8 .ds RF FORMFEED[Page %]
17 Network Working Group P. Riikonen
19 draft-riikonen-silc-pp-00.txt 28 June 2000
26 <draft-riikonen-silc-pp-00.txt>
31 This document is an Internet-Draft and is in full conformance with
32 all provisions of Section 10 of RFC 2026. Internet-Drafts are
33 working documents of the Internet Engineering Task Force (IETF), its
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35 distribute working documents as Internet-Drafts.
37 Internet-Drafts are draft documents valid for a maximum of six months
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39 time. It is inappropriate to use Internet-Drafts as reference
40 material or to cite them other than as "work in progress."
42 The list of current Internet-Drafts can be accessed at
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45 The list of Internet-Draft Shadow Directories can be accessed at
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48 The distribution of this memo is unlimited.
54 This memo describes a Packet Protocol used in the Secure Internet Live
55 Conferencing (SILC) protocol specified in the Secure Internet Live
56 Conferencing, Protocol Specification Internet Draft [SILC1]. This
57 protocol describes the packet types and packet payloads which defines
58 the contents of the packets. The protocol provides secure binary packet
59 protocol that assures that the contents of the packets are secured and
74 1 Introduction .................................................. 3
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 ......................................... 7
79 2.3.1 SILC Packet Payloads ................................ 15
80 2.3.2 Disconnect Payload .................................. 15
81 2.3.3 Success Payload ..................................... 16
82 2.3.4 Failure Payload ..................................... 16
83 2.3.5 Reject Payload ...................................... 17
84 2.3.6 Notify Payload ...................................... 17
85 2.3.7 Error Payload ....................................... 18
86 2.3.8 Channel Message Payload ............................. 19
87 2.3.9 Channel Key Payload ................................. 20
88 2.3.10 Private Message Payload ............................ 23
89 2.3.11 Private Message Key Payload ........................ 24
90 2.3.12 Command Payload .................................... 25
91 2.3.12.1 Command Argument Payload .................. 25
92 2.3.13 Command Reply Payload .............................. 26
93 2.3.14 Connection Auth Request Payload .................... 27
94 2.3.15 New ID Payload ..................................... 28
95 2.3.16 New ID List Payload ................................ 29
96 2.3.17 New Client Payload ................................. 29
97 2.3.18 New Server Payload ................................. 31
98 2.3.19 New Channel Payload ................................ 31
99 2.3.20 New Channel User Payload ........................... 32
100 2.3.21 New Channel List Payload ........................... 33
101 2.3.22 New Channel User List Payload ...................... 34
102 2.3.23 Replace ID Payload ................................. 34
103 2.3.24 Remove ID Payload .................................. 35
104 2.4 SILC ID Types ............................................. 36
105 2.5 Packet Encryption And Decryption .......................... 37
106 2.5.1 Normal Packet Encryption And Decryption ............. 37
107 2.5.2 Channel Message Encryption And Decryption ........... 37
108 2.5.3 Private Message Encryption And Decryption ........... 38
109 2.6 Packet MAC Generation ..................................... 39
110 2.7 Packet Padding Generation ................................. 39
111 2.8 Packet Compression ........................................ 40
112 2.9 Packet Sending ............................................ 40
113 2.10 Packet Reception ......................................... 41
114 2.11 Packet Routing ........................................... 42
115 2.12 Packet Forwarding ........................................
116 2.13 Packet Broadcasting ...................................... 41
117 2.14 Packet Tunneling ......................................... 42
118 3 Security Considerations ....................................... 43
119 4 References .................................................... 43
120 5 Author's Address .............................................. 44
126 Figure 1: Typical SILC Packet
127 Figure 2: SILC Packet Header
128 Figure 3: Disconnect Payload
129 Figure 4: Success Payload
130 Figure 5: Failure Payload
131 Figure 6: Reject Payload
132 Figure 7: Notify Payload
133 Figure 8: Error Payload
134 Figure 9: Channel Message Payload
135 Figure 10: Channel Key Payload
136 Figure 11: Private Message Payload
137 Figure 12: Private Message Key Payload
138 Figure 13: Command Payload
139 Figure 14: Command Argument Payload
140 Figure 15: Connection Auth Request Payload
141 Figure 16: New ID Payload
142 Figure 17: New Client Payload
143 Figure 18: New Server Payload
144 Figure 19: New Channel Payload
145 Figure 20: New Channel User Payload
146 Figure 21: Replace ID Payload
147 Figure 22: Remove ID Payload
153 This document describes a Packet Protocol used in the Secure Internet
154 Live Conferencing (SILC) protocol specified in the Secure Internet Live
155 Conferencing, Protocol Specification Internet Draft [SILC1]. This
156 protocol describes the packet types and packet payloads which defines
157 the contents of the packets. The protocol provides secure binary packet
158 protocol that assures that the contents of the packets are secured and
161 The basis of SILC protocol relies in the SILC packets and it is with
162 out a doubt the most important part of the protocol. It is also probably
163 the most complicated part of the protocol. Packets are used all the
164 time in the SILC network to send messages, commands and other information.
165 All packets in SILC network are always encrypted and their integrity
166 is assured by computed MACs. The protocol defines several packet types
167 and packet payloads. Each packet type usually has a specific packet
168 payload that actually defines the contents of the packet. Each packet
169 also includes a default SILC Packet Header that provides sufficient
170 information about the origin of the packet and destination of the
175 2 SILC Packet Protocol
180 SILC packets deliver messages from sender to receiver securely by
181 encrypting important fields of the packet. The packet consists of
182 default SILC Packet Header, Padding, Packet Payload data, and, packet
185 The following diagram illustrates typical SILC packet.
190 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
191 | n bytes | 1 - n bytes | n bytes | n bytes
192 | SILC Header | Padding | Data Payload | MAC
193 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
197 Figure 1: Typical SILC Packet
200 SILC Header is always the first part of the packet and its purpose
201 is to provide information about the packet. It provides for example
202 the packet type, origin of the packet and the destination of the packet.
203 The header is variable in length and first two (2) bytes of the
204 header (thus first two bytes of the packet) are not encrypted. The
205 first two (2) bytes are the length of the packet which is not encrypted.
206 See following section for description of SILC Packet header. Packets
207 without SILC header or with malformed SILC header must be dropped.
209 Padding follows the packet header. The purpose of the padding is to
210 make the packet multiple by eight (8) or by the block size of the
211 cipher used in the encryption, which ever is larger. The maximum
212 length of padding is currently 16 bytes. The padding is always
215 Data payload area follows padding and it is the actual data of the
216 packet. The packet data is the packet payloads defined in this
217 protocol. The data payload area is always encrypted.
219 The last part of SILC packet is the packet MAC that assures the
220 integrity of the packet. The MAC is always computed from the packet
221 before the encryption is applied to the packet. If compression is used
222 in the packet the MAC is computed after the compression has been
223 applied. The compression, on the other hand, is always applied before
226 All fields in all packet payloads are always in MSB (most significant
231 2.2 SILC Packet Header
233 The default SILC packet header is applied to all SILC packets and it is
234 variable in length. The purpose of SILC Packet header is to provide
235 detailed information about the packet. The receiver of the packet uses
236 the packet header to parse the packet and gain other relevant parameters
239 Following diagram represents the default SILC header format.
240 (*) indicates that this field is never encrypted. Other fields are
247 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
248 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
249 | Payload Length * | Flags | Packet Type |
250 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
251 | Source ID Length | Destination ID Length |
252 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
258 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
264 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
268 Figure 2: SILC Packet Header
272 o Payload Length (2 bytes) - Is the length of the packet
273 not including the padding of the packet. This field must
274 not be encrypted but must always be authenticated.
276 o Flags (1 byte) - Indicates flags to be used in packet
277 processing. Several flags may be set by ORing the flags
280 Following flags are reserved for this field:
287 In this case the field is ignored.
290 Private Message Key 0x01
292 Indicates that the packet must include private
293 message that is encrypted using private key set by
294 client. Servers does not know anything about this
295 key and this causes that the private message is
296 not handled by the server at all, it is just
297 passed along. See section 2.5.3 Private Message
298 Encryption And Decryption for more information.
303 Marks the packet to be forwarded. Some specific
304 packet types may be forwarded. Receiver of packet
305 with this flag set must not forward the packet any
306 further. See section 2.12 Packet Forwarding for
307 desribtion of packet forwarding.
312 Marks the packet to be broadcasted. Client cannot
313 send broadcast packet and normal server cannot send
314 broadcast packet. Only router server may send broadcast
315 packet. The router receiving of packet with this flag
316 set must send (broadcast) the packet to its primary
317 route. If router has several router connections the
318 packet may be sent only to the primary route. See
319 section 2.13 Packet Broadcasting for description of
325 Marks that the packet is tunneled. Tunneling means
326 that extra SILC Packet Header has been applied to the
327 original packet. The outer header has this flag
328 set. See section 2.14 Packet Tunneling for more
334 o Packet Type (1 byte) - Is the type of the packet. Receiver
335 uses this field to parse the packet. See section 2.3
336 SILC Packets for list of defined packet types.
338 o Source ID Length (2 bytes) - Indicates the length of the
339 Source ID field in the header, not including this or any
344 o Destination ID Length (2 bytes) - Indicates the length of the
345 Destination ID field in the header, not including this or
348 o Src ID Type (1 byte) - Indicates the type of ID in the
349 Source ID field. See section 2.4 SILC ID Types for
352 o Source ID (variable length) - The actual source ID that
353 indicates who is the original sender of the packet.
355 o Dst ID Type (1 byte) - Indicates the type of ID in the
356 Destination ID field. See section 2.4 SILC ID Types for
359 o Destination ID (variable length) - The actual source ID that
360 indicates who is the end receiver of the packet.
364 2.3 SILC Packet Types
366 SILC packet types defines the contents of the packet and it is used by
367 the receiver to parse the packet. The packet type is 8 bits, as a one
368 byte, in length. The range for the packet types are from 0 - 255,
369 where 0 is never sent and 255 is currently reserved for future
370 extensions and must not be defined to any other purpose. Every SILC
371 specification compliant implementation should support all of these packet
374 The below list of the SILC Packet types includes reference to the packet
375 payload as well. Packet payloads are the actual packet, that is, the data
376 that the packet consists of. Each packet type defines packet payload
377 which usually may only be sent with the specific packet type.
379 Most of the packets are packets that must be destined directly to entity
380 that is connected to the sender. It is not allowed, for example, for
381 router to send disconnect packet to client that is not directly connected
382 to the router. However, there are some special packet types that may
383 be destined to some entity that the sender has not direct connection
384 with. These packets are for example private message packets, channel
385 message packets, command packets and some other packets that may be
386 broadcasted in the SILC network. If the packet is allowed to be sent to
387 indirectly connected entity it is mentioned separately in the packet
388 description (unless it is obvious as in private and channel message
389 packets). Other packets must not be sent or accepted, if sent, to
390 indirectly connected entities.
392 List of SILC Packet types are defined as follows.
397 This type is reserved and it is never sent.
400 1 SILC_PACKET_DISCONNECT
402 This packet is sent to disconnect the remote end. Reason of
403 the disconnection is sent inside the packet payload. Client
404 usually does not send this packet.
406 Payload of the packet: See section 2.3.2 Disconnect Payload
409 2 SILC_PACKET_SUCCESS
411 This packet is sent upon successful execution of some protocol.
412 The status of the success is sent in the packet.
414 Payload of the packet: See section 2.3.3 Success Payload
417 3 SILC_PACKET_FAILURE
419 This packet is sent upon failure of some protocol. The status
420 of the failure is sent in the packet.
422 Payload of the packet: See section 2.3.4 Failure Payload
427 This packet may be sent upon rejection of some protocol.
428 The status of the rejection is sent in the packet.
430 Payload of the packet: See section 2.3.5 Reject Payload
435 This packet is used to send notify message, usually from
436 server to client, although it may be sent from server to another
437 server as well. Client never sends this packet. Server may
438 send this packet to channel as well when the packet is
439 distributed to all clients on the channel. Receiver of this
440 packet may ignore the packet if it chooses so. However, it
441 should not be ignored.
443 Payload of the packet: See section 2.3.6 Notify Payload.
448 This packet is sent when an error occurs. Server may
449 send this packet. Client never sends this packet. The
450 client may entirely ignore the packet, however, server is
451 most likely to take action anyway. This packet may be sent
452 to entity that is indirectly connected to the sender.
454 Payload of the packet: See section 2.3.7 Error Payload.
457 7 SILC_PACKET_CHANNEL_MESSAGE
459 This packet is used to send messages to channels. The packet
460 includes Channel ID of the channel and the actual message to
461 the channel. Messages sent to the channel are always protected
462 by channel specific keys. Channel Keys are distributed by
463 SILC_PACKET_CHANNEL_KEY packet.
465 When client sends this packet the destination ID in the SILC
466 header must be the Channel ID of the channel the message is
467 destined to. If server sends this packet to a client the
468 destination ID in the SILC header must be the Client ID of
469 the client receiving the packet.
471 If server sends this packet to router or if router sends this
472 packet to server or another router the destination ID in the
473 SILC header must be the Channel ID of the channel. Server
474 (including router) distributes this packet only to its local
475 clients who are joined to the channel. Servers and routers
476 also determines who are on the channel and when this packet
477 needs to be sent, as described in section Client To Client
480 Payload of the packet: See section 2.3.8 Channel Message
484 8 SILC_PACKET_CHANNEL_KEY
486 This packet is used to distribute new key for particular
487 channel. Each channel has their own independent keys that
488 is used to protect the traffic on the channel. Only server
489 may send this packet. This packet may be sent to entity
490 that is indirectly connected to the sender.
492 Payload of the packet: See section 2.3.9 Channel Key Payload
495 9 SILC_PACKET_PRIVATE_MESSAGE
497 This packet is used to send private messages from client
498 to another client. By default, private messages are protected
499 by session keys established by normal key exchange protocol.
500 However, it is possible to use specific key to protect private
501 messages. SILC_PACKET_PRIVATE_MESSAGE_KEY packet is used to
502 agree the key with the remote client. Pre-shared key may be
503 used as well if both of the client knows it, however, it needs
504 to be agreed outside SILC. See more of this in [SILC1].
506 Payload of the packet: See section 2.3.10 Private Message
510 10 SILC_PACKET_PRIVATE_MESSAGE_KEY
512 This packet is used to agree about a key to be used to protect
513 the private messages between two clients. If this is not sent
514 the normal session key is used to protect the private messages
515 inside SILC network. Agreeing to use specific key to protect
516 private messages adds security, as no server between the two
517 clients will be able to decrypt the private message. However,
518 servers inside SILC network are considered to be trusted, thus
519 using normal session key to protect private messages does not
520 degree security. Whether to agree to use specific keys by
521 default or to use normal session keys by default, is
522 implementation specific issue. See more of this in [SILC1].
524 Payload of the packet: See section 2.3.11 Private Message
528 11 SILC_PACKET_COMMAND
530 This packet is used to send commands from client to server.
531 Server may send this packet to other servers as well. All
532 commands are listed in their own section SILC Command Types
533 in [SILC1]. The contents of this packet is command specific.
534 This packet may be sent to entity that is indirectly connected
537 Payload of the packet: See section 2.3.12 Command Payload
540 12 SILC_PACKET_COMMAND_REPLY
542 This packet is send as reply to the SILC_PACKET_COMMAND packet.
543 The contents of this packet is command specific. This packet
544 maybe sent to entity that is indirectly connected to the sender.
546 Payload of the packet: See section 2.3.13 Command Reply
547 Payload and section 2.3.12 Command
551 13 SILC_PACKET_KEY_EXCHANGE
553 This packet is used to start SILC Key Exchange Protocol,
554 described in detail in [SILC3].
556 Payload of the packet: Payload of this packet is described
557 in the section SILC Key Exchange
558 Protocol and its sub sections in
562 14 SILC_PACKET_KEY_EXCHANGE_1
564 This packet is used as part of the SILC Key Exchange Protocol.
566 Payload of the packet: Payload of this packet is described
567 in the section SILC Key Exchange
568 Protocol and its sub sections in
572 15 SILC_PACKET_KEY_EXCHANGE_2
574 This packet is used as part of the SILC Key Exchange Protocol.
576 Payload of the packet: Payload of this packet is described
577 in the section SILC Key Exchange
578 Protocol and its sub sections in
582 16 SILC_PACKET_CONNECTION_AUTH_REQUEST
584 This packet is used to request the authentication method to
585 be used in the SILC Connection Authentication Protocol. If
586 initiator of the protocol does not know the mandatory
587 authentication method this packet is used to determine it.
589 The party receiving this payload must respond with the same
590 packet including the mandatory authentication method.
592 Payload of the packet: See section 2.3.14 Connection Auth
596 17 SILC_PACKET_CONNECTION_AUTH
598 This packet is used to start and perform the SILC Connection
599 Authentication Protocol. This protocol is used to authenticate
600 the connecting party. The protocol is described in detail in
603 Payload of the packet: Payload of this packet is described
604 in the section SILC Authentication
605 Protocol and it sub sections in [SILC].
608 18 SILC_PACKET_NEW_ID
610 This packet is used to distribute new ID's from server to
611 router and from router to all routers in the SILC network.
612 This is used when for example new client is registered to
613 SILC network. The newly created ID's of these operations are
614 distributed by this packet. Only server may send this packet,
615 however, client must be able to receive this packet.
617 Payload of the packet: See section 2.3.15 New ID Payload
620 19 SILC_PACKET_NEW_ID_LIST
622 This packet is used to distribute list of new ID's from
623 server to routers. This is equivalent to previous packet
624 type except that it may include several ID's. Client must
625 not send this packet.
627 Payload of the packet: See section 2.3.16 New ID List
631 20 SILC_PACKET_NEW_CLIENT
633 This packet is used by client to register itself to the
634 SILC network. This is sent after key exchange and
635 authentication protocols has been completed. Client sends
636 various information about itself in this packet.
638 Payload of the packet: See section 2.3.17 New Client Payload
641 21 SILC_PACKET_NEW_SERVER
643 This packet is used by server to register itself to the
644 SILC network. This is sent after key exchange and
645 authentication protocols has been completed. Server sends
646 this to the router it connected to, or, if router was
647 connecting, to the connected router. Server sends
648 its Server ID and other information in this packet.
649 Client must not send or receive this packet.
651 Payload of the packet: See section 2.3.18 New Server Payload
654 22 SILC_PACKET_NEW_CHANNEL
656 This packet is used to notify routers about newly created
657 channel. Channels are always created by the router and it must
658 notify other routers about the created channel. Router sends
659 this packet to its primary route. Client must not send this
660 packet. This packet maybe sent to entity that is indirectly
661 connected to the sender.
663 Payload of the packet: See section 2.3.19 New Channel Payload
666 23 SILC_PACKET_NEW_CHANNEL_USER
668 This packet is used to notify routers about new user on channel.
669 The packet is sent after user has joined to the channel. Server
670 may send this packet to its router and router may send this to
671 its primary router. Client must not send this packet. This
672 packet maybe sent to entity that is indirectly connected to the
675 Payload of the packet: See section 2.3.20 New Channel User
679 24 SILC_PACKET_NEW_CHANNEL_LIST
681 This packet is used to distribute list of created channels
682 from server to routers. This is equivalent to the packet
683 SILC_PACKET_NEW_CHANNEL except that it may include several
684 payloads. Client must not send this packet.
686 Payload of the packet: See section 2.3.21 New Channel List
690 25 SILC_PACKET_NEW_CHANNEL_USER_LIST
692 This packet is used to distribute list of users on specific
693 channel from server to routers. This is equivalent to the
694 packet SILC_PACKET_NEW_CHANNEL_USER except that it may
695 include several payloads. Client must not send this packet.
697 Payload of the packet: See section 2.3.22 New Channel User
701 26 SILC_PACKET_REPLACE_ID
703 This packet is used to replace old ID with new ID sent in
704 the packet payload. For example, when client changes its
705 nickname new ID is created and this packet can be used to
706 distribute the new ID and the old ID is removed when it is
707 send in the packet. Client cannot send or receive this
708 packet. This packet maybe sent to entity that is indirectly
709 connected to the sender.
711 Payload of the packet: See section 2.3.23 Replace ID Payload
714 27 SILC_PACKET_REMOVE_ID
716 This packet is used to removed ID. For example, when client
717 exits SILC network its ID is removed. Client must not send
718 this packet. This packet maybe sent to entity that is
719 indirectly connected to the sender.
721 Payload of the packet: See section 2.3.24 Remove ID Payload
726 This packet is used to indicate that re-key must be performed
727 for session keys. See section Session Key Regeneration in
728 [SILC1] for more information. This packet does not have
734 29 SILC_PACKET_REKEY_DONE
736 This packet is used to indicate that re-key is performed and
737 new keys must be used hereafter. This is sent only if re-key
738 was done without PFS option. If PFS is set, this is not sent
739 as SILC Key Exchange protocol is executed. This packet does
745 Currently undefined commands.
750 This type is reserved for future extensions and currently it
756 2.3.1 SILC Packet Payloads
758 All payloads resides in the main data area of the SILC packet. However
759 all payloads must be at the start of the data area after the default
760 SILC packet header and padding. All fields in the packet payload are
761 always encrypted, as, they reside in the data area of the packet which
764 Payloads described in this section are common payloads that must be
765 accepted anytime during SILC session. Most of the payloads may only
766 be sent with specific packet type which is defined in the description
769 There are a lot of other payloads in the SILC as well. However, they
770 are not common in the sense that they could be sent at any time.
771 These payloads are not described in this section. These are payloads
772 such as SILC Key Exchange payloads and so on. These are described
773 in [SILC1] and [SILC3].
777 2.3.2 Disconnect Payload
779 Disconnect payload is sent upon disconnection. The payload is simple;
780 reason of disconnection is sent to the disconnected party.
782 The payload may only be sent with SILC_PACKET_DISCONNECT packet. It
783 must not be sent in any other packet type. Following diagram represents
784 the Disconnect Payload.
790 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
791 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
793 ~ Disconnect Message ~
795 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
799 Figure 3: Disconnect Payload
805 o Disconnect Message (variable length) - Human readable
806 reason of the disconnection.
811 2.3.3 Success Payload
813 Success payload is sent when some protocol execution is successfully
814 completed. The payload is simple; indication of the success is sent.
815 This maybe any data, including binary or human readable data.
820 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
821 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
823 ~ Success Indication ~
825 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
829 Figure 4: Success Payload
833 o Success Indication (variable length) - Indication of
834 the success. This maybe for example some flag that
835 indicates the protocol and the success status or human
836 readable success message. The true length of this
837 payload is available by calculating it from the SILC
843 2.3.4 Failure Payload
845 This is opposite of Success Payload. Indication of failure of
846 some protocol is sent in the payload.
852 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
853 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
855 ~ Failure Indication ~
857 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
861 Figure 5: Failure Payload
865 o Failure Indication (variable length) - Indication of
866 the failure. This maybe for example some flag that
867 indicates the protocol and the failure status or human
868 readable failure message. The true length of this
869 payload is available by calculating it from the SILC
877 This payload is sent when some protocol is rejected to be executed.
878 Other operations may send this as well that was rejected. The
879 indication of the rejection is sent in the payload. The indication
880 may be binary or human readable data.
886 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
887 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
889 ~ Reject Indication ~
891 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
895 Figure 6: Reject Payload
899 o Reject Indication (variable length) - Indication of
900 the rejection. This maybe for example some flag that
901 indicates the protocol and the rejection status or human
902 readable rejection message. The true length of this
903 payload is available by calculating it from the SILC
914 Notify payload is used to send notify messages. The payload is usually
915 sent from server to client, however, server may send it to another
916 server as well. Client must not send this payload. The receiver of
917 this payload may totally ignore the contents of the payload, however,
918 notify message should be noted and possibly logged.
920 The payload may only be sent with SILC_PACKET_NOTIFY packet. It must
921 not be sent in any other packet type. Following diagram represents the
927 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
928 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
932 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
936 Figure 7: Notify Payload
940 o Notify Message (variable length) - Human readable notify
948 Error payload is sent upon error. Error may occur in various
949 conditions when server sends this packet. Client may not send this
950 payload but must be able to accept it. However, client may
951 totally ignore the contents of the packet as server is going to
952 take action on the error anyway. However, it is recommended
953 that the client takes error packet seriously.
959 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
960 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
964 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
968 Figure 8: Error Payload
972 o Error Message (variable length) - Human readable error
978 2.3.8 Channel Message Payload
980 Channel messages are the most common messages sent in the SILC.
981 Channel Message Payload is used to send message to channels. These
982 messages can only be sent if client has joined to some channel.
983 Even though this packet is the most common in SILC it is still
984 special packet. Some special handling on sending and reception
985 of channel message is required.
987 Padding must be applied into this payload since the payload is
988 encrypted separately from other parts of the packet with the
989 channel specific key. Hence the requirement of the padding.
990 The padding should be random data. The packet must be made
991 multiple by eight (8) or by the block size of the cipher, which
994 The SILC header in this packet is encrypted with the session key
995 of the next receiver of the packet. Nothing else is encrypted
996 with that key. Thus, the actual packet and padding to be
997 encrypted with the session key is SILC Header plus padding to it
998 to make it multiple by eight (8) or multiple by the block size
999 of the cipher, which ever is larger.
1001 Receiver of the the channel message packet is able to determine
1002 the channel the message is destined to by checking the destination
1003 ID from the SILC Packet header which tells the destination channel.
1004 The original sender of the packet is also determined by checking
1005 the source ID from the header which tells the who client sent
1008 The payload may only be sent with SILC_PACKET_CHANNEL_MESSAGE packet.
1009 It must not be sent in any other packet type. Following diagram
1010 represents the Channel Message Payload.
1012 (*) indicates that the field is not encrypted.
1038 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
1039 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1040 | Nickname Length | |
1041 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1045 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1046 | Message Length | |
1047 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1051 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1052 | Padding Length | |
1053 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1057 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1059 ~ Initial Vector * ~
1061 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1065 Figure 9: Channel Message Payload
1069 o Nickname Length (2 bytes) - Indicates the length of the
1070 Nickname field, not including any other field.
1072 o Nickname (variable length) - Nickname of the sender of the
1073 channel message. This should not be trusted as a definite
1074 sender of the channel message. The SILC Packet Header in
1075 the packet indicates the true sender of the packet and
1076 client should verify that the nickname sent here belongs
1077 to the Client ID in the SILC Packet Header. This nickname
1078 is merely provided to be displayed by the client.
1080 If server is sending this packet this field is not included
1081 and zero (0) length must be set to the Nickname Length field.
1083 o Message Length (2 bytes) - Indicates the length of the
1084 the Message Data field in the payload, not including any
1088 o Message Data (variable length) - The actual message to
1091 o Padding Length (2 bytes) - Indicates the length of the
1092 Padding field in the payload, not including any other
1095 o Padding (variable length) - The padding that must be
1096 applied because this payload is encrypted separately from
1097 other parts of the packet.
1099 o Initial Vector (variable length) - The initial vector
1100 that has been used in packet encryption. It needs to be
1101 used in the packet decryption as well. What this field
1102 includes is implementation issue. However, it is
1103 recommended that it would be random data or, perhaps,
1104 a timestamp. It is not recommended to use zero (0) as
1105 initial vector. This field is not encrypted. This field
1106 is not included into the padding calculation. Length
1107 of this field equals the cipher's block size. This field
1108 is, however, authenticated.
1113 2.3.9 Channel Key Payload
1115 All traffic in channels are protected by channel specific keys.
1116 Channel Key Payload is used to distribute channel keys to all
1117 clients on the particular channel. Channel keys are sent when
1118 the channel is created, when new user joins to the channel and
1119 whenever a user leaves a channel. Server creates the new
1120 channel key and distributes it to the clients by encrypting this
1121 payload with the session key shared between the server and
1122 the client. After that, client starts using the key received
1123 in this payload to protect the traffic on the channel.
1125 Channel keys are cell specific thus every router in cell have
1126 to create a channel key and distribute it if any client in the
1127 cell has joined to a channel. Channel traffic between cell's
1128 are not encrypted using channel keys, they are encrypted using
1129 normal session keys between two routers. Inside a cell, all
1130 channel traffic is encrypted with the specified channel key.
1131 Channel key should expire peridiocally, say, in one hour, in
1132 which case new channel key is created and distributed.
1134 The payload may only be sent with SILC_PACKET_CHANNEL_KEY packet.
1135 It must not be sent in any other packet type. Following diagram
1136 represents the Channel Key Payload.
1142 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
1143 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1144 | Channel ID Length | |
1145 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1149 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1150 | Cipher Name Length | |
1151 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1155 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1156 | Channel Key Length | |
1157 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1161 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1165 Figure 10: Channel Key Payload
1170 o Channel ID Length (2 bytes) - Indicates the length of the
1171 Channel ID field in the payload, not including any other
1174 o Channel ID (variable length) - The Channel ID of the
1175 channel this key is meant for.
1177 o Cipher Name Length (2 bytes) - Indicates the length of the
1178 Cipher name field in the payload, not including any other
1181 o Cipher Name (variable length) - Name of the cipher used
1182 in the protection of channel traffic. This name is
1183 initially decided by the creator of the channel but it
1184 may change during the life time of the channel as well.
1186 o Channel Key Length (2 bytes) - Indicates the length of the
1187 Channel Key field in the payload, not including any other
1190 o Channel Key (variable length) - The actual channel key
1191 material. This key is used as such as key material for
1192 encryption function.
1197 2.3.10 Private Message Payload
1199 Private Message Payload is used to send private message between
1200 two clients (or users for that matter). The messages are sent only
1201 to the specified user and no other user inside SILC network is
1202 able to see the message. The message is protected by the session
1203 key established by the SILC Key Exchange Protocol. However,
1204 it is also possible to agree to use specific keys to protect
1205 just the private messages. See section 2.3.11 Private Message
1206 Key Payload for detailed description of how to agree to use
1209 If normal session key is used to protect the message, every
1210 server between the sender client and the receiving client needs
1211 to decrypt the packet and always re-encrypt it with the session
1212 key of the next receiver of the packet. See section Client
1213 To Client in [SILC1].
1215 When specific key is used to protect the message, servers between
1216 the sender and the receiver needs not to decrypt/re-encrypt the
1217 packet. Section 4.8.2 Client To Client in [SILC1] gives example of
1218 this scheme as well.
1220 The payload may only be sent with SILC_PACKET_PRIVATE_MESSAGE
1221 packet. It must not be sent in any other packet type. Following
1222 diagram represents the Private Message Payload.
1228 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
1229 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1230 | Nickname Length | |
1231 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1235 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1239 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1243 Figure 11: Private Message Payload
1247 o Nickname Length (2 bytes) - Indicates the length of the
1248 Nickname field, not including any other field.
1250 o Nickname (variable length) - Nickname of the sender of the
1251 private message. This should not be trusted as a definite
1252 sender of the private message. The SILC Packet Header in
1253 the packet indicates the true sender of the packet and
1254 client should verify that the nickname sent here belongs
1255 to the Client ID in the SILC Packet Header. This nickname
1256 is merely provided to be displayed by the client.
1258 o Message Data (variable length) - The actual message to
1259 the client. Rest of the packet is reserved for the message
1265 2.3.11 Private Message Key Payload
1267 This payload is used to send key from client to another client that
1268 is going to be used to protect the private messages between these
1269 two clients. If this payload is not sent normal session key
1270 established by the SILC Key Exchange Protocol is used to protect
1271 the private messages.
1273 This payload may only be sent by client to another client. Server
1274 must not send this payload at any time. After sending this payload
1275 the sender of private messages must set the Private Message Key
1276 flag into SILC Packet Header.
1278 The payload may only be sent with SILC_PACKET_PRIVATE_MESSAGE_KEY
1279 packet. It must not be sent in any other packet type. Following
1280 diagram represents the Private Message Key Payload.
1286 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
1287 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1288 | Private Message Key Length | |
1289 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1291 ~ Private Message Key ~
1293 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1297 Figure 12: Private Message Key Payload
1303 o Private Message Key Length (2 bytes) - Indicates the length
1304 of the Private Message Key field in the payload, not including
1307 o Private Message Key (variable length) - The actual private
1308 message key material. This key is used as such as key material
1309 for encryption function.
1314 2.3.12 Command Payload
1316 Command Payload is used to send SILC commands from client to server.
1317 Also server may send commands to other servers. Following diagram
1318 represents the Command Payload.
1324 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
1325 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1326 | Payload Length | SILC Command | Arguments Num |
1327 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1329 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1333 Figure 13: Command Payload
1337 o Payload Length (2 bytes) - Length of the entire command
1338 payload including any command argument payloads associated
1341 o SILC Command (1 byte) - SILC Command identifier. This must
1342 be set to non-zero value. If zero (0) value is found in this
1343 field the packet must be discarded.
1345 o Arguments Num (1 byte) - Indicates the number of arguments
1346 associated with the command. If there are no arguments this
1347 field is set to zero (0). The arguments must follow the
1350 o Command Unifier (2 bytes) - Unifies this command at the
1351 sender's end. The entity who replies to this command must
1352 set the value found from this field into the Command Payload
1353 used to send the reply to the sender. This way the sender
1354 can identify which command reply belongs to which originally
1355 sent command. What this field includes is implementation
1356 issue but it is recommended that wrapping counter value is
1360 See [SILC1] for detailed description of different SILC commands,
1361 their arguments and their reply messages.
1365 2.3.12.1 Command Argument Payload
1367 Command Argument Payload is used to set arguments for SILC commands.
1368 Number of arguments associated with a command are indicated by the
1369 Command Payload in the Arguments Num field. Command argument
1370 payloads may only be used with a command payload and they must
1371 always reside right after the command payload. Incorrect amount of
1372 argument payloads must cause rejection of the packet. Following
1373 diagram represents the Command Argument Payload.
1379 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
1380 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1381 | Argument Num | Argument Type | Payload Length |
1382 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1386 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1390 Figure 14: Command Argument Payload
1394 o Argument Num (1 byte) - Indicates the number of this argument.
1395 For first argument this is set to 1, for second argument this
1396 is set to 2, and so forth. If incorrect value is found
1397 in this field the packet must be discarded. Value is
1398 incorrect if it is zero (0) or, for example, a third argument
1399 does not include value 3.
1401 o Argument Type (1 byte) - Indicates the type of the argument.
1402 Every command specify a number for each argument that maybe
1403 associated with the command. By using this number the receiver
1404 of the packet knows what type of argument this is. The numbers
1405 are command specific and has been defined in section SILC
1406 Commands in [SILC1]. This field makes it possible to send
1407 arguments in free order as this field is used to identify
1408 the specific type of the argument.
1410 o Payload Length (2 bytes) - Length of the argument payload data
1411 area not including the length of any other fields in the
1414 o Argument Data (variable length) - Argument data.
1419 2.3.13 Command Reply Payload
1421 Command Reply Payload is used to send replies to the commands. The
1422 Command Reply Payload is identical to the Command Payload thus see the
1423 upper sections for Command Payload and for Command Argument Payload
1424 specifications. Command Reply message uses the Command Argument Payload
1427 The entity who sends the reply packet must set the Command Unifier
1428 field in the reply packet's Command Payload to the value it received
1429 in the original command packet.
1431 See SILC Commands in [SILC1] for detailed description of different
1432 SILC commands, their arguments and their reply messages.
1436 2.3.14 Connection Auth Request Payload
1438 Client may send this payload to server to request the authentication
1439 method that must be used in authentication protocol. If client knows
1440 this information beforehand this payload is not necessary to be sent.
1441 Server performing authentication with another server may also send
1442 this payload to request the authentication method. If the connecting
1443 server already knows this information this payload is not necessary
1446 Server receiving this request must reply with same payload sending
1447 the mandatory authentication method. Algorithms that may be required
1448 to be used by the authentication method are the ones already
1449 established by the SILC Key Exchange protocol. See section Key
1450 Exchange Start Payload in [SILC3] for detailed information.
1452 The payload may only be sent with SILC_PACKET_CONNECTION_AUTH_REQUEST
1453 packet. It must not be sent in any other packet type. Following
1454 diagram represents the Connection Auth Request Payload.
1460 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
1461 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1462 | Connection Type | Authentication Method |
1463 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1467 Figure 15: Connection Auth Request Payload
1471 o Connection Type (2 bytes) - Indicates the type of the ID.
1472 Following connection types are defined:
1478 If any other type is found in this field the packet must be
1479 discarded and the authentication must be failed.
1481 o Authentication Method (2 bytes) - Indicates the authentication
1482 method to be used in the authentication protocol. Following
1483 authentication methods are defined:
1488 1 password (mandatory)
1489 2 public key (mandatory)
1491 If any other type is found in this field the packet must be
1492 discarded and the authentication must be failed. If this
1493 payload is sent as request to receive the mandatory
1494 authentication method this field must be set to zero (0),
1495 indicating that receiver should send the mandatory
1496 authentication method. The receiver sending this payload
1497 to the requesting party, may also set this field to zero (0)
1498 to indicate that authentication is not required. In this
1499 case authentication protocol still must be started but
1500 server is most likely to respond with SILC_PACKET_SUCCESS
1506 2.3.15 New ID Payload
1508 New ID Payload is a multipurpose payload. It is used to send newly
1509 created ID's from clients and servers. When client connects to server
1510 and registers itself to the server by sending SILC_PACKET_NEW_CLIENT
1511 packet, server replies with this packet by sending the created ID for
1512 the client. Server always creates the ID for the client.
1514 This payload is also used when server tells its router that new client
1515 has registered to the SILC network. In this case the server sends
1516 the Client ID of the client to the router. Similiary when router
1517 distributes information to other routers about the client in the SILC
1518 network this payload is used.
1520 Also, when server connects to router, router uses this payload to inform
1521 other routers about new server in the SILC network. However, every
1522 server (or router) creates their own ID's thus the ID distributed by
1523 this payload is not created by the distributor in this case. Servers
1524 create their own ID's. Server registers itself to the network by sending
1525 SILC_PACKET_NEW_SERVER to the router it connected to. The case is same
1526 when router connects to another router.
1528 Hence, this payload is very important and used every time when some
1529 new entity is registered to the SILC network. Client never sends this
1530 payload. Both client and server (and router) may receive this payload.
1532 The payload may only be sent with SILC_PACKET_NEW_ID packet. It must
1533 not be sent in any other packet type. Following diagram represents the
1540 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
1541 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1542 | ID Type | ID Length |
1543 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1547 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1551 Figure 16: New ID Payload
1555 o ID Type (2 bytes) - Indicates the type of the ID. See
1556 section 2.4 SILC ID Types for list of defined ID types.
1558 o ID Length (2 bytes) - Length of the ID Data area not
1559 including the length of any other fields in the payload.
1561 o ID Data (variable length) - The actual ID data.
1567 2.3.16 New ID List Payload
1569 New ID List Payload is used to distribute list of ID's usually from
1570 server to router but also from router to other routers in the network.
1571 This payload is used, for example, when server is connected to router
1572 and the server wants to distribute all of its locally connected clients
1573 and locally created channels to the router. It is convenient in this
1574 case to use this payload instead of sending all the information one
1575 by one using New ID Payload.
1577 There is no specific payload for this packet type. The packet type
1578 uses same payload as described in previous section. To form a list
1579 several payloads is put in the packet each after each. The payload
1580 is variable in length but can be calculated by calculating the ID
1581 Type field, Length field and the ID Data fields together. This forms
1582 one New ID Payload in the list.
1584 The list of payloads may only be sent with SILC_PACKET_NEW_ID_LIST
1585 packet. They must not be sent in any other packet type.
1589 2.3.17 New Client Payload
1591 When client is connected to the server, keys has been exchanged and
1592 connection has been authenticated client must register itself to the
1593 server. Clients first packet after key exchange and authentication
1594 protocols must be SILC_PACKET_NEW_CLIENT. This payload tells server all
1595 the relevant information about the connected user. Server creates a new
1596 client ID for the client when received this payload and sends it to the
1597 client in New ID Payload.
1599 This payload sends username and real name of the user on the remote host
1600 which is connected to the SILC server with SILC client. The server
1601 creates the client ID according the information sent in this payload.
1602 The nickname of the user becomes the username sent in this payload.
1603 However, client should call NICK command after sending this payload to
1604 set the real nickname of the user which is then used to create new
1607 The payload may only be sent with SILC_PACKET_NEW_CLIENT packet. It
1608 must not be sent in any other packet type. Following diagram represents
1609 the New Client Payload.
1615 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
1616 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1617 | Username Length | |
1618 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1622 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1623 | Real Name Length | |
1624 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1628 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1632 Figure 17: New Client Payload
1636 o Username Length (2 bytes) - Length of the username.
1638 o Username (variable length) - The username of the user on
1639 the host where connecting to the SILC server.
1641 o Real Name Length (2 bytes) - Length of the Real Name.
1643 o Real Name (variable length) - The real name of the user
1644 on the host where connecting to the SILC server.
1649 2.3.18 New Server Payload
1651 This payload is sent by server when it has completed successfully both
1652 key exchange and connection authentication protocols. The server
1653 uses this payload to register itself to the SILC network. The
1654 first packet after these key exchange and authentication protocols
1655 is SILC_PACKET_NEW_SERVER packet. The payload includes the Server ID
1656 of the server that it has created by itself. It also includes a
1657 name of the server that is associated to the Server ID.
1659 The payload may only be sent with SILC_PACKET_NEW_SERVER packet. It
1660 must not be sent in any other packet type. Following diagram represents
1661 the New Server Payload.
1667 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
1668 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1669 | Server ID Length | |
1670 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1674 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1675 | Server Name Length | |
1676 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1680 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1684 Figure 18: New Server Payload
1688 o Server ID Length (2 bytes) - Length of the ID Data area not
1689 including the length of any other fields in the payload.
1691 o Server ID Data (variable length) - The actual Server ID
1694 o Server Name Length (2 bytes) - Length of the server name.
1696 o Server Name (variable length) - The server name.
1701 2.3.19 New Channel Payload
1703 Information about newly created channel is broadcasted to all routers
1704 in the SILC network by sending this packet payload. Channels are
1705 created by router of the cell. Server never creates channels unless
1706 it is a standalone server and it does not have router connection,
1707 in this case server acts as router. Normal server forwards JOIN command
1708 to the router (after it has received JOIN command from client) which
1709 then processes the command and creates the channel. Client never sends
1712 The payload may only be sent with SILC_PACKET_NEW_CHANNEL packet.
1713 It must not be sent in any other packet type. Following diagram
1714 represents the New Channel Payload.
1720 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
1721 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1722 | Channel Name Length | |
1723 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1727 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1728 | Channel ID Length | |
1729 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1733 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1737 Figure 19: New Channel Payload
1742 o Channel Name Length (2 bytes) - Length of the channel name.
1744 o Channel Name (variable length) - The name of the created
1747 o Channel ID Length (2 bytes) - Length of the Channel ID.
1749 o Channel ID (variable length) - The created Channel ID.
1754 2.3.20 New Channel User Payload
1756 When client (user) joins to a channel, server must notify routers
1757 about the new user on the channel. Normal server sends this packet
1758 payload to its router which then broadcasts the packet further.
1759 Router sends this packet always to its primary router. Client must
1760 not send this packet payload. The mode of the user is NONE after
1761 user has joined to the channel.
1763 The payload may only be sent with SILC_PACKET_NEW_CHANNEL_USER
1764 packet. It must not be sent in any other packet type. Following
1765 diagram represents the New Channel User Payload.
1771 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
1772 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1773 | Channel ID Length | |
1774 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1778 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1779 | Client ID Length | |
1780 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1784 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1788 Figure 20: New Channel User Payload
1792 o Channel ID Length (2 bytes) - Length of the Channel ID.
1794 o Channel ID (variable length) - The Channel ID of the channel
1795 to which the client has joined.
1797 o Client ID Length (2 bytes) - Length of the Client ID.
1799 o Client ID (variable length) - The Client ID of the client
1800 who has joined the channel.
1805 2.3.21 New Channel List Payload
1807 This payload is used to distribute list of new channels from server
1808 to routers. It might convenient to send list of new channels when
1809 existing server connects to router, instead of sending them one
1812 There is no specific payload for this packet type. The packet type
1813 uses same payload as described in 2.3.19 New Channel Payload. To form
1814 a list several payloads is put in the packet each after each. The
1815 payload is variable in length but can be calculated by calculating
1816 the length of the fields together. This forms one New Channel Payload
1819 The list of payloads may only be sent with SILC_PACKET_NEW_CHANNEL_LIST
1820 packet. They must not be sent in any other packet type.
1824 2.3.22 New Channel User List Payload
1826 This payload is used to distribute list of channel users on specific
1827 channel from server to routers. It might convenient to send list of
1828 channel users when existing server connects to router, instead of
1829 sending them one by one.
1831 There is no specific payload for this packet type. The packet type
1832 uses same payload as described in 2.3.20 New Channel User Payload.
1833 To form a list several payloads is put in the packet each after each.
1834 The payload is variable in length but can be calculated by calculating
1835 the length of the fields together. This forms one New Channel User
1836 Payload in the list.
1838 The list of payloads may only be sent with packet
1839 SILC_PACKET_NEW_CHANNEL_USER_LIST. They must not be sent in any other
1844 2.3.23 Replace ID Payload
1846 This payload is used to replace old ID with new ID sent in the payload.
1847 When ID changes for some entity and the new ID is wanted to replace the
1848 old one this payload must be used. Client cannot send or receive this
1849 payload. Normal server and router server may send and receive this
1850 payload. After this packet has been sent the old ID must not be used
1853 The payload may only be sent with SILC_PACKET_REPLACE_ID packet. It must
1854 not be sent in any other packet type. Following diagram represents the
1855 Replace Payload Payload.
1868 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
1869 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1870 | Old ID Type | Old ID Length |
1871 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1875 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1876 | New ID Type | New ID Length |
1877 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1881 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1885 Figure 21: Replace ID Payload
1889 o Old ID Type (2 bytes) - Indicates the type of the old ID. See
1890 section 2.4 SILC ID Types for list of defined ID types.
1892 o Old ID Length (2 bytes) - Length of the old ID Data area not
1893 including the length of any other fields in the payload.
1895 o Old ID Data (variable length) - The actual old ID data.
1897 o New ID Type (2 bytes) - Indicates the type of the new ID. See
1898 section 2.4 SILC ID Types for list of defined ID types.
1900 o New ID Length (2 bytes) - Length of the new ID Data area not
1901 including the length of any other fields in the payload.
1903 o New ID Data (variable length) - The actual new ID data.
1908 2.3.24 Remove ID Payload
1910 Remove ID payload is used to remove ID from SILC network. This is used
1911 for example when client exits SILC network. The server must in this
1912 case send this payload to notify that this ID is not valid anymore.
1913 After this has been send the old ID must not be used anymore. Client
1914 must not send this payload.
1916 The payload may only be sent with SILC_PACKET_REMOVE_ID packet. It must
1917 not be sent in any other packet type. Following diagram represents the
1918 Remove Payload Payload.
1924 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
1925 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1926 | ID Type | ID Length |
1927 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1931 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1935 Figure 22: Remove ID Payload
1939 o ID Type (2 bytes) - Indicates the type of the ID to be
1940 removed. See section 2.4 SILC ID Types for list of defined
1943 o ID Length (2 bytes) - Length of the D Data area not including
1944 the length of any other fields in the payload.
1946 o ID Data (variable length) - The actual ID data to be removed.
1953 ID's are extensively used in the SILC network to associate different
1954 entities. Following ID's has been defined to be used in the SILC
1960 When ever specific ID cannot be used this is used.
1964 Server ID to associate servers. See the format of
1969 Client ID to associate clients. See the format of
1974 Channel ID to associate channels. See the format of
1980 2.5 Packet Encryption And Decryption
1982 SILC packets are encrypted almost entirely. Only small part of SILC
1983 header is not encrypted as described in section 5.2 SILC Packet Header.
1984 The SILC Packet header is the first part of a packet to be encrypted
1985 and it is always encrypted with the key of the next receiver of the
1986 packet. The data payload area of the packet is always entirely
1987 encrypted and it is usually encrypted with the next receiver's key.
1988 However, there are some special packet types and packet payloads
1989 that require special encryption process. These special cases are
1990 described in the next sections. First is described the normal packet
1995 2.5.1 Normal Packet Encryption And Decryption
1997 Normal SILC packets are encrypted with the session key of the next
1998 receiver of the packet. The entire SILC Packet header and the packet
1999 data payload is is also encrypted with the same key. Padding of the
2000 packet is also encrypted always with the session key, also in special
2001 cases. Computed MAC of the packet must not be encrypted.
2003 Decryption process in these cases are straightforward. The receiver
2004 of the packet must first decrypt the SILC Packet header, or some parts
2005 of it, usually first 16 bytes of it. Then the receiver checks the
2006 packet type from the decrypted part of the header and can determine
2007 how the rest of the packet must be decrypted. If the packet type is
2008 any of the special cases described in following sections the packet
2009 decryption is special. If the packet type is not among those special
2010 packet types rest of the packet may be decrypted with the same key.
2012 Also, note that two bytes of the SILC Packet header are not encrypted
2013 thus it must be noticed in the decryption process by starting the
2014 decryption from the second byte of the header. This sets some rules
2015 to padding generation as well, see the section 2.7 Packet Padding
2018 With out a doubt, this sort of decryption processing causes some
2019 overhead to packet decryption, but never the less, is required.
2023 2.5.2 Channel Message Encryption And Decryption
2025 Channel Messages (Channel Message Payload) are always encrypted with
2026 the channel specific key. However, the SILC Packet header is not
2027 encrypted with that key. As in normal case, the header is encrypted
2028 with the key of the next receiver of the packet, who ever that might
2029 be. Note that in this case the encrypted data area is not touched
2030 at all; it must not be re-encrypted with the session key.
2032 Receiver of a channel message, who ever that is, is required to decrypt
2033 the SILC Packet header to be able to even recognize the packet to be as
2034 channel message. This is same procedure as for normal SILC packets.
2035 As the receiver founds the packet to be channel message, rest of the
2036 packet processing is special. Rest of the SILC Packet header is
2037 decrypted with the same session key along with the padding of the
2038 packet. After that the packet is protected with the channel specific
2039 key and hence can be decrypted only if the receiver is the client on
2040 the channel. See section 2.7 Packet Padding Generation for more
2041 information about padding on special packets.
2043 If the receiver of the channel message is router who is routing the
2044 message to another router then it must decrypt the Channel Message
2045 payload. Between routers (that is, between cells) channel messages
2046 are protected with session keys shared between the routers. This
2047 causes another special packet processing for channel messages. If
2048 the channel message is received from another router then the entire
2049 packet, including Channel Message payload, is encrypted with the
2050 session key shared between the routers. In this case the packet
2051 decryption process is as with normal SILC packets. Hence, if the
2052 router is sending channel message to another router the Channel
2053 Message payload must have been decrypted and must be re-encrypted
2054 with the session key shared between the another router. In this
2055 case the packet encryption is as with any normal SILC packet.
2057 It must be noted that this is only when the channel messages are sent
2058 from router to another router. In all other cases the channel
2059 message encryption and decryption is as described above. This
2060 different processing of channel messages with router to router
2061 connection is because channel keys are cell specific. All cells has
2062 their own channel keys thus the channel message traveling from one
2063 cell to another must be protected as it would be any normal SILC
2068 2.5.3 Private Message Encryption And Decryption
2070 By default, private message in SILC are protected by session keys.
2071 In this case the private message encryption and decryption process is
2072 equivalent to normal packet encryption and decryption.
2074 However, private messages can be protected with private message key
2075 which causes the packet to be special packet. The procedure in this
2076 case is very much alike to channel packets. The actual private message
2077 is encrypted with the private message key and other parts of the
2078 packet is encrypted with the session key. See 2.7 Packet Padding
2079 Generation for more information about padding on special packets.
2081 The difference from channel message processing is that server or router
2082 en route never decrypts the actual private message, as it does not
2083 have the key to do that. Thus, when sending packets between router
2084 the processing is same as in any other case as well; the packet's header
2085 and padding is protected by the session key and the data area is not
2088 The true receiver of the private message, client, that is, is able
2089 to decrypt the private message as it shares the key with the sender
2094 2.6 Packet MAC Generation
2096 Data integrity of a packet is protected by including a message
2097 authentication code (MAC) at the end of the packet. The MAC is computed
2098 from shared secret MAC key, that is established by the SILC Key Exchange
2099 protocol, and from the original contents of the packet. The MAC is
2100 always computed before the packet is encrypted, although after it is
2101 compressed if compression is used.
2103 The MAC is computed from entire packet. Every bit of data in the packet,
2104 including SILC Packet Header is used in the MAC computing. This way
2105 the entire packet becomes authenticated.
2107 If the packet is special packet MAC is computed from the entire packet
2108 but part of the packet may be encrypted before the MAC is computed.
2109 This is case, for example, with channel messages where the message data
2110 is encrypted with key that server may not now. In this case the MAC
2111 has been computed from the encrypted data.
2113 See [SILC1] for defined and allowed MAC algorithms.
2117 2.7 Packet Padding Generation
2119 Padding is needed in the packet because the packet is encrypted. It
2120 must always be multiple by eight (8) or multiple by the size of the
2121 cipher's block size, which ever is larger. The padding is always
2124 For normal packets the padding is added after the SILC Packet Header
2125 and between the Data Payload area. The padding for normal packets
2126 are calculated as follows:
2129 padding length = 16 - ((packet length - 2) % 16)
2132 The 16 is the maximum padding allowed in SILC packet. Two (2) is
2133 subtracted from the true length of the packet because two (2) bytes
2134 is not encrypted in SILC Packet Header, see section 2.2 SILC Packet
2135 Header. Those two bytes that are not encrypted must not be calculated
2136 to the padding length.
2138 For special packets the padding calculation may be different as special
2139 packets may be encrypted differently. In these cases the encrypted
2140 data area must already be multiple by the block size thus in this case
2141 the padding is calculated only for SILC Packet Header, not for any
2142 other area of the packet. The same algorithm works in this case as
2143 well, except that the `packet length' is now the SILC Packet Header
2144 length. In this case, as well, two (2) is subtracted from the
2147 The padding must be random data, preferably, generated by
2148 cryptographically strong random number generator.
2152 2.8 Packet Compression
2154 SILC Packets may be compressed. In this case the data payload area
2155 is compressed and all other areas of the packet must remain as they
2156 are. After compression is performed for the data area, the length
2157 field of Packet Header must be set to the compressed length of the
2160 The compression must always be applied before encryption. When
2161 the packet is received and decrypted the data area must be decompressed.
2162 Note that the true sender of the packet must apply the compression and
2163 the true receiver of the packet must apply the decompression. Any
2164 server or router en route must not decompress the packet.
2170 The sender of the packet must assemble the SILC Packet Header with
2171 correct values. It must set the Source ID of the header as its own
2172 ID, unless it is forwarding the packet. It must also set the Destination
2173 ID of the header to the true destination. If the destination is client
2174 it will be Client ID, if it is server it will be Server ID and if it is
2175 channel it will be Channel ID.
2177 If the sender wants to compress the packet it must apply the
2178 compression now. Sender must also compute the padding as described
2179 in above sections. Then sender must compute the MAC of the packet.
2181 Then sender encrypts the packet as has been described in above
2182 sections according whether the packet is normal packet or special
2183 packet. The computed MAC must not be encrypted.
2187 2.10 Packet Reception
2189 On packet reception the receiver must check that all fields in the
2190 SILC Packet Header are valid sain. It must check the flags of the
2191 header and act accordingly. It must also check the MAC of the packet
2192 and if it is to be failed the packet must be discarded. Also if the
2193 header of the packet includes any bad fields the packet must be
2196 See above sections on the decryption process of the received packet.
2198 The receiver must also check that the ID's in the header are valid
2199 ID's. Unsupported ID types or malformed ID's must cause packet
2200 rejection. The padding on the reception is always ignored.
2202 The receiver must also check the packet type and start parsing the
2203 packet according to the type. However, note the above sections on
2204 special packet types and their parsing.
2210 Routers are the primary entities in the SILC network that takes care
2211 of packet routing. However, normal servers routes packets as well, for
2212 example, when they are routing channel message to the local clients.
2213 Routing is quite simple as every packet tells the true origin and the
2214 true destination of the packet.
2216 It is still recommended for routers that has several routing connections
2217 to create route cache for those destinations that has faster route than
2218 the router's primary route. This information is available for the router
2219 when other router connects to the router. The connecting party then
2220 sends all of its locally connected clients, server and channels. These
2221 informations helps to create the route cache. Also, when new channels
2222 are created to a cell its information is broadcasted to all routers
2223 in the network. Channel ID's are based on router's ID thus it is easy
2224 to create route cache based on these informations. If faster route for
2225 destination does not exist in router's route cache the packet must be
2226 routed to the primary route (default route).
2228 For server who receives a packet to be routed to its locally connected
2229 client the server must check whether the particular packet type is
2230 allowed to be routed to the client. Not all packets may be sent by
2231 some odd entity to client that is indirectly connected to the sender.
2232 See section 2.3 SILC Packet Types and paragraph about indirectly connected
2233 entities and sending packets to them. The section mentions the packets
2234 that may be sent to indirectly connected entities. It is clear that some
2235 server cannot send, for example, disconnect packet to client that is not
2236 directly connected to the server.
2240 2.12 Packet Forwarding
2242 Currently SILC command packets may be forwarded from one entity to another.
2243 Any other packet currently cannot be forwarded but support for more packet
2244 types may be added if needed. Forwarding is usually used by server to
2245 forward some command request coming from client to the router as the server
2246 may be incapable to handle the request. Forwarding may be only one hop
2247 long; the receiver of the packet with Forwarded flag set in the SILC
2248 Packet header must not forward the packet any further.
2250 The normal scenario is that client sends JOIN command to the server which
2251 is not able to create the channel as there are no local clients on the
2252 channel. Channels are created always by the router of the cell thus the
2253 packet must be forwarded to the router. The server forwards the original
2254 packet coming from client to the router after it has set the Forwarded
2255 flag to the SILC Packet header.
2257 Router receiving the packet knows that the packet has to be processed
2258 specially by checking the flags and the Forwarded flag in the SILC Packet
2259 header. After router has joined the client to the channel (and perhaps
2260 created a new channel) it sends normal command reply packet to the
2261 client. However, as the router doesn't have direct connection to the
2262 client the packet is sent through the server. Server detects that
2263 the command reply packet is destined to the client and sends it to
2268 2.13 Packet Broadcasting
2270 SILC packets may be broadcasted in SILC network. However, only router
2271 server may send or receive broadcast packets. Client and normal server
2272 must not send broadcast packets and they must ignore broadcast packets
2273 if they receive them. Broadcast packets are sent by setting Broadcast
2274 flag to the SILC packet header.
2276 Broadcasting packets means that the packet is sent to all routers in
2277 the SILC network, except to the router that sent the packet. The router
2278 receiving broadcast packet must send the packet to its primary route.
2279 The fact that SILC routers may have several router connections may
2280 cause problems, such as race conditions inside the SILC network, if
2281 care is not taken when broadcasting packets. Router must not send
2282 the broadcast packet to any other route except to its primary route.
2284 If the primary route of the router is the original sender of the packet
2285 the packet must not be sent to the primary route. This may happen
2286 if router has several router connections and some other router uses
2287 the router as its primary route.
2289 Routers use broadcast packets to broadcast for example information
2290 about newly registered clients, servers, channels etc. so that all the
2291 routers may keep these informations up to date.
2295 2.14 Packet Tunneling
2297 Tunneling is a feature that is available in SILC protocol. Tunneling
2298 means that extra SILC Packet Header is applied to the original packet
2299 and thus hiding the original packet entirely. There can be some
2300 interesting applications using tunneling, such as, using ID's based on
2301 private network IP addresses inside in the tunneled packet. This can
2302 open many interesting features relating to connecting to private network
2303 from the Internet with SILC and many more. However, this feature is
2304 optional currently in SILC as there does not exist thorough analysis of
2305 this feature. It is with out a doubt that there will be many more
2306 applications that has not yet been discovered. Thus, it is left
2307 to Internet Community to investigate the use of tunneling in SILC
2308 protocol. This document is updated according those investigations
2309 and additional documents on the issue may be written.
2313 3 Security Considerations
2315 Security is central to the design of this protocol, and these security
2316 considerations permeate the specification.
2322 [SILC1] Riikonen, P., "Secure Internet Live Conferencing (SILC),
2323 Protocol Specification", Internet Draft, June 2000.
2325 [SILC3] Riikonen, P., "SILC Key Exchange and Authentication
2326 Protocols", Internet Draft, June 2000.
2328 [IRC] Oikarinen, J., and Reed D., "Internet Relay Chat Protocol",
2331 [SSH-TRANS] Ylonen, T., et al, "SSH Transport Layer Protocol",
2334 [PGP] Callas, J., et al, "OpenPGP Message Format", RFC 2440,
2337 [SPKI] Ellison C., et al, "SPKI Certificate Theory", RFC 2693,
2340 [PKIX-Part1] Housley, R., et al, "Internet X.509 Public Key
2341 Infrastructure, Certificate and CRL Profile", RFC 2459,
2344 [Schneier] Schneier, B., "Applied Cryptography Second Edition",
2345 John Wiley & Sons, New York, NY, 1996.
2347 [Menezes] Menezes, A., et al, "Handbook of Applied Cryptography",
2350 [OAKLEY] Orman, H., "The OAKLEY Key Determination Protocol",
2351 RFC 2412, November 1998.
2353 [ISAKMP] Maughan D., et al, "Internet Security Association and
2354 Key Management Protocol (ISAKMP)", RFC 2408, November
2357 [IKE] Harkins D., and Carrel D., "The Internet Key Exhange
2358 (IKE)", RFC 2409, November 1998.
2360 [HMAC] Krawczyk, H., "HMAC: Keyed-Hashing for Message
2361 Authentication", RFC 2104, February 1997.
2373 EMail: priikone@poseidon.pspt.fi
2375 This Internet-Draft expires 28 Jan 2001
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