. The rest of the arguments
1425 are the Client ID's of the client's which are coming from this
1426 server and are thus quitting the SILC network also. If the
1427 maximum number of arguments are reached another
1428 SILC_NOTIFY_TYPE_SERVER_SIGNOFF notify packet MUST be sent.
1429 When this notify packet is sent between routers the Client ID's
1430 MAY be omitted. Server receiving the Client ID's in the payload
1431 may use them directly to remove the client.
1434 12 SILC_NOTIFY_TYPE_KICKED
1436 Sent when a client has been kicked from a channel. This is
1437 sent also to the client which was kicked from the channel.
1438 The client which was kicked from the channel MUST be removed
1439 from the channel. This notify type is always destined to the
1440 channel. The router or server receiving the packet distributes
1441 this type to the local clients on the channel and broadcast it
1445 Arguments: (1) <Client ID> (2) [<comment>]
1446 (3) <Kicker's Client ID>
1448 The <Client ID> is the client which was kicked from the channel.
1449 The kicker may have set the <comment> to indicate the reason for
1450 the kicking. The <Kicker's Client ID> is the kicker.
1453 13 SILC_NOTIFY_TYPE_KILLED
1455 Sent when a client has been killed from the network. This is sent
1456 also to the client which was killed from the network. The client
1457 which was killed from the network MUST be removed from the network.
1458 This notify type is destined directly to the client which was
1459 killed and to channel if the client is on any channel. The router
1460 or server receiving the packet distributes this type to the local
1461 clients on the channel and broadcast it to the network.
1464 Arguments: (1) <Client ID> (2) [<comment>]
1467 The <Client ID> is the client which was killed from the network.
1468 The killer may have set the <comment> to indicate the reason for
1469 the killing. The <Killer's ID> is the killer, which may be
1470 client but also router server.
1473 14 SILC_NOTIFY_TYPE_UMODE_CHANGE
1475 Sent when user's mode in the SILC changes. This type is sent
1476 only between routers as broadcast packet.
1479 Arguments: (1) <Client ID> (2) <mode mask>
1481 The <Client ID> is the client which mode was changed. The
1482 <mode mask> is the new mode mask.
1485 15 SILC_NOTIFY_TYPE_BAN
1487 Sent when the ban list of the channel is changed. This type is
1488 sent only between routers as broadcast packet.
1491 Arguments: (1) <Channel ID> (2) [<adding client>]
1492 (3) [<removing client>]
1494 The <Channel ID> is the channel which ban list was changed. The
1495 <adding client> is used to indicate that a ban was added and the
1496 <removing client> is used to indicate that a ban was removed from
1497 the ban list. The format of the <adding client> and the
1498 <removing client> is defined in the [SILC4] with SILC_COMMAND_BAN
1502 16 SILC_NOTIFY_TYPE_ERROR
1504 Sent when an error occurs during processing some SILC procedure.
1505 This is not used when error occurs during command processing, see
1506 [SILC3] for more information about commands and command replies.
1507 This type is sent directly to the sender of the packet whose packet
1508 caused the error. See [SILC1] for definition when this type
1512 Arguments: (1) <Status Type> (n) [...]
1514 The <Status Type> is the error type defined in [SILC3]. Note that
1515 same types are also used with command replies to indicate the
1516 status of a command. Both commands and this notify type share
1517 same status types. Rest of the arguments are status type
1518 dependent and are specified with those status types that can be
1519 sent currently inside this notify type in [SILC3]. The <Status
1520 Type> is of size of 1 byte.
1523 17 SILC_NOTIFY_TYPE_WATCH
1525 Sent to indicate change in a watched user. Client can set
1526 nicknames to be watched with SILC_COMMAND_WATCH command, and
1527 receive notifications when they login to network, signoff from
1528 the network or their user mode is changed. This notify type
1529 is used to deliver these notifications. The notify type is
1530 sent directly to the watching client.
1533 Arguments: (1) <Client ID> (2) [<nickname>]
1534 (3) <user mode> (4) [<Notify Type>]
1536 The <Client ID> is the user's Client ID which is being watched,
1537 and the <nickname> is its nickname. If the client just
1538 changed the nickname, then <nickname> is the new nickname, but
1539 the <Client ID> is the old client ID. The <user mode> is the
1540 user's current user mode. The <Notify Type> can be same as the
1541 Notify Payload's Notify Type, and is 16 bit MSB first order value.
1542 If provided it may indicate the notify that occurred for the
1543 client. If client logged in to the network the <Notify Type>
1544 MUST NOT be present.
1547 Notify types starting from 16384 are reserved for private notify
1550 Router server which receives SILC_NOTIFY_TYPE_SIGNOFF,
1551 SILC_NOTIFY_TYPE_SERVER_SIGNOFF, SILC_NOTIFY_TYPE_KILLED,
1552 SILC_NOTIFY_TYPE_NICK_CHANGE and SILC_NOTIFY_TYPE_UMODE_CHANGE
1553 MUST check whether someone in the local cell is watching the nickname
1554 the client has, and send the SILC_NOTIFY_TYPE_WATCH notify to the
1555 watcher, unless the client in case has the SILC_UMODE_REJECT_WATCHING
1556 user mode set. If the watcher client and the client that was
1557 watched is same the notify SHOULD NOT be sent.
1565 Error payload is sent upon error. Error may occur in various
1566 conditions when server sends this packet. Client MUST NOT send this
1567 payload but MUST be able to accept it. However, client MAY
1568 totally ignore the contents of the packet as server is going to
1569 take action on the error anyway. However, it is recommended
1570 that the client takes error packet seriously.
1576 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
1577 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1581 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1585 Figure 12: Error Payload
1589 o Error Message (variable length) - Human readable error
1595 2.3.9 Channel Message Payload
1597 Channel messages are the most common messages sent in the SILC.
1598 Channel Message Payload is used to send message to channels. These
1599 messages can only be sent if client has joined to some channel.
1600 Even though this packet is the most common in SILC it is still
1601 special packet. Some special handling on sending and reception
1602 of channel message is required.
1604 Padding MUST be applied into this payload since the payload is
1605 encrypted separately from other parts of the packet with the
1606 channel specific key. Hence the requirement of the padding.
1607 The padding SHOULD be random data. The packet MUST be made
1608 multiple by eight (8) or by the block size of the cipher, which
1611 The SILC header in this packet is encrypted with the session key
1612 of the next receiver of the packet. Nothing else is encrypted
1613 with that key. Thus, the actual packet and padding to be
1614 encrypted with the session key is SILC Header plus padding to it
1615 to make it multiple by eight (8) or multiple by the block size
1616 of the cipher, which ever is larger.
1618 Receiver of the the channel message packet is able to determine
1619 the channel the message is destined to by checking the destination
1620 ID from the SILC Packet header which tells the destination channel.
1621 The original sender of the packet is also determined by checking
1622 the source ID from the header which tells the client which sent
1625 The payload may only be sent with SILC_PACKET_CHANNEL_MESSAGE packet.
1626 It MUST NOT be sent in any other packet type. The following diagram
1627 represents the Channel Message Payload.
1629 (*) indicates that the field is not encrypted.
1635 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
1636 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1637 | Message Flags | Message Length |
1638 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1642 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1643 | Padding Length | |
1644 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1648 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1652 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1654 ~ Initial Vector * ~
1656 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1660 Figure 13: Channel Message Payload
1664 o Message Flags (2 bytes) - Includes the Message Flags of
1665 the channel messages. The flags can indicate a reason or
1666 purpose for the channel message. Note that the Private
1667 Message Payload use these same Message Flags for the same
1668 purpose. The following Message Flags are defined:
1670 0x0000 SILC_MESSAGE_FLAG_NONE
1672 No specific flags set.
1674 0x0001 SILC_MESSAGE_FLAG_AUTOREPLY
1676 This message is an automatic reply to an earlier
1679 0x0002 SILC_MESSAGE_FLAG_NOREPLY
1681 There should not be reply messages to this
1684 0x0004 SILC_MESSAGE_FLAG_ACTION
1686 The sender is performing an action and the message
1687 is the indication of the action.
1689 0x0008 SILC_MESSAGE_FLAG_NOTICE
1691 The message is for example an informational notice
1694 0x0010 SILC_MESSAGE_FLAG_REQUEST
1696 This is a generic request flag to send request
1697 messages. A separate document should define any
1698 payloads associated to this flag.
1700 0x0020 SILC_MESSAGE_FLAG_SIGNED
1702 This flag indicates that the message is signed
1703 with sender's private key and thus can be verified
1704 by the receiver using the sender's public key. A
1705 separate document should define the detailed procedure
1706 of the signing process and any associated payloads
1709 0x0040 SILC_MESSAGE_FLAG_REPLY
1711 This is a generic reply flag to send a reply to
1712 previously received request. A separate document
1713 should define any payloads associated to this flag.
1715 0x0080 SILC_MESSAGE_FLAG_DATA
1717 This is a generic data flag, indicating that the
1718 message includes some data which can be interpreted
1719 in a specific way. Using this flag any kind of data
1720 can be delivered inside message payload. A separate
1721 document should define how this flag is interpreted
1722 and define any associated payloads.
1724 0x0100 SILC_MESSAGE_FLAG_UTF8
1726 This flag indicates that the message is UTF-8 encoded
1727 textual message. When sending text messages this
1728 flag SHOULD be used. When this flag is used the text
1729 sent as message MUST be UTF-8 encoded.
1731 0x0200 - 0x0800 RESERVED
1733 Reserved for future flags
1735 0x1000 - 0x8000 PRIVATE RANGE
1737 Private range for free use.
1739 o Message Length (2 bytes) - Indicates the length of the
1740 Message Data field in the payload, not including any
1743 o Message Data (variable length) - The actual message to
1746 o Padding Length (2 bytes) - Indicates the length of the
1747 Padding field in the payload, not including any other
1750 o Padding (variable length) - The padding that MUST be
1751 applied because this payload is encrypted separately from
1752 other parts of the packet.
1754 o MAC (variable length) - The MAC computed from the
1755 Message Flags, Message Length, Message Data, Padding Length,
1756 Padding and Initial Vector fields in that order. This
1757 protects the integrity of the plaintext channel message.
1758 The receiver can verify from the MAC whether the message
1759 decrypted correctly. Also, if more than one private key
1760 has been set for the channel, the receiver can verify which
1761 of the keys decrypted the message correctly. Note that,
1762 this field is encrypted and MUST be added to the padding
1765 o Initial Vector (variable length) - The initial vector
1766 that has been used in packet encryption. It needs to be
1767 used in the packet decryption as well. What this field
1768 includes is implementation issue. However, it is
1769 RECOMMENDED that it would be random data, or perhaps
1770 a timestamp. It is NOT RECOMMENDED to use zero (0) as an
1771 initial vector. This field is not encrypted. This field
1772 is not included into the padding calculation. Length
1773 of this field equals the cipher's block size. This field
1774 is, however authenticated.
1779 2.3.10 Channel Key Payload
1781 All traffic in channels are protected by channel specific keys.
1782 Channel Key Payload is used to distribute channel keys to all
1783 clients on the particular channel. Channel keys are sent when
1784 the channel is created, when new user joins to the channel and
1785 whenever a user has left a channel. Server creates the new
1786 channel key and distributes it to the clients by encrypting this
1787 payload with the session key shared between the server and
1788 the client. After that, client starts using the key received
1789 in this payload to protect the traffic on the channel.
1791 The client which is joining to the channel receives its key in the
1792 SILC_COMMAND_JOIN command reply message thus it is not necessary to
1793 send this payload to the entity which sent the SILC_COMMAND_JOIN
1796 Channel keys are cell specific thus every router in the cell have
1797 to create a channel key and distribute it if any client in the
1798 cell has joined to a channel. Channel traffic between cell's
1799 are not encrypted using channel keys, they are encrypted using
1800 normal session keys between two routers. Inside a cell, all
1801 channel traffic is encrypted with the specified channel key.
1802 Channel key should expire periodically, say, in one hour, in
1803 which case new channel key is created and distributed.
1805 The payload may only be sent with SILC_PACKET_CHANNEL_KEY packet.
1806 It MUST NOT be sent in any other packet type. The following diagram
1807 represents the Channel Key Payload.
1813 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
1814 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1815 | Channel ID Length | |
1816 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1820 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1821 | Cipher Name Length | |
1822 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1826 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1827 | Channel Key Length | |
1828 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1832 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1836 Figure 14: Channel Key Payload
1841 o Channel ID Length (2 bytes) - Indicates the length of the
1842 Channel ID field in the payload, not including any other
1845 o Channel ID (variable length) - The Channel ID of the
1846 channel this key is meant for.
1848 o Cipher Name Length (2 bytes) - Indicates the length of the
1849 Cipher name field in the payload, not including any other
1852 o Cipher Name (variable length) - Name of the cipher used
1853 in the protection of channel traffic. This name is
1854 initially decided by the creator of the channel but it
1855 MAY change during the life time of the channel as well.
1857 o Channel Key Length (2 bytes) - Indicates the length of the
1858 Channel Key field in the payload, not including any other
1861 o Channel Key (variable length) - The actual channel key
1867 2.3.11 Private Message Payload
1869 Private Message Payload is used to send private message between
1870 two clients (or users for that matter). The messages are sent only
1871 to the specified user and no other user inside SILC network is
1872 able to see the message. The message is protected by the session
1873 key established by the SILC Key Exchange Protocol. However,
1874 it is also possible to agree to use a private key to protect
1875 just the private messages. See section 2.3.11 Private Message
1876 Key Payload for detailed description of how to agree to use
1879 If normal session key is used to protect the message, every server
1880 between the sender client and the receiving client MUST decrypt the
1881 packet and always re-encrypt it with the session key of the next
1882 receiver of the packet. See section Client To Client in [SILC1].
1884 When private key is used to protect the message, servers between
1885 the sender and the receiver needs not to decrypt/re-encrypt the
1886 packet. Section Client To Client in [SILC1] gives example of this
1889 The payload may only be sent with SILC_PACKET_PRIVATE_MESSAGE
1890 packet. It MUST NOT be sent in any other packet type. The following
1891 diagram represents the Private Message Payload.
1897 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
1898 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1899 | Message Flags | Message Data Length |
1900 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1904 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1908 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1912 Figure 15: Private Message Payload
1916 o Message Flags (2 bytes) - This field includes the Message
1917 Flags of the private message. They can indicate a different
1918 reason or purpose for the private message. See the section
1919 2.3.9 Channel Message Payload for defined flags. Note that
1920 the Channel Message Payload use the same flags for the
1923 o Message Data Length (2 bytes) - Indicates the length of the
1924 Message Data field, not includes any other field.
1926 o Message Data (variable length) - The actual message to
1927 the client. Rest of the packet is reserved for the message
1930 o Padding (variable length) - This field is present only
1931 when the private message payload is encrypted with private
1932 message key. In this case the padding is applied to make
1933 the payload multiple by eight (8), or by the block size of
1934 the cipher, which ever is larger. When encrypted with
1935 normal session keys, this field MUST NOT be included.
1940 2.3.12 Private Message Key Payload
1942 This payload is optional and can be used to send private message
1943 key between two clients in the network. The packet is secured with
1944 normal session keys. By default private messages are encrypted
1945 with session keys, and with this payload it is possible to set
1946 private key for private message encryption between two clients.
1948 The receiver of this payload SHOULD verify for example from user
1949 whether user wants to receive private message key. Note that there
1950 are other, more secure ways of exchanging private message keys in
1951 the SILC network. Instead of sending this payload it is possible to
1952 negotiate the private message key with SKE protocol using the Key
1953 Agreement payload directly peer to peer.
1955 This payload may only be sent by client to another client. Server
1956 MUST NOT send this payload at any time. After sending this payload
1957 the sender of private messages must set the Private Message Key
1958 flag into SILC Packet Header.
1960 The payload may only be sent with SILC_PACKET_PRIVATE_MESSAGE_KEY
1961 packet. It MUST NOT be sent in any other packet type. The following
1962 diagram represents the Private Message Key Payload.
1968 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
1969 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1970 | Private Message Key Length | |
1971 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1973 ~ Private Message Key ~
1975 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1976 | Cipher Name Length | |
1977 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1981 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1985 Figure 16: Private Message Key Payload
1991 o Private Message Key Length (2 bytes) - Indicates the length
1992 of the Private Message Key field in the payload, not including
1995 o Private Message Key (variable length) - The actual private
1996 message key material.
1998 o Cipher Name Length (2 bytes) - Indicates the length of the
1999 Cipher Name field in the payload, not including any other
2002 o Cipher Name (variable length) - Name of the cipher to use
2003 in the private message encryption. If this field does not
2004 exist then the default cipher of the SILC protocol is used.
2005 See the [SILC1] for defined ciphers.
2011 2.3.13 Command Payload
2013 Command Payload is used to send SILC commands from client to server.
2014 Also server MAY send commands to other servers. The following diagram
2015 represents the Command Payload.
2021 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
2022 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2023 | Payload Length | SILC Command | Arguments Num |
2024 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2025 | Command Identifier |
2026 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2030 Figure 17: Command Payload
2034 o Payload Length (2 bytes) - Length of the entire command
2035 payload including any command argument payloads associated
2038 o SILC Command (1 byte) - Indicates the SILC command. This MUST
2039 be set to non-zero value. If zero (0) value is found in this
2040 field the packet MUST be discarded.
2042 o Arguments Num (1 byte) - Indicates the number of arguments
2043 associated with the command. If there are no arguments this
2044 field is set to zero (0). The arguments MUST follow the
2045 command payload. See section 2.3.2.2 for definition of the
2048 o Command Identifier (2 bytes) - Identifies this command at the
2049 sender's end. The entity which replies to this command MUST
2050 set the value found from this field into the Command Payload
2051 used to send the reply to the sender. This way the sender
2052 can identify which command reply belongs to which originally
2053 sent command. What this field includes is implementation
2054 issue but it is RECOMMENDED that wrapping counter value is
2055 used in the field. Value zero (0) in this field means that
2056 no specific value is set.
2059 See [SILC4] for detailed description of different SILC commands,
2060 their arguments and their reply messages.
2066 2.3.14 Command Reply Payload
2068 Command Reply Payload is used to send replies to the commands. The
2069 Command Reply Payload is identical to the Command Payload thus see
2070 the upper section for the Command Payload specification.
2072 The entity which sends the reply packet MUST set the Command Identifier
2073 field in the reply packet's Command Payload to the value it received
2074 in the original command packet.
2076 See SILC Commands in [SILC4] for detailed description of different
2077 SILC commands, their arguments and their reply messages.
2081 2.3.15 Connection Auth Request Payload
2083 Client MAY send this payload to server to request the authentication
2084 method that must be used in authentication protocol. If client knows
2085 this information beforehand this payload is not necessary to be sent.
2086 Server performing authentication with another server MAY also send
2087 this payload to request the authentication method. If the connecting
2088 server already knows this information this payload is not necessary
2091 Server receiving this request MUST reply with same payload sending
2092 the mandatory authentication method. Algorithms that may be required
2093 to be used by the authentication method are the ones already
2094 established by the SILC Key Exchange protocol. See section Key
2095 Exchange Start Payload in [SILC3] for detailed information.
2097 The payload may only be sent with SILC_PACKET_CONNECTION_AUTH_REQUEST
2098 packet. It MUST NOT be sent in any other packet type. The following
2099 diagram represents the Connection Auth Request Payload.
2105 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
2106 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2107 | Connection Type | Authentication Method |
2108 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2112 Figure 18: Connection Auth Request Payload
2116 o Connection Type (2 bytes) - Indicates the type of the
2117 connection. The following connection types are defined:
2124 If any other type is found in this field the packet MUST be
2125 discarded and the authentication MUST be failed.
2127 o Authentication Method (2 bytes) - Indicates the authentication
2128 method to be used in the authentication protocol. The following
2129 authentication methods are defined:
2132 1 password (mandatory)
2133 2 public key (mandatory)
2135 If any other type is found in this field the packet MUST be
2136 discarded and the authentication MUST be failed. If this
2137 payload is sent as request to receive the mandatory
2138 authentication method this field MUST be set to zero (0),
2139 indicating that receiver should send the mandatory
2140 authentication method. The receiver sending this payload
2141 to the requesting party, MAY also set this field to zero (0)
2142 to indicate that authentication is not required. In this
2143 case authentication protocol still MUST be started but
2144 server is most likely to respond with SILC_PACKET_SUCCESS
2152 2.3.16 New ID Payload
2154 New ID Payload is a multipurpose payload. It is used to send newly
2155 created ID's from clients and servers. When client connects to server
2156 and registers itself to the server by sending SILC_PACKET_NEW_CLIENT
2157 packet, server replies with this packet by sending the created ID for
2158 the client. Server always creates the ID for the client.
2160 This payload is also used when server tells its router that new client
2161 has registered to the SILC network. In this case the server sends
2162 the Client ID of the client to the router. Similarly when router
2163 distributes information to other routers about the client in the SILC
2164 network this payload is used.
2166 Also, when server connects to router, router uses this payload to inform
2167 other routers about new server in the SILC network. However, every
2168 server (or router) creates their own ID's thus the ID distributed by
2169 this payload is not created by the distributor in this case. Servers
2170 create their own ID's. Server registers itself to the network by
2171 sending SILC_PACKET_NEW_SERVER to the router it connected to. The case
2172 is same when router connects to another router.
2174 However, this payload MUST NOT be used to send information about new
2175 channels. New channels are always distributed by sending the dedicated
2176 SILC_PACKET_NEW_CHANNEL packet.
2178 Thus, this payload is very important and used every time when some
2179 new entity is registered to the SILC network. Client MUST NOT send this
2180 payload. Both client and server (and router) MAY receive this payload.
2182 The packet uses generic ID Payload as New ID Payload. See section
2183 2.3.2.1 for generic ID Payload.
2187 2.3.17 New Client Payload
2189 When client is connected to the server, keys has been exchanged and
2190 connection has been authenticated client MUST register itself to the
2191 server. Client's first packet after key exchange and authentication
2192 protocols must be SILC_PACKET_NEW_CLIENT. This payload tells server all
2193 the relevant information about the connected user. Server creates a new
2194 client ID for the client when received this payload and sends it to the
2195 client in New ID Payload.
2197 This payload sends username and real name of the user on the remote host
2198 which is connected to the SILC server with SILC client. The server
2199 creates the client ID according the information sent in this payload.
2200 The nickname of the user becomes the username sent in this payload.
2201 However, client should call NICK command after sending this payload to
2202 set the real nickname of the user which is then used to create new
2205 The payload may only be sent with SILC_PACKET_NEW_CLIENT packet. It
2206 MUST NOT be sent in any other packet type. The following diagram
2207 represents the New Client Payload.
2213 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
2214 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2215 | Username Length | |
2216 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
2220 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2221 | Real Name Length | |
2222 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
2226 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2230 Figure 19: New Client Payload
2234 o Username Length (2 bytes) - Length of the Username field.
2236 o Username (variable length) - The username of the user on
2237 the host where connecting to the SILC server.
2239 o Real Name Length (2 bytes) - Length of the Real Name field.
2241 o Real Name (variable length) - The real name of the user
2242 on the host where connecting to the SILC server.
2247 2.3.18 New Server Payload
2249 This payload is sent by server when it has completed successfully both
2250 key exchange and connection authentication protocols. The server
2251 MUST register itself to the SILC Network by sending this payload.
2252 The first packet after these key exchange and authentication protocols
2253 is SILC_PACKET_NEW_SERVER packet. The payload includes the Server ID
2254 of the server that it has created by itself. It also includes a
2255 name of the server that is associated to the Server ID.
2257 The payload may only be sent with SILC_PACKET_NEW_SERVER packet. It
2258 MUST NOT be sent in any other packet type. The following diagram
2259 represents the New Server Payload.
2266 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
2267 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2268 | Server ID Length | |
2269 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
2273 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2274 | Server Name Length | |
2275 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
2279 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2283 Figure 20: New Server Payload
2287 o Server ID Length (2 bytes) - Length of the Server ID Data
2290 o Server ID Data (variable length) - The actual Server ID
2293 o Server Name Length (2 bytes) - Length of the server name
2296 o Server Name (variable length) - The server name.
2301 2.3.19 New Channel Payload
2303 Information about newly created channel is broadcasted to all routers
2304 in the SILC network by sending this packet payload. Channels are
2305 created by router of the cell. Server never creates channels unless
2306 it is a standalone server and it does not have router connection,
2307 in this case server acts as router. Normal server send JOIN command
2308 to the router (after it has received JOIN command from client) which
2309 then processes the command and creates the channel. Client MUST NOT
2310 send this packet. Server may send this packet to a router when it is
2311 announcing its existing channels to the router after it has connected
2314 The packet uses generic Channel Payload as New Channel Payload. See
2315 section 2.3.2.3 for generic Channel Payload. The Mode Mask field in the
2316 Channel Payload is the mode of the channel.
2320 2.3.20 Key Agreement Payload
2322 This payload is used by clients to request key negotiation between
2323 another client in the SILC Network. The key agreement protocol used
2324 is the SKE protocol. The result of the protocol, the secret key
2325 material, can be used for example as private message key between the
2326 two clients. This significantly adds security as the key agreement
2327 is performed outside the SILC network. The server and router MUST NOT
2330 The sender MAY tell the receiver of this payload the hostname and the
2331 port where the SKE protocol is running in the sender's end. The
2332 receiver MAY then initiate the SKE negotiation with the sender. The
2333 sender MAY also optionally not to include the hostname and the port
2334 of its SKE protocol. In this case the receiver MAY reply to the
2335 request by sending the same payload filled with the receiver's hostname
2336 and the port where the SKE protocol is running. The sender MAY then
2337 initiate the SKE negotiation with the receiver.
2339 This payload may be sent with SILC_PACKET_KEY_AGREEMENT and
2340 SILC_PACKET_FTP packet types. It MUST NOT be sent in any other packet
2341 types. The following diagram represents the Key Agreement Payload.
2347 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
2348 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2349 | Hostname Length | |
2350 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
2354 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2356 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2360 Figure 21: Key Agreement Payload
2364 o Hostname Length (2 bytes) - Indicates the length of the
2367 o Hostname (variable length) - The hostname or IP address where
2368 the SKE protocol is running. The sender MAY fill this field
2369 when sending the payload. If the receiver sends this payload
2370 as reply to the request it MUST fill this field.
2372 o Port (4 bytes) - The port where the SKE protocol is bound.
2373 The sender MAY fill this field when sending the payload. If
2374 the receiver sends this payload as reply to the request it
2375 MUST fill this field. This is a 32 bit MSB first order value.
2379 After the key material has been received from the SKE protocol it is
2380 processed as the [SILC3] describes. If the key material is used as
2381 channel private key then the Sending Encryption Key, as defined in
2382 [SILC3] is used as the channel private key. Other key material must
2383 be discarded. The [SILC1] defines the way to use the key material if
2384 it is intended to be used as private message keys. Any other use for
2385 the key material is undefined.
2389 2.3.21 Resume Router Payload
2391 The payload may only be sent with SILC_PACKET_RESUME_ROUTER packet. It
2392 MUST NOT be sent in any other packet type. The Following diagram
2393 represents the Resume Router Payload.
2399 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
2400 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2401 | Type | Session ID |
2402 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2406 Figure 22: Resume Router Payload
2410 o Type (1 byte) - Indicates the type of the backup resume
2411 protocol packet. The type values are defined in [SILC1].
2413 o Session ID (1 bytes) - Indicates the session ID for the
2414 backup resume protocol. The sender of the packet sets this
2415 value and the receiver MUST set the same value in subsequent
2421 2.3.22 File Transfer Payload
2423 File Transfer Payload is used to perform file transfer protocol
2424 between two entities in the network. The actual file transfer
2425 protocol is always encapsulated inside the SILC Packet. The actual
2426 data stream is also sent peer to peer outside SILC network.
2428 When an entity, usually a client wishes to perform file transfer
2429 protocol with another client in the network, they perform Key Agreement
2430 protocol as described in the section 2.3.20 Key Agreement Payload and
2431 in [SILC3], inside File Transfer Payload. After the Key Agreement
2432 protocol has been performed the subsequent packets in the data stream
2433 will be protected using the new key material. The actual file transfer
2434 protocol is also initialized in this stage. All file transfer protocol
2435 packets are always encapsulated in the File Transfer Payload and
2436 protected with the negotiated key material.
2438 The payload may only be sent with SILC_PACKET_FTP packet. It MUST NOT
2439 be sent in any other packet type. The following diagram represents the
2440 File Transfer Payload.
2445 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
2446 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2452 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2456 Figure 23: File Transfer Payload
2460 o Type (1 byte) - Indicates the type of the file transfer
2461 protocol. The following file transfer protocols has been
2464 1 SSH File Transfer Protocol (SFTP) (mandatory)
2466 If zero (0) value or any unsupported file transfer protocol
2467 type is found in this field the packet must be discarded.
2468 The currently mandatory file transfer protocol is SFTP.
2469 The SFTP protocol is defined in [SFTP].
2471 o Data (variable length) - Arbitrary file transfer data. The
2472 contents and encoding of this field is dependent of the usage
2473 of this payload and the type of the file transfer protocol.
2474 When this payload is used to perform the Key Agreement
2475 protocol, this field include the Key Agreement Payload,
2476 as defined in the section 2.3.20 Key Agreement Payload.
2477 When this payload is used to send the actual file transfer
2478 protocol data, the encoding is defined in the corresponding
2479 file transfer protocol.
2484 2.3.23 Resume Client Payload
2486 This payload is used by client to resume its detached session in the
2487 SILC Network. A client is able to detach itself from the network by
2488 sending SILC_COMMAND_DETACH command to its server. The network
2489 connection to the client is lost but the client remains as valid
2490 client in the network. The client is able to resume the session back
2491 by sending this packet and including the old Client ID, and an
2492 Authentication Payload [SILC1] which the server uses to verify with
2493 the detached client's public key. This also implies that the
2494 mandatory authentication method is public key authentication.
2496 Server or router that receives this from the client also sends this,
2497 without the Authentication Payload, to routers in the network so that
2498 they know the detached client has resumed. Refer to the [SILC1] for
2499 detailed description how the detaching and resuming procedure is
2502 The payload may only be sent with SILC_PACKET_RESUME CLIENT packet. It
2503 MUST NOT be sent in any other packet type. The following diagram
2504 represents the Resume Client Payload.
2509 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
2510 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2511 | Client ID Length | |
2512 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
2516 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2518 ~ Authentication Payload ~
2520 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2524 Figure 24: Resume Client Payload
2528 o Client ID Length (1 byte) - The length of the Client ID
2529 field not including any other field.
2531 o Client ID (variable length) - The detached client's Client
2532 ID. The client that sends this payload must know the Client
2535 o Authentication Payload (variable length) - The authentication
2536 payload that the server will verify with the detached client's
2537 public key. If the server doesn't know the public key, it must
2538 retrieve it for example with SILC_COMMAND_GETKEY command.
2546 ID's are extensively used in the SILC network to associate different
2547 entities. The following ID's has been defined to be used in the SILC
2553 When ever specific ID cannot be used this is used.
2557 Server ID to associate servers. See the format of
2562 Client ID to associate clients. See the format of
2567 Channel ID to associate channels. See the format of
2571 When encoding different IDs into the ID Payload, all fields are always
2572 in MSB first order. The IP address, port, and/or the random number
2573 are encoded in the MSB first order.
2577 2.5 Packet Encryption And Decryption
2579 SILC packets are encrypted almost entirely. Only small part of SILC
2580 header is not encrypted as described in section 5.2 SILC Packet Header.
2581 The SILC Packet header is the first part of a packet to be encrypted
2582 and it is always encrypted with the key of the next receiver of the
2583 packet. The data payload area of the packet is always entirely
2584 encrypted and it is usually encrypted with the next receiver's key.
2585 However, there are some special packet types and packet payloads
2586 that require special encryption process. These special cases are
2587 described in the next sections. First is described the normal packet
2592 2.5.1 Normal Packet Encryption And Decryption
2594 Normal SILC packets are encrypted with the session key of the next
2595 receiver of the packet. The entire SILC Packet header and the packet
2596 data payload is is also encrypted with the same key. Padding of the
2597 packet is also encrypted always with the session key, also in special
2598 cases. Computed MAC of the packet must not be encrypted.
2600 Decryption process in these cases are straightforward. The receiver
2601 of the packet MUST first decrypt the SILC Packet header, or some parts
2602 of it, usually first 16 bytes of it. Then the receiver checks the
2603 packet type from the decrypted part of the header and can determine
2604 how the rest of the packet must be decrypted. If the packet type is
2605 any of the special cases described in the following sections the packet
2606 decryption is special. If the packet type is not among those special
2607 packet types rest of the packet can be decrypted with the same key.
2609 With out a doubt, this sort of decryption processing causes some
2610 overhead to packet decryption, but never the less, is required.
2614 2.5.2 Channel Message Encryption And Decryption
2616 Channel Messages (Channel Message Payload) are always encrypted with
2617 the channel specific key. However, the SILC Packet header is not
2618 encrypted with that key. As in normal case, the header is encrypted
2619 with the key of the next receiver of the packet, who ever that might
2620 be. Note that in this case the encrypted data area is not touched
2621 at all; it MUST NOT be re-encrypted with the session key.
2623 Receiver of a channel message, who ever that is, is REQUIRED to decrypt
2624 the SILC Packet header to be able to even recognize the packet to be as
2625 channel message. This is same procedure as for normal SILC packets.
2626 As the receiver founds the packet to be channel message, rest of the
2627 packet processing is special. Rest of the SILC Packet header is
2628 decrypted with the same session key along with the padding of the
2629 packet. After that the packet is protected with the channel specific
2630 key and thus can be decrypted only if the receiver is the client on
2631 the channel. See section 2.7 Packet Padding Generation for more
2632 information about padding on special packets.
2634 If the receiver of the channel message is router which is routing the
2635 message to another router then it MUST decrypt the Channel Message
2636 payload. Between routers (that is, between cells) channel messages
2637 are protected with session keys shared between the routers. This
2638 causes another special packet processing for channel messages. If
2639 the channel message is received from another router then the entire
2640 packet, including Channel Message payload, MUST be encrypted with the
2641 session key shared between the routers. In this case the packet
2642 decryption process is as with normal SILC packets. Hence, if the
2643 router is sending channel message to another router the Channel
2644 Message payload MUST have been decrypted and MUST be re-encrypted
2645 with the session key shared between the another router. In this
2646 case the packet encryption is as with any normal SILC packet.
2648 It must be noted that this is only when the channel messages are sent
2649 from router to another router. In all other cases the channel
2650 message encryption and decryption is as described above. This
2651 different processing of channel messages with router to router
2652 connection is because channel keys are cell specific. All cells have
2653 their own channel keys thus the channel message traveling from one
2654 cell to another MUST be protected as it would be any normal SILC
2657 If the SILC_CMODE_PRIVKEY channel mode has been set for the channel
2658 then the router cannot decrypt the packet as it does not know the
2659 private key. In this case the entire packet MUST be encrypted with
2660 the session key and sent to the router. The router receiving the
2661 packet MUST check the channel mode and decrypt the packet accordingly.
2665 2.5.3 Private Message Encryption And Decryption
2667 By default, private message in SILC are protected by session keys.
2668 In this case the private message encryption and decryption process is
2669 equivalent to normal packet encryption and decryption.
2671 However, private messages MAY be protected with private message key
2672 which causes the packet to be special packet. The procedure in this
2673 case is very much alike to channel packets. The actual private message
2674 is encrypted with the private message key and other parts of the
2675 packet is encrypted with the session key. See 2.7 Packet Padding
2676 Generation for more information about padding on special packets.
2678 The difference from channel message processing is that server or router
2679 en route never decrypts the actual private message, as it does not
2680 have the key to do that. Thus, when sending packets between router
2681 the processing is same as in any other case as well; the packet's header
2682 and padding is protected by the session key and the data area is not
2685 The true receiver of the private message, client, that is, is able
2686 to decrypt the private message as it shares the key with the sender
2691 2.6 Packet MAC Generation
2693 Data integrity of a packet is protected by including a message
2694 authentication code (MAC) at the end of the packet. The MAC is computed
2695 from shared secret MAC key, that is established by the SILC Key Exchange
2696 protocol, from packet sequence number, and from the original contents
2697 of the packet. The MAC is always computed before the packet is
2698 encrypted, although after it is compressed if compression is used.
2700 The MAC is computed from entire packet. Every bit of data in the packet,
2701 including SILC Packet Header is used in the MAC computing. This way
2702 the entire packet becomes authenticated.
2704 If the packet is special packet MAC is computed from the entire packet
2705 but part of the packet may be encrypted before the MAC is computed.
2706 This is case, for example, with channel messages where the message data
2707 is encrypted with key that server may not now. In this case the MAC
2708 has been computed from the encrypted data.
2710 Hence, packet's MAC generation is as follows:
2712 mac = MAC(key, sequence number | SILC packet)
2714 The MAC key is negotiated during the SKE protocol. The sequence number
2715 is a 32 bit MSB first value starting from zero for first packet and
2716 increasing for subsequent packets, finally wrapping after 2^32 packets.
2717 The value is never reset, not even after rekey has been performed.
2718 However, rekey SHOULD be performed before the sequence number repeats
2719 from zero. Note that the sequence number is incremented only when MAC is
2720 computed for a packet. If packet is not encrypted and MAC is not computed
2721 then the sequence number is not incremented. Hence, the sequence number
2722 is zero for first encrypted packet.
2724 See [SILC1] for defined and allowed MAC algorithms.
2728 2.7 Packet Padding Generation
2730 Padding is needed in the packet because the packet is encrypted. It
2731 MUST always be multiple by eight (8) or multiple by the block size
2732 of the cipher, which ever is larger. The padding is always encrypted.
2734 For normal packets the padding is added after the SILC Packet Header
2735 and between the Data Payload area. The padding for normal packets
2736 may be calculated as follows:
2739 padding length = 16 - (packet_length mod block_size)
2742 The `block_size' is the block size of the cipher. The maximum padding
2743 length is 128 bytes, and minimum is 1 byte. The above algorithm calculates
2744 the padding to the next block size, and always returns the padding
2745 length between 1 - 16 bytes. However, implementations may add padding
2746 up to 128 bytes. For example packets that include a passphrase or a
2747 password for authentication purposes SHOULD pad the packet up to the
2748 maximum padding length.
2750 For special packets the padding calculation is different as special
2751 packets may be encrypted differently. In these cases the encrypted
2752 data area MUST already be multiple by the block size thus in this case
2753 the padding is calculated only for SILC Packet Header, not for any
2754 other area of the packet. The same algorithm works in this case as
2755 well, except that the `packet length' is now the SILC Packet Header
2758 The padding MUST be random data, preferably, generated by
2759 cryptographically strong random number generator.
2763 2.8 Packet Compression
2765 SILC Packets MAY be compressed. In this case the data payload area
2766 is compressed and all other areas of the packet MUST remain as they
2767 are. After compression is performed for the data area, the length
2768 field of Packet Header MUST be set to the compressed length of the
2771 The compression MUST always be applied before encryption. When
2772 the packet is received and decrypted the data area MUST be decompressed.
2773 Note that the true sender of the packet MUST apply the compression and
2774 the true receiver of the packet MUST apply the decompression. Any
2775 server or router en route SHOULD NOT decompress the packet.
2781 The sender of the packet MUST assemble the SILC Packet Header with
2782 correct values. It MUST set the Source ID of the header as its own
2783 ID, unless it is forwarding the packet. It MUST also set the Destination
2784 ID of the header to the true destination. If the destination is client
2785 it will be Client ID, if it is server it will be Server ID and if it is
2786 channel it will be Channel ID.
2788 If the sender wants to compress the packet it MUST apply the
2789 compression now. Sender MUST also compute the padding as described
2790 in above sections. Then sender MUST compute the MAC of the packet.
2792 Then sender MUST encrypt the packet as has been described in above
2793 sections according whether the packet is normal packet or special
2794 packet. The computed MAC MUST NOT be encrypted.
2798 2.10 Packet Reception
2800 On packet reception the receiver MUST check that all fields in the
2801 SILC Packet Header are valid. It MUST check the flags of the
2802 header and act accordingly. It MUST also check the MAC of the packet
2803 and if it is to be failed the packet MUST be discarded. Also if the
2804 header of the packet includes any bad fields the packet MUST be
2807 See above sections on the decryption process of the received packet.
2809 The receiver MUST also check that the ID's in the header are valid
2810 ID's. Unsupported ID types or malformed ID's MUST cause packet
2811 rejection. The padding on the reception is always ignored.
2813 The receiver MUST also check the packet type and start parsing the
2814 packet according to the type. However, note the above sections on
2815 special packet types and their parsing.
2821 Routers are the primary entities in the SILC network that takes care
2822 of packet routing. However, normal servers routes packets as well, for
2823 example, when they are routing channel message to the local clients.
2824 Routing is quite simple as every packet tells the true origin and the
2825 true destination of the packet.
2827 It is still RECOMMENDED for routers that has several routing connections
2828 to create route cache for those destinations that has faster route than
2829 the router's primary route. This information is available for the router
2830 when other router connects to the router. The connecting party then
2831 sends all of its locally connected clients, servers and channels. These
2832 informations helps to create the route cache. Also, when new channels
2833 are created to a cell its information is broadcasted to all routers
2834 in the network. Channel ID's are based on router's ID thus it is easy
2835 to create route cache based on these informations. If faster route for
2836 destination does not exist in router's route cache the packet MUST be
2837 routed to the primary route (default route).
2839 However, there are some issues when routing channel messages to group
2840 of users. Routers are responsible of routing the channel message to
2841 other routers, local servers and local clients as well. Routers MUST
2842 send the channel message to only one router in the network, preferably
2843 to the shortest route to reach the channel users. The message can be
2844 routed into either upstream or downstream. After the message is sent
2845 to a router in the network it MUST NOT be sent to any other router in
2846 either same route or other route. The message MUST NOT be routed to
2847 the router it came from.
2849 When routing for example private messages they should be routed to the
2850 shortest route always to reach the destination client as fast as possible.
2852 For server which receives a packet to be routed to its locally connected
2853 client the server MUST check whether the particular packet type is
2854 allowed to be routed to the client. Not all packets may be sent by
2855 some odd entity to client that is indirectly connected to the sender.
2856 See section 2.3 SILC Packet Types and paragraph about indirectly connected
2857 entities and sending packets to them. The section mentions the packets
2858 that may be sent to indirectly connected entities. It is clear that
2859 server cannot send, for example, disconnect packet to client that is not
2860 directly connected to the server.
2862 Routers form a ring in the SILC network. However, routers may have other
2863 direct connections to other routers in the network too. This can cause
2864 interesting routing problems in the network. Since the network is a ring,
2865 the packets usually should be routed into clock-wise direction, or if it
2866 cannot be used then always counter clock-wise (primary route) direction.
2867 Problems may arise when a faster direct route exists and router is routing
2868 a channel message. Currently channel messages must be routed either
2869 in upstream or downstream, they cannot be routed to other direct routes.
2870 The SILC protocol should have a shortest path discovery protocol, and some
2871 existing routing protocol, that can handle a ring network with other
2872 direct routes inside the ring (so called hybrid ring-mesh topology),
2873 MAY be defined to be used with the SILC protocol. Additional
2874 specifications MAY be written on the subject to permeate this
2879 2.12 Packet Broadcasting
2881 SILC packets MAY be broadcasted in SILC network. However, only router
2882 server may send or receive broadcast packets. Client and normal server
2883 MUST NOT send broadcast packets and they MUST ignore broadcast packets
2884 if they receive them. Broadcast packets are sent by setting Broadcast
2885 flag to the SILC packet header.
2887 Broadcasting packets means that the packet is sent to all routers in
2888 the SILC network, except to the router that sent the packet. The router
2889 receiving broadcast packet MUST send the packet to its primary route.
2890 The fact that SILC routers may have several router connections can
2891 cause problems, such as race conditions inside the SILC network, if
2892 care is not taken when broadcasting packets. Router MUST NOT send
2893 the broadcast packet to any other route except to its primary route.
2895 If the primary route of the router is the original sender of the packet
2896 the packet MUST NOT be sent to the primary route. This may happen
2897 if router has several router connections and some other router uses
2898 the router as its primary route.
2900 Routers use broadcast packets to broadcast for example information
2901 about newly registered clients, servers, channels etc. so that all the
2902 routers may keep these informations up to date.
2906 3 Security Considerations
2908 Security is central to the design of this protocol, and these security
2909 considerations permeate the specification. Common security considerations
2910 such as keeping private keys truly private and using adequate lengths for
2911 symmetric and asymmetric keys must be followed in order to maintain the
2912 security of this protocol.
2918 [SILC1] Riikonen, P., "Secure Internet Live Conferencing (SILC),
2919 Protocol Specification", Internet Draft, May 2002.
2921 [SILC3] Riikonen, P., "SILC Key Exchange and Authentication
2922 Protocols", Internet Draft, May 2002.
2924 [SILC4] Riikonen, P., "SILC Commands", Internet Draft, May 2002.
2926 [IRC] Oikarinen, J., and Reed D., "Internet Relay Chat Protocol",
2929 [IRC-ARCH] Kalt, C., "Internet Relay Chat: Architecture", RFC 2810,
2932 [IRC-CHAN] Kalt, C., "Internet Relay Chat: Channel Management", RFC
2935 [IRC-CLIENT] Kalt, C., "Internet Relay Chat: Client Protocol", RFC
2938 [IRC-SERVER] Kalt, C., "Internet Relay Chat: Server Protocol", RFC
2941 [SSH-TRANS] Ylonen, T., et al, "SSH Transport Layer Protocol",
2944 [PGP] Callas, J., et al, "OpenPGP Message Format", RFC 2440,
2947 [SPKI] Ellison C., et al, "SPKI Certificate Theory", RFC 2693,
2950 [PKIX-Part1] Housley, R., et al, "Internet X.509 Public Key
2951 Infrastructure, Certificate and CRL Profile", RFC 2459,
2954 [Schneier] Schneier, B., "Applied Cryptography Second Edition",
2955 John Wiley & Sons, New York, NY, 1996.
2957 [Menezes] Menezes, A., et al, "Handbook of Applied Cryptography",
2960 [OAKLEY] Orman, H., "The OAKLEY Key Determination Protocol",
2961 RFC 2412, November 1998.
2963 [ISAKMP] Maughan D., et al, "Internet Security Association and
2964 Key Management Protocol (ISAKMP)", RFC 2408, November
2967 [IKE] Harkins D., and Carrel D., "The Internet Key Exchange
2968 (IKE)", RFC 2409, November 1998.
2970 [HMAC] Krawczyk, H., "HMAC: Keyed-Hashing for Message
2971 Authentication", RFC 2104, February 1997.
2973 [PKCS1] Kalinski, B., and Staddon, J., "PKCS #1 RSA Cryptography
2974 Specifications, Version 2.0", RFC 2437, October 1998.
2976 [RFC2119] Bradner, S., "Key Words for use in RFCs to Indicate
2977 Requirement Levels", BCP 14, RFC 2119, March 1997.
2979 [SFTP] Ylonen T., and Lehtinen S., "Secure Shell File Transfer
2980 Protocol", Internet Draft, March 2001.
2982 [RFC2279] Yergeau, F., "UTF-8, a transformation format of ISO
2983 10646", RFC 2279, January 1998.
2990 Snellmaninkatu 34 A 15
2994 EMail: priikone@iki.fi
2996 This Internet-Draft expires 15 November 2002