8 .ds RF FORMFEED[Page %]
17 Network Working Group P. Riikonen
19 draft-riikonen-silc-pp-05.txt XXX
26 <draft-riikonen-silc-pp-05.txt>
31 This document is an Internet-Draft and is in full conformance with
32 all provisions of Section 10 of RFC 2026. Internet-Drafts are
33 working documents of the Internet Engineering Task Force (IETF), its
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37 Internet-Drafts are draft documents valid for a maximum of six months
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39 time. It is inappropriate to use Internet-Drafts as reference
40 material or to cite them other than as "work in progress."
42 The list of current Internet-Drafts can be accessed at
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45 The list of Internet-Draft Shadow Directories can be accessed at
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48 The distribution of this memo is unlimited.
54 This memo describes a Packet Protocol used in the Secure Internet Live
55 Conferencing (SILC) protocol, specified in the Secure Internet Live
56 Conferencing, Protocol Specification Internet Draft [SILC1]. This
57 protocol describes the packet types and packet payloads which defines
58 the contents of the packets. The protocol provides secure binary packet
59 protocol that assures that the contents of the packets are secured and
73 1 Introduction .................................................. 3
74 1.1 Requirements Terminology .................................. 4
75 2 SILC Packet Protocol .......................................... 4
76 2.1 SILC Packet ............................................... 4
77 2.2 SILC Packet Header ........................................ 5
78 2.3 SILC Packet Types ......................................... 7
79 2.3.1 SILC Packet Payloads ................................ 16
80 2.3.2 Generic payloads .................................... 16
81 2.3.2.1 ID Payload .................................. 17
82 2.3.2.2 Argument Payload ............................ 18
83 2.3.2.3 Channel Payload ............................. 18
84 2.3.2.4 Public Key Payload .......................... 19
85 2.3.3 Disconnect Payload .................................. 20
86 2.3.4 Success Payload ..................................... 21
87 2.3.5 Failure Payload ..................................... 21
88 2.3.6 Reject Payload ...................................... 22
89 2.3.7 Notify Payload ...................................... 22
90 2.3.8 Error Payload ....................................... 28
91 2.3.9 Channel Message Payload ............................. 29
92 2.3.10 Channel Key Payload ................................ 32
93 2.3.11 Private Message Payload ............................ 34
94 2.3.12 Private Message Key Payload ........................ 35
95 2.3.13 Command Payload .................................... 37
96 2.3.14 Command Reply Payload .............................. 38
97 2.3.15 Connection Auth Request Payload .................... 38
98 2.3.16 New ID Payload ..................................... 39
99 2.3.17 New Client Payload ................................. 40
100 2.3.18 New Server Payload ................................. 41
101 2.3.19 New Channel Payload ................................ 42
102 2.3.20 Key Agreement Payload .............................. 43
103 2.3.21 Resume Router Payload .............................. 44
104 2.3.22 File Transfer Payload .............................. 44
105 2.3.23 Resume Client Payload .............................. XXXXXX
106 2.4 SILC ID Types ............................................. 46
107 2.5 Packet Encryption And Decryption .......................... 46
108 2.5.1 Normal Packet Encryption And Decryption ............. 46
109 2.5.2 Channel Message Encryption And Decryption ........... 47
110 2.5.3 Private Message Encryption And Decryption ........... 48
111 2.6 Packet MAC Generation ..................................... 48
112 2.7 Packet Padding Generation ................................. 49
113 2.8 Packet Compression ........................................ 50
114 2.9 Packet Sending ............................................ 50
115 2.10 Packet Reception ......................................... 51
116 2.11 Packet Routing ........................................... 51
117 2.12 Packet Broadcasting ...................................... 52
118 3 Security Considerations ....................................... 53
119 4 References .................................................... 53
120 5 Author's Address .............................................. 54
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 bandwith 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 receipient 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.
477 This packet is sent when an error occurs. Server MAY
478 send this packet. Client MUST NOT send this packet. The
479 client MAY entirely ignore the packet, however, server is
480 most likely to take action anyway. This packet MAY be sent
481 to entity that is indirectly connected to the sender.
483 This packet MUST NOT be sent as list and the List flag MUST
486 Payload of the packet: See section 2.3.8 Error Payload.
489 7 SILC_PACKET_CHANNEL_MESSAGE
491 This packet is used to send messages to channels. The packet
492 includes Channel ID of the channel and the actual message to
493 the channel. Messages sent to the channel are always protected
494 by channel specific keys. Channel Keys are distributed by
495 SILC_PACKET_CHANNEL_KEY packet.
497 This packet MUST NOT be sent as list and the List flag MUST
500 Payload of the packet: See section 2.3.9 Channel Message
504 8 SILC_PACKET_CHANNEL_KEY
506 This packet is used to distribute new key for particular
507 channel. Each channel has their own independent keys that
508 is used to protect the traffic on the channel. Only server
509 may send this packet. This packet MAY be sent to entity
510 that is indirectly connected to the sender.
512 This packet MUST NOT be sent as list and the List flag MUST
515 Payload of the packet: See section 2.3.10 Channel Key Payload
518 9 SILC_PACKET_PRIVATE_MESSAGE
520 This packet is used to send private messages from client
521 to another client. By default, private messages are protected
522 by session keys established by normal key exchange protocol.
523 However, it is possible to use specific key to protect private
524 messages. SILC_PACKET_PRIVATE_MESSAGE_KEY packet is used to
525 agree the key with the remote client. Pre-shared key MAY be
526 used as well if both of the client knows it, however, it needs
527 to be agreed outside SILC. See more of this in [SILC1].
529 This packet MUST NOT be sent as list and the List flag MUST
532 Payload of the packet: See section 2.3.11 Private Message
536 10 SILC_PACKET_PRIVATE_MESSAGE_KEY
538 This packet is used to agree about a key to be used to protect
539 the private messages between two clients. If this is not sent
540 the normal session key is used to protect the private messages
541 inside SILC network. Agreeing to use specific key to protect
542 private messages adds security, as no server between the two
543 clients will be able to decrypt the private message. However,
544 servers inside SILC network are considered to be trusted, thus
545 using normal session key to protect private messages does not
546 degrade security. Whether to agree to use specific keys by
547 default or to use normal session keys by default, is
548 implementation specific issue. See more of this in [SILC1].
550 This packet MUST NOT be sent as list and the List flag MUST
553 Payload of the packet: See section 2.3.12 Private Message
557 11 SILC_PACKET_COMMAND
559 This packet is used to send commands from client to server.
560 Server MAY send this packet to other servers as well. All
561 commands are listed in their own section SILC Command Types
562 in [SILC4]. The contents of this packet is command specific.
563 This packet MAY be sent to entity that is indirectly connected
566 This packet MUST NOT be sent as list and the List flag MUST
569 Payload of the packet: See section 2.3.13 Command Payload
572 12 SILC_PACKET_COMMAND_REPLY
574 This packet is sent as reply to the SILC_PACKET_COMMAND packet.
575 The contents of this packet is command specific. This packet
576 MAY be sent to entity that is indirectly connected to the
579 This packet MUST NOT be sent as list and the List flag MUST
582 Payload of the packet: See section 2.3.14 Command Reply
583 Payload and section 2.3.13 Command
589 13 SILC_PACKET_KEY_EXCHANGE
591 This packet is used to start SILC Key Exchange Protocol,
592 described in detail in [SILC3].
594 This packet MUST NOT be sent as list and the List flag MUST
597 Payload of the packet: Payload of this packet is described
598 in the section SILC Key Exchange
599 Protocol and its sub sections in
603 14 SILC_PACKET_KEY_EXCHANGE_1
605 This packet is used as part of the SILC Key Exchange Protocol.
607 This packet MUST NOT be sent as list and the List flag MUST
610 Payload of the packet: Payload of this packet is described
611 in the section SILC Key Exchange
612 Protocol and its sub sections in
616 15 SILC_PACKET_KEY_EXCHANGE_2
618 This packet is used as part of the SILC Key Exchange Protocol.
620 This packet MUST NOT be sent as list and the List flag MUST
623 Payload of the packet: Payload of this packet is described
624 in the section SILC Key Exchange
625 Protocol and its sub sections in
629 16 SILC_PACKET_CONNECTION_AUTH_REQUEST
631 This packet is used to request the authentication method to
632 be used in the SILC Connection Authentication Protocol. If
633 initiator of the protocol does not know the mandatory
634 authentication method this packet MAY be used to determine it.
636 The party receiving this payload MUST respond with the same
637 packet including the mandatory authentication method.
639 This packet MUST NOT be sent as list and the List flag MUST
642 Payload of the packet: See section 2.3.15 Connection Auth
648 17 SILC_PACKET_CONNECTION_AUTH
650 This packet is used to start and perform the SILC Connection
651 Authentication Protocol. This protocol is used to authenticate
652 the connecting party. The protocol is described in detail in
655 This packet MUST NOT be sent as list and the List flag MUST
658 Payload of the packet: Payload of this packet is described
659 in the section SILC Authentication
660 Protocol and it sub sections in [SILC].
663 18 SILC_PACKET_NEW_ID
665 This packet is used to distribute new ID's from server to
666 router and from router to all routers in the SILC network.
667 This is used when for example new client is registered to
668 SILC network. The newly created ID's of these operations are
669 distributed by this packet. Only server may send this packet,
670 however, client MUST be able to receive this packet. This
671 packet MAY be sent to entity that is indirectly connected
674 Payload of the packet: See section 2.3.16 New ID Payload
677 19 SILC_PACKET_NEW_CLIENT
679 This packet is used by client to register itself to the
680 SILC network. This is sent after key exchange and
681 authentication protocols has been completed. Client sends
682 various information about itself in this packet.
684 This packet MUST NOT be sent as list and the List flag MUST
687 Payload of the packet: See section 2.3.17 New Client Payload
690 20 SILC_PACKET_NEW_SERVER
692 This packet is used by server to register itself to the
693 SILC network. This is sent after key exchange and
694 authentication protocols has been completed. Server sends
695 this to the router it connected to, or, if router was
696 connecting, to the connected router. Server sends its
697 Server ID and other information in this packet. The client
698 MUST NOT send or receive this packet.
700 This packet MUST NOT be sent as list and the List flag MUST
703 Payload of the packet: See section 2.3.18 New Server Payload
706 21 SILC_PACKET_NEW_CHANNEL
708 This packet is used to notify routers about newly created
709 channel. Channels are always created by the router and it MUST
710 notify other routers about the created channel. Router sends
711 this packet to its primary route. Client MUST NOT send this
712 packet. This packet MAY be sent to entity that is indirectly
713 connected to the sender.
715 Payload of the packet: See section 2.3.19 New Channel Payload
720 This packet is used to indicate that re-key must be performed
721 for session keys. See section Session Key Regeneration in
722 [SILC1] for more information. This packet does not have
725 This packet MUST NOT be sent as list and the List flag MUST
729 23 SILC_PACKET_REKEY_DONE
731 This packet is used to indicate that re-key is performed and
732 new keys must be used hereafter.
734 This packet MUST NOT be sent as list and the List flag MUST
738 24 SILC_PACKET_HEARTBEAT
740 This packet is used by clients, servers and routers to keep the
741 connection alive. It is recommended that all servers implement
742 keepalive actions and perform it to both direction in a link.
743 This packet does not have a payload.
745 This packet MUST NOT be sent as list and the List flag MUST
749 25 SILC_PACKET_KEY_AGREEMENT
751 This packet is used by clients to request key negotiation
752 between another client in the SILC network. If the negotiation
753 is started it is performed using the SKE protocol. The result of
754 the negotiation, the secret key material, can be used for
755 example as private message key. The server and router MUST NOT
758 This packet MUST NOT be sent as list and the List flag MUST
761 Payload of the packet: See section 2.3.20 Key Agreement Payload
764 26 SILC_PACKET_RESUME_ROUTER
766 This packet is used during backup router protocol when the
767 original primary router of the cell comes back online and wishes
768 to resume the position as being the primary router of the cell.
770 Payload of the packet: See section 2.3.21 Resume Router Payload
775 This packet is used to perform an file transfer protocol in the
776 SILC session with some entity in the network. The packet is
777 multi purpose. The packet is used to tell other entity in the
778 network that the sender wishes to perform an file transfer
779 protocol. The packet is also used to actually tunnel the
780 file transfer protocol stream. The file transfer protocol
781 stream is always protected with the SILC packet.
783 This packet MUST NOT be sent as list and the List flag MUST
786 Payload of the packet: See section 2.3.22 File Transfer Payload
789 28 SILC_PACKET_RESUME_CLIENT
791 This packet is used to resume a client back to the network
792 after it has been detached. A client is able to detach from
793 the network but the client is still valid client in the network.
794 The client may then later resume its session back by sending
795 this packet to a server. Routers also use this packet to notify
796 other routers in the network that the detached client has resumed.
798 This packet MUST NOT be sent as list and the List flag MUST
801 Payload of the packet: See section 2.3.23 Resume Client Payload
806 Currently undefined commands.
811 These packet types are reserved for private use and they will
812 not be defined by this document.
819 This type is reserved for future extensions and currently it
825 2.3.1 SILC Packet Payloads
827 All payloads resides in the main data area of the SILC packet. However
828 all payloads MUST be at the start of the data area after the SILC
829 packet header and padding. All fields in the packet payload are always
830 encrypted, as they reside in the data area of the packet which is
833 Payloads described in this section are common payloads that MUST be
834 accepted anytime during SILC session. Most of the payloads may only
835 be sent with specific packet type which is defined in the description
838 There are a lot of other payloads in the SILC as well. However, they
839 are not common in the sense that they could be sent at any time.
840 These payloads are not described in this section. These are payloads
841 such as SILC Key Exchange payloads and so on. These are described
842 in [SILC1], [SILC3] and [SILC4].
846 2.3.2 Generic payloads
848 This section describes generic payloads that are not associated to any
849 specific packet type. They can be used for example inside some other
856 This payload can be used to send an ID. ID's are variable in length
857 thus this payload provides a way to send variable length ID's.
859 The following diagram represents the ID Payload.
864 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
865 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
866 | ID Type | ID Length |
867 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
871 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
879 o ID Type (2 bytes) - Indicates the type of the ID. See
880 section 2.4 SILC ID Types for list of defined ID types.
882 o ID Length (2 bytes) - Length of the ID Data area not
883 including the length of any other fields in the payload.
885 o ID Data (variable length) - The actual ID data.
890 2.3.2.2 Argument Payload
892 Argument Payload is used to set arguments for any packet payload that
893 needs and supports arguments, such as commands. Number of arguments
894 associated with a packet MUST be indicated by the packet payload which
895 needs the arguments. Argument Payloads MUST always reside right after
896 the packet payload needing the arguments. Incorrect amount of argument
897 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.
963 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
964 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
965 | Channel Name Length | |
966 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
970 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
971 | Channel ID Length | |
972 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
976 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
978 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
982 Figure 5: New Channel Payload
986 o Channel Name Length (2 bytes) - Length of the channel name
989 o Channel Name (variable length) - The name of the channel.
991 o Channel ID Length (2 bytes) - Length of the Channel ID field.
993 o Channel ID (variable length) - The Channel ID.
995 o Mode Mask (4 bytes) - A mode. This can be the mode of the
996 channel but it can also be the mode of the client on the
997 channel. The contents of this field is dependent of the
998 usage of this payload. The usage is defined separately
999 when this payload is used. This is a 32 bit MSB first value.
1004 2.3.2.4 Public Key Payload
1006 Generic Public Key Payload may be used to send different types of
1007 public keys and certificates.
1009 The following diagram represents the Public Key Payload.
1018 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
1019 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1020 | Public Key Length | Public Key Type |
1021 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1023 ~ Public Key of the party (or certificate) ~
1025 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1029 Figure 6: Public Key Payload
1033 o Public Key Length (2 bytes) - The length of the Public Key
1034 (or certificate) field, not including any other field.
1036 o Public Key Type (2 bytes) - The public key (or certificate)
1037 type. This field indicates the type of the public key in
1038 the packet. See the [SILC3] for defined public key types.
1040 o Public Key (or certificate) (variable length) - The
1041 public key or certificate.
1046 2.3.3 Disconnect Payload
1048 Disconnect payload is sent upon disconnection. The payload is simple;
1049 reason of disconnection is sent to the disconnected party.
1051 The payload may only be sent with SILC_PACKET_DISCONNECT packet. It
1052 MUST NOT be sent in any other packet type. The following diagram
1053 represents the Disconnect Payload.
1059 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
1060 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1064 ~ Disconnect Message ~
1066 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1070 Figure 7: Disconnect Payload
1073 o Status (1 byte) - Indicates the Status Type, defined in [SILC3]
1074 for the reason of disconnection.
1076 o Disconnect Message (variable length) - Human readable UTF-8
1077 encoded string indicating reason of the disconnection. This
1083 2.3.4 Success Payload
1085 Success payload is sent when some protocol execution is successfully
1086 completed. The payload is simple; indication of the success is sent.
1087 This may be any data, including binary or human readable data.
1092 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
1093 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1095 ~ Success Indication ~
1097 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1101 Figure 8: Success Payload
1105 o Success Indication (variable length) - Indication of
1106 the success. This may be for example some flag that
1107 indicates the protocol and the success status or human
1108 readable success message. The true length of this
1109 payload is available by calculating it from the SILC
1116 2.3.5 Failure Payload
1118 This is opposite of Success Payload. Indication of failure of
1119 some protocol is sent in the payload.
1125 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
1126 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1128 ~ Failure Indication ~
1130 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1134 Figure 9: Failure Payload
1138 o Failure Indication (variable length) - Indication of
1139 the failure. This may be for example some flag that
1140 indicates the protocol and the failure status or human
1141 readable failure message. The true length of this
1142 payload is available by calculating it from the SILC
1148 2.3.6 Reject Payload
1150 This payload is sent when some protocol is rejected to be executed.
1151 Other operations MAY send this as well that was rejected. The
1152 indication of the rejection is sent in the payload. The indication
1153 may be binary or human readable data.
1159 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
1160 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1162 ~ Reject Indication ~
1164 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1168 Figure 10: Reject Payload
1172 o Reject Indication (variable length) - Indication of
1173 the rejection. This maybe for example some flag that
1174 indicates the protocol and the rejection status or human
1175 readable rejection message. The true length of this
1176 payload is available by calculating it from the SILC
1182 2.3.7 Notify Payload
1184 Notify payload is used to send notify messages. The payload is usually
1185 sent from server to client, however, server MAY send it to another
1186 server as well. This payload MAY also be sent to a channel. Client
1187 MUST NOT send this payload. The receiver of this payload MAY ignore
1188 the contents of the payload, however, notify message SHOULD be audited.
1190 The payload may only be sent with SILC_PACKET_NOTIFY packet. It MUST
1191 not be sent in any other packet type. The following diagram represents
1200 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
1201 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1202 | Notify Type | Payload Length |
1203 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1209 Figure 11: Notify Payload
1213 o Notify Type (2 bytes) - Indicates the type of the notify
1216 o Payload Length (2 bytes) - Length of the entire Notify Payload
1217 including any associated Argument Payloads.
1219 o Argument Nums (2 bytes) - Indicates the number of Argument
1220 Payloads associated to this payload. Notify types may define
1221 arguments to be send along the notify message.
1224 The following list of currently defined notify types. The format for
1225 notify arguments is same as in SILC commands described in [SILC4].
1226 Note that all ID's sent in arguments are sent inside ID Payload. Also
1227 note that all passphrases that may be sent inside arguments MUST be
1228 UTF-8 [RFC2279] encoded.
1231 0 SILC_NOTIFY_TYPE_NONE
1233 If no specific notify type apply for the notify message this type
1237 Arguments: (1) <message>
1239 The <message> is implementation specific free text string.
1240 Receiver MAY ignore this message.
1243 1 SILC_NOTIFY_TYPE_INVITE
1245 Sent when an client is invited to a channel. This is also sent
1246 when the invite list of the channel is changed. This notify type
1247 is sent between routers and if an client was invited, to the
1248 client as well. In this case the packet is destined to the client.
1251 Arguments: (1) <Channel ID> (2) <channel name>
1252 (3) [<sender Client ID>] (4) [<adding client>]
1253 (5) [<removing client>]
1255 The <Channel ID> is the channel. The <channel name> is the name
1256 of the channel and is provided because the client which receives
1257 this notify packet may not have a way to resolve the name of the
1258 channel from the <Channel ID>. The <sender Client ID> is the
1259 Client ID which invited the client to the channel. The <adding
1260 client> and the <removing client> indicates the added or removed
1261 client from the channel's invite list. The format of the <adding
1262 client> and the <removing client> is defined in the [SILC4] with
1263 SILC_COMMAND_INVITE command.
1265 The <adding client> and <removing client> MUST NOT be sent when
1266 the packet is destined to a client.
1269 2 SILC_NOTIFY_TYPE_JOIN
1271 Sent when client has joined to a channel. The server MUST
1272 distribute this type only to the local clients on the channel
1273 and then send it to its primary router. The router or server
1274 receiving the packet distributes this type to the local clients
1275 on the channel and broadcast it to the network.
1278 Arguments: (1) [<Client ID>] (2) <Channel ID>
1280 The <Client ID> is the client that joined to the channel indicated
1281 by the <Channel ID>.
1284 3 SILC_NOTIFY_TYPE_LEAVE
1286 Sent when client has left a channel. The server must distribute
1287 this type only to the local clients on the channel and then send
1288 it to its primary router. The router or server receiving the
1289 packet distributes this type to the local clients on the channel
1290 and broadcast it to the network.
1293 Arguments: (1) <Client ID>
1295 The <Client ID> is the client which left the channel.
1298 4 SILC_NOTIFY_TYPE_SIGNOFF
1300 Sent when client signoff from SILC network. The server MUST
1301 distribute this type only to the local clients on the channel and
1302 then send it to its primary router. The router or server receiving
1303 the packet distributes this type to the local clients on the
1304 channel and broadcast it to the network.
1307 Arguments: (1) <Client ID> (2) <message>
1309 The <Client ID> is the client which left SILC network. The
1310 <message> is free text string indicating the reason of the signoff.
1313 5 SILC_NOTIFY_TYPE_TOPIC_SET
1315 Sent when topic is set/changed on a channel. This type must be
1316 sent only to the clients which is joined on the channel which
1317 topic was set or changed.
1320 Arguments: (1) <ID Payload> (2) <topic>
1322 The <ID Payload> is the ID of the entity who set the topic. It
1323 usually is Client ID but it can be Server ID and Channel ID as well.
1326 6 SILC_NOTIFY_TYPE_NICK_CHANGE
1328 Sent when client changes nick on a channel. The server MUST
1329 distribute this type only to the local clients on the channel
1330 and then send it to its primary router. The router or server
1331 receiving the packet distributes this type to the local clients
1332 on the channel and broadcast it to the network.
1335 Arguments: (1) <Old Client ID> (2) <New Client ID>
1338 The <Old Client ID> is the old ID of the client which changed
1339 the nickname. The <New Client ID> is the new ID generated by
1340 the change of the nickname. The <nickname> is the new nickname.
1341 Note that it is possible to send this notify even if the nickname
1342 hasn't changed, but client ID has changed.
1345 7 SILC_NOTIFY_TYPE_CMODE_CHANGE
1347 Sent when channel mode has changed. This type MUST be sent only
1348 to the clients which is joined on the channel which mode was
1352 Arguments: (1) <ID Payload> (2) <mode mask>
1353 (3) [<cipher>] (4) <[hmac>]
1354 (5) [<passphrase>] (6) [<founder public key>]
1356 The <ID Payload> is the ID (usually Client ID but it can be
1357 Server ID as well when the router is enforcing channel mode
1358 change) of the entity which changed the mode. The <mode mask>
1359 is the new mode mask of the channel. The client can safely
1360 ignore the <cipher> argument since the SILC_PACKET_CHANNEL_KEY
1361 packet will force the new channel key change anyway. The <hmac>
1362 argument is important since the client is responsible of setting
1363 the new HMAC and the hmac key into use. The <passphrase> is
1364 the passphrase of the channel, if it was now set. The <founder
1365 public key> argument is sent when the founder mode on the
1366 channel was set. All routers and servers that receive the packet
1367 MUST save the founder's public key so that the founder can
1368 reclaim the channel founder rights back for the channel on any
1369 server in the network.
1372 8 SILC_NOTIFY_TYPE_CUMODE_CHANGE
1374 Sent when user mode on channel has changed. This type MUST be
1375 sent only to the clients which is joined on the channel where
1376 the target client is on.
1379 Arguments: (1) <ID Payload> (2) <mode mask>
1380 (3) <Target Client ID>
1382 The <ID Payload> is the ID (usually Client ID but it can be
1383 Server ID as well when the router is enforcing user's mode
1384 change) of the entity which changed the mode. The <mode mask>
1385 is the new mode mask of the channel. The <Target Client ID>
1386 is the client which mode was changed.
1389 9 SILC_NOTIFY_TYPE_MOTD
1391 Sent when Message of the Day (motd) is sent to a client.
1394 Arguments: (1) <motd>
1396 The <motd> is the Message of the Day.
1399 10 SILC_NOTIFY_TYPE_CHANNEL_CHANGE
1401 Sent when channel's ID has changed for a reason or another.
1402 This is sent by normal server to the client. This can also be
1403 sent by router to other server to force the Channel ID change.
1404 The Channel ID MUST be changed to use the new one. When sent
1405 to clients, this type MUST be sent only to the clients which is
1406 joined on the channel.
1409 Arguments: (1) <Old Channel ID> (2) <New Channel ID>
1411 The <Old Channel ID> is the channel's old ID and the <New
1412 Channel ID> is the new one that MUST replace the old one.
1415 11 SILC_NOTIFY_TYPE_SERVER_SIGNOFF
1417 Sent when server quits SILC network. Those clients from this
1418 server that are on channels must be removed from the channel.
1421 Arguments: (1) <Server ID> (n) [<Client ID>] [...]
1423 The <Server ID> is the server's ID. The rest of the arguments
1424 are the Client ID's of the client's which are coming from this
1425 server and are thus quitting the SILC network also. If the
1426 maximum number of arguments are reached another
1427 SILC_NOTIFY_TYPE_SERVER_SIGNOFF notify packet MUST be sent.
1428 When this notify packet is sent between routers the Client ID's
1429 MAY be omitted. Server receiving the Client ID's in the payload
1430 may use them directly to remove the client.
1433 12 SILC_NOTIFY_TYPE_KICKED
1435 Sent when a client has been kicked from a channel. This is
1436 sent also to the client which was kicked from the channel.
1437 The client which was kicked from the channel MUST be removed
1438 from the channel. This notify type is always destined to the
1439 channel. The router or server receiving the packet distributes
1440 this type to the local clients on the channel and broadcast it
1444 Arguments: (1) <Client ID> (2) [<comment>]
1445 (3) <Kicker's Client ID>
1447 The <Client ID> is the client which was kicked from the channel.
1448 The kicker may have set the <comment> to indicate the reason for
1449 the kicking. The <Kicker's Client ID> is the kicker.
1452 13 SILC_NOTIFY_TYPE_KILLED
1454 Sent when a client has been killed from the network. This is sent
1455 also to the client which was killed from the network. The client
1456 which was killed from the network MUST be removed from the network.
1457 This notify type is destined directly to the client which was
1458 killed and to channel if the client is on any channel. The router
1459 or server receiving the packet distributes this type to the local
1460 clients on the channel and broadcast it to the network.
1463 Arguments: (1) <Client ID> (2) [<comment>]
1466 The <Client ID> is the client which was killed from the network.
1467 The killer may have set the <comment> to indicate the reason for
1468 the killing. The <Killer's ID> is the killer, which may be
1469 client but also router server.
1472 14 SILC_NOTIFY_TYPE_UMODE_CHANGE
1474 Sent when user's mode in the SILC changes. This type is sent
1475 only between routers as broadcast packet.
1478 Arguments: (1) <Client ID> (2) <mode mask>
1480 The <Client ID> is the client which mode was changed. The
1481 <mode mask> is the new mode mask.
1484 15 SILC_NOTIFY_TYPE_BAN
1486 Sent when the ban list of the channel is changed. This type is
1487 sent only between routers as broadcast packet.
1490 Arguments: (1) <Channel ID> (2) [<adding client>]
1491 (3) [<removing client>]
1493 The <Channel ID> is the channel which ban list was changed. The
1494 <adding client> is used to indicate that a ban was added and the
1495 <removing client> is used to indicate that a ban was removed from
1496 the ban list. The format of the <adding client> and the
1497 <removing client> is defined in the [SILC4] with SILC_COMMAND_BAN
1501 16 SILC_NOTIFY_TYPE_ERROR
1503 Sent when an error occurs during processing some SILC procedure.
1504 This is not used when error occurs during command processing, see
1505 [SILC3] for more information about commands and command replies.
1506 This type is sent directly to the sender of the packet whose packet
1507 caused the error. See [SILC1] for definition when this type
1511 Arguments: (1) <Status Type> (n) [...]
1513 The <Status Type> is the error type defined in [SILC3]. Note that
1514 same types are also used with command replies to indicate the
1515 status of a command. Both commands and this notify type share
1516 same status types. Rest of the arguments are status type
1517 dependent and are specified with those status types that can be
1518 sent currently inside this notify type in [SILC3]. The <Status
1519 Type> is of size of 1 byte.
1522 17 SILC_NOTIFY_TYPE_WATCH
1524 Sent to indicate change in a watched user. Client can set
1525 nicknames to be watched with SILC_COMMAND_WATCH command, and
1526 receive notifications when they login to network, signoff from
1527 the network or their user mode is changed. This notify type
1528 is used to deliver these notifications. The notify type is
1529 sent directly to the watching client.
1532 Arguments: (1) <Client ID> (2) [<nickname>]
1533 (3) <user mode> (4) [<Notify Type>]
1535 The <Client ID> is the user's Client ID which is being watched,
1536 and the <nickname> is its nickname. If the client just
1537 changed the nickname, then <nickname> is the new nickname, but
1538 the <Client ID> is the old client ID. The <user mode> is the
1539 user's current user mode. The <Notify Type> can be same as the
1540 Notify Payload's Notify Type, and is 16 bit MSB first order value.
1541 If provided it may indicate the notify that occurred for the
1542 client. If client logged in to the network the <Notify Type>
1543 MUST NOT be present.
1546 Notify types starting from 16384 are reserved for private notify
1549 Router server which receives SILC_NOTIFY_TYPE_SIGNOFF,
1550 SILC_NOTIFY_TYPE_SERVER_SIGNOFF, SILC_NOTIFY_TYPE_KILLED,
1551 SILC_NOTIFY_TYPE_NICK_CHANGE and SILC_NOTIFY_TYPE_UMODE_CHANGE
1552 MUST chech whether someone in the local cell is watching the nickname
1553 the client has, and send the SILC_NOTIFY_TYPE_WATCH notify to the
1554 watcher, unless the client in case has the SILC_UMODE_REJECT_WATCHING
1555 user mode set. If the watcher client and the client that was
1556 watched is same the notify SHOULD NOT be sent.
1562 Error payload is sent upon error. Error may occur in various
1563 conditions when server sends this packet. Client MUST NOT send this
1564 payload but MUST be able to accept it. However, client MAY
1565 totally ignore the contents of the packet as server is going to
1566 take action on the error anyway. However, it is recommended
1567 that the client takes error packet seriously.
1573 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
1574 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1578 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1582 Figure 12: Error Payload
1586 o Error Message (variable length) - Human readable error
1592 2.3.9 Channel Message Payload
1594 Channel messages are the most common messages sent in the SILC.
1595 Channel Message Payload is used to send message to channels. These
1596 messages can only be sent if client has joined to some channel.
1597 Even though this packet is the most common in SILC it is still
1598 special packet. Some special handling on sending and reception
1599 of channel message is required.
1601 Padding MUST be applied into this payload since the payload is
1602 encrypted separately from other parts of the packet with the
1603 channel specific key. Hence the requirement of the padding.
1604 The padding SHOULD be random data. The packet MUST be made
1605 multiple by eight (8) or by the block size of the cipher, which
1608 The SILC header in this packet is encrypted with the session key
1609 of the next receiver of the packet. Nothing else is encrypted
1610 with that key. Thus, the actual packet and padding to be
1611 encrypted with the session key is SILC Header plus padding to it
1612 to make it multiple by eight (8) or multiple by the block size
1613 of the cipher, which ever is larger.
1615 Receiver of the the channel message packet is able to determine
1616 the channel the message is destined to by checking the destination
1617 ID from the SILC Packet header which tells the destination channel.
1618 The original sender of the packet is also determined by checking
1619 the source ID from the header which tells the client which sent
1622 The payload may only be sent with SILC_PACKET_CHANNEL_MESSAGE packet.
1623 It MUST NOT be sent in any other packet type. The following diagram
1624 represents the Channel Message Payload.
1626 (*) indicates that the field is not encrypted.
1632 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
1633 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1634 | Message Flags | Message Length |
1635 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1639 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1640 | Padding Length | |
1641 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1645 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1649 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1651 ~ Initial Vector * ~
1653 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1657 Figure 13: Channel Message Payload
1661 o Message Flags (2 bytes) - Includes the Message Flags of
1662 the channel messages. The flags can indicate a reason or
1663 purpose for the channel message. Note that the Private
1664 Message Payload use these same Message Flags for the same
1665 purpose. The following Message Flags are defined:
1667 0x0000 SILC_MESSAGE_FLAG_NONE
1669 No specific flags set.
1671 0x0001 SILC_MESSAGE_FLAG_AUTOREPLY
1673 This message is an automatic reply to an earlier
1676 0x0002 SILC_MESSAGE_FLAG_NOREPLY
1678 There should not be reply messages to this
1681 0x0004 SILC_MESSAGE_FLAG_ACTION
1683 The sender is performing an action and the message
1684 is the indication of the action.
1686 0x0008 SILC_MESSAGE_FLAG_NOTICE
1688 The message is for example an informational notice
1691 0x0010 SILC_MESSAGE_FLAG_REQUEST
1693 This is a generic request flag to send request
1694 messages. A separate document should define any
1695 payloads associated to this flag.
1697 0x0020 SILC_MESSAGE_FLAG_SIGNED
1699 This flag indicates that the message is signed
1700 with sender's private key and thus can be verified
1701 by the receiver using the sender's public key. A
1702 separate document should define the detailed procedure
1703 of the signing process and any associated payloads
1706 0x0040 SILC_MESSAGE_FLAG_REPLY
1708 This is a generic reply flag to send a reply to
1709 previously received request. A separate document
1710 should define any payloads associated to this flag.
1712 0x0080 SILC_MESSAGE_FLAG_DATA
1714 This is a generic data flag, indicating that the
1715 message includes some data which can be interpreted
1716 in a specific way. Using this flag any kind of data
1717 can be delivered inside message payload. A separate
1718 document should define how this flag is interpreted
1719 and define any associated payloads.
1721 0x0100 - 0x0800 RESERVED
1723 Reserved for future flags
1725 0x1000 - 0x8000 PRIVATE RANGE
1727 Private range for free use.
1729 o Message Length (2 bytes) - Indicates the length of the
1730 Message Data field in the payload, not including any
1733 o Message Data (variable length) - The actual message to
1736 o Padding Length (2 bytes) - Indicates the length of the
1737 Padding field in the payload, not including any other
1740 o Padding (variable length) - The padding that MUST be
1741 applied because this payload is encrypted separately from
1742 other parts of the packet.
1744 o MAC (variable length) - The MAC computed from the
1745 Message Flags, Message Length, Message Data, Padding Length,
1746 Padding and Initial Vector fields in that order. This
1747 protects the integrity of the plaintext channel message.
1748 The receiver can verify from the MAC whether the message
1749 decrypted correctly. Also, if more than one private key
1750 has been set for the channel, the receiver can verify which
1751 of the keys decrypted the message correctly. Note that,
1752 this field is encrypted and MUST be added to the padding
1755 o Initial Vector (variable length) - The initial vector
1756 that has been used in packet encryption. It needs to be
1757 used in the packet decryption as well. What this field
1758 includes is implementation issue. However, it is
1759 RECOMMENDED that it would be random data, or perhaps
1760 a timestamp. It is NOT RECOMMENDED to use zero (0) as an
1761 initial vector. This field is not encrypted. This field
1762 is not included into the padding calculation. Length
1763 of this field equals the cipher's block size. This field
1764 is, however authenticated.
1769 2.3.10 Channel Key Payload
1771 All traffic in channels are protected by channel specific keys.
1772 Channel Key Payload is used to distribute channel keys to all
1773 clients on the particular channel. Channel keys are sent when
1774 the channel is created, when new user joins to the channel and
1775 whenever a user has left a channel. Server creates the new
1776 channel key and distributes it to the clients by encrypting this
1777 payload with the session key shared between the server and
1778 the client. After that, client starts using the key received
1779 in this payload to protect the traffic on the channel.
1781 The client which is joining to the channel receives its key in the
1782 SILC_COMMAND_JOIN command reply message thus it is not necessary to
1783 send this payload to the entity which sent the SILC_COMMAND_JOIN
1786 Channel keys are cell specific thus every router in the cell have
1787 to create a channel key and distribute it if any client in the
1788 cell has joined to a channel. Channel traffic between cell's
1789 are not encrypted using channel keys, they are encrypted using
1790 normal session keys between two routers. Inside a cell, all
1791 channel traffic is encrypted with the specified channel key.
1792 Channel key should expire periodically, say, in one hour, in
1793 which case new channel key is created and distributed.
1795 The payload may only be sent with SILC_PACKET_CHANNEL_KEY packet.
1796 It MUST NOT be sent in any other packet type. The following diagram
1797 represents the Channel Key Payload.
1803 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
1804 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1805 | Channel ID Length | |
1806 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1810 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1811 | Cipher Name Length | |
1812 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1816 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1817 | Channel Key Length | |
1818 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1822 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1826 Figure 14: Channel Key Payload
1831 o Channel ID Length (2 bytes) - Indicates the length of the
1832 Channel ID field in the payload, not including any other
1835 o Channel ID (variable length) - The Channel ID of the
1836 channel this key is meant for.
1838 o Cipher Name Length (2 bytes) - Indicates the length of the
1839 Cipher name field in the payload, not including any other
1842 o Cipher Name (variable length) - Name of the cipher used
1843 in the protection of channel traffic. This name is
1844 initially decided by the creator of the channel but it
1845 MAY change during the life time of the channel as well.
1847 o Channel Key Length (2 bytes) - Indicates the length of the
1848 Channel Key field in the payload, not including any other
1851 o Channel Key (variable length) - The actual channel key
1857 2.3.11 Private Message Payload
1859 Private Message Payload is used to send private message between
1860 two clients (or users for that matter). The messages are sent only
1861 to the specified user and no other user inside SILC network is
1862 able to see the message. The message is protected by the session
1863 key established by the SILC Key Exchange Protocol. However,
1864 it is also possible to agree to use a private key to protect
1865 just the private messages. See section 2.3.11 Private Message
1866 Key Payload for detailed description of how to agree to use
1869 If normal session key is used to protect the message, every server
1870 between the sender client and the receiving client MUST decrypt the
1871 packet and always re-encrypt it with the session key of the next
1872 receiver of the packet. See section Client To Client in [SILC1].
1874 When private key is used to protect the message, servers between
1875 the sender and the receiver needs not to decrypt/re-encrypt the
1876 packet. Section Client To Client in [SILC1] gives example of this
1879 The payload may only be sent with SILC_PACKET_PRIVATE_MESSAGE
1880 packet. It MUST NOT be sent in any other packet type. The following
1881 diagram represents the Private Message Payload.
1893 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
1894 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1895 | Message Flags | Message Data Length |
1896 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1900 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1904 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1908 Figure 15: Private Message Payload
1912 o Message Flags (2 bytes) - This field includes the Message
1913 Flags of the private message. They can indicate a different
1914 reason or purpose for the private message. See the section
1915 2.3.9 Channel Message Payload for defined flags. Note that
1916 the Channel Message Payload use the same flags for the
1919 o Message Data Length (2 bytes) - Indicates the length of the
1920 Message Data field, not includes any other field.
1922 o Message Data (variable length) - The actual message to
1923 the client. Rest of the packet is reserved for the message
1926 o Padding (variable length) - This field is present only
1927 when the private message payload is encrypted with private
1928 message key. In this case the padding is applied to make
1929 the payload multiple by eight (8), or by the block size of
1930 the cipher, which ever is larger. When encrypted with
1931 normal session keys, this field MUST NOT be included.
1936 2.3.12 Private Message Key Payload
1938 This payload is optional and can be used to send private message
1939 key between two clients in the network. The packet is secured with
1940 normal session keys. By default private messages are encrypted
1941 with session keys, and with this payload it is possible to set
1942 private key for private message encryption between two clients.
1944 The receiver of this payload SHOULD verify for example from user
1945 whether user wants to receive private message key. Note that there
1946 are other, more secure ways of exchanging private message keys in
1947 the SILC network. Instead of sending this payload it is possible to
1948 negotiate the private message key with SKE protocol using the Key
1949 Agreement payload directly peer to peer.
1951 This payload may only be sent by client to another client. Server
1952 MUST NOT send this payload at any time. After sending this payload
1953 the sender of private messages must set the Private Message Key
1954 flag into SILC Packet Header.
1956 The payload may only be sent with SILC_PACKET_PRIVATE_MESSAGE_KEY
1957 packet. It MUST NOT be sent in any other packet type. The following
1958 diagram represents the Private Message Key Payload.
1964 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
1965 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1966 | Private Message Key Length | |
1967 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1969 ~ Private Message Key ~
1971 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1972 | Cipher Name Length | |
1973 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1977 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1981 Figure 16: Private Message Key Payload
1987 o Private Message Key Length (2 bytes) - Indicates the length
1988 of the Private Message Key field in the payload, not including
1991 o Private Message Key (variable length) - The actual private
1992 message key material.
1994 o Cipher Name Length (2 bytes) - Indicates the length of the
1995 Cipher Name field in the payload, not including any other
1998 o Cipher Name (variable length) - Name of the cipher to use
1999 in the private message encryption. If this field does not
2000 exist then the default cipher of the SILC protocol is used.
2001 See the [SILC1] for defined ciphers.
2007 2.3.13 Command Payload
2009 Command Payload is used to send SILC commands from client to server.
2010 Also server MAY send commands to other servers. The following diagram
2011 represents the Command Payload.
2017 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
2018 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2019 | Payload Length | SILC Command | Arguments Num |
2020 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2021 | Command Identifier |
2022 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2026 Figure 17: Command Payload
2030 o Payload Length (2 bytes) - Length of the entire command
2031 payload including any command argument payloads associated
2034 o SILC Command (1 byte) - Indicates the SILC command. This MUST
2035 be set to non-zero value. If zero (0) value is found in this
2036 field the packet MUST be discarded.
2038 o Arguments Num (1 byte) - Indicates the number of arguments
2039 associated with the command. If there are no arguments this
2040 field is set to zero (0). The arguments MUST follow the
2041 command payload. See section 2.3.2.2 for definition of the
2044 o Command Identifier (2 bytes) - Identifies this command at the
2045 sender's end. The entity which replies to this command MUST
2046 set the value found from this field into the Command Payload
2047 used to send the reply to the sender. This way the sender
2048 can identify which command reply belongs to which originally
2049 sent command. What this field includes is implementation
2050 issue but it is RECOMMENDED that wrapping counter value is
2051 used in the field. Value zero (0) in this field means that
2052 no specific value is set.
2055 See [SILC4] for detailed description of different SILC commands,
2056 their arguments and their reply messages.
2062 2.3.14 Command Reply Payload
2064 Command Reply Payload is used to send replies to the commands. The
2065 Command Reply Payload is identical to the Command Payload thus see
2066 the upper section for the Command Payload specification.
2068 The entity which sends the reply packet MUST set the Command Identifier
2069 field in the reply packet's Command Payload to the value it received
2070 in the original command packet.
2072 See SILC Commands in [SILC4] for detailed description of different
2073 SILC commands, their arguments and their reply messages.
2077 2.3.15 Connection Auth Request Payload
2079 Client MAY send this payload to server to request the authentication
2080 method that must be used in authentication protocol. If client knows
2081 this information beforehand this payload is not necessary to be sent.
2082 Server performing authentication with another server MAY also send
2083 this payload to request the authentication method. If the connecting
2084 server already knows this information this payload is not necessary
2087 Server receiving this request MUST reply with same payload sending
2088 the mandatory authentication method. Algorithms that may be required
2089 to be used by the authentication method are the ones already
2090 established by the SILC Key Exchange protocol. See section Key
2091 Exchange Start Payload in [SILC3] for detailed information.
2093 The payload may only be sent with SILC_PACKET_CONNECTION_AUTH_REQUEST
2094 packet. It MUST NOT be sent in any other packet type. The following
2095 diagram represents the Connection Auth Request Payload.
2101 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
2102 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2103 | Connection Type | Authentication Method |
2104 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2108 Figure 18: Connection Auth Request Payload
2112 o Connection Type (2 bytes) - Indicates the type of the
2113 connection. The following connection types are defined:
2120 If any other type is found in this field the packet MUST be
2121 discarded and the authentication MUST be failed.
2123 o Authentication Method (2 bytes) - Indicates the authentication
2124 method to be used in the authentication protocol. The following
2125 authentication methods are defined:
2128 1 password (mandatory)
2129 2 public key (mandatory)
2131 If any other type is found in this field the packet MUST be
2132 discarded and the authentication MUST be failed. If this
2133 payload is sent as request to receive the mandatory
2134 authentication method this field MUST be set to zero (0),
2135 indicating that receiver should send the mandatory
2136 authentication method. The receiver sending this payload
2137 to the requesting party, MAY also set this field to zero (0)
2138 to indicate that authentication is not required. In this
2139 case authentication protocol still MUST be started but
2140 server is most likely to respond with SILC_PACKET_SUCCESS
2146 2.3.16 New ID Payload
2148 New ID Payload is a multipurpose payload. It is used to send newly
2149 created ID's from clients and servers. When client connects to server
2150 and registers itself to the server by sending SILC_PACKET_NEW_CLIENT
2151 packet, server replies with this packet by sending the created ID for
2152 the client. Server always creates the ID for the client.
2154 This payload is also used when server tells its router that new client
2155 has registered to the SILC network. In this case the server sends
2156 the Client ID of the client to the router. Similarly when router
2157 distributes information to other routers about the client in the SILC
2158 network this payload is used.
2160 Also, when server connects to router, router uses this payload to inform
2161 other routers about new server in the SILC network. However, every
2162 server (or router) creates their own ID's thus the ID distributed by
2163 this payload is not created by the distributor in this case. Servers
2164 create their own ID's. Server registers itself to the network by
2165 sending SILC_PACKET_NEW_SERVER to the router it connected to. The case
2166 is same when router connects to another router.
2168 However, this payload MUST NOT be used to send information about new
2169 channels. New channels are always distributed by sending the dedicated
2170 SILC_PACKET_NEW_CHANNEL packet.
2172 Thus, this payload is very important and used every time when some
2173 new entity is registered to the SILC network. Client MUST NOT send this
2174 payload. Both client and server (and router) MAY receive this payload.
2176 The packet uses generic ID Payload as New ID Payload. See section
2177 2.3.2.1 for generic ID Payload.
2181 2.3.17 New Client Payload
2183 When client is connected to the server, keys has been exchanged and
2184 connection has been authenticated client MUST register itself to the
2185 server. Client's first packet after key exchange and authentication
2186 protocols must be SILC_PACKET_NEW_CLIENT. This payload tells server all
2187 the relevant information about the connected user. Server creates a new
2188 client ID for the client when received this payload and sends it to the
2189 client in New ID Payload.
2191 This payload sends username and real name of the user on the remote host
2192 which is connected to the SILC server with SILC client. The server
2193 creates the client ID according the information sent in this payload.
2194 The nickname of the user becomes the username sent in this payload.
2195 However, client should call NICK command after sending this payload to
2196 set the real nickname of the user which is then used to create new
2199 The payload may only be sent with SILC_PACKET_NEW_CLIENT packet. It
2200 MUST NOT be sent in any other packet type. The following diagram
2201 represents the New Client Payload.
2218 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
2219 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2220 | Username Length | |
2221 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
2225 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2226 | Real Name Length | |
2227 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
2231 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2235 Figure 19: New Client Payload
2239 o Username Length (2 bytes) - Length of the Username field.
2241 o Username (variable length) - The username of the user on
2242 the host where connecting to the SILC server.
2244 o Real Name Length (2 bytes) - Length of the Real Name field.
2246 o Real Name (variable length) - The real name of the user
2247 on the host where connecting to the SILC server.
2252 2.3.18 New Server Payload
2254 This payload is sent by server when it has completed successfully both
2255 key exchange and connection authentication protocols. The server
2256 MUST register itself to the SILC Network by sending this payload.
2257 The first packet after these key exchange and authentication protocols
2258 is SILC_PACKET_NEW_SERVER packet. The payload includes the Server ID
2259 of the server that it has created by itself. It also includes a
2260 name of the server that is associated to the Server ID.
2262 The payload may only be sent with SILC_PACKET_NEW_SERVER packet. It
2263 MUST NOT be sent in any other packet type. The following diagram
2264 represents the New Server Payload.
2273 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
2274 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2275 | Server ID Length | |
2276 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
2280 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2281 | Server Name Length | |
2282 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
2286 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2290 Figure 20: New Server Payload
2294 o Server ID Length (2 bytes) - Length of the Server ID Data
2297 o Server ID Data (variable length) - The actual Server ID
2300 o Server Name Length (2 bytes) - Length of the server name
2303 o Server Name (variable length) - The server name.
2308 2.3.19 New Channel Payload
2310 Information about newly created channel is broadcasted to all routers
2311 in the SILC network by sending this packet payload. Channels are
2312 created by router of the cell. Server never creates channels unless
2313 it is a standalone server and it does not have router connection,
2314 in this case server acts as router. Normal server send JOIN command
2315 to the router (after it has received JOIN command from client) which
2316 then processes the command and creates the channel. Client MUST NOT
2317 send this packet. Server may send this packet to a router when it is
2318 announcing its existing channels to the router after it has connected
2321 The packet uses generic Channel Payload as New Channel Payload. See
2322 section 2.3.2.3 for generic Channel Payload. The Mode Mask field in the
2323 Channel Payload is the mode of the channel.
2327 2.3.20 Key Agreement Payload
2329 This payload is used by clients to request key negotiation between
2330 another client in the SILC Network. The key agreement protocol used
2331 is the SKE protocol. The result of the protocol, the secret key
2332 material, can be used for example as private message key between the
2333 two clients. This significantly adds security as the key agreement
2334 is performed outside the SILC network. The server and router MUST NOT
2337 The sender MAY tell the receiver of this payload the hostname and the
2338 port where the SKE protocol is running in the sender's end. The
2339 receiver MAY then initiate the SKE negotiation with the sender. The
2340 sender MAY also optionally not to include the hostname and the port
2341 of its SKE protocol. In this case the receiver MAY reply to the
2342 request by sending the same payload filled with the receiver's hostname
2343 and the port where the SKE protocol is running. The sender MAY then
2344 initiate the SKE negotiation with the receiver.
2346 This payload may be sent with SILC_PACKET_KEY_AGREEMENT and
2347 SILC_PACKET_FTP packet types. It MUST NOT be sent in any other packet
2348 types. The following diagram represents the Key Agreement Payload.
2354 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
2355 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2356 | Hostname Length | |
2357 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
2361 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2363 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2367 Figure 21: Key Agreement Payload
2371 o Hostname Length (2 bytes) - Indicates the length of the
2374 o Hostname (variable length) - The hostname or IP address where
2375 the SKE protocol is running. The sender MAY fill this field
2376 when sending the payload. If the receiver sends this payload
2377 as reply to the request it MUST fill this field.
2379 o Port (4 bytes) - The port where the SKE protocol is bound.
2380 The sender MAY fill this field when sending the payload. If
2381 the receiver sends this payload as reply to the request it
2382 MUST fill this field. This is a 32 bit MSB first order value.
2386 After the key material has been received from the SKE protocol it is
2387 processed as the [SILC3] describes. If the key material is used as
2388 channel private key then the Sending Encryption Key, as defined in
2389 [SILC3] is used as the channel private key. Other key material must
2390 be discarded. The [SILC1] defines the way to use the key material if
2391 it is intended to be used as private message keys. Any other use for
2392 the key material is undefined.
2396 2.3.21 Resume Router Payload
2398 The payload may only be sent with SILC_PACKET_RESUME_ROUTER packet. It
2399 MUST NOT be sent in any other packet type. The Following diagram
2400 represents the Resume Router Payload.
2406 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
2407 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2408 | Type | Session ID |
2409 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2413 Figure 22: Resume Router Payload
2417 o Type (1 byte) - Indicates the type of the backup resume
2418 protocol packet. The type values are defined in [SILC1].
2420 o Session ID (1 bytes) - Indicates the session ID for the
2421 backup resume protocol. The sender of the packet sets this
2422 value and the receiver MUST set the same value in subsequent
2428 2.3.22 File Transfer Payload
2430 File Transfer Payload is used to perform file transfer protocol
2431 between two entities in the network. The actual file transfer
2432 protocol is always encapsulated inside the SILC Packet. The actual
2433 data stream is also sent peer to peer outside SILC network.
2435 When an entity, usually a client wishes to perform file transfer
2436 protocol with another client in the network, they perform Key Agreement
2437 protocol as described in the section 2.3.20 Key Agreement Payload and
2438 in [SILC3], inside File Transfer Payload. After the Key Agreement
2439 protocol has been performed the subsequent packets in the data stream
2440 will be protected using the new key material. The actual file transfer
2441 protocol is also initialized in this stage. All file transfer protocol
2442 packets are always encapsulated in the File Transfer Payload and
2443 protected with the negotiated key material.
2445 The payload may only be sent with SILC_PACKET_FTP packet. It MUST NOT
2446 be sent in any other packet type. The following diagram represents the
2447 File Transfer Payload.
2452 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
2453 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2459 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2463 Figure 23: File Transfer Payload
2467 o Type (1 byte) - Indicates the type of the file transfer
2468 protocol. The following file transfer protocols has been
2471 1 SSH File Transfer Protocol (SFTP) (mandatory)
2473 If zero (0) value or any unsupported file transfer protocol
2474 type is found in this field the packet must be discarded.
2475 The currently mandatory file transfer protocol is SFTP.
2476 The SFTP protocol is defined in [SFTP].
2478 o Data (variable length) - Arbitrary file transfer data. The
2479 contents and encoding of this field is dependent of the usage
2480 of this payload and the type of the file transfer protocol.
2481 When this payload is used to perform the Key Agreement
2482 protocol, this field include the Key Agreement Payload,
2483 as defined in the section 2.3.20 Key Agreement Payload.
2484 When this payload is used to send the actual file transfer
2485 protocol data, the encoding is defined in the corresponding
2486 file transfer protocol.
2491 2.3.23 Resume Client Payload
2493 This payload is used by client to resume its detached session in the
2494 SILC Network. A client is able to detach itself from the network by
2495 sending SILC_COMMAND_DETACH command to its server. The network
2496 connection to the client is lost but the client remains as valid
2497 client in the network. The client is able to resume the session back
2498 by sending this packet and including the old Client ID, and an
2499 Authentication Payload [SILC1] which the server uses to verify with
2500 the detached client's public key. This also implies that the
2501 mandatory authentication method is public key authentication.
2503 Server or router that receives this from the client also sends this,
2504 without the Authentication Payload, to routers in the network so that
2505 they know the detached client has resumed. Refer to the [SILC1] for
2506 detailed description how the detaching and resuming prodecure is
2509 The payload may only be sent with SILC_PACKET_RESUME CLIENT packet. It
2510 MUST NOT be sent in any other packet type. The following diagram
2511 represents the Resume Client Payload.
2516 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
2517 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2518 | Client ID Length | |
2519 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
2523 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2525 ~ Authentication Payload ~
2527 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2531 Figure 24: Resume Client Payload
2535 o Client ID Length (1 byte) - The length of the Client ID
2536 field not including any other field.
2538 o Client ID (variable length) - The detached client's Client
2539 ID. The client that sends this payload must know the Client
2542 o Authentication Payload (variable length) - The authentication
2543 payload that the server will verify with the detached client's
2544 public key. If the server doesn't know the public key, it must
2545 retrieve it for example with SILC_COMMAND_GETKEY command.
2553 ID's are extensively used in the SILC network to associate different
2554 entities. The following ID's has been defined to be used in the SILC
2560 When ever specific ID cannot be used this is used.
2564 Server ID to associate servers. See the format of
2569 Client ID to associate clients. See the format of
2574 Channel ID to associate channels. See the format of
2578 When encoding different IDs into the ID Payload, all fields are always
2579 in MSB first order. The IP address, port, and/or the random number
2580 are encoded in the MSB first order.
2584 2.5 Packet Encryption And Decryption
2586 SILC packets are encrypted almost entirely. Only small part of SILC
2587 header is not encrypted as described in section 5.2 SILC Packet Header.
2588 The SILC Packet header is the first part of a packet to be encrypted
2589 and it is always encrypted with the key of the next receiver of the
2590 packet. The data payload area of the packet is always entirely
2591 encrypted and it is usually encrypted with the next receiver's key.
2592 However, there are some special packet types and packet payloads
2593 that require special encryption process. These special cases are
2594 described in the next sections. First is described the normal packet
2599 2.5.1 Normal Packet Encryption And Decryption
2601 Normal SILC packets are encrypted with the session key of the next
2602 receiver of the packet. The entire SILC Packet header and the packet
2603 data payload is is also encrypted with the same key. Padding of the
2604 packet is also encrypted always with the session key, also in special
2605 cases. Computed MAC of the packet must not be encrypted.
2607 Decryption process in these cases are straightforward. The receiver
2608 of the packet MUST first decrypt the SILC Packet header, or some parts
2609 of it, usually first 16 bytes of it. Then the receiver checks the
2610 packet type from the decrypted part of the header and can determine
2611 how the rest of the packet must be decrypted. If the packet type is
2612 any of the special cases described in the following sections the packet
2613 decryption is special. If the packet type is not among those special
2614 packet types rest of the packet can be decrypted with the same key.
2616 With out a doubt, this sort of decryption processing causes some
2617 overhead to packet decryption, but never the less, is required.
2621 2.5.2 Channel Message Encryption And Decryption
2623 Channel Messages (Channel Message Payload) are always encrypted with
2624 the channel specific key. However, the SILC Packet header is not
2625 encrypted with that key. As in normal case, the header is encrypted
2626 with the key of the next receiver of the packet, who ever that might
2627 be. Note that in this case the encrypted data area is not touched
2628 at all; it MUST NOT be re-encrypted with the session key.
2630 Receiver of a channel message, who ever that is, is REQUIRED to decrypt
2631 the SILC Packet header to be able to even recognize the packet to be as
2632 channel message. This is same procedure as for normal SILC packets.
2633 As the receiver founds the packet to be channel message, rest of the
2634 packet processing is special. Rest of the SILC Packet header is
2635 decrypted with the same session key along with the padding of the
2636 packet. After that the packet is protected with the channel specific
2637 key and thus can be decrypted only if the receiver is the client on
2638 the channel. See section 2.7 Packet Padding Generation for more
2639 information about padding on special packets.
2641 If the receiver of the channel message is router which is routing the
2642 message to another router then it MUST decrypt the Channel Message
2643 payload. Between routers (that is, between cells) channel messages
2644 are protected with session keys shared between the routers. This
2645 causes another special packet processing for channel messages. If
2646 the channel message is received from another router then the entire
2647 packet, including Channel Message payload, MUST be encrypted with the
2648 session key shared between the routers. In this case the packet
2649 decryption process is as with normal SILC packets. Hence, if the
2650 router is sending channel message to another router the Channel
2651 Message payload MUST have been decrypted and MUST be re-encrypted
2652 with the session key shared between the another router. In this
2653 case the packet encryption is as with any normal SILC packet.
2655 It must be noted that this is only when the channel messages are sent
2656 from router to another router. In all other cases the channel
2657 message encryption and decryption is as described above. This
2658 different processing of channel messages with router to router
2659 connection is because channel keys are cell specific. All cells have
2660 their own channel keys thus the channel message traveling from one
2661 cell to another MUST be protected as it would be any normal SILC
2664 If the SILC_CMODE_PRIVKEY channel mode has been set for the channel
2665 then the router cannot decrypt the packet as it does not know the
2666 private key. In this case the entire packet MUST be encrypted with
2667 the session key and sent to the router. The router receiving the
2668 packet MUST check the channel mode and decrypt the packet accordingly.
2672 2.5.3 Private Message Encryption And Decryption
2674 By default, private message in SILC are protected by session keys.
2675 In this case the private message encryption and decryption process is
2676 equivalent to normal packet encryption and decryption.
2678 However, private messages MAY be protected with private message key
2679 which causes the packet to be special packet. The procedure in this
2680 case is very much alike to channel packets. The actual private message
2681 is encrypted with the private message key and other parts of the
2682 packet is encrypted with the session key. See 2.7 Packet Padding
2683 Generation for more information about padding on special packets.
2685 The difference from channel message processing is that server or router
2686 en route never decrypts the actual private message, as it does not
2687 have the key to do that. Thus, when sending packets between router
2688 the processing is same as in any other case as well; the packet's header
2689 and padding is protected by the session key and the data area is not
2692 The true receiver of the private message, client, that is, is able
2693 to decrypt the private message as it shares the key with the sender
2698 2.6 Packet MAC Generation
2700 Data integrity of a packet is protected by including a message
2701 authentication code (MAC) at the end of the packet. The MAC is computed
2702 from shared secret MAC key, that is established by the SILC Key Exchange
2703 protocol, from packet sequence number, and from the original contents
2704 of the packet. The MAC is always computed before the packet is
2705 encrypted, although after it is compressed if compression is used.
2707 The MAC is computed from entire packet. Every bit of data in the packet,
2708 including SILC Packet Header is used in the MAC computing. This way
2709 the entire packet becomes authenticated.
2711 If the packet is special packet MAC is computed from the entire packet
2712 but part of the packet may be encrypted before the MAC is computed.
2713 This is case, for example, with channel messages where the message data
2714 is encrypted with key that server may not now. In this case the MAC
2715 has been computed from the encrypted data.
2717 Hence, packet's MAC generation is as follows:
2719 mac = MAC(key, sequence number | SILC packet)
2721 The MAC key is negotiated during the SKE protocol. The sequence number
2722 is a 32 bit MSB first value starting from zero for first packet and
2723 increasing for subsequent packets, finally wrapping after 2^32 packets.
2724 The value is never reset, not even after rekey has been performed. Note
2725 that the sequence number is incremented only when MAC is computed for a
2726 packet. If packet is not encrypted and MAC is not computed then the
2727 sequence number is not incremented. Hence, the sequence number is zero
2728 for first encrypted packet.
2730 See [SILC1] for defined and allowed MAC algorithms.
2734 2.7 Packet Padding Generation
2736 Padding is needed in the packet because the packet is encrypted. It
2737 MUST always be multiple by eight (8) or multiple by the block size
2738 of the cipher, which ever is larger. The padding is always encrypted.
2740 For normal packets the padding is added after the SILC Packet Header
2741 and between the Data Payload area. The padding for normal packets
2742 may be calculated as follows:
2745 padding length = 16 - (packet_length mod block_size)
2748 The `block_size' is the block size of the cipher. The maximum padding
2749 length is 128 bytes, and minimum is 1 byte. The above algorithm calculates
2750 the padding to the next block size, and always returns the padding
2751 length between 1 - 16 bytes. However, implementations may add padding
2752 up to 128 bytes. For example packets that include a passphrase or a
2753 password for authentication purposes SHOULD pad the packet up to the
2754 maximum padding length.
2756 For special packets the padding calculation is different as special
2757 packets may be encrypted differently. In these cases the encrypted
2758 data area MUST already be multiple by the block size thus in this case
2759 the padding is calculated only for SILC Packet Header, not for any
2760 other area of the packet. The same algorithm works in this case as
2761 well, except that the `packet length' is now the SILC Packet Header
2764 The padding MUST be random data, preferably, generated by
2765 cryptographically strong random number generator.
2769 2.8 Packet Compression
2771 SILC Packets MAY be compressed. In this case the data payload area
2772 is compressed and all other areas of the packet MUST remain as they
2773 are. After compression is performed for the data area, the length
2774 field of Packet Header MUST be set to the compressed length of the
2777 The compression MUST always be applied before encryption. When
2778 the packet is received and decrypted the data area MUST be decompressed.
2779 Note that the true sender of the packet MUST apply the compression and
2780 the true receiver of the packet MUST apply the decompression. Any
2781 server or router en route SHOULD NOT decompress the packet.
2787 The sender of the packet MUST assemble the SILC Packet Header with
2788 correct values. It MUST set the Source ID of the header as its own
2789 ID, unless it is forwarding the packet. It MUST also set the Destination
2790 ID of the header to the true destination. If the destination is client
2791 it will be Client ID, if it is server it will be Server ID and if it is
2792 channel it will be Channel ID.
2794 If the sender wants to compress the packet it MUST apply the
2795 compression now. Sender MUST also compute the padding as described
2796 in above sections. Then sender MUST compute the MAC of the packet.
2798 Then sender MUST encrypt the packet as has been described in above
2799 sections according whether the packet is normal packet or special
2800 packet. The computed MAC MUST NOT be encrypted.
2804 2.10 Packet Reception
2806 On packet reception the receiver MUST check that all fields in the
2807 SILC Packet Header are valid. It MUST check the flags of the
2808 header and act accordingly. It MUST also check the MAC of the packet
2809 and if it is to be failed the packet MUST be discarded. Also if the
2810 header of the packet includes any bad fields the packet MUST be
2813 See above sections on the decryption process of the received packet.
2815 The receiver MUST also check that the ID's in the header are valid
2816 ID's. Unsupported ID types or malformed ID's MUST cause packet
2817 rejection. The padding on the reception is always ignored.
2819 The receiver MUST also check the packet type and start parsing the
2820 packet according to the type. However, note the above sections on
2821 special packet types and their parsing.
2827 Routers are the primary entities in the SILC network that takes care
2828 of packet routing. However, normal servers routes packets as well, for
2829 example, when they are routing channel message to the local clients.
2830 Routing is quite simple as every packet tells the true origin and the
2831 true destination of the packet.
2833 It is still RECOMMENDED for routers that has several routing connections
2834 to create route cache for those destinations that has faster route than
2835 the router's primary route. This information is available for the router
2836 when other router connects to the router. The connecting party then
2837 sends all of its locally connected clients, servers and channels. These
2838 informations helps to create the route cache. Also, when new channels
2839 are created to a cell its information is broadcasted to all routers
2840 in the network. Channel ID's are based on router's ID thus it is easy
2841 to create route cache based on these informations. If faster route for
2842 destination does not exist in router's route cache the packet MUST be
2843 routed to the primary route (default route).
2845 However, there are some issues when routing channel messages to group
2846 of users. Routers are responsible of routing the channel message to
2847 other routers, local servers and local clients as well. Routers MUST
2848 send the channel message to only one router in the network, preferrably
2849 to the shortest route to reach the channel users. The message can be
2850 routed into either upstream or downstream. After the message is sent
2851 to a router in the network it MUST NOT be sent to any other router in
2852 either same route or other route. The message MUST NOT be routed to
2853 the router it came from.
2855 When routing for example private messages they should be routed to the
2856 shortest route always to reach the destination client as fast as possible.
2858 For server which receives a packet to be routed to its locally connected
2859 client the server MUST check whether the particular packet type is
2860 allowed to be routed to the client. Not all packets may be sent by
2861 some odd entity to client that is indirectly connected to the sender.
2862 See section 2.3 SILC Packet Types and paragraph about indirectly connected
2863 entities and sending packets to them. The section mentions the packets
2864 that may be sent to indirectly connected entities. It is clear that
2865 server cannot send, for example, disconnect packet to client that is not
2866 directly connected to the server.
2868 Routers form a ring in the SILC network. However, routers may have other
2869 direct connections to other routers in the network too. This can cause
2870 interesting routing problems in the network. Since the network is a ring,
2871 the packets usually should be routed into clock-wise direction, or if it
2872 cannot be used then always counter clock-wise (primary route) direction.
2873 Problems may arise when a faster direct route exists and router is routing
2874 a channel message. Currently channel messages must be routed either
2875 in upstream or downstream, they cannot be routed to other direct routes.
2876 The SILC protocol should have a shortest path discovery protocol, and some
2877 existing routing protocol, that can handle a ring network with other
2878 direct routes inside the ring (so called hybrid ring-mesh topology),
2879 MAY be defined to be used with the SILC protocol. Additional
2880 specifications MAY be written on the subject to permeate this
2885 2.12 Packet Broadcasting
2887 SILC packets MAY be broadcasted in SILC network. However, only router
2888 server may send or receive broadcast packets. Client and normal server
2889 MUST NOT send broadcast packets and they MUST ignore broadcast packets
2890 if they receive them. Broadcast packets are sent by setting Broadcast
2891 flag to the SILC packet header.
2893 Broadcasting packets means that the packet is sent to all routers in
2894 the SILC network, except to the router that sent the packet. The router
2895 receiving broadcast packet MUST send the packet to its primary route.
2896 The fact that SILC routers may have several router connections can
2897 cause problems, such as race conditions inside the SILC network, if
2898 care is not taken when broadcasting packets. Router MUST NOT send
2899 the broadcast packet to any other route except to its primary route.
2901 If the primary route of the router is the original sender of the packet
2902 the packet MUST NOT be sent to the primary route. This may happen
2903 if router has several router connections and some other router uses
2904 the router as its primary route.
2906 Routers use broadcast packets to broadcast for example information
2907 about newly registered clients, servers, channels etc. so that all the
2908 routers may keep these informations up to date.
2912 3 Security Considerations
2914 Security is central to the design of this protocol, and these security
2915 considerations permeate the specification. Common security considerations
2916 such as keeping private keys truly private and using adequate lengths for
2917 symmetric and asymmetric keys must be followed in order to maintain the
2918 security of this protocol.
2924 [SILC1] Riikonen, P., "Secure Internet Live Conferencing (SILC),
2925 Protocol Specification", Internet Draft, April 2001.
2927 [SILC3] Riikonen, P., "SILC Key Exchange and Authentication
2928 Protocols", Internet Draft, April 2001.
2930 [SILC4] Riikonen, P., "SILC Commands", Internet Draft, April 2001.
2932 [IRC] Oikarinen, J., and Reed D., "Internet Relay Chat Protocol",
2935 [IRC-ARCH] Kalt, C., "Internet Relay Chat: Architecture", RFC 2810,
2938 [IRC-CHAN] Kalt, C., "Internet Relay Chat: Channel Management", RFC
2941 [IRC-CLIENT] Kalt, C., "Internet Relay Chat: Client Protocol", RFC
2944 [IRC-SERVER] Kalt, C., "Internet Relay Chat: Server Protocol", RFC
2947 [SSH-TRANS] Ylonen, T., et al, "SSH Transport Layer Protocol",
2950 [PGP] Callas, J., et al, "OpenPGP Message Format", RFC 2440,
2953 [SPKI] Ellison C., et al, "SPKI Certificate Theory", RFC 2693,
2956 [PKIX-Part1] Housley, R., et al, "Internet X.509 Public Key
2957 Infrastructure, Certificate and CRL Profile", RFC 2459,
2960 [Schneier] Schneier, B., "Applied Cryptography Second Edition",
2961 John Wiley & Sons, New York, NY, 1996.
2963 [Menezes] Menezes, A., et al, "Handbook of Applied Cryptography",
2966 [OAKLEY] Orman, H., "The OAKLEY Key Determination Protocol",
2967 RFC 2412, November 1998.
2969 [ISAKMP] Maughan D., et al, "Internet Security Association and
2970 Key Management Protocol (ISAKMP)", RFC 2408, November
2973 [IKE] Harkins D., and Carrel D., "The Internet Key Exchange
2974 (IKE)", RFC 2409, November 1998.
2976 [HMAC] Krawczyk, H., "HMAC: Keyed-Hashing for Message
2977 Authentication", RFC 2104, February 1997.
2979 [PKCS1] Kalinski, B., and Staddon, J., "PKCS #1 RSA Cryptography
2980 Specifications, Version 2.0", RFC 2437, October 1998.
2982 [RFC2119] Bradner, S., "Key Words for use in RFCs to Indicate
2983 Requirement Levels", BCP 14, RFC 2119, March 1997.
2985 [SFTP] Ylonen T., and Lehtinen S., "Secure Shell File Transfer
2986 Protocol", Internet Draft, March 2001.
2988 [RFC2279] Yergeau, F., "UTF-8, a transformation format of ISO
2989 10646", RFC 2279, January 1998.
2996 Snellmanninkatu 34 A 15
3000 EMail: priikone@iki.fi
3002 This Internet-Draft expires XXX