8 .ds RF FORMFEED[Page %]
11 .ds RH 13 September 2000
17 Network Working Group P. Riikonen
19 draft-riikonen-silc-pp-01.txt 13 September 2000
26 <draft-riikonen-silc-pp-01.txt>
31 This document is an Internet-Draft and is in full conformance with
32 all provisions of Section 10 of RFC 2026. Internet-Drafts are
33 working documents of the Internet Engineering Task Force (IETF), its
34 areas, and its working groups. Note that other groups may also
35 distribute working documents as Internet-Drafts.
37 Internet-Drafts are draft documents valid for a maximum of six months
38 and may be updated, replaced, or obsoleted by other documents at any
39 time. It is inappropriate to use Internet-Drafts as reference
40 material or to cite them other than as "work in progress."
42 The list of current Internet-Drafts can be accessed at
43 http://www.ietf.org/ietf/1id-abstracts.txt
45 The list of Internet-Draft Shadow Directories can be accessed at
46 http://www.ietf.org/shadow.html
48 The distribution of this memo is unlimited.
54 This memo describes a Packet Protocol used in the Secure Internet Live
55 Conferencing (SILC) protocol specified in the Secure Internet Live
56 Conferencing, Protocol Specification Internet Draft [SILC1]. This
57 protocol describes the packet types and packet payloads which defines
58 the contents of the packets. The protocol provides secure binary packet
59 protocol that assures that the contents of the packets are secured and
74 1 Introduction .................................................. 3
75 2 SILC Packet Protocol .......................................... 4
76 2.1 SILC Packet ............................................... 4
77 2.2 SILC Packet Header ........................................ 5
78 2.3 SILC Packet Types ......................................... 7
79 2.3.1 SILC Packet Payloads ................................ 15
80 2.3.2 Generic paylods .....................................
81 2.3.2.1 ID Payload ..................................
82 2.3.2.2 Argument Payload ............................
83 2.3.3 Disconnect Payload .................................. 15
84 2.3.4 Success Payload ..................................... 16
85 2.3.5 Failure Payload ..................................... 16
86 2.3.6 Reject Payload ...................................... 17
87 2.3.7 Notify Payload ...................................... 17
88 2.3.8 Error Payload ....................................... 18
89 2.3.9 Channel Message Payload ............................. 19
90 2.3.10 Channel Key Payload ................................ 20
91 2.3.11 Private Message Payload ............................ 23
92 2.3.12 Private Message Key Payload ........................ 24
93 2.3.13 Command Payload .................................... 25
94 2.3.14 Command Reply Payload .............................. 26
95 2.3.15 Connection Auth Request Payload .................... 27
96 2.3.16 New ID Payload ..................................... 28
97 2.3.17 New ID List Payload ................................ 29
98 2.3.18 New Client Payload ................................. 29
99 2.3.19 New Server Payload ................................. 31
100 2.3.20 New Channel Payload ................................ 31
101 2.3.21 New Channel User Payload ........................... 32
102 2.3.22 New Channel List Payload ........................... 33
103 2.3.23 New Channel User List Payload ...................... 34
104 2.3.24 Replace ID Payload ................................. 34
105 2.3.25 Remove ID Payload .................................. 35
106 2.3.26 Remove Channel User Payload ........................
107 2.4 SILC ID Types ............................................. 36
108 2.5 Packet Encryption And Decryption .......................... 37
109 2.5.1 Normal Packet Encryption And Decryption ............. 37
110 2.5.2 Channel Message Encryption And Decryption ........... 37
111 2.5.3 Private Message Encryption And Decryption ........... 38
112 2.6 Packet MAC Generation ..................................... 39
113 2.7 Packet Padding Generation ................................. 39
114 2.8 Packet Compression ........................................ 40
115 2.9 Packet Sending ............................................ 40
116 2.10 Packet Reception ......................................... 41
117 2.11 Packet Routing ........................................... 42
118 2.12 Packet Forwarding ........................................
119 2.13 Packet Broadcasting ...................................... 41
120 2.14 Packet Tunneling ......................................... 42
121 3 Security Considerations ....................................... 43
122 4 References .................................................... 43
123 5 Author's Address .............................................. 44
129 Figure 1: Typical SILC Packet
130 Figure 2: SILC Packet Header
131 Figure 3: Disconnect Payload
132 Figure 4: Success Payload
133 Figure 5: Failure Payload
134 Figure 6: Reject Payload
135 Figure 7: Notify Payload
136 Figure 8: Error Payload
137 Figure 9: Channel Message Payload
138 Figure 10: Channel Key Payload
139 Figure 11: Private Message Payload
140 Figure 12: Private Message Key Payload
141 Figure 13: Command Payload
142 Figure 15: Connection Auth Request Payload
143 Figure 16: New ID Payload
144 Figure 17: New Client Payload
145 Figure 18: New Server Payload
146 Figure 19: New Channel Payload
147 Figure 20: New Channel User Payload
148 Figure 21: Replace ID Payload
149 Figure 22: Remove ID Payload
150 Figure 23: Remove Channel User Payload
156 This document describes a Packet Protocol used in the Secure Internet
157 Live Conferencing (SILC) protocol specified in the Secure Internet Live
158 Conferencing, Protocol Specification Internet Draft [SILC1]. This
159 protocol describes the packet types and packet payloads which defines
160 the contents of the packets. The protocol provides secure binary packet
161 protocol that assures that the contents of the packets are secured and
164 The basis of SILC protocol relies in the SILC packets and it is with
165 out a doubt the most important part of the protocol. It is also probably
166 the most complicated part of the protocol. Packets are used all the
167 time in the SILC network to send messages, commands and other information.
168 All packets in SILC network are always encrypted and their integrity
169 is assured by computed MACs. The protocol defines several packet types
170 and packet payloads. Each packet type usually has a specific packet
171 payload that actually defines the contents of the packet. Each packet
172 also includes a default SILC Packet Header that provides sufficient
173 information about the origin of the packet and destination of the
178 2 SILC Packet Protocol
183 SILC packets deliver messages from sender to receiver securely by
184 encrypting important fields of the packet. The packet consists of
185 default SILC Packet Header, Padding, Packet Payload data, and, packet
188 The following diagram illustrates typical SILC packet.
193 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
194 | n bytes | 1 - n bytes | n bytes | n bytes
195 | SILC Header | Padding | Data Payload | MAC
196 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
200 Figure 1: Typical SILC Packet
203 SILC Header is always the first part of the packet and its purpose
204 is to provide information about the packet. It provides for example
205 the packet type, origin of the packet and the destination of the packet.
206 The header is variable in length and first two (2) bytes of the
207 header (thus first two bytes of the packet) are not encrypted. The
208 first two (2) bytes are the length of the packet which is not encrypted.
209 See following section for description of SILC Packet header. Packets
210 without SILC header or with malformed SILC header must be dropped.
212 Padding follows the packet header. The purpose of the padding is to
213 make the packet multiple by eight (8) or by the block size of the
214 cipher used in the encryption, which ever is larger. The maximum
215 length of padding is currently 16 bytes. The padding is always
218 Data payload area follows padding and it is the actual data of the
219 packet. The packet data is the packet payloads defined in this
220 protocol. The data payload area is always encrypted.
222 The last part of SILC packet is the packet MAC that assures the
223 integrity of the packet. The MAC is always computed from the packet
224 before the encryption is applied to the packet. If compression is used
225 in the packet the MAC is computed after the compression has been
226 applied. The compression, on the other hand, is always applied before
229 All fields in all packet payloads are always in MSB (most significant
234 2.2 SILC Packet Header
236 The default SILC packet header is applied to all SILC packets and it is
237 variable in length. The purpose of SILC Packet header is to provide
238 detailed information about the packet. The receiver of the packet uses
239 the packet header to parse the packet and gain other relevant parameters
242 Following diagram represents the default SILC header format.
243 (*) indicates that this field is never encrypted. Other fields are
250 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
251 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
252 | Payload Length * | Flags | Packet Type |
253 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
254 | Source ID Length | Destination ID Length |
255 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
261 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
267 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
271 Figure 2: SILC Packet Header
275 o Payload Length (2 bytes) - Is the length of the packet
276 not including the padding of the packet. This field must
277 not be encrypted but must always be authenticated.
279 o Flags (1 byte) - Indicates flags to be used in packet
280 processing. Several flags may be set by ORing the flags
283 Following flags are reserved for this field:
290 In this case the field is ignored.
293 Private Message Key 0x01
295 Indicates that the packet must include private
296 message that is encrypted using private key set by
297 client. Servers does not know anything about this
298 key and this causes that the private message is
299 not handled by the server at all, it is just
300 passed along. See section 2.5.3 Private Message
301 Encryption And Decryption for more information.
306 Marks the packet to be forwarded. Some specific
307 packet types may be forwarded. Receiver of packet
308 with this flag set must not forward the packet any
309 further. See section 2.12 Packet Forwarding for
310 desribtion of packet forwarding.
315 Marks the packet to be broadcasted. Client cannot
316 send broadcast packet and normal server cannot send
317 broadcast packet. Only router server may send broadcast
318 packet. The router receiving of packet with this flag
319 set must send (broadcast) the packet to its primary
320 route. If router has several router connections the
321 packet may be sent only to the primary route. See
322 section 2.13 Packet Broadcasting for description of
328 Marks that the packet is tunneled. Tunneling means
329 that extra SILC Packet Header has been applied to the
330 original packet. The outer header has this flag
331 set. See section 2.14 Packet Tunneling for more
337 o Packet Type (1 byte) - Is the type of the packet. Receiver
338 uses this field to parse the packet. See section 2.3
339 SILC Packets for list of defined packet types.
341 o Source ID Length (2 bytes) - Indicates the length of the
342 Source ID field in the header, not including this or any
347 o Destination ID Length (2 bytes) - Indicates the length of the
348 Destination ID field in the header, not including this or
351 o Src ID Type (1 byte) - Indicates the type of ID in the
352 Source ID field. See section 2.4 SILC ID Types for
355 o Source ID (variable length) - The actual source ID that
356 indicates who is the original sender of the packet.
358 o Dst ID Type (1 byte) - Indicates the type of ID in the
359 Destination ID field. See section 2.4 SILC ID Types for
362 o Destination ID (variable length) - The actual source ID that
363 indicates who is the end receiver of the packet.
367 2.3 SILC Packet Types
369 SILC packet types defines the contents of the packet and it is used by
370 the receiver to parse the packet. The packet type is 8 bits, as a one
371 byte, in length. The range for the packet types are from 0 - 255,
372 where 0 is never sent and 255 is currently reserved for future
373 extensions and must not be defined to any other purpose. Every SILC
374 specification compliant implementation should support all of these packet
377 The below list of the SILC Packet types includes reference to the packet
378 payload as well. Packet payloads are the actual packet, that is, the data
379 that the packet consists of. Each packet type defines packet payload
380 which usually may only be sent with the specific packet type.
382 Most of the packets are packets that must be destined directly to entity
383 that is connected to the sender. It is not allowed, for example, for
384 router to send disconnect packet to client that is not directly connected
385 to the router. However, there are some special packet types that may
386 be destined to some entity that the sender has not direct connection
387 with. These packets are for example private message packets, channel
388 message packets, command packets and some other packets that may be
389 broadcasted in the SILC network. If the packet is allowed to be sent to
390 indirectly connected entity it is mentioned separately in the packet
391 description (unless it is obvious as in private and channel message
392 packets). Other packets must not be sent or accepted, if sent, to
393 indirectly connected entities.
395 List of SILC Packet types are defined as follows.
400 This type is reserved and it is never sent.
403 1 SILC_PACKET_DISCONNECT
405 This packet is sent to disconnect the remote end. Reason of
406 the disconnection is sent inside the packet payload. Client
407 usually does not send this packet.
409 Payload of the packet: See section 2.3.2 Disconnect Payload
412 2 SILC_PACKET_SUCCESS
414 This packet is sent upon successful execution of some protocol.
415 The status of the success is sent in the packet.
417 Payload of the packet: See section 2.3.3 Success Payload
420 3 SILC_PACKET_FAILURE
422 This packet is sent upon failure of some protocol. The status
423 of the failure is sent in the packet.
425 Payload of the packet: See section 2.3.4 Failure Payload
430 This packet may be sent upon rejection of some protocol.
431 The status of the rejection is sent in the packet.
433 Payload of the packet: See section 2.3.5 Reject Payload
438 This packet is used to send notify message, usually from
439 server to client, although it may be sent from server to another
440 server as well. Client never sends this packet. Server may
441 send this packet to channel as well when the packet is
442 distributed to all clients on the channel. Receiver of this
443 packet may ignore the packet if it chooses so. However, it
444 should not be ignored.
446 Payload of the packet: See section 2.3.6 Notify Payload.
451 This packet is sent when an error occurs. Server may
452 send this packet. Client never sends this packet. The
453 client may entirely ignore the packet, however, server is
454 most likely to take action anyway. This packet may be sent
455 to entity that is indirectly connected to the sender.
457 Payload of the packet: See section 2.3.7 Error Payload.
460 7 SILC_PACKET_CHANNEL_MESSAGE
462 This packet is used to send messages to channels. The packet
463 includes Channel ID of the channel and the actual message to
464 the channel. Messages sent to the channel are always protected
465 by channel specific keys. Channel Keys are distributed by
466 SILC_PACKET_CHANNEL_KEY packet.
468 Payload of the packet: See section 2.3.8 Channel Message
472 8 SILC_PACKET_CHANNEL_KEY
474 This packet is used to distribute new key for particular
475 channel. Each channel has their own independent keys that
476 is used to protect the traffic on the channel. Only server
477 may send this packet. This packet may be sent to entity
478 that is indirectly connected to the sender.
480 Payload of the packet: See section 2.3.9 Channel Key Payload
483 9 SILC_PACKET_PRIVATE_MESSAGE
485 This packet is used to send private messages from client
486 to another client. By default, private messages are protected
487 by session keys established by normal key exchange protocol.
488 However, it is possible to use specific key to protect private
489 messages. SILC_PACKET_PRIVATE_MESSAGE_KEY packet is used to
490 agree the key with the remote client. Pre-shared key may be
491 used as well if both of the client knows it, however, it needs
492 to be agreed outside SILC. See more of this in [SILC1].
494 Payload of the packet: See section 2.3.10 Private Message
498 10 SILC_PACKET_PRIVATE_MESSAGE_KEY
500 This packet is used to agree about a key to be used to protect
501 the private messages between two clients. If this is not sent
502 the normal session key is used to protect the private messages
503 inside SILC network. Agreeing to use specific key to protect
504 private messages adds security, as no server between the two
505 clients will be able to decrypt the private message. However,
506 servers inside SILC network are considered to be trusted, thus
507 using normal session key to protect private messages does not
508 degree security. Whether to agree to use specific keys by
509 default or to use normal session keys by default, is
510 implementation specific issue. See more of this in [SILC1].
512 Payload of the packet: See section 2.3.11 Private Message
516 11 SILC_PACKET_COMMAND
518 This packet is used to send commands from client to server.
519 Server may send this packet to other servers as well. All
520 commands are listed in their own section SILC Command Types
521 in [SILC1]. The contents of this packet is command specific.
522 This packet may be sent to entity that is indirectly connected
525 Payload of the packet: See section 2.3.12 Command Payload
528 12 SILC_PACKET_COMMAND_REPLY
530 This packet is send as reply to the SILC_PACKET_COMMAND packet.
531 The contents of this packet is command specific. This packet
532 maybe sent to entity that is indirectly connected to the sender.
534 Payload of the packet: See section 2.3.13 Command Reply
535 Payload and section 2.3.12 Command
539 13 SILC_PACKET_KEY_EXCHANGE
541 This packet is used to start SILC Key Exchange Protocol,
542 described in detail in [SILC3].
544 Payload of the packet: Payload of this packet is described
545 in the section SILC Key Exchange
546 Protocol and its sub sections in
550 14 SILC_PACKET_KEY_EXCHANGE_1
552 This packet is used as part of the SILC Key Exchange Protocol.
554 Payload of the packet: Payload of this packet is described
555 in the section SILC Key Exchange
556 Protocol and its sub sections in
560 15 SILC_PACKET_KEY_EXCHANGE_2
562 This packet is used as part of the SILC Key Exchange Protocol.
564 Payload of the packet: Payload of this packet is described
565 in the section SILC Key Exchange
566 Protocol and its sub sections in
570 16 SILC_PACKET_CONNECTION_AUTH_REQUEST
572 This packet is used to request the authentication method to
573 be used in the SILC Connection Authentication Protocol. If
574 initiator of the protocol does not know the mandatory
575 authentication method this packet is used to determine it.
577 The party receiving this payload must respond with the same
578 packet including the mandatory authentication method.
580 Payload of the packet: See section 2.3.14 Connection Auth
584 17 SILC_PACKET_CONNECTION_AUTH
586 This packet is used to start and perform the SILC Connection
587 Authentication Protocol. This protocol is used to authenticate
588 the connecting party. The protocol is described in detail in
591 Payload of the packet: Payload of this packet is described
592 in the section SILC Authentication
593 Protocol and it sub sections in [SILC].
596 18 SILC_PACKET_NEW_ID
598 This packet is used to distribute new ID's from server to
599 router and from router to all routers in the SILC network.
600 This is used when for example new client is registered to
601 SILC network. The newly created ID's of these operations are
602 distributed by this packet. Only server may send this packet,
603 however, client must be able to receive this packet.
605 Payload of the packet: See section 2.3.15 New ID Payload
608 19 SILC_PACKET_NEW_ID_LIST
610 This packet is used to distribute list of new ID's from
611 server to routers. This is equivalent to previous packet
612 type except that it may include several ID's. Client must
613 not send this packet.
615 Payload of the packet: See section 2.3.16 New ID List
619 20 SILC_PACKET_NEW_CLIENT
621 This packet is used by client to register itself to the
622 SILC network. This is sent after key exchange and
623 authentication protocols has been completed. Client sends
624 various information about itself in this packet.
626 Payload of the packet: See section 2.3.17 New Client Payload
629 21 SILC_PACKET_NEW_SERVER
631 This packet is used by server to register itself to the
632 SILC network. This is sent after key exchange and
633 authentication protocols has been completed. Server sends
634 this to the router it connected to, or, if router was
635 connecting, to the connected router. Server sends
636 its Server ID and other information in this packet.
637 Client must not send or receive this packet.
639 Payload of the packet: See section 2.3.18 New Server Payload
642 22 SILC_PACKET_NEW_CHANNEL
644 This packet is used to notify routers about newly created
645 channel. Channels are always created by the router and it must
646 notify other routers about the created channel. Router sends
647 this packet to its primary route. Client must not send this
648 packet. This packet maybe sent to entity that is indirectly
649 connected to the sender.
651 Payload of the packet: See section 2.3.20 New Channel Payload
654 23 SILC_PACKET_NEW_CHANNEL_USER
656 This packet is used to notify routers about new user on channel.
657 The packet is sent after user has joined to the channel. Server
658 may send this packet to its router and router may send this to
659 its primary router. Client must not send this packet. This
660 packet maybe sent to entity that is indirectly connected to
663 Payload of the packet: See section 2.3.21 New Channel User
667 24 SILC_PACKET_NEW_CHANNEL_LIST
669 This packet is used to distribute list of created channels
670 from server to routers. This is equivalent to the packet
671 SILC_PACKET_NEW_CHANNEL except that it may include several
672 payloads. Client must not send this packet.
674 Payload of the packet: See section 2.3.22 New Channel List
678 25 SILC_PACKET_NEW_CHANNEL_USER_LIST
680 This packet is used to distribute list of users on specific
681 channel from server to routers. This is equivalent to the
682 packet SILC_PACKET_NEW_CHANNEL_USER except that it may
683 include several payloads. Client must not send this packet.
685 Payload of the packet: See section 2.3.23 New Channel User
689 26 SILC_PACKET_REPLACE_ID
691 This packet is used to replace old ID with new ID sent in
692 the packet payload. For example, when client changes its
693 nickname new ID is created and this packet can be used to
694 distribute the new ID and the old ID is removed when it is
695 send in the packet. Client cannot send or receive this
696 packet. This packet maybe sent to entity that is indirectly
697 connected to the sender.
699 Payload of the packet: See section 2.3.24 Replace ID Payload
702 27 SILC_PACKET_REMOVE_ID
704 This packet is used to removed ID. For example, when client
705 exits SILC network its ID is removed. Client must not send
706 this packet. This packet maybe sent to entity that is
707 indirectly connected to the sender.
709 Payload of the packet: See section 2.3.25 Remove ID Payload
712 28 SILC_PACKET_REMOVE_CHANNEL_USER
714 This packet is used to remove user from a channel. This is
715 used by router to notify other routers in the network that a
716 client has leaved a channel. This packet maybe sent to entity
717 that is indirectly connected to the sender.
719 Payload of the packet: See section 2.3.26 Remove Channel User
725 This packet is used to indicate that re-key must be performed
726 for session keys. See section Session Key Regeneration in
727 [SILC1] for more information. This packet does not have
731 30 SILC_PACKET_REKEY_DONE
733 This packet is used to indicate that re-key is performed and
734 new keys must be used hereafter. This is sent only if re-key
735 was done without PFS option. If PFS is set, this is not sent
736 as SILC Key Exchange protocol is executed. This packet does
742 Currently undefined commands.
747 This type is reserved for future extensions and currently it
753 2.3.1 SILC Packet Payloads
755 All payloads resides in the main data area of the SILC packet. However
756 all payloads must be at the start of the data area after the default
757 SILC packet header and padding. All fields in the packet payload are
758 always encrypted, as, they reside in the data area of the packet which
761 Payloads described in this section are common payloads that must be
762 accepted anytime during SILC session. Most of the payloads may only
763 be sent with specific packet type which is defined in the description
766 There are a lot of other payloads in the SILC as well. However, they
767 are not common in the sense that they could be sent at any time.
768 These payloads are not described in this section. These are payloads
769 such as SILC Key Exchange payloads and so on. These are described
770 in [SILC1] and [SILC3].
774 2.3.2 Generic paylods
776 This sections describes generic payloads that are not associated to any
777 specific packet type. They can be used for example inside some other
784 This payload can be used to send an ID. ID's are variable length thus
785 this payload provides a way to send variable length ID's.
787 Following diagram represents the ID Payload.
792 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
793 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
794 | ID Type | ID Length |
795 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
799 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
807 o ID Type (2 bytes) - Indicates the type of the ID. See
808 section 2.4 SILC ID Types for list of defined ID types.
810 o ID Length (2 bytes) - Length of the ID Data area not
811 including the length of any other fields in the payload.
813 o ID Data (variable length) - The actual ID data.
818 2.3.2.2 Argument Payload
820 Argument Payload is used to set arguments for any packet payload that
821 needs and supports arguments, such as commands. Number of arguments
822 associated with a packet must be indicated by the packet payload who
823 needs the arguments. Argument Payloads must always reside right after
824 the packet payload needing the arguments. Incorrect amount of argument
825 payloads must cause rejection of the packet. Following diagram represents
826 the Argument Payload.
832 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
833 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
834 | Payload Length | Argument Type | |
835 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
839 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
843 Figure 4: Argument Payload
847 o Payload Length (2 bytes) - Length of the argument payload data
848 area not including the length of any other fields in the
851 o Argument Type (1 byte) - Indicates the type of the argument.
852 Every argument may have a specific type that must be defined
853 by the packet payload needing the argument. For example
854 every command specify a number for each argument that maybe
855 associated with the command. By using this number the receiver
856 of the packet knows what type of argument this is. If there is
857 no specific argument type this field is set to zero (0).
859 o Argument Data (variable length) - Argument data.
864 2.3.3 Disconnect Payload
866 Disconnect payload is sent upon disconnection. The payload is simple;
867 reason of disconnection is sent to the disconnected party.
869 The payload may only be sent with SILC_PACKET_DISCONNECT packet. It
870 must not be sent in any other packet type. Following diagram represents
871 the Disconnect Payload.
877 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
878 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
880 ~ Disconnect Message ~
882 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
886 Figure 3: Disconnect Payload
892 o Disconnect Message (variable length) - Human readable
893 reason of the disconnection.
898 2.3.4 Success Payload
900 Success payload is sent when some protocol execution is successfully
901 completed. The payload is simple; indication of the success is sent.
902 This maybe any data, including binary or human readable data.
907 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
908 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
910 ~ Success Indication ~
912 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
916 Figure 4: Success Payload
920 o Success Indication (variable length) - Indication of
921 the success. This maybe for example some flag that
922 indicates the protocol and the success status or human
923 readable success message. The true length of this
924 payload is available by calculating it from the SILC
930 2.3.5 Failure Payload
932 This is opposite of Success Payload. Indication of failure of
933 some protocol is sent in the payload.
939 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
940 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
942 ~ Failure Indication ~
944 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
948 Figure 5: Failure Payload
952 o Failure Indication (variable length) - Indication of
953 the failure. This maybe for example some flag that
954 indicates the protocol and the failure status or human
955 readable failure message. The true length of this
956 payload is available by calculating it from the SILC
964 This payload is sent when some protocol is rejected to be executed.
965 Other operations may send this as well that was rejected. The
966 indication of the rejection is sent in the payload. The indication
967 may be binary or human readable data.
973 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
974 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
976 ~ Reject Indication ~
978 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
982 Figure 6: Reject Payload
986 o Reject Indication (variable length) - Indication of
987 the rejection. This maybe for example some flag that
988 indicates the protocol and the rejection status or human
989 readable rejection message. The true length of this
990 payload is available by calculating it from the SILC
1001 Notify payload is used to send notify messages. The payload is usually
1002 sent from server to client, however, server may send it to another
1003 server as well. Client must not send this payload. The receiver of
1004 this payload may totally ignore the contents of the payload, however,
1005 notify message should be noted and possibly logged.
1007 The payload may only be sent with SILC_PACKET_NOTIFY packet. It must
1008 not be sent in any other packet type. Following diagram represents the
1014 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
1015 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1016 | Notify Type | Argument Nums | |
1017 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1021 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1025 Figure 7: Notify Payload
1029 o Notify Type (2 bytes) - Indicates the type of the notify
1032 o Argument Nums (2 bytes) - Indicates the number of Argument
1033 Payloads associated to this payload. Notify types may define
1034 arguments to be send along the notify message.
1036 o Notify Message (variable length) - Human readable notify
1037 message. The format of this message is implementation specific.
1038 The message can be for example "%s has joined channel %s".
1041 Following notify types has been defined:
1044 0 SILC_NOTIFY_TYPE_NONE
1046 If no specific notify type apply for the notify
1047 message this type may be used.
1049 No arguments associated to this type.
1051 1 SILC_NOTIFY_TYPE_INVITE
1053 Sent when receiver has been invited to a channel.
1055 This type includes three arguments: nickname and channel name.
1057 2 SILC_NOTIFY_TYPE_JOIN
1059 Sent when client has joined to a channel.
1061 This type includes six arguments: Client ID, nickname, username,
1062 hostname, Channel ID and channel name. The Client ID and Channel ID
1063 are sent inside ID Payload.
1065 3 SILC_NOTIFY_TYPE_LEAVE
1067 Sent when client has left a channel.
1069 This type includes three arguments: nickname, server name,
1070 Channel ID and channel name. The Channel ID is sent inside ID
1073 4 SILC_NOTIFY_TYPE_SIGNOFF
1075 Sent when client signoffs from SILC network.
1077 This type includes three arguments: nickname, server name and
1078 Channel ID. The Channel ID is sent inside ID Payload.
1081 Notify types starting from 16384 are reserved for private notify
1088 Error payload is sent upon error. Error may occur in various
1089 conditions when server sends this packet. Client may not send this
1090 payload but must be able to accept it. However, client may
1091 totally ignore the contents of the packet as server is going to
1092 take action on the error anyway. However, it is recommended
1093 that the client takes error packet seriously.
1099 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
1100 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1104 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1108 Figure 8: Error Payload
1112 o Error Message (variable length) - Human readable error
1118 2.3.9 Channel Message Payload
1120 Channel messages are the most common messages sent in the SILC.
1121 Channel Message Payload is used to send message to channels. These
1122 messages can only be sent if client has joined to some channel.
1123 Even though this packet is the most common in SILC it is still
1124 special packet. Some special handling on sending and reception
1125 of channel message is required.
1127 Padding must be applied into this payload since the payload is
1128 encrypted separately from other parts of the packet with the
1129 channel specific key. Hence the requirement of the padding.
1130 The padding should be random data. The packet must be made
1131 multiple by eight (8) or by the block size of the cipher, which
1134 The SILC header in this packet is encrypted with the session key
1135 of the next receiver of the packet. Nothing else is encrypted
1136 with that key. Thus, the actual packet and padding to be
1137 encrypted with the session key is SILC Header plus padding to it
1138 to make it multiple by eight (8) or multiple by the block size
1139 of the cipher, which ever is larger.
1141 Receiver of the the channel message packet is able to determine
1142 the channel the message is destined to by checking the destination
1143 ID from the SILC Packet header which tells the destination channel.
1144 The original sender of the packet is also determined by checking
1145 the source ID from the header which tells the client who sent
1148 The payload may only be sent with SILC_PACKET_CHANNEL_MESSAGE packet.
1149 It must not be sent in any other packet type. Following diagram
1150 represents the Channel Message Payload.
1152 (*) indicates that the field is not encrypted.
1178 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
1179 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1180 | Message Length | |
1181 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1185 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1186 | Padding Length | |
1187 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1191 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1193 ~ Initial Vector * ~
1195 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1199 Figure 9: Channel Message Payload
1203 o Message Length (2 bytes) - Indicates the length of the
1204 the Message Data field in the payload, not including any
1207 o Message Data (variable length) - The actual message to
1210 o Padding Length (2 bytes) - Indicates the length of the
1211 Padding field in the payload, not including any other
1214 o Padding (variable length) - The padding that must be
1215 applied because this payload is encrypted separately from
1216 other parts of the packet.
1218 o Initial Vector (variable length) - The initial vector
1219 that has been used in packet encryption. It needs to be
1220 used in the packet decryption as well. What this field
1221 includes is implementation issue. However, it is
1222 recommended that it would be random data or, perhaps,
1223 a timestamp. It is not recommended to use zero (0) as
1224 initial vector. This field is not encrypted. This field
1225 is not included into the padding calculation. Length
1226 of this field equals the cipher's block size. This field
1227 is, however, authenticated.
1232 2.3.10 Channel Key Payload
1234 All traffic in channels are protected by channel specific keys.
1235 Channel Key Payload is used to distribute channel keys to all
1236 clients on the particular channel. Channel keys are sent when
1237 the channel is created, when new user joins to the channel and
1238 whenever a user leaves a channel. Server creates the new
1239 channel key and distributes it to the clients by encrypting this
1240 payload with the session key shared between the server and
1241 the client. After that, client starts using the key received
1242 in this payload to protect the traffic on the channel.
1244 Channel keys are cell specific thus every router in cell have
1245 to create a channel key and distribute it if any client in the
1246 cell has joined to a channel. Channel traffic between cell's
1247 are not encrypted using channel keys, they are encrypted using
1248 normal session keys between two routers. Inside a cell, all
1249 channel traffic is encrypted with the specified channel key.
1250 Channel key should expire peridiocally, say, in one hour, in
1251 which case new channel key is created and distributed.
1253 The payload may only be sent with SILC_PACKET_CHANNEL_KEY packet.
1254 It must not be sent in any other packet type. Following diagram
1255 represents the Channel Key Payload.
1261 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
1262 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1263 | Channel ID Length | |
1264 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1268 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1269 | Cipher Name Length | |
1270 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1274 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1275 | Channel Key Length | |
1276 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1280 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1284 Figure 10: Channel Key Payload
1289 o Channel ID Length (2 bytes) - Indicates the length of the
1290 Channel ID field in the payload, not including any other
1293 o Channel ID (variable length) - The Channel ID of the
1294 channel this key is meant for.
1296 o Cipher Name Length (2 bytes) - Indicates the length of the
1297 Cipher name field in the payload, not including any other
1300 o Cipher Name (variable length) - Name of the cipher used
1301 in the protection of channel traffic. This name is
1302 initially decided by the creator of the channel but it
1303 may change during the life time of the channel as well.
1305 o Channel Key Length (2 bytes) - Indicates the length of the
1306 Channel Key field in the payload, not including any other
1309 o Channel Key (variable length) - The actual channel key
1310 material. This key is used as such as key material for
1311 encryption function.
1316 2.3.11 Private Message Payload
1318 Private Message Payload is used to send private message between
1319 two clients (or users for that matter). The messages are sent only
1320 to the specified user and no other user inside SILC network is
1321 able to see the message. The message is protected by the session
1322 key established by the SILC Key Exchange Protocol. However,
1323 it is also possible to agree to use specific keys to protect
1324 just the private messages. See section 2.3.11 Private Message
1325 Key Payload for detailed description of how to agree to use
1328 If normal session key is used to protect the message, every
1329 server between the sender client and the receiving client needs
1330 to decrypt the packet and always re-encrypt it with the session
1331 key of the next receiver of the packet. See section Client
1332 To Client in [SILC1].
1334 When specific key is used to protect the message, servers between
1335 the sender and the receiver needs not to decrypt/re-encrypt the
1336 packet. Section 4.8.2 Client To Client in [SILC1] gives example of
1337 this scheme as well.
1339 The payload may only be sent with SILC_PACKET_PRIVATE_MESSAGE
1340 packet. It must not be sent in any other packet type. Following
1341 diagram represents the Private Message Payload.
1347 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
1348 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1349 | Nickname Length | |
1350 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1354 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1358 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1362 Figure 11: Private Message Payload
1366 o Nickname Length (2 bytes) - Indicates the length of the
1367 Nickname field, not including any other field.
1369 o Nickname (variable length) - Nickname of the sender of the
1370 private message. This should not be trusted as a definite
1371 sender of the private message. The SILC Packet Header in
1372 the packet indicates the true sender of the packet and
1373 client should verify that the nickname sent here belongs
1374 to the Client ID in the SILC Packet Header. This nickname
1375 is merely provided to be displayed by the client.
1377 o Message Data (variable length) - The actual message to
1378 the client. Rest of the packet is reserved for the message
1384 2.3.12 Private Message Key Payload
1386 This payload is used to send key from client to another client that
1387 is going to be used to protect the private messages between these
1388 two clients. If this payload is not sent normal session key
1389 established by the SILC Key Exchange Protocol is used to protect
1390 the private messages.
1392 This payload may only be sent by client to another client. Server
1393 must not send this payload at any time. After sending this payload
1394 the sender of private messages must set the Private Message Key
1395 flag into SILC Packet Header.
1397 The payload may only be sent with SILC_PACKET_PRIVATE_MESSAGE_KEY
1398 packet. It must not be sent in any other packet type. Following
1399 diagram represents the Private Message Key Payload.
1405 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
1406 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1407 | Private Message Key Length | |
1408 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1410 ~ Private Message Key ~
1412 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1416 Figure 12: Private Message Key Payload
1422 o Private Message Key Length (2 bytes) - Indicates the length
1423 of the Private Message Key field in the payload, not including
1426 o Private Message Key (variable length) - The actual private
1427 message key material. This key is used as such as key material
1428 for encryption function.
1433 2.3.13 Command Payload
1435 Command Payload is used to send SILC commands from client to server.
1436 Also server may send commands to other servers. Following diagram
1437 represents the Command Payload.
1443 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
1444 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1445 | Payload Length | SILC Command | Arguments Num |
1446 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1448 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1452 Figure 13: Command Payload
1456 o Payload Length (2 bytes) - Length of the entire command
1457 payload including any command argument payloads associated
1460 o SILC Command (1 byte) - SILC Command identifier. This must
1461 be set to non-zero value. If zero (0) value is found in this
1462 field the packet must be discarded.
1464 o Arguments Num (1 byte) - Indicates the number of arguments
1465 associated with the command. If there are no arguments this
1466 field is set to zero (0). The arguments must follow the
1467 command payload. See section 2.3.2.2 for definition of the
1470 o Command Unifier (2 bytes) - Unifies this command at the
1471 sender's end. The entity who replies to this command must
1472 set the value found from this field into the Command Payload
1473 used to send the reply to the sender. This way the sender
1474 can identify which command reply belongs to which originally
1475 sent command. What this field includes is implementation
1476 issue but it is recommended that wrapping counter value is
1480 See [SILC1] for detailed description of different SILC commands,
1481 their arguments and their reply messages.
1485 2.3.14 Command Reply Payload
1487 Command Reply Payload is used to send replies to the commands. The
1488 Command Reply Payload is identical to the Command Payload thus see the
1489 upper sections for Command Payload and for Command Argument Payload
1490 specifications. Command Reply message uses the Command Argument Payload
1493 The entity who sends the reply packet must set the Command Unifier
1494 field in the reply packet's Command Payload to the value it received
1495 in the original command packet.
1497 See SILC Commands in [SILC1] for detailed description of different
1498 SILC commands, their arguments and their reply messages.
1502 2.3.15 Connection Auth Request Payload
1504 Client may send this payload to server to request the authentication
1505 method that must be used in authentication protocol. If client knows
1506 this information beforehand this payload is not necessary to be sent.
1507 Server performing authentication with another server may also send
1508 this payload to request the authentication method. If the connecting
1509 server already knows this information this payload is not necessary
1512 Server receiving this request must reply with same payload sending
1513 the mandatory authentication method. Algorithms that may be required
1514 to be used by the authentication method are the ones already
1515 established by the SILC Key Exchange protocol. See section Key
1516 Exchange Start Payload in [SILC3] for detailed information.
1518 The payload may only be sent with SILC_PACKET_CONNECTION_AUTH_REQUEST
1519 packet. It must not be sent in any other packet type. Following
1520 diagram represents the Connection Auth Request Payload.
1526 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
1527 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1528 | Connection Type | Authentication Method |
1529 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1533 Figure 15: Connection Auth Request Payload
1537 o Connection Type (2 bytes) - Indicates the type of the ID.
1538 Following connection types are defined:
1544 If any other type is found in this field the packet must be
1545 discarded and the authentication must be failed.
1547 o Authentication Method (2 bytes) - Indicates the authentication
1548 method to be used in the authentication protocol. Following
1549 authentication methods are defined:
1554 1 password (mandatory)
1555 2 public key (mandatory)
1557 If any other type is found in this field the packet must be
1558 discarded and the authentication must be failed. If this
1559 payload is sent as request to receive the mandatory
1560 authentication method this field must be set to zero (0),
1561 indicating that receiver should send the mandatory
1562 authentication method. The receiver sending this payload
1563 to the requesting party, may also set this field to zero (0)
1564 to indicate that authentication is not required. In this
1565 case authentication protocol still must be started but
1566 server is most likely to respond with SILC_PACKET_SUCCESS
1572 2.3.16 New ID Payload
1574 New ID Payload is a multipurpose payload. It is used to send newly
1575 created ID's from clients and servers. When client connects to server
1576 and registers itself to the server by sending SILC_PACKET_NEW_CLIENT
1577 packet, server replies with this packet by sending the created ID for
1578 the client. Server always creates the ID for the client.
1580 This payload is also used when server tells its router that new client
1581 has registered to the SILC network. In this case the server sends
1582 the Client ID of the client to the router. Similiary when router
1583 distributes information to other routers about the client in the SILC
1584 network this payload is used.
1586 Also, when server connects to router, router uses this payload to inform
1587 other routers about new server in the SILC network. However, every
1588 server (or router) creates their own ID's thus the ID distributed by
1589 this payload is not created by the distributor in this case. Servers
1590 create their own ID's. Server registers itself to the network by sending
1591 SILC_PACKET_NEW_SERVER to the router it connected to. The case is same
1592 when router connects to another router.
1594 Hence, this payload is very important and used every time when some
1595 new entity is registered to the SILC network. Client never sends this
1596 payload. Both client and server (and router) may receive this payload.
1598 The packet uses generic ID Payload as New ID Payload. See section
1599 2.3.2.1 for generic ID Payload.
1603 2.3.17 New ID List Payload
1605 New ID List Payload is used to distribute list of ID's usually from
1606 server to router but also from router to other routers in the network.
1607 This payload is used, for example, when server is connected to router
1608 and the server wants to distribute all of its locally connected clients
1609 and locally created channels to the router. It is convenient in this
1610 case to use this payload instead of sending all the information one
1611 by one using New ID Payload.
1613 There is no specific payload for this packet type. The packet type
1614 uses same payload as described in previous section. To form a list
1615 several payloads is put in the packet each after each. The payload
1616 is variable in length but can be calculated by calculating the ID
1617 Type field, Length field and the ID Data fields together. This forms
1618 one New ID Payload in the list.
1620 The list of payloads may only be sent with SILC_PACKET_NEW_ID_LIST
1621 packet. They must not be sent in any other packet type.
1625 2.3.18 New Client Payload
1627 When client is connected to the server, keys has been exchanged and
1628 connection has been authenticated client must register itself to the
1629 server. Clients first packet after key exchange and authentication
1630 protocols must be SILC_PACKET_NEW_CLIENT. This payload tells server all
1631 the relevant information about the connected user. Server creates a new
1632 client ID for the client when received this payload and sends it to the
1633 client in New ID Payload.
1635 This payload sends username and real name of the user on the remote host
1636 which is connected to the SILC server with SILC client. The server
1637 creates the client ID according the information sent in this payload.
1638 The nickname of the user becomes the username sent in this payload.
1639 However, client should call NICK command after sending this payload to
1640 set the real nickname of the user which is then used to create new
1643 The payload may only be sent with SILC_PACKET_NEW_CLIENT packet. It
1644 must not be sent in any other packet type. Following diagram represents
1645 the New Client Payload.
1651 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
1652 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1653 | Username Length | |
1654 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1658 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1659 | Real Name Length | |
1660 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1664 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1668 Figure 17: New Client Payload
1672 o Username Length (2 bytes) - Length of the username.
1674 o Username (variable length) - The username of the user on
1675 the host where connecting to the SILC server.
1677 o Real Name Length (2 bytes) - Length of the Real Name.
1679 o Real Name (variable length) - The real name of the user
1680 on the host where connecting to the SILC server.
1685 2.3.19 New Server Payload
1687 This payload is sent by server when it has completed successfully both
1688 key exchange and connection authentication protocols. The server
1689 uses this payload to register itself to the SILC network. The
1690 first packet after these key exchange and authentication protocols
1691 is SILC_PACKET_NEW_SERVER packet. The payload includes the Server ID
1692 of the server that it has created by itself. It also includes a
1693 name of the server that is associated to the Server ID.
1695 The payload may only be sent with SILC_PACKET_NEW_SERVER packet. It
1696 must not be sent in any other packet type. Following diagram represents
1697 the New Server Payload.
1703 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
1704 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1705 | Server ID Length | |
1706 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1710 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1711 | Server Name Length | |
1712 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1716 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1720 Figure 18: New Server Payload
1724 o Server ID Length (2 bytes) - Length of the ID Data area not
1725 including the length of any other fields in the payload.
1727 o Server ID Data (variable length) - The actual Server ID
1730 o Server Name Length (2 bytes) - Length of the server name.
1732 o Server Name (variable length) - The server name.
1737 2.3.20 New Channel Payload
1739 Information about newly created channel is broadcasted to all routers
1740 in the SILC network by sending this packet payload. Channels are
1741 created by router of the cell. Server never creates channels unless
1742 it is a standalone server and it does not have router connection,
1743 in this case server acts as router. Normal server forwards JOIN command
1744 to the router (after it has received JOIN command from client) which
1745 then processes the command and creates the channel. Client never sends
1748 The payload may only be sent with SILC_PACKET_NEW_CHANNEL packet.
1749 It must not be sent in any other packet type. Following diagram
1750 represents the New Channel Payload.
1756 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
1757 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1758 | Channel Name Length | |
1759 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1763 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1764 | Channel ID Length | |
1765 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1769 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1773 Figure 19: New Channel Payload
1778 o Channel Name Length (2 bytes) - Length of the channel name.
1780 o Channel Name (variable length) - The name of the created
1783 o Channel ID Length (2 bytes) - Length of the Channel ID.
1785 o Channel ID (variable length) - The created Channel ID.
1790 2.3.21 New Channel User Payload
1792 When client (user) joins to a channel, server must notify routers
1793 about the new user on the channel. Normal server sends this packet
1794 payload to its router which then broadcasts the packet further.
1795 Router sends this packet always to its primary router. Client must
1796 not send this packet payload. The mode of the user is NONE after
1797 user has joined to the channel.
1799 The payload may only be sent with SILC_PACKET_NEW_CHANNEL_USER
1800 packet. It must not be sent in any other packet type. Following
1801 diagram represents the New Channel User Payload.
1807 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
1808 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1809 | Channel ID Length | |
1810 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1814 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1815 | Client ID Length | |
1816 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1820 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1824 Figure 20: New Channel User Payload
1828 o Channel ID Length (2 bytes) - Length of the Channel ID.
1830 o Channel ID (variable length) - The Channel ID of the channel
1831 to which the client has joined.
1833 o Client ID Length (2 bytes) - Length of the Client ID.
1835 o Client ID (variable length) - The Client ID of the client
1836 who has joined the channel.
1841 2.3.22 New Channel List Payload
1843 This payload is used to distribute list of new channels from server
1844 to routers. It might convenient to send list of new channels when
1845 existing server connects to router, instead of sending them one
1848 There is no specific payload for this packet type. The packet type
1849 uses same payload as described in 2.3.19 New Channel Payload. To form
1850 a list several payloads is put in the packet each after each. The
1851 payload is variable in length but can be calculated by calculating
1852 the length of the fields together. This forms one New Channel Payload
1855 The list of payloads may only be sent with SILC_PACKET_NEW_CHANNEL_LIST
1856 packet. They must not be sent in any other packet type.
1860 2.3.23 New Channel User List Payload
1862 This payload is used to distribute list of channel users on specific
1863 channel from server to routers. It might convenient to send list of
1864 channel users when existing server connects to router, instead of
1865 sending them one by one.
1867 There is no specific payload for this packet type. The packet type
1868 uses same payload as described in 2.3.20 New Channel User Payload.
1869 To form a list several payloads is put in the packet each after each.
1870 The payload is variable in length but can be calculated by calculating
1871 the length of the fields together. This forms one New Channel User
1872 Payload in the list.
1874 The list of payloads may only be sent with packet
1875 SILC_PACKET_NEW_CHANNEL_USER_LIST. They must not be sent in any other
1880 2.3.24 Replace ID Payload
1882 This payload is used to replace old ID with new ID sent in the payload.
1883 When ID changes for some entity and the new ID is wanted to replace the
1884 old one this payload must be used. Client cannot send or receive this
1885 payload. Normal server and router server may send and receive this
1886 payload. After this packet has been sent the old ID must not be used
1889 The payload may only be sent with SILC_PACKET_REPLACE_ID packet. It must
1890 not be sent in any other packet type. Following diagram represents the
1891 Replace Payload Payload.
1904 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
1905 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1906 | Old ID Type | Old ID Length |
1907 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1911 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1912 | New ID Type | New ID Length |
1913 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1917 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1921 Figure 21: Replace ID Payload
1925 o Old ID Type (2 bytes) - Indicates the type of the old ID. See
1926 section 2.4 SILC ID Types for list of defined ID types.
1928 o Old ID Length (2 bytes) - Length of the old ID Data area not
1929 including the length of any other fields in the payload.
1931 o Old ID Data (variable length) - The actual old ID data.
1933 o New ID Type (2 bytes) - Indicates the type of the new ID. See
1934 section 2.4 SILC ID Types for list of defined ID types.
1936 o New ID Length (2 bytes) - Length of the new ID Data area not
1937 including the length of any other fields in the payload.
1939 o New ID Data (variable length) - The actual new ID data.
1944 2.3.25 Remove ID Payload
1946 Remove ID payload is used to remove ID from SILC network. This is used
1947 for example when client exits SILC network. The server must in this
1948 case send this payload to notify that this ID is not valid anymore.
1949 After this has been send the old ID must not be used anymore. Client
1950 must not send this payload.
1952 The packet uses generic ID Payload as New ID Payload. See section
1953 2.3.2.1 for generic ID Payload.
1957 2.3.26 Remove Channel User Payload
1959 Remove Channel User payload is used to remove a user from a channel network
1960 wide. This is used by routers to notify other routers that a user has
1961 leaved a channel. As routers keep information about users on channels a
1962 user leaving channel must be removed from all routers. Normal server may
1963 send this payload as well. Client must not send this payload.
1965 The payload may only be sent with SILC_PACKET_REMOVE_CHANNEL USER packet.
1966 It must not be sent in any other packet type. Following diagram
1967 represents the Remove Payload Payload.
1973 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
1974 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1975 | Client ID Length | |
1976 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1980 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1981 | Channel ID Length | |
1982 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
1986 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1990 Figure 23: Remove Channel User Payload
1994 o Client ID Length (2 bytes) - Length of the Client ID Data area
1995 not including the length of any other fields in the payload.
1997 o Client ID Data (variable length) - The Client ID of the user
1998 that has left the channel.
2000 o Channel ID Length (2 bytes) - Length of the Channel ID Data area
2001 not including the length of any other fields in the payload.
2003 o Channel ID Data (variable length) - The Channel ID of the channel
2011 ID's are extensively used in the SILC network to associate different
2012 entities. Following ID's has been defined to be used in the SILC
2018 When ever specific ID cannot be used this is used.
2022 Server ID to associate servers. See the format of
2027 Client ID to associate clients. See the format of
2032 Channel ID to associate channels. See the format of
2038 2.5 Packet Encryption And Decryption
2040 SILC packets are encrypted almost entirely. Only small part of SILC
2041 header is not encrypted as described in section 5.2 SILC Packet Header.
2042 The SILC Packet header is the first part of a packet to be encrypted
2043 and it is always encrypted with the key of the next receiver of the
2044 packet. The data payload area of the packet is always entirely
2045 encrypted and it is usually encrypted with the next receiver's key.
2046 However, there are some special packet types and packet payloads
2047 that require special encryption process. These special cases are
2048 described in the next sections. First is described the normal packet
2053 2.5.1 Normal Packet Encryption And Decryption
2055 Normal SILC packets are encrypted with the session key of the next
2056 receiver of the packet. The entire SILC Packet header and the packet
2057 data payload is is also encrypted with the same key. Padding of the
2058 packet is also encrypted always with the session key, also in special
2059 cases. Computed MAC of the packet must not be encrypted.
2061 Decryption process in these cases are straightforward. The receiver
2062 of the packet must first decrypt the SILC Packet header, or some parts
2063 of it, usually first 16 bytes of it. Then the receiver checks the
2064 packet type from the decrypted part of the header and can determine
2065 how the rest of the packet must be decrypted. If the packet type is
2066 any of the special cases described in following sections the packet
2067 decryption is special. If the packet type is not among those special
2068 packet types rest of the packet may be decrypted with the same key.
2070 Also, note that two bytes of the SILC Packet header are not encrypted
2071 thus it must be noticed in the decryption process by starting the
2072 decryption from the second byte of the header. This sets some rules
2073 to padding generation as well, see the section 2.7 Packet Padding
2076 With out a doubt, this sort of decryption processing causes some
2077 overhead to packet decryption, but never the less, is required.
2081 2.5.2 Channel Message Encryption And Decryption
2083 Channel Messages (Channel Message Payload) are always encrypted with
2084 the channel specific key. However, the SILC Packet header is not
2085 encrypted with that key. As in normal case, the header is encrypted
2086 with the key of the next receiver of the packet, who ever that might
2087 be. Note that in this case the encrypted data area is not touched
2088 at all; it must not be re-encrypted with the session key.
2090 Receiver of a channel message, who ever that is, is required to decrypt
2091 the SILC Packet header to be able to even recognize the packet to be as
2092 channel message. This is same procedure as for normal SILC packets.
2093 As the receiver founds the packet to be channel message, rest of the
2094 packet processing is special. Rest of the SILC Packet header is
2095 decrypted with the same session key along with the padding of the
2096 packet. After that the packet is protected with the channel specific
2097 key and hence can be decrypted only if the receiver is the client on
2098 the channel. See section 2.7 Packet Padding Generation for more
2099 information about padding on special packets.
2101 If the receiver of the channel message is router who is routing the
2102 message to another router then it must decrypt the Channel Message
2103 payload. Between routers (that is, between cells) channel messages
2104 are protected with session keys shared between the routers. This
2105 causes another special packet processing for channel messages. If
2106 the channel message is received from another router then the entire
2107 packet, including Channel Message payload, is encrypted with the
2108 session key shared between the routers. In this case the packet
2109 decryption process is as with normal SILC packets. Hence, if the
2110 router is sending channel message to another router the Channel
2111 Message payload must have been decrypted and must be re-encrypted
2112 with the session key shared between the another router. In this
2113 case the packet encryption is as with any normal SILC packet.
2115 It must be noted that this is only when the channel messages are sent
2116 from router to another router. In all other cases the channel
2117 message encryption and decryption is as described above. This
2118 different processing of channel messages with router to router
2119 connection is because channel keys are cell specific. All cells has
2120 their own channel keys thus the channel message traveling from one
2121 cell to another must be protected as it would be any normal SILC
2126 2.5.3 Private Message Encryption And Decryption
2128 By default, private message in SILC are protected by session keys.
2129 In this case the private message encryption and decryption process is
2130 equivalent to normal packet encryption and decryption.
2132 However, private messages can be protected with private message key
2133 which causes the packet to be special packet. The procedure in this
2134 case is very much alike to channel packets. The actual private message
2135 is encrypted with the private message key and other parts of the
2136 packet is encrypted with the session key. See 2.7 Packet Padding
2137 Generation for more information about padding on special packets.
2139 The difference from channel message processing is that server or router
2140 en route never decrypts the actual private message, as it does not
2141 have the key to do that. Thus, when sending packets between router
2142 the processing is same as in any other case as well; the packet's header
2143 and padding is protected by the session key and the data area is not
2146 The true receiver of the private message, client, that is, is able
2147 to decrypt the private message as it shares the key with the sender
2152 2.6 Packet MAC Generation
2154 Data integrity of a packet is protected by including a message
2155 authentication code (MAC) at the end of the packet. The MAC is computed
2156 from shared secret MAC key, that is established by the SILC Key Exchange
2157 protocol, and from the original contents of the packet. The MAC is
2158 always computed before the packet is encrypted, although after it is
2159 compressed if compression is used.
2161 The MAC is computed from entire packet. Every bit of data in the packet,
2162 including SILC Packet Header is used in the MAC computing. This way
2163 the entire packet becomes authenticated.
2165 If the packet is special packet MAC is computed from the entire packet
2166 but part of the packet may be encrypted before the MAC is computed.
2167 This is case, for example, with channel messages where the message data
2168 is encrypted with key that server may not now. In this case the MAC
2169 has been computed from the encrypted data.
2171 See [SILC1] for defined and allowed MAC algorithms.
2175 2.7 Packet Padding Generation
2177 Padding is needed in the packet because the packet is encrypted. It
2178 must always be multiple by eight (8) or multiple by the size of the
2179 cipher's block size, which ever is larger. The padding is always
2182 For normal packets the padding is added after the SILC Packet Header
2183 and between the Data Payload area. The padding for normal packets
2184 are calculated as follows:
2187 padding length = 16 - ((packet length - 2) % 16)
2190 The 16 is the maximum padding allowed in SILC packet. Two (2) is
2191 subtracted from the true length of the packet because two (2) bytes
2192 is not encrypted in SILC Packet Header, see section 2.2 SILC Packet
2193 Header. Those two bytes that are not encrypted must not be calculated
2194 to the padding length.
2196 For special packets the padding calculation may be different as special
2197 packets may be encrypted differently. In these cases the encrypted
2198 data area must already be multiple by the block size thus in this case
2199 the padding is calculated only for SILC Packet Header, not for any
2200 other area of the packet. The same algorithm works in this case as
2201 well, except that the `packet length' is now the SILC Packet Header
2202 length. In this case, as well, two (2) is subtracted from the
2205 The padding must be random data, preferably, generated by
2206 cryptographically strong random number generator.
2210 2.8 Packet Compression
2212 SILC Packets may be compressed. In this case the data payload area
2213 is compressed and all other areas of the packet must remain as they
2214 are. After compression is performed for the data area, the length
2215 field of Packet Header must be set to the compressed length of the
2218 The compression must always be applied before encryption. When
2219 the packet is received and decrypted the data area must be decompressed.
2220 Note that the true sender of the packet must apply the compression and
2221 the true receiver of the packet must apply the decompression. Any
2222 server or router en route must not decompress the packet.
2228 The sender of the packet must assemble the SILC Packet Header with
2229 correct values. It must set the Source ID of the header as its own
2230 ID, unless it is forwarding the packet. It must also set the Destination
2231 ID of the header to the true destination. If the destination is client
2232 it will be Client ID, if it is server it will be Server ID and if it is
2233 channel it will be Channel ID.
2235 If the sender wants to compress the packet it must apply the
2236 compression now. Sender must also compute the padding as described
2237 in above sections. Then sender must compute the MAC of the packet.
2239 Then sender encrypts the packet as has been described in above
2240 sections according whether the packet is normal packet or special
2241 packet. The computed MAC must not be encrypted.
2245 2.10 Packet Reception
2247 On packet reception the receiver must check that all fields in the
2248 SILC Packet Header are valid sain. It must check the flags of the
2249 header and act accordingly. It must also check the MAC of the packet
2250 and if it is to be failed the packet must be discarded. Also if the
2251 header of the packet includes any bad fields the packet must be
2254 See above sections on the decryption process of the received packet.
2256 The receiver must also check that the ID's in the header are valid
2257 ID's. Unsupported ID types or malformed ID's must cause packet
2258 rejection. The padding on the reception is always ignored.
2260 The receiver must also check the packet type and start parsing the
2261 packet according to the type. However, note the above sections on
2262 special packet types and their parsing.
2268 Routers are the primary entities in the SILC network that takes care
2269 of packet routing. However, normal servers routes packets as well, for
2270 example, when they are routing channel message to the local clients.
2271 Routing is quite simple as every packet tells the true origin and the
2272 true destination of the packet.
2274 It is still recommended for routers that has several routing connections
2275 to create route cache for those destinations that has faster route than
2276 the router's primary route. This information is available for the router
2277 when other router connects to the router. The connecting party then
2278 sends all of its locally connected clients, server and channels. These
2279 informations helps to create the route cache. Also, when new channels
2280 are created to a cell its information is broadcasted to all routers
2281 in the network. Channel ID's are based on router's ID thus it is easy
2282 to create route cache based on these informations. If faster route for
2283 destination does not exist in router's route cache the packet must be
2284 routed to the primary route (default route).
2286 For server who receives a packet to be routed to its locally connected
2287 client the server must check whether the particular packet type is
2288 allowed to be routed to the client. Not all packets may be sent by
2289 some odd entity to client that is indirectly connected to the sender.
2290 See section 2.3 SILC Packet Types and paragraph about indirectly connected
2291 entities and sending packets to them. The section mentions the packets
2292 that may be sent to indirectly connected entities. It is clear that some
2293 server cannot send, for example, disconnect packet to client that is not
2294 directly connected to the server.
2298 2.12 Packet Forwarding
2300 Currently SILC command packets may be forwarded from one entity to another.
2301 Any other packet currently cannot be forwarded but support for more packet
2302 types may be added if needed. Forwarding is usually used by server to
2303 forward some command request coming from client to the router as the server
2304 may be incapable to handle the request. Forwarding may be only one hop
2305 long; the receiver of the packet with Forwarded flag set in the SILC
2306 Packet header must not forward the packet any further.
2308 The normal scenario is that client sends JOIN command to the server which
2309 is not able to create the channel as there are no local clients on the
2310 channel. Channels are created always by the router of the cell thus the
2311 packet must be forwarded to the router. The server forwards the original
2312 packet coming from client to the router after it has set the Forwarded
2313 flag to the SILC Packet header.
2315 Router receiving the packet knows that the packet has to be processed
2316 specially by checking the flags and the Forwarded flag in the SILC Packet
2317 header. After router has joined the client to the channel (and perhaps
2318 created a new channel) it sends normal command reply packet to the
2319 client. However, as the router doesn't have direct connection to the
2320 client the packet is sent through the server. Server detects that
2321 the command reply packet is destined to the client and sends it to
2326 2.13 Packet Broadcasting
2328 SILC packets may be broadcasted in SILC network. However, only router
2329 server may send or receive broadcast packets. Client and normal server
2330 must not send broadcast packets and they must ignore broadcast packets
2331 if they receive them. Broadcast packets are sent by setting Broadcast
2332 flag to the SILC packet header.
2334 Broadcasting packets means that the packet is sent to all routers in
2335 the SILC network, except to the router that sent the packet. The router
2336 receiving broadcast packet must send the packet to its primary route.
2337 The fact that SILC routers may have several router connections may
2338 cause problems, such as race conditions inside the SILC network, if
2339 care is not taken when broadcasting packets. Router must not send
2340 the broadcast packet to any other route except to its primary route.
2342 If the primary route of the router is the original sender of the packet
2343 the packet must not be sent to the primary route. This may happen
2344 if router has several router connections and some other router uses
2345 the router as its primary route.
2347 Routers use broadcast packets to broadcast for example information
2348 about newly registered clients, servers, channels etc. so that all the
2349 routers may keep these informations up to date.
2353 2.14 Packet Tunneling
2355 Tunneling is a feature that is available in SILC protocol. Tunneling
2356 means that extra SILC Packet Header is applied to the original packet
2357 and thus hiding the original packet entirely. There can be some
2358 interesting applications using tunneling, such as, using ID's based on
2359 private network IP addresses inside in the tunneled packet. This can
2360 open many interesting features relating to connecting to private network
2361 from the Internet with SILC and many more. However, this feature is
2362 optional currently in SILC as there does not exist thorough analysis of
2363 this feature. It is with out a doubt that there will be many more
2364 applications that has not yet been discovered. Thus, it is left
2365 to Internet Community to investigate the use of tunneling in SILC
2366 protocol. This document is updated according those investigations
2367 and additional documents on the issue may be written.
2371 3 Security Considerations
2373 Security is central to the design of this protocol, and these security
2374 considerations permeate the specification.
2380 [SILC1] Riikonen, P., "Secure Internet Live Conferencing (SILC),
2381 Protocol Specification", Internet Draft, June 2000.
2383 [SILC3] Riikonen, P., "SILC Key Exchange and Authentication
2384 Protocols", Internet Draft, June 2000.
2386 [IRC] Oikarinen, J., and Reed D., "Internet Relay Chat Protocol",
2389 [SSH-TRANS] Ylonen, T., et al, "SSH Transport Layer Protocol",
2392 [PGP] Callas, J., et al, "OpenPGP Message Format", RFC 2440,
2395 [SPKI] Ellison C., et al, "SPKI Certificate Theory", RFC 2693,
2398 [PKIX-Part1] Housley, R., et al, "Internet X.509 Public Key
2399 Infrastructure, Certificate and CRL Profile", RFC 2459,
2402 [Schneier] Schneier, B., "Applied Cryptography Second Edition",
2403 John Wiley & Sons, New York, NY, 1996.
2405 [Menezes] Menezes, A., et al, "Handbook of Applied Cryptography",
2408 [OAKLEY] Orman, H., "The OAKLEY Key Determination Protocol",
2409 RFC 2412, November 1998.
2411 [ISAKMP] Maughan D., et al, "Internet Security Association and
2412 Key Management Protocol (ISAKMP)", RFC 2408, November
2415 [IKE] Harkins D., and Carrel D., "The Internet Key Exhange
2416 (IKE)", RFC 2409, November 1998.
2418 [HMAC] Krawczyk, H., "HMAC: Keyed-Hashing for Message
2419 Authentication", RFC 2104, February 1997.
2431 EMail: priikone@poseidon.pspt.fi
2433 This Internet-Draft expires 13 May 2001
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