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-.ds RH 6 October 2000
+.ds RH XX April 2001
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.nf
Network Working Group P. Riikonen
Internet-Draft
-draft-riikonen-silc-ke-auth-02.txt XXXXXXXXXXXXXX
-Expires: XXX
+draft-riikonen-silc-ke-auth-02.txt XX April 2001
+Expires: XX October 2001
.in 3
Abstract
This memo describes two protocols used in the Secure Internet Live
-Conferencing (SILC) protocol specified in the Secure Internet Live
+Conferencing (SILC) protocol, specified in the Secure Internet Live
Conferencing, Protocol Specification internet-draft [SILC1]. The
SILC Key Exchange (SKE) protocol provides secure key exchange between
two parties resulting into shared secret key material. The protocol
-is based on Diffie Hellman key exchange algorithm and its functionality
+is based on Diffie-Hellman key exchange algorithm and its functionality
is derived from several key exchange protocols. SKE uses best parts
of the SSH2 Key Exchange protocol, Station-To-Station (STS) protocol
and the OAKLEY Key Determination protocol [OAKLEY].
The SILC Connection Authentication protocol provides user level
authentication used when creating connections in SILC network. The
protocol is transparent to the authentication data which means that it
-can be used to authenticate the user with, for example, passphrase
+can be used to authenticate the user with, for example, pass phrase
(pre-shared- secret) or public key (and certificate).
.nf
1 Introduction .................................................. 2
+ 1.1 Requirements Terminology .................................. 3
2 SILC Key Exchange Protocol .................................... 3
- 2.1 Key Exchange Payloads ..................................... 3
+ 2.1 Key Exchange Payloads ..................................... 4
2.1.1 Key Exchange Start Payload .......................... 4
- 2.1.2 Key Exchange Payload ................................ 7
+ 2.1.2 Key Exchange Payload ................................ 8
2.2 Key Exchange Procedure .................................... 10
2.3 Processing the Key Material ............................... 12
2.4 SILC Key Exchange Groups .................................. 13
- 2.4.1 diffie-hellman-group1 ............................... 13
+ 2.4.1 diffie-hellman-group1 ............................... 14
2.4.2 diffie-hellman-group2 ............................... 14
- 2.5 Key Exchange Status Types ................................. 14
+ 2.5 Key Exchange Status Types ................................. 15
3 SILC Connection Authentication Protocol ....................... 16
3.1 Connection Auth Payload ................................... 17
3.2 Connection Authentication Types ........................... 18
3.2.1 Passphrase Authentication ........................... 18
- 3.2.2 Public Key Authentication ........................... 18
+ 3.2.2 Public Key Authentication ........................... 19
3.3 Connection Authentication Status Types .................... 19
-4 Security Considerations ....................................... 19
-5 References .................................................... 19
-6 Author's Address .............................................. 20
+4 Security Considerations ....................................... 20
+5 References .................................................... 20
+6 Author's Address .............................................. 21
.ti 0
Conferencing, Protocol Specification Internet-Draft [SILC1]. The
SILC Key Exchange (SKE) protocol provides secure key exchange between
two parties resulting into shared secret key material. The protocol
-is based on Diffie Hellman key exchange algorithm and its functionality
+is based on Diffie-Hellman key exchange algorithm and its functionality
is derived from several key exchange protocols. SKE uses best parts
of the SSH2 Key Exchange protocol, Station-To-Station (STS) protocol
and the OAKLEY Key Determination protocol.
The SILC Connection Authentication protocol provides user level
authentication used when creating connections in SILC network. The
protocol is transparent to the authentication data which means that it
-can be used to authenticate the user with, for example, passphrase
+can be used to authenticate the user with, for example, pass phrase
(pre-shared- secret) or public key (and certificate).
The basis of secure SILC session requires strong and secure key exchange
provided by the SILC protocol.
+.ti 0
+1.1 Requirements Terminology
+
+The keywords MUST, MUST NOT, REQUIRED, SHOULD, SHOULD NOT, RECOMMENDED,
+MAY, and OPTIONAL, when they appear in this document, are to be
+interpreted as described in [RFC2119].
+
+
.ti 0
2 SILC Key Exchange Protocol
with this key except channel messages; channels has their own keys and
they are not exchanged with this protocol.
-The Diffie-Hellman implementation used in the SILC should be compliant
+The Diffie-Hellman implementation used in the SILC SHOULD be compliant
to the PKCS #3.
During the key exchange procedure public data is sent between initiator
and responder. This data is later used in the key exchange procedure.
There are several payloads used in the key exchange. As for all SILC
-packets, SILC Packet Header, described in [SILC2], is at the start of all
-packets, the same is done with these payloads as well. All fields in
-all payloads are always in MSB (most significant byte first) order.
-Following descriptions of these payloads.
+packets, SILC Packet Header, described in [SILC2], is at the start of
+all packets, the same is done with these payloads as well. All the
+fields in the payloads are always in MSB (most significant byte first)
+order. Following descriptions of these payloads.
.ti 0
2.1.1 Key Exchange Start Payload
-Key exchange between two entities always begins with the
+The key exchange between two entities MUST be started by sending the
SILC_PACKET_KEY_EXCHANGE packet containing Key Exchange Start Payload.
-Initiator sends the Key Exchange Start Payload to the responder filled with
-all security properties it supports. The responders then checks whether
-it supports the security properties.
+Initiator sends the Key Exchange Start Payload to the responder filled
+with all security properties it supports. The responder then checks
+whether it supports the security properties.
It then sends a Key Exchange Start Payload to the initiator filled with
-security properties it selected from the original payload. The payload sent
-by responder must include only one chosen property per list.
+security properties it selected from the original payload. The payload
+sent by responder MUST include only one chosen property per list.
The Key Exchange Start Payload is used to tell connecting entities what
security properties and algorithms should be used in the communication.
The Key Exchange Start Payload is sent only once per session. Even if
-the PFS (Perfect Forward Secrecy) flag is se the Key Exchange Start Payload
-is not re-sent. When PFS is desired the Key Exchange Payloads are sent
-to negotiate new key material. The procedure is equivalent to the very
-first negotiation except that the Key Exchange Start Payload is not sent.
+the PFS (Perfect Forward Secrecy) flag is set the Key Exchange Start
+Payload is not re-sent. When PFS is desired the Key Exchange Payloads
+are sent to negotiate new key material. The procedure is equivalent to
+the very first negotiation except that the Key Exchange Start Payload
+is not sent.
-As this payload is used only with the very first key exchnage the payload
+As this payload is used only with the very first key exchange the payload
is never encrypted, as there are no keys to encrypt it with.
-A cookie is also sent in this payload. A cookie is used to uniform the
+A cookie is also sent in this payload. A cookie is used to randomize the
payload so that none of the key exchange parties can determine this
-payload before hand. The cookie must be returned to the original sender
-by the responder.
+payload before the key exchange procedure starts. The cookie MUST be
+returned to the original sender by the responder.
Following diagram represents the Key Exchange Start Payload. The lists
-mentioned below are always comma (`,') separated and the list must
+mentioned below are always comma (`,') separated and the list MUST
not include spaces (` ').
-
-
-
-
-
-
.in 5
.nf
1 2 3
o Flags (1 byte) - Indicates flags to be used in the key
exchange. Several flags can be set at once by ORing the
- flags together. Following flags are reserved for this field.
+ flags together. The following flags are reserved for this
+ field:
No flags 0x00
Perfect Forward Secrecy (PFS) to be used in the
key exchange protocol. If not set, re-keying
is performed using the old key. See the [SILC1]
- for more information on this issue. When PFS is used,
- re-keying and creating new keys for any particular
- purpose will cause new key exchange. In this key
- exchange only the Key Exchange Payload is sent and
- the Key Exchange Start Payload must not be sent.
- When doing PFS the Key Exchange Payloads are
- encrypted with the old keys. With the PFS, the
- Mutual Authentication flag must be ignored.
+ for more information on this issue. When PFS is
+ used, re-keying and creating new keys for any
+ particular purpose MUST cause new key exchange.
+ In this key exchange only the Key Exchange Payload
+ is sent and the Key Exchange Start Payload MUST
+ NOT be sent. When doing PFS the Key Exchange
+ Payloads are encrypted with the old keys. With
+ the PFS, the Mutual Authentication flag MUST be
+ ignored.
Mutual Authentication 0x04
- Both of the parties will perform authenetication
+ Both of the parties will perform authentication
by providing signed data for the other party to
verify. By default, only responder will provide
the signature data. If this is set then the
- inititator must also provide it. Initiator may
- set this but also responder may set this even if
+ initiator must also provide it. Initiator MAY
+ set this but also responder MAY set this even if
initiator did not set it.
Rest of the flags are reserved for the future and
- must not be set.
+ MUST NOT be set.
o Payload Length (2 bytes) - Length of the entire Key Exchange
Start payload, not including any other field.
Key Exchange payload is used to deliver the public key (or certificate),
the computed Diffie-Hellman public value and possibly signature data
from one party to the other. When initiator is using this payload
-and the Mutual Authentication flag is not set then the initiator must
-not provide the signature data. If the flag is set then the initiator
-must provide the signature data so that the responder may verify it.
+and the Mutual Authentication flag is not set then the initiator MUST
+NOT provide the signature data. If the flag is set then the initiator
+MUST provide the signature data so that the responder can verify it.
The Mutual Authentication flag is usually used only if a separate
authentication protocol will not be executed for the initiator of the
-prtocool. This is case for example when the SKE is performed between
+protocol. This is case for example when the SKE is performed between
two SILC clients. In normal case, where client is connecting to the
-server or server is connecting to the router the Mutual Authentication
+server, or server is connecting to the router the Mutual Authentication
flag is not necessary.
When performing re-key with PFS selected this is the only payload that
-is sent in the SKE protocol. The Key Exchange Start Payload is not sent
-at all. However, this payload does not have all the fields present.
-In re-key with PFS the public key and a possible signature data should
-not be present. If they are present they must be ignored. The only
-field that is present is the public data that is used to create the
-new key material. In the re-key the Mutual Authentication flag must
+is sent in the SKE protocol. The Key Exchange Start Payload MUST NOT
+be sent at all. However, this payload does not have all the fields
+present. In the re-key with PFS the public key and a possible signature
+data SHOULD NOT be present. If they are present they MUST be ignored.
+The only field that is present is the Public Data that is used to create
+the new key material. In the re-key the Mutual Authentication flag MUST
also be ignored.
This payload is sent inside SILC_PACKET_KEY_EXCHANGE_1 and inside
certificate specification in [PKIX-Part1]. See OpenPGP
certificate specification in [PGP]. See SPKI certificate
specification in [SPKI]. If this field includes zero (0)
- or unsupported type number the protocol must be aborted
- sending SILC_PACKET_FAILURE message and the connection should
+ or unsupported type number the protocol MUST be aborted
+ sending SILC_PACKET_FAILURE message and the connection SHOULD
be closed immediately.
-o Public Key (or certicicate) (variable length) - The
+o Public Key (or certificate) (variable length) - The
public key or certificate.
o Public Data Length (2 bytes) - The length of the Public Data
not including any other field.
o Signature Data (variable length) - The signature signed
- by the sender. The receiver of this signature must
- verify it. The verification is done using the public
- key received in this same payload. See section 2.2
- Key Exchange Procedure for detailed description how
- to produce the signature. If the Mutual Authentication
- flag is not set then initiator must not provide this
- field and the Signature Length field must be set to zero (0)
- value. If the flag is set then also the initiator must
- provide this field. The responder always provides this
- field.
+ by the sender. The receiver of this signature MUST
+ verify it. The verification is done using the sender's
+ public key. See section 2.2 Key Exchange Procedure for
+ detailed description how to produce the signature. If
+ the Mutual Authentication flag is not set then initiator
+ MUST NOT provide this field and the Signature Length field
+ MUST be set to zero (0) value. If the flag is set then
+ also the initiator MUST provide this field. The responder
+ MUST always provide this field.
.in 3
responder.
If the Mutual Authentication flag is set then initiator
- must also produce signature data SIGN_i which the responder
- will verify. The initiator must compute a hash value
+ MUST also produce signature data SIGN_i which the responder
+ will verify. The initiator MUST compute a hash value
HASH_i = hash(Key Exchange Start Payload | public key
(or certificate) | e). It then signs the HASH_i value with
its private key resulting a signature SIGN_i.
initiator.
If the Mutual Authentication flag is set then the responder
- should verify that the public key provided in the payload
+ SHOULD verify that the public key provided in the payload
is authentic, or if certificates are used it verifies the
- certificate. The responder may accept the public key without
+ certificate. The responder MAY accept the public key without
verifying it, however, doing so may result to insecure key
exchange (accepting the public key without verifying may be
desirable for practical reasons on many environments. For
3. Initiator verifies that the public key provided in
the payload is authentic, or if certificates are used
- it verifies the certificate. The initiator may accept
+ it verifies the certificate. The initiator MAY accept
the public key without verifying it, however, doing
so may result to insecure key exchange (accepting the
public key without verifying may be desirable for
HASH using the received public key.
-If any of these phases is to fail SILC_PACKET_FAILURE is sent to
-indicate that the key exchange protocol has failed, and the connection
-should be closed immediately. Any other packets must not be sent or
+If any of these phases is to fail the SILC_PACKET_FAILURE MUST be sent
+to indicate that the key exchange protocol has failed, and the connection
+SHOULD be closed immediately. Any other packets MUST NOT be sent or
accepted during the key exchange except the SILC_PACKET_KEY_EXCHANGE_*,
SILC_PACKET_FAILURE and SILC_PACKET_SUCCESS packets.
each other. After this both parties will start using the new keys.
-
-
.ti 0
2.3 Processing the Key Material
other security parameters used in the communication. Key Exchange
protocol produces a hash value HASH as well.
-Keys are derived from the key material as follows:
+The keys MUST be derived from the key material as follows:
.in 6
Sending Initial Vector (IV) = hash(0 | KEY | HASH)
receiving IV for receiving).
The Encryption Keys are derived as well from the hash(). If the hash()
-output is too short for the encryption algorithm more key material is
-produced in following manner:
+output is too short for the encryption algorithm more key material MUST
+be produced in the following manner:
.in 6
K1 = hash(2 | KEY | HASH)
output.
These procedures are performed by all parties of the key exchange
-protocol. This must be done before the protocol has been ended by
+protocol. This MUST be done before the protocol has been ended by
sending the SILC_PACKET_SUCCESS packet.
+This same procedure is used in the SILC is some other circumstances
+as well. Any changes to this procedure is mentioned separately when
+this procedure is needed. See the [SILC1] and the [SILC2] for these
+circumstances.
+
.ti 0
2.4 SILC Key Exchange Groups
Following groups may be used in the SILC Key Exchange protocol. The
-first group diffie-hellman-group1 is mandatory, other groups maybe
+first group diffie-hellman-group1 is REQUIRED, other groups MAY be
negotiated to be used in the connection with Key Exchange Start Payload
-and SILC_PACKET_KEY_EXCHANGE packet. However, the first group must be
+and SILC_PACKET_KEY_EXCHANGE packet. However, the first group MUST be
proposed in the Key Exchange Start Payload regardless of any other
requested group (however, it does not have to be the first in the list).
.ti 0
2.4.1 diffie-hellman-group1
-The length of this group is 1024 bits. This is mandatory group.
+The length of this group is 1024 bits. This is REQUIRED group.
The prime is 2^1024 - 2^960 - 1 + 2^64 * { [2^894 pi] + 129093 }.
Its decimal value is
.ti 0
2.4.2 diffie-hellman-group2
-The length of this group is 1536 bits. This is optional group.
+The length of this group is 1536 bits. This is OPTIONAL group.
The prime is 2^1536 - 2^1472 - 1 + 2^64 * { [2^1406 pi] + 741804 }.
Its decimal value is
.ti 0
2.5 Key Exchange Status Types
-This section defines all key exchange protocol status types that may be
-returned in the SILC_PACKET_SUCCESS or SILC_PACKET_FAILURE packets to
-indicate the status of the protocol. Implementations may map the
+This section defines all key exchange protocol status types that may
+be returned in the SILC_PACKET_SUCCESS or SILC_PACKET_FAILURE packets
+to indicate the status of the protocol. Implementations may map the
status types to human readable error message. All types except the
-SILC_SKE_STATUS_OK type must be sent in SILC_PACKET_FAILURE packet.
-The length of status is 32 bits (4 bytes). Following status types are
-defined:
+SILC_SKE_STATUS_OK type MUST be sent in SILC_PACKET_FAILURE packet.
+The length of status is 32 bits (4 bytes). The following status types
+are defined:
.in 6
0 SILC_SKE_STATUS_OK
1 SILC_SKE_STATUS_ERROR
- Unknown error occured. No specific error type is defined.
+ Unknown error occurred. No specific error type is defined.
2 SILC_SKE_STATUS_BAD_PAYLOAD
.in 3
-
-
-
.ti 0
3 SILC Connection Authentication Protocol
Purpose of Connection Authentication protocol is to authenticate the
connecting party with server. Usually connecting party is client but
-server may connect to server as well. Its other purpose is to provide
-information for the server about which type of connection this is.
-The type defines whether this is client, server or router connection.
-Server uses this information to create the ID for the connection. After
-the authentication protocol has been successfully completed
-SILC_PACKET_NEW_ID must be sent to the connecting party by the server.
-See section New ID Payload in [SILC2] for detailed description for this
-packet's payload.
-
-Server must verify the authentication data received and if it is to fail
-the authentication must be failed by sending SILC_PACKET_FAILURE packet.
+server may connect to router server as well. Its other purpose is to
+provide information for the server about which type of connection this
+is. The type defines whether this is client, server or router
+connection. Server uses this information to create the ID for the
+connection.
+
+After the authentication protocol has been successfully completed
+SILC_PACKET_NEW_ID must be sent to the connecting client by the server.
+See the [SILC1] for the details of the connecting procedure.
+
+Server MUST verify the authentication data received and if it is to fail
+the authentication MUST be failed by sending SILC_PACKET_FAILURE packet.
If everything checks out fine the protocol is ended by server by sending
SILC_PACKET_SUCCESS packet.
-The protocol is executed after the SILC Key Exchange protocol. It must
-not be executed in any other time. As it is performed after key exchange
+The protocol is executed after the SILC Key Exchange protocol. It MUST
+NOT be executed in any other time. As it is performed after key exchange
protocol all traffic in the connection authentication protocol is
encrypted with the exchanged keys.
-The protocol is started by the connecting party by sending
+The protocol MUST be started by the connecting party by sending the
SILC_PACKET_CONNECTION_AUTH packet with Connection Auth Payload,
-described in the next section. This payload must include the
-authentication data. Authentication data is set according
-authentication method that must be known by both parties. If connecting
-party does not know what is the mandatory authentication method it may
+described in the next section. This payload MUST include the
+authentication data. The authentication data is set according
+authentication method that MUST be known by both parties. If connecting
+party does not know what is the mandatory authentication method it MAY
request it from the server by sending SILC_PACKET_CONNECTION_AUTH_REQUEST
packet. This packet is not part of this protocol and is described in
section Connection Auth Request Payload in [SILC2]. However, if
See [SILC1] and section Connection Auth Request Payload in [SILC2] also
for the list of different authentication methods. Authentication method
-may also be NONE, in which case the server does not require
-authentication at all. However, in this case the protocol still must be
+MAY also be NONE, in which case the server does not require
+authentication at all. However, in this case the protocol still MUST be
executed; the authentication data just is empty indicating no
authentication is required.
to have plaintext passphrase. 3.2.1 Passphrase Authentication for
more information.
-
If authentication method is public key authentication the authentication
data is signature of the hash value HASH plus Key Exchange Start Payload,
-established by the SILC Key Exchange protocol. This signature must then
+established by the SILC Key Exchange protocol. This signature MUST then
be verified by the server. See section 3.2.2 Public Key Authentication
for more information.
-The connecting party of this protocol must wait after successful execution
+The connecting client of this protocol MUST wait after successful execution
of this protocol for the SILC_PACKET_NEW_ID packet where it will receive
-the ID it will be using in the SILC network. Connecting party cannot
+the ID it will be using in the SILC network. The connecting client cannot
start normal SILC session (sending messages or commands) until it has
received its ID. The ID's are always created by the server except
-for server to server connection where servers create their own ID's.
-
+for server to router connection where servers create their own ID's.
.ti 0
Client sends this payload to authenticate itself to the server. Server
connecting to another server also sends this payload. Server receiving
-this payload must verify all the data in it and if something is to fail
-the authentication must be failed by sending SILC_PACKET_FAILURE packet.
+this payload MUST verify all the data in it and if something is to fail
+the authentication MUST be failed by sending SILC_PACKET_FAILURE packet.
The payload may only be sent with SILC_PACKET_CONNECTION_AUTH packet.
-It must not be sent in any other packet type. Following diagram
+It MUST NOT be sent in any other packet type. Following diagram
represent the Connection Auth Payload.
o Connection Type (2 bytes) - Indicates the type of the
connection. See section Connection Auth Request Payload
- in [SILC2] for the list of connection types. This field must
- include valid connection type or the packet must be discarded
- and authentication must be failed.
+ in [SILC2] for the list of connection types. This field MUST
+ include valid connection type or the packet MUST be discarded
+ and authentication MUST be failed.
o Authentication Data (variable length) - The actual
authentication data. Contents of this depends on the
the other end, for example server.
If the passphrase matches with the one in the server's end the
-authentication is successful. Otherwise SILC_PACKET_FAILURE must be
+authentication is successful. Otherwise SILC_PACKET_FAILURE MUST be
sent to the sender and the protocol execution fails.
-This is required authentication method to be supported by all SILC
+This is REQUIRED authentication method to be supported by all SILC
implementations.
Public key authentication may be used if passphrase based authentication
is not desired. The public key authentication works by sending a
signature as authentication data to the other end, say, server. The
-server must then verify the signature by the public key of the sender,
+server MUST then verify the signature by the public key of the sender,
which the server has received earlier in SKE protocol.
The signature is computed using the private key of the sender by signing
the HASH value provided by the SKE protocol previously, and the Key
Exchange Start Payload from SKE protocol that was sent to the server.
-The server must verify the data, thus it must keep the HASH and the
+The server MUST verify the data, thus it must keep the HASH and the
Key Exchange Start Payload saved during SKE and authentication protocols.
If the verified signature matches the sent signature, the authentication
were successful and SILC_PACKET_SUCCESS is sent. If it failed the protocol
execution is stopped and SILC_PACKET_FAILURE is sent.
-This is required authentication method to be supported by all SILC
+This is REQUIRED authentication method to be supported by all SILC
implementations.
may be returned in the SILC_PACKET_SUCCESS or SILC_PACKET_FAILURE packets
to indicate the status of the protocol. Implementations may map the
status types to human readable error message. All types except the
-SILC_AUTH_STATUS_OK type must be sent in SILC_PACKET_FAILURE packet.
-The length of status is 32 bits (4 bytes). Following status types are
-defined:
+SILC_AUTH_STATUS_OK type MUST be sent in SILC_PACKET_FAILURE packet.
+The length of status is 32 bits (4 bytes). The following status types
+are defined:
0 SILC_AUTH_OK
5 References
[SILC1] Riikonen, P., "Secure Internet Live Conferencing (SILC),
- Protocol Specification", Internet Draft, June 2000.
+ Protocol Specification", Internet Draft, April 2001.
[SILC2] Riikonen, P., "SILC Packet Protocol", Internet Draft,
- June 2000.
+ April 2001.
+
+[SILC4] Riikonen, P., "SILC Commands", Internet Draft, April 2001.
[IRC] Oikarinen, J., and Reed D., "Internet Relay Chat Protocol",
RFC 1459, May 1993.
[PKCS1] Kalinski, B., and Staddon, J., "PKCS #1 RSA Cryptography
Specifications, Version 2.0", RFC 2437, October 1998.
+[RFC2119] Bradner, S., "Key Words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
.ti 0
6 Author's Address
EMail: priikone@poseidon.pspt.fi
-This Internet-Draft expires 6 Jun 2001
\ No newline at end of file
+This Internet-Draft expires XX October 2001
\ No newline at end of file
.ds RF FORMFEED[Page %]
.ds CF
.ds LH Internet Draft
-.ds RH 6 October 2000
+.ds RH XX April 2001
.ds CH
.na
.hy 0
.nf
Network Working Group P. Riikonen
Internet-Draft
-draft-riikonen-silc-pp-02.txt XXXXXXXXXXXXXX
-Expires: XXX
+draft-riikonen-silc-pp-02.txt XX April 2001
+Expires: XX October 2001
.in 3
Abstract
This memo describes a Packet Protocol used in the Secure Internet Live
-Conferencing (SILC) protocol specified in the Secure Internet Live
+Conferencing (SILC) protocol, specified in the Secure Internet Live
Conferencing, Protocol Specification Internet Draft [SILC1]. This
protocol describes the packet types and packet payloads which defines
the contents of the packets. The protocol provides secure binary packet
.nf
1 Introduction .................................................. 3
+ 1.1 Requirements Terminology .................................. 4
2 SILC Packet Protocol .......................................... 4
2.1 SILC Packet ............................................... 4
2.2 SILC Packet Header ........................................ 5
2.3 SILC Packet Types ......................................... 7
- 2.3.1 SILC Packet Payloads ................................ 15
+ 2.3.1 SILC Packet Payloads ................................ 16
2.3.2 Generic payloads .................................... 16
2.3.2.1 ID Payload .................................. 16
- 2.3.2.2 Argument Payload ............................ 16
- 2.3.2.3 Channel Payload ............................. XXX
- 2.3.2.4 Public Key Payload .......................... XXX
- 2.3.3 Disconnect Payload .................................. 17
- 2.3.4 Success Payload ..................................... 18
- 2.3.5 Failure Payload ..................................... 18
- 2.3.6 Reject Payload ...................................... 19
- 2.3.7 Notify Payload ...................................... 20
+ 2.3.2.2 Argument Payload ............................ 17
+ 2.3.2.3 Channel Payload ............................. 18
+ 2.3.2.4 Public Key Payload .......................... 19
+ 2.3.3 Disconnect Payload .................................. 19
+ 2.3.4 Success Payload ..................................... 19
+ 2.3.5 Failure Payload ..................................... 20
+ 2.3.6 Reject Payload ...................................... 21
+ 2.3.7 Notify Payload ...................................... 22
2.3.8 Error Payload ....................................... 21
- 2.3.9 Channel Message Payload ............................. 22
- 2.3.10 Channel Key Payload ................................ 24
- 2.3.11 Private Message Payload ............................ 26
- 2.3.12 Private Message Key Payload ........................ 27
- 2.3.13 Command Payload .................................... 28
- 2.3.14 Command Reply Payload .............................. 29
- 2.3.15 Connection Auth Request Payload .................... 29
- 2.3.16 New ID Payload ..................................... 30
- 2.3.17 New Client Payload ................................. 31
- 2.3.18 New Server Payload ................................. 32
- 2.3.19 New Channel Payload ................................ 33
- 2.3.20 Key Agreement Payload .............................. XXX
- 2.4 SILC ID Types ............................................. 39
- 2.5 Packet Encryption And Decryption .......................... 39
- 2.5.1 Normal Packet Encryption And Decryption ............. 39
- 2.5.2 Channel Message Encryption And Decryption ........... 40
- 2.5.3 Private Message Encryption And Decryption ........... 41
- 2.6 Packet MAC Generation ..................................... 41
- 2.7 Packet Padding Generation ................................. 42
- 2.8 Packet Compression ........................................ 42
- 2.9 Packet Sending ............................................ 43
- 2.10 Packet Reception ......................................... 43
- 2.11 Packet Routing ........................................... 44
- 2.12 Packet Broadcasting ...................................... 45
-3 Security Considerations ....................................... 46
-4 References .................................................... 46
-5 Author's Address .............................................. 47
+ 2.3.9 Channel Message Payload ............................. 28
+ 2.3.10 Channel Key Payload ................................ 31
+ 2.3.11 Private Message Payload ............................ 33
+ 2.3.12 Private Message Key Payload ........................ 34
+ 2.3.13 Command Payload .................................... 36
+ 2.3.14 Command Reply Payload .............................. 37
+ 2.3.15 Connection Auth Request Payload .................... 37
+ 2.3.16 New ID Payload ..................................... 38
+ 2.3.17 New Client Payload ................................. 39
+ 2.3.18 New Server Payload ................................. 40
+ 2.3.19 New Channel Payload ................................ 41
+ 2.3.20 Key Agreement Payload .............................. 42
+ 2.3.21 Cell Routers Payload ............................... 43
+ 2.4 SILC ID Types ............................................. 44
+ 2.5 Packet Encryption And Decryption .......................... 44
+ 2.5.1 Normal Packet Encryption And Decryption ............. 45
+ 2.5.2 Channel Message Encryption And Decryption ........... 45
+ 2.5.3 Private Message Encryption And Decryption ........... 46
+ 2.6 Packet MAC Generation ..................................... 47
+ 2.7 Packet Padding Generation ................................. 47
+ 2.8 Packet Compression ........................................ 48
+ 2.9 Packet Sending ............................................ 48
+ 2.10 Packet Reception ......................................... 49
+ 2.11 Packet Routing ........................................... 49
+ 2.12 Packet Broadcasting ...................................... 50
+3 Security Considerations ....................................... 50
+4 References .................................................... 50
+5 Author's Address .............................................. 52
.ti 0
List of Figures
packet.
+.ti 0
+1.1 Requirements Terminology
+
+The keywords MUST, MUST NOT, REQUIRED, SHOULD, SHOULD NOT, RECOMMENDED,
+MAY, and OPTIONAL, when they appear in this document, are to be
+interpreted as described in [RFC2119].
+
+
.ti 0
2 SILC Packet Protocol
The header is variable in length and first two (2) bytes of the
header (thus first two bytes of the packet) are not encrypted. The
first two (2) bytes are the length of the packet which is not encrypted.
-See The following section for description of SILC Packet header. Packets
+See the following section for description of SILC Packet header. Packets
without SILC header or with malformed SILC header must be dropped.
Padding follows the packet header. The purpose of the padding is to
.ti 0
2.2 SILC Packet Header
-The default SILC packet header is applied to all SILC packets and it is
+The SILC packet header is applied to all SILC packets and it is
variable in length. The purpose of SILC Packet header is to provide
-detailed information about the packet. The receiver of the packet uses
-the packet header to parse the packet and gain other relevant parameters
-of the packet.
-
-The following diagram represents the default SILC header format.
-(*) indicates that this field is never encrypted. Other fields are
-always encrypted.
+detailed information about the packet. The receiver of the packet
+uses the packet header to parse the packet and gain other relevant
+parameters of the packet.
+The following diagram represents the SILC packet header. (*) indicates
+that this field is never encrypted. Other fields are always encrypted.
.in 5
.nf
send broadcast packet and normal server cannot send
broadcast packet. Only router server may send broadcast
packet. The router receiving of packet with this flag
- set must send (broadcast) the packet to its primary
+ set MUST send (broadcast) the packet to its primary
route. If router has several router connections the
packet may be sent only to the primary route. See
section 2.13 Packet Broadcasting for description of
+
o Packet Type (1 byte) - Is the type of the packet. Receiver
uses this field to parse the packet. See section 2.3
SILC Packets for list of defined packet types.
defined ID types.
o Source ID (variable length) - The actual source ID that
- indicates who is the original sender of the packet.
+ indicates which is the original sender of the packet.
o Dst ID Type (1 byte) - Indicates the type of ID in the
Destination ID field. See section 2.4 SILC ID Types for
defined ID types.
o Destination ID (variable length) - The actual source ID that
- indicates who is the end receiver of the packet.
+ indicates which is the end receiver of the packet.
.ti 0
the receiver to parse the packet. The packet type is 8 bits, as a one
byte, in length. The range for the packet types are from 0 - 255,
where 0 is never sent and 255 is currently reserved for future
-extensions and must not be defined to any other purpose. Every SILC
-specification compliant implementation should support all of these packet
+extensions and MUST NOT be defined to any other purpose. Every SILC
+specification compliant implementation SHOULD support all of these packet
types.
The below list of the SILC Packet types includes reference to the packet
broadcasted in the SILC network. If the packet is allowed to be sent to
indirectly connected entity it is mentioned separately in the packet
description (unless it is obvious as in private and channel message
-packets). Other packets must not be sent or accepted, if sent, to
+packets). Other packets MUST NOT be sent or accepted, if sent, to
indirectly connected entities.
List of SILC Packet types are defined as follows.
the disconnection is sent inside the packet payload. Client
usually does not send this packet.
- This packet must not be sent as list and the List flag must
- not be set.
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
Payload of the packet: See section 2.3.3 Disconnect Payload
This packet is sent upon successful execution of some protocol.
The status of the success is sent in the packet.
- This packet must not be sent as list and the List flag must
- not be set.
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
Payload of the packet: See section 2.3.4 Success Payload
This packet is sent upon failure of some protocol. The status
of the failure is sent in the packet.
- This packet must not be sent as list and the List flag must
- not be set.
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
Payload of the packet: See section 2.3.5 Failure Payload
4 SILC_PACKET_REJECT
- This packet may be sent upon rejection of some protocol.
+ This packet MAY be sent upon rejection of some protocol.
The status of the rejection is sent in the packet.
- This packet must not be sent as list and the List flag must
- not be set.
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
Payload of the packet: See section 2.3.6 Reject Payload
5 SILC_PACKET_NOTIFY
This packet is used to send notify message, usually from
- server to client, although it may be sent from server to another
- server as well. Client never sends this packet. Server may
+ server to client, although it MAY be sent from server to another
+ server as well. Client MUST NOT send this packet. Server MAY
send this packet to channel as well when the packet is
distributed to all clients on the channel.
6 SILC_PACKET_ERROR
- This packet is sent when an error occurs. Server may
- send this packet. Client never sends this packet. The
- client may entirely ignore the packet, however, server is
- most likely to take action anyway. This packet may be sent
+ This packet is sent when an error occurs. Server MAY
+ send this packet. Client MUST NOT send this packet. The
+ client MAY entirely ignore the packet, however, server is
+ most likely to take action anyway. This packet MAY be sent
to entity that is indirectly connected to the sender.
- This packet must not be sent as list and the List flag must
- not be set.
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
Payload of the packet: See section 2.3.8 Error Payload.
by channel specific keys. Channel Keys are distributed by
SILC_PACKET_CHANNEL_KEY packet.
- This packet must not be sent as list and the List flag must
- not be set.
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
Payload of the packet: See section 2.3.9 Channel Message
Payload
This packet is used to distribute new key for particular
channel. Each channel has their own independent keys that
is used to protect the traffic on the channel. Only server
- may send this packet. This packet may be sent to entity
+ may send this packet. This packet MAY be sent to entity
that is indirectly connected to the sender.
- This packet must not be sent as list and the List flag must
- not be set.
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
Payload of the packet: See section 2.3.10 Channel Key Payload
by session keys established by normal key exchange protocol.
However, it is possible to use specific key to protect private
messages. SILC_PACKET_PRIVATE_MESSAGE_KEY packet is used to
- agree the key with the remote client. Pre-shared key may be
+ agree the key with the remote client. Pre-shared key MAY be
used as well if both of the client knows it, however, it needs
to be agreed outside SILC. See more of this in [SILC1].
- This packet must not be sent as list and the List flag must
- not be set.
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
Payload of the packet: See section 2.3.11 Private Message
Payload
default or to use normal session keys by default, is
implementation specific issue. See more of this in [SILC1].
- This packet must not be sent as list and the List flag must
- not be set.
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
Payload of the packet: See section 2.3.12 Private Message
Key Payload
11 SILC_PACKET_COMMAND
This packet is used to send commands from client to server.
- Server may send this packet to other servers as well. All
+ Server MAY send this packet to other servers as well. All
commands are listed in their own section SILC Command Types
- in [SILC1]. The contents of this packet is command specific.
- This packet may be sent to entity that is indirectly connected
+ in [SILC4]. The contents of this packet is command specific.
+ This packet MAY be sent to entity that is indirectly connected
to the sender.
- This packet must not be sent as list and the List flag must
- not be set.
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
Payload of the packet: See section 2.3.13 Command Payload
This packet is send as reply to the SILC_PACKET_COMMAND packet.
The contents of this packet is command specific. This packet
- maybe sent to entity that is indirectly connected to the sender.
+ MAY be sent to entity that is indirectly connected to the
+ sender.
- This packet must not be sent as list and the List flag must
- not be set.
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
Payload of the packet: See section 2.3.14 Command Reply
Payload and section 2.3.13 Command
This packet is used to start SILC Key Exchange Protocol,
described in detail in [SILC3].
- This packet must not be sent as list and the List flag must
- not be set.
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
Payload of the packet: Payload of this packet is described
in the section SILC Key Exchange
This packet is used as part of the SILC Key Exchange Protocol.
- This packet must not be sent as list and the List flag must
- not be set.
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
Payload of the packet: Payload of this packet is described
in the section SILC Key Exchange
This packet is used as part of the SILC Key Exchange Protocol.
- This packet must not be sent as list and the List flag must
- not be set.
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
Payload of the packet: Payload of this packet is described
in the section SILC Key Exchange
This packet is used to request the authentication method to
be used in the SILC Connection Authentication Protocol. If
initiator of the protocol does not know the mandatory
- authentication method this packet may be used to determine it.
+ authentication method this packet MAY be used to determine it.
- The party receiving this payload must respond with the same
+ The party receiving this payload MUST respond with the same
packet including the mandatory authentication method.
- This packet must not be sent as list and the List flag must
- not be set.
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
Payload of the packet: See section 2.3.15 Connection Auth
Request Payload
+
+
17 SILC_PACKET_CONNECTION_AUTH
This packet is used to start and perform the SILC Connection
the connecting party. The protocol is described in detail in
[SILC3].
- This packet must not be sent as list and the List flag must
- not be set.
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
Payload of the packet: Payload of this packet is described
in the section SILC Authentication
This is used when for example new client is registered to
SILC network. The newly created ID's of these operations are
distributed by this packet. Only server may send this packet,
- however, client must be able to receive this packet.
+ however, client MUST be able to receive this packet.
Payload of the packet: See section 2.3.16 New ID Payload
authentication protocols has been completed. Client sends
various information about itself in this packet.
- This packet must not be sent as list and the List flag must
- not be set.
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
Payload of the packet: See section 2.3.17 New Client Payload
SILC network. This is sent after key exchange and
authentication protocols has been completed. Server sends
this to the router it connected to, or, if router was
- connecting, to the connected router. Server sends
- its Server ID and other information in this packet.
- Client must not send or receive this packet.
+ connecting, to the connected router. Server sends its
+ Server ID and other information in this packet. The client
+ MUST NOT send or receive this packet.
- This packet must not be sent as list and the List flag must
- not be set.
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
Payload of the packet: See section 2.3.18 New Server Payload
This packet is used to notify routers about newly created
channel. Channels are always created by the router and it must
notify other routers about the created channel. Router sends
- this packet to its primary route. Client must not send this
- packet. This packet maybe sent to entity that is indirectly
+ this packet to its primary route. Client MUST NOT send this
+ packet. This packet MAY be sent to entity that is indirectly
connected to the sender.
Payload of the packet: See section 2.3.19 New Channel Payload
[SILC1] for more information. This packet does not have
a payload.
- This packet must not be sent as list and the List flag must
- not be set.
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
23 SILC_PACKET_REKEY_DONE
This packet is used to indicate that re-key is performed and
new keys must be used hereafter. This is sent only if re-key
- was done without PFS option. If PFS is set, this is not sent
- as SILC Key Exchange protocol is executed. This packet does
- not have a payload.
+ was done without PFS option.
- This packet must not be sent as list and the List flag must
- not be set.
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
24 SILC_PACKET_HEARTBEAT
keepalive actions and perform it to both direction in a link.
This packet does not have a payload.
- This packet must not be sent as list and the List flag must
- not be set.
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
25 SILC_PACKET_KEY_AGREEMENT
between another client in the SILC network. If the negotiation
is started it is performed using the SKE protocol. The result of
the negotiation, the secret key material, can be used for
- example as private message key. The server and router must not
+ example as private message key. The server and router MUST NOT
send this packet.
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
+
Payload of the packet: See section 2.3.20 Key Agreement Payload
primary router what other routers (backup routers) exist in the
cell. In case of failure of the primary router in the cell the
first router in the list will act as primary router of the cell.
- This packet may be sent at anytime after connection has been
- registered to the primary router. The client must not send this
+ This packet MAY be sent at anytime after connection has been
+ registered to the primary router. The client MUST NOT send this
packet.
+ This packet MUST NOT be sent as list and the List flag MUST
+ NOT be set.
+
Payload of the packet: See section 2.3.21 Cell Routers Payload
27 - 199
- Currently undefined commands.
+ Currently undefined commands.
200 - 254
- These packet types are reserved for private use and they will not
- be defined by this document.
+ These packet types are reserved for private use and they will
+ not be defined by this document.
- 255 SILC_PACKET_MAX
- This type is reserved for future extensions and currently it
- is not sent.
+
+ 255 SILC_PACKET_MAX
+
+ This type is reserved for future extensions and currently it
+ MUST NOT be sent.
.in 3
2.3.1 SILC Packet Payloads
All payloads resides in the main data area of the SILC packet. However
-all payloads must be at the start of the data area after the default
-SILC packet header and padding. All fields in the packet payload are
-always encrypted, as, they reside in the data area of the packet which
-is always encrypted.
+all payloads MUST be at the start of the data area after the SILC
+packet header and padding. All fields in the packet payload are always
+encrypted, as, they reside in the data area of the packet which is
+always encrypted.
-Payloads described in this section are common payloads that must be
+Payloads described in this section are common payloads that MUST be
accepted anytime during SILC session. Most of the payloads may only
be sent with specific packet type which is defined in the description
of the payload.
are not common in the sense that they could be sent at any time.
These payloads are not described in this section. These are payloads
such as SILC Key Exchange payloads and so on. These are described
-in [SILC1] and [SILC3].
+in [SILC1], [SILC3] and [SILC4].
.ti 0
This payload can be used to send an ID. ID's are variable length thus
this payload provides a way to send variable length ID's.
+
+
+
+
+
+
+
+
+
+
+
The following diagram represents the ID Payload.
.in 5
Argument Payload is used to set arguments for any packet payload that
needs and supports arguments, such as commands. Number of arguments
-associated with a packet must be indicated by the packet payload who
-needs the arguments. Argument Payloads must always reside right after
+associated with a packet MUST be indicated by the packet payload which
+needs the arguments. Argument Payloads MUST always reside right after
the packet payload needing the arguments. Incorrect amount of argument
-payloads must cause rejection of the packet. The following diagram represents
-the Argument Payload.
+payloads MUST cause rejection of the packet. The following diagram
+represents the Argument Payload.
The following diagram represents the Argument Payload.
payload.
o Argument Type (1 byte) - Indicates the type of the argument.
- Every argument may have a specific type that must be defined
+ Every argument may have a specific type that MUST be defined
by the packet payload needing the argument. For example
every command specify a number for each argument that maybe
associated with the command. By using this number the receiver
.ti 0
2.3.2.3 Channel Payload
-Generic Channel Payload may be used information about channel, its name,
-the Channel ID and a mode.
+Generic Channel Payload may be used to send information about channel,
+its name, the Channel ID and a mode.
The following diagram represents the Channel Payload Payload.
type. This field indicates the type of the public key in
the packet. See the [SILC3] for defined public key types.
-o Public Key (or certicicate) (variable length) - The
+o Public Key (or certificate) (variable length) - The
public key or certificate.
.in 3
reason of disconnection is sent to the disconnected party.
The payload may only be sent with SILC_PACKET_DISCONNECT packet. It
-must not be sent in any other packet type. The following diagram represents
-the Disconnect Payload.
-
-
-
-
-
+MUST NOT be sent in any other packet type. The following diagram
+represents the Disconnect Payload.
.in 5
Success payload is sent when some protocol execution is successfully
completed. The payload is simple; indication of the success is sent.
-This maybe any data, including binary or human readable data.
+This may be any data, including binary or human readable data.
.in 5
.nf
.in 6
o Success Indication (variable length) - Indication of
- the success. This maybe for example some flag that
+ the success. This may be for example some flag that
indicates the protocol and the success status or human
readable success message. The true length of this
payload is available by calculating it from the SILC
.in 3
+
.ti 0
2.3.5 Failure Payload
.in 6
o Failure Indication (variable length) - Indication of
- the failure. This maybe for example some flag that
+ the failure. This may be for example some flag that
indicates the protocol and the failure status or human
readable failure message. The true length of this
payload is available by calculating it from the SILC
2.3.6 Reject Payload
This payload is sent when some protocol is rejected to be executed.
-Other operations may send this as well that was rejected. The
+Other operations MAY send this as well that was rejected. The
indication of the rejection is sent in the payload. The indication
may be binary or human readable data.
.in 3
-
-
-
.ti 0
2.3.7 Notify Payload
Notify payload is used to send notify messages. The payload is usually
-sent from server to client, however, server may send it to another
-server as well. This payload may also be sent to a channel. Client must
-not send this payload. The receiver of this payload may totally ignore the
-contents of the payload, however, notify message should be audited.
+sent from server to client, however, server MAY send it to another
+server as well. This payload MAY also be sent to a channel. Client
+MUST NOT send this payload. The receiver of this payload MAY ignore
+the contents of the payload, however, notify message should be audited.
-The payload may only be sent with SILC_PACKET_NOTIFY packet. It must
-not be sent in any other packet type. The following diagram represents the
-Notify Payload.
+The payload may only be sent with SILC_PACKET_NOTIFY packet. It MUST
+not be sent in any other packet type. The following diagram represents
+the Notify Payload.
.in 5
.nf
arguments to be send along the notify message.
.in 3
-The following list of currently defined notify types. The format for notify
-arguments is same as in SILC commands described in [SILC1]. Also, all
-ID's sent in arguments are sent inside ID Payload.
+The following list of currently defined notify types. The format for
+notify arguments is same as in SILC commands described in [SILC4].
+Also, all ID's sent in arguments are sent inside ID Payload.
.in 6
0 SILC_NOTIFY_TYPE_NONE
If no specific notify type apply for the notify message this type
- may be used.
+ MAY be used.
Max Arguments: 1
Arguments: (1) <message>
- The <message> is implementation specific free text string. Receiver
- may ignore this message.
+ The <message> is implementation specific free text string.
+ Receiver MAY ignore this message.
1 SILC_NOTIFY_TYPE_INVITE
Sent when an client is invited to a channel. This is also sent
when the invite list of the channel is changed. This notify type
- is sent between routers and if an client was invited to the
+ is sent between routers and if an client was invited, to the
client as well. In this case the packet is destined to the client.
Max Arguments: 5
of the channel and is provided because the client which receives
this notify packet may not have a way to resolve the name of the
channel from the <Channel ID>. The <sender Client ID> is the
- Client ID who invited the client to the channel. The <adding client>
- and the <removing client> indicates the added or removed client
- from the channel's invite list. The format of the <adding client
- and the <removing client> is defined in the [SILC1] with
+ Client ID which invited the client to the channel. The <adding
+ client> and the <removing client> indicates the added or removed
+ client from the channel's invite list. The format of the <adding
+ client> and the <removing client> is defined in the [SILC4] with
SILC_COMMAND_INVITE command.
- The <adding client> and <removing client> is never sent when the
- packet is destined to a client.
+ The <adding client> and <removing client> MUST NOT be sent when
+ the packet is destined to a client.
2 SILC_NOTIFY_TYPE_JOIN
- Sent when client has joined to a channel. The server must distribute
- this type only to the local clients on the channel and then send
- it to its primary router. The router or server receiving the packet
- distributes this type to the local clients on the channel and
- broadcast it to the network.
+ Sent when client has joined to a channel. The server MUST
+ distribute this type only to the local clients on the channel
+ and then send it to its primary router. The router or server
+ receiving the packet distributes this type to the local clients
+ on the channel and broadcast it to the network.
Max Arguments: 2
Arguments: (1) [<Client ID>] (2) <Channel ID>
Sent when client has left a channel. The server must distribute
this type only to the local clients on the channel and then send
- it to its primary router. The router or server receiving the packet
- distributes this type to the local clients on the channel and
- broadcast it to the network.
+ it to its primary router. The router or server receiving the
+ packet distributes this type to the local clients on the channel
+ and broadcast it to the network.
Max Arguments: 1
Arguments: (1) <Client ID>
- The <Client ID> is the client who left the channel.
+ The <Client ID> is the client which left the channel.
4 SILC_NOTIFY_TYPE_SIGNOFF
- Sent when client signoffs from SILC network. The server must
+ Sent when client signoff from SILC network. The server MUST
distribute this type only to the local clients on the channel and
then send it to its primary router. The router or server receiving
- the packet distributes this type to the local clients on the channel
- and broadcast it to the network.
+ the packet distributes this type to the local clients on the
+ channel and broadcast it to the network.
Max Arguments: 2
Arguments: (1) <Client ID> (2) <message>
- The <Client ID> is the client who left SILC network. The <message>
- is free text string indicating the reason of signoff.
+ The <Client ID> is the client which left SILC network. The
+ <message> is free text string indicating the reason of the signoff.
5 SILC_NOTIFY_TYPE_TOPIC_SET
- Sent when topic is set/changed on a channel. This type must be sent
- only to the clients who is joined on the channel whose topic was
- set or changed.
+ Sent when topic is set/changed on a channel. This type must be
+ sent only to the clients which is joined on the channel which
+ topic was set or changed.
Max Arguments: 2
Arguments: (1) <Client ID> (2) <topic>
- The <Client ID> is the client who set or changed the <topic>.
+ The <Client ID> is the client which set or changed the <topic>.
6 SILC_NOTIFY_TYPE_NICK_CHANGE
- Sent when client changes nick on a channel. The server must
- distribute this type only to the local clients on the channel and
- then send it to its primary router. The router or server receiving
- the packet distributes this type to the local clients on the channel
- and broadcast it to the network.
+ Sent when client changes nick on a channel. The server MUST
+ distribute this type only to the local clients on the channel
+ and then send it to its primary router. The router or server
+ receiving the packet distributes this type to the local clients
+ on the channel and broadcast it to the network.
Max Arguments: 2
Arguments: (1) <Old Client ID> (2) <New Client ID>
- The <Old Client ID> is the old ID of the client who changed the
- nickname. The <New Client ID> is the new ID generated by the change
- of the nickname.
+ The <Old Client ID> is the old ID of the client which changed
+ the nickname. The <New Client ID> is the new ID generated by
+ the change of the nickname.
7 SILC_NOTIFY_TYPE_CMODE_CHANGE
- Sent when channel mode has changed. This type must be sent only to
- the clients who is joined on the channel whose mode was changed.
+ Sent when channel mode has changed. This type MUST be sent only
+ to the clients which is joined on the channel which mode was
+ changed.
Max Arguments: 4
Arguments: (1) <ID Payload> (2) <mode mask>
(3) [<cipher>] (4) <[hmac>]
- The <ID Payload> is the ID (usually Client ID but it can be Server ID
- as well when the router is enforcing channel mode change) of the
- entity which changed the mode. The <mode mask> is the new mode mask
- of the channel. The client can safely ignore the <cipher> argument
- since the SILC_PACKET_CHANNEL_KEY packet will force the new channel
- key change anyway. The <hmac> argument is important since the client
- is responsible of setting the new HMAC and the hmac key into use.
+ The <ID Payload> is the ID (usually Client ID but it can be
+ Server ID as well when the router is enforcing channel mode
+ change) of the entity which changed the mode. The <mode mask>
+ is the new mode mask of the channel. The client can safely
+ ignore the <cipher> argument since the SILC_PACKET_CHANNEL_KEY
+ packet will force the new channel key change anyway. The <hmac>
+ argument is important since the client is responsible of setting
+ the new HMAC and the hmac key into use.
8 SILC_NOTIFY_TYPE_CUMODE_CHANGE
- Sent when user mode on channel has changed. This type must be sent
- only to the clients who is joined on the channel where the target
- client is on.
+ Sent when user mode on channel has changed. This type MUST be
+ sent only to the clients which is joined on the channel where
+ the target client is on.
Max Arguments: 3
Arguments: (1) <Client ID> (2) <mode mask>
(3) <Target Client ID>
- The <Client ID> is the client who changed the mode. The <mode mask>
- is the new mode mask of the channel. The <Target Client ID> is the
- client which mode was changed.
+ The <Client ID> is the client which changed the mode. The
+ <mode mask> is the new mode mask of the channel. The <Target
+ Client ID> is the client which mode was changed.
9 SILC_NOTIFY_TYPE_MOTD
- Sent when Message of the Day (motd) is sent to client.
+ Sent when Message of the Day (motd) is sent to a client.
Max Arguments: 1
Arguments: (1) <motd>
10 SILC_NOTIFY_TYPE_CHANNEL_CHANGE
- Sent when channel's ID has changed for a reason or another. This
- is sent by normal server to the client. This can also be sent by
- router to other server to force the Channel ID change. The Channel
- ID must be changed to use the new one. When sent to clients, this
- type must be sent only to the clients who is joined on the channel.
+ Sent when channel's ID has changed for a reason or another.
+ This is sent by normal server to the client. This can also be
+ sent by router to other server to force the Channel ID change.
+ The Channel ID MUST be changed to use the new one. When sent
+ to clients, this type MUST be sent only to the clients which is
+ joined on the channel.
Max Arguments: 2
Arguments: (1) <Old Channel ID> (2) <New Channel ID>
- The <Old Channel ID> is the channel's old ID and the <New Channel ID>
- is the new one that must replace the old one.
+ The <Old Channel ID> is the channel's old ID and the <New
+ Channel ID> is the new one that MUST replace the old one.
11 SILC_NOTIFY_TYPE_SERVER_SIGNOFF
- Sent when server quits SILC network. Those clients from this server
- that are on channels must be removed from the channel.
+ Sent when server quits SILC network. Those clients from this
+ server that are on channels must be removed from the channel.
Max Arguments: 2000
Arguments: (1) <Server ID> (n) [<Client ID> [...]
- The <Server ID> is the server's ID. The rest of the arguments are
- the Client ID's of the client's who are coming from this server and
- are thus quitting the SILC network also. If the maximum number of
- arguments are reached another SILC_NOTIFY_TYPE_SERVER_SIGNOFF notify
- packet must be sent. When this notify packet is sent between routers
- the Client ID's may be omitted.
+ The <Server ID> is the server's ID. The rest of the arguments
+ are the Client ID's of the client's which are coming from this
+ server and are thus quitting the SILC network also. If the
+ maximum number of arguments are reached another
+ SILC_NOTIFY_TYPE_SERVER_SIGNOFF notify packet MUST be sent.
+ When this notify packet is sent between routers the Client ID's
+ MAY be omitted.
12 SILC_NOTIFY_TYPE_KICKED
- Sent when a client has been kicked from a channel. This is sent
- also to the client who was kicked from the channel. The client
- who was kicked from the channel must be removed from the channel.
- This notify type is always destined to the channel. The router or
- server receiving the packet distributes this type to the local
- clients on the channel and broadcast it to the network.
+ Sent when a client has been kicked from a channel. This is
+ sent also to the client which was kicked from the channel.
+ The client which was kicked from the channel MUST be removed
+ from the channel. This notify type is always destined to the
+ channel. The router or server receiving the packet distributes
+ this type to the local clients on the channel and broadcast it
+ to the network.
Max Arguments: 2
Arguments: (1) <Client ID> (2) [<comment>]
- The <Client ID> is the client who was kicked from the channel.
+ The <Client ID> is the client which was kicked from the channel.
The kicker may have set the <comment> to indicate the reason for
the kicking.
13 SILC_NOTIFY_TYPE_KILLED
Sent when a client has been killed from the network. This is sent
- also to the client who was killed from the network. The client
- who was killed from the network must be removed from the network.
- This notify type is destined directly to the client who was killed
- and to channel if the client is on any channel. The router or
- server receiving the packet distributes this type to the local
+ also to the client which was killed from the network. The client
+ which was killed from the network MUST be removed from the network.
+ This notify type is destined directly to the client which was
+ killed and to channel if the client is on any channel. The router
+ or server receiving the packet distributes this type to the local
clients on the channel and broadcast it to the network.
Max Arguments: 2
Arguments: (1) <Client ID> (2) [<comment>]
- The <Client ID> is the client who was killed from the network.
+ The <Client ID> is the client which was killed from the network.
The killer may have set the <comment> to indicate the reason for
the killing.
14 SILC_NOTIFY_TYPE_UMODE_CHANGE
- Sent when user's mode in the SILC changes. This type is sent only
- between routers as broadcast packet.
+ Sent when user's mode in the SILC changes. This type is sent
+ only between routers as broadcast packet.
Max Arguments: 2
Arguments: (1) <Client ID> (2) <mode mask>
- The <Client ID> is the client which mode was changed. The <mode mask>
- is the new mode mask.
+ The <Client ID> is the client which mode was changed. The
+ <mode mask> is the new mode mask.
15 SILC_NOTIFY_TYPE_BAN
- Sent when the ban list of the channel is changed. This type is sent
- only between routers as broadcast packet.
+ Sent when the ban list of the channel is changed. This type is
+ sent only between routers as broadcast packet.
Max Arguments: 3
Arguments: (1) <Channel ID> (2) [<adding client>]
<adding client> is used to indicate the a ban was added and the
<removing client> is used to indicate that a ban was removed from
the ban list. The format of the <adding client> and the
- <removing client> is defined in the [SILC1] with SILC_COMMAND_BAN
+ <removing client> is defined in the [SILC4] with SILC_COMMAND_BAN
command.
.in 3
2.3.8 Error Payload
Error payload is sent upon error. Error may occur in various
-conditions when server sends this packet. Client may not send this
-payload but must be able to accept it. However, client may
+conditions when server sends this packet. Client MUST NOT send this
+payload but MUST be able to accept it. However, client MAY
totally ignore the contents of the packet as server is going to
take action on the error anyway. However, it is recommended
that the client takes error packet seriously.
special packet. Some special handling on sending and reception
of channel message is required.
-Padding must be applied into this payload since the payload is
+Padding MUST be applied into this payload since the payload is
encrypted separately from other parts of the packet with the
channel specific key. Hence the requirement of the padding.
-The padding should be random data. The packet must be made
+The padding SHOULD be random data. The packet MUST be made
multiple by eight (8) or by the block size of the cipher, which
ever is larger.
the channel the message is destined to by checking the destination
ID from the SILC Packet header which tells the destination channel.
The original sender of the packet is also determined by checking
-the source ID from the header which tells the client who sent
+the source ID from the header which tells the client which sent
the message.
The payload may only be sent with SILC_PACKET_CHANNEL_MESSAGE packet.
-It must not be sent in any other packet type. The following diagram
+It MUST NOT be sent in any other packet type. The following diagram
represents the Channel Message Payload.
(*) indicates that the field is not encrypted.
.in 6
o Flags (2 bytes) - Includes the flags of the channel
messages. The flags can indicate a reason or purpose
- for the channel message. Note, that the Private Message
+ for the channel message. Note that the Private Message
Payload use these same flags for the same purpose. The
following flags are defined:
Padding field in the payload, not including any other
field.
-o Padding (variable length) - The padding that must be
+o Padding (variable length) - The padding that MUST be
applied because this payload is encrypted separately from
other parts of the packet.
-o MAC (variable legnth) - The MAC computed from the
+o MAC (variable length) - The MAC computed from the
Message Length, Message Data, Padding Length and Padding
fields. This protects the integrity of the plaintext
channel message. The receiver can verify from the MAC
whether the message decrypted correctly. Also, if more than
one private key has been set for the channel, the receiver
can verify which of the keys decrypted the message
- correctly. Note that, this field is encrypted and must
+ correctly. Note that, this field is encrypted and MUST
be added to the padding calculation.
o Initial Vector (variable length) - The initial vector
that has been used in packet encryption. It needs to be
used in the packet decryption as well. What this field
includes is implementation issue. However, it is
- recommended that it would be random data or, perhaps,
- a timestamp. It is not recommended to use zero (0) as
+ RECOMMENDED that it would be random data or, perhaps,
+ a timestamp. It is NOT RECOMMENDED to use zero (0) as
initial vector. This field is not encrypted. This field
is not included into the padding calculation. Length
of this field equals the cipher's block size. This field
the client. After that, client starts using the key received
in this payload to protect the traffic on the channel.
-The client who is joining to the channel receives its key in the
+The client which is joining to the channel receives its key in the
SILC_COMMAND_JOIN command reply message thus it is not necessary to
-send this payload to the entity who sent the SILC_COMMAND_JOIN command.
+send this payload to the entity which sent the SILC_COMMAND_JOIN
+command.
-Channel keys are cell specific thus every router in cell have
+Channel keys are cell specific thus every router in the cell have
to create a channel key and distribute it if any client in the
cell has joined to a channel. Channel traffic between cell's
are not encrypted using channel keys, they are encrypted using
which case new channel key is created and distributed.
The payload may only be sent with SILC_PACKET_CHANNEL_KEY packet.
-It must not be sent in any other packet type. The following diagram
+It MUST NOT be sent in any other packet type. The following diagram
represents the Channel Key Payload.
-
-
-
-
-
-
-
-
-
-
-
.in 5
.nf
1 2 3
o Cipher Name (variable length) - Name of the cipher used
in the protection of channel traffic. This name is
initially decided by the creator of the channel but it
- may change during the life time of the channel as well.
+ MAY change during the life time of the channel as well.
o Channel Key Length (2 bytes) - Indicates the length of the
Channel Key field in the payload, not including any other
to the specified user and no other user inside SILC network is
able to see the message. The message is protected by the session
key established by the SILC Key Exchange Protocol. However,
-it is also possible to agree to use specific keys to protect
+it is also possible to agree to use a private key to protect
just the private messages. See section 2.3.11 Private Message
Key Payload for detailed description of how to agree to use
specific key.
-If normal session key is used to protect the message, every
-server between the sender client and the receiving client needs
-to decrypt the packet and always re-encrypt it with the session
-key of the next receiver of the packet. See section Client
-To Client in [SILC1].
+If normal session key is used to protect the message, every server
+between the sender client and the receiving client MUST decrypt the
+packet and always re-encrypt it with the session key of the next
+receiver of the packet. See section Client To Client in [SILC1].
-When specific key is used to protect the message, servers between
+When private key is used to protect the message, servers between
the sender and the receiver needs not to decrypt/re-encrypt the
packet. Section 4.8.2 Client To Client in [SILC1] gives example of
this scheme as well.
The payload may only be sent with SILC_PACKET_PRIVATE_MESSAGE
-packet. It must not be sent in any other packet type. The following
+packet. It MUST NOT be sent in any other packet type. The following
diagram represents the Private Message Payload.
+
+
+
+
+
+
+
.in 5
.nf
1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Flags | Nickname Length |
+| Flags | Message Data Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
-~ Nickname ~
-| |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-| Message Data Length | |
-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
-| |
~ Message Data ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o Flags (2 bytes) - This field includes the flags of the
private message. They can indicate a different reason or
purpose for the private message. See the section 2.3.9
- Channel Message Payload for defined flags. Note, that
+ Channel Message Payload for defined flags. Note that
the Channel Message Payload use the same flags for the
same purpose.
-o Nickname Length (2 bytes) - Indicates the length of the
- Nickname field, not including any other field.
-
-o Nickname (variable length) - Nickname of the sender of the
- private message. This should not be trusted as a definite
- sender of the private message. The SILC Packet Header in
- the packet indicates the true sender of the packet and
- client should verify that the nickname sent here belongs
- to the Client ID in the SILC Packet Header. This nickname
- is merely provided to be displayed by the client.
-
o Message Data Length (2 bytes) - Indicates the length of the
Message Data field, not includes any other field.
message key. In this case the padding is applied to make
the packet multiple by eight (8), or by the block size of
the cipher, which ever is larger. When encrypted with
- normal session keys, this field must not be included.
+ normal session keys, this field MUST NOT be included.
.in 3
the private messages.
This payload may only be sent by client to another client. Server
-must not send this payload at any time. After sending this payload
+MUST NOT send this payload at any time. After sending this payload
the sender of private messages must set the Private Message Key
flag into SILC Packet Header.
The payload may only be sent with SILC_PACKET_PRIVATE_MESSAGE_KEY
-packet. It must not be sent in any other packet type. The following
+packet. It MUST NOT be sent in any other packet type. The following
diagram represents the Private Message Key Payload.
2.3.13 Command Payload
Command Payload is used to send SILC commands from client to server.
-Also server may send commands to other servers. The following diagram
+Also server MAY send commands to other servers. The following diagram
represents the Command Payload.
payload including any command argument payloads associated
with this payload.
-o SILC Command (1 byte) - Indicates the SILC command. This must
+o SILC Command (1 byte) - Indicates the SILC command. This MUST
be set to non-zero value. If zero (0) value is found in this
- field the packet must be discarded.
+ field the packet MUST be discarded.
o Arguments Num (1 byte) - Indicates the number of arguments
associated with the command. If there are no arguments this
- field is set to zero (0). The arguments must follow the
+ field is set to zero (0). The arguments MUST follow the
command payload. See section 2.3.2.2 for definition of the
Argument Payload.
o Command Identifier (2 bytes) - Identifies this command at the
- sender's end. The entity who replies to this command must
+ sender's end. The entity which replies to this command MUST
set the value found from this field into the Command Payload
used to send the reply to the sender. This way the sender
can identify which command reply belongs to which originally
sent command. What this field includes is implementation
- issue but it is recommended that wrapping counter value is
+ issue but it is RECOMMENDED that wrapping counter value is
used in the field. Value zero (0) in this field means that
no specific value is set.
.in 3
-See [SILC1] for detailed description of different SILC commands,
+See [SILC4] for detailed description of different SILC commands,
their arguments and their reply messages.
+
+
.ti 0
2.3.14 Command Reply Payload
Command Reply Payload is used to send replies to the commands. The
-Command Reply Payload is identical to the Command Payload thus see the
-upper sections for Command Payload and for Command Argument Payload
-specifications. Command Reply message uses the Command Argument Payload
-as well.
+Command Reply Payload is identical to the Command Payload thus see
+the upper sections for Command Payload and for Command Argument
+Payload specifications. Command Reply message uses the Command
+Argument Payload as well.
-The entity who sends the reply packet must set the Command Unifier
+The entity which sends the reply packet MUST set the Command Identifier
field in the reply packet's Command Payload to the value it received
in the original command packet.
-See SILC Commands in [SILC1] for detailed description of different
+See SILC Commands in [SILC4] for detailed description of different
SILC commands, their arguments and their reply messages.
.ti 0
2.3.15 Connection Auth Request Payload
-Client may send this payload to server to request the authentication
+Client MAY send this payload to server to request the authentication
method that must be used in authentication protocol. If client knows
this information beforehand this payload is not necessary to be sent.
-Server performing authentication with another server may also send
+Server performing authentication with another server MAY also send
this payload to request the authentication method. If the connecting
server already knows this information this payload is not necessary
to be sent.
-Server receiving this request must reply with same payload sending
+Server receiving this request MUST reply with same payload sending
the mandatory authentication method. Algorithms that may be required
to be used by the authentication method are the ones already
established by the SILC Key Exchange protocol. See section Key
Exchange Start Payload in [SILC3] for detailed information.
The payload may only be sent with SILC_PACKET_CONNECTION_AUTH_REQUEST
-packet. It must not be sent in any other packet type. The following
+packet. It MUST NOT be sent in any other packet type. The following
diagram represents the Connection Auth Request Payload.
method to be used in the authentication protocol. The following
authentication methods are defined:
-
-
0 NONE (mandatory)
1 password (mandatory)
2 public key (mandatory)
- If any other type is found in this field the packet must be
- discarded and the authentication must be failed. If this
+ If any other type is found in this field the packet MUST be
+ discarded and the authentication MUST be failed. If this
payload is sent as request to receive the mandatory
- authentication method this field must be set to zero (0),
+ authentication method this field MUST be set to zero (0),
indicating that receiver should send the mandatory
authentication method. The receiver sending this payload
- to the requesting party, may also set this field to zero (0)
+ to the requesting party, MAY also set this field to zero (0)
to indicate that authentication is not required. In this
- case authentication protocol still must be started but
+ case authentication protocol still MUST be started but
server is most likely to respond with SILC_PACKET_SUCCESS
immediately.
.in 3
SILC_PACKET_NEW_SERVER to the router it connected to. The case is same
when router connects to another router.
-However, this payload is not and must not be used to send information
-about new channels. New channels are always distributed by sending the
-dedicated SILC_PACKET_NEW_CHANNEL packet.
+However, this payload MUST NOT be used to send information about new
+channels. New channels are always distributed by sending the dedicated
+SILC_PACKET_NEW_CHANNEL packet.
-Hence, this payload is very important and used every time when some
-new entity is registered to the SILC network. Client never sends this
-payload. Both client and server (and router) may receive this payload.
+Thus, this payload is very important and used every time when some
+new entity is registered to the SILC network. Client MUST NOT send this
+payload. Both client and server (and router) MAY receive this payload.
The packet uses generic ID Payload as New ID Payload. See section
2.3.2.1 for generic ID Payload.
2.3.17 New Client Payload
When client is connected to the server, keys has been exchanged and
-connection has been authenticated client must register itself to the
+connection has been authenticated client MUST register itself to the
server. Clients first packet after key exchange and authentication
protocols must be SILC_PACKET_NEW_CLIENT. This payload tells server all
the relevant information about the connected user. Server creates a new
client ID.
The payload may only be sent with SILC_PACKET_NEW_CLIENT packet. It
-must not be sent in any other packet type. The following diagram
+MUST NOT be sent in any other packet type. The following diagram
represents the New Client Payload.
+
+
+
+
+
+
+
+
+
+
.in 5
.nf
1 2 3
This payload is sent by server when it has completed successfully both
key exchange and connection authentication protocols. The server
-uses this payload to register itself to the SILC network. The
-first packet after these key exchange and authentication protocols
+MUST register itself to the SILC Network by sending this payload.
+The first packet after these key exchange and authentication protocols
is SILC_PACKET_NEW_SERVER packet. The payload includes the Server ID
of the server that it has created by itself. It also includes a
name of the server that is associated to the Server ID.
The payload may only be sent with SILC_PACKET_NEW_SERVER packet. It
-must not be sent in any other packet type. The following diagram represents
-the New Server Payload.
+MUST NOT be sent in any other packet type. The following diagram
+represents the New Server Payload.
it is a standalone server and it does not have router connection,
in this case server acts as router. Normal server send JOIN command
to the router (after it has received JOIN command from client) which
-then processes the command and creates the channel. Client never sends
-this packet.
+then processes the command and creates the channel. Client MUST NOT
+send this packet.
The packet uses generic Channel Payload as New Channel Payload. See
section 2.3.2.3 for generic Channel Payload. The Mode Mask field in the
Channel Payload is the mode of the channel.
+
+
.ti 0
2.3.20 Key Agreement Payload
is the SKE protocol. The result of the protocol, the secret key
material, can be used for example as private message key between the
two clients. This significantly adds security as the key agreement
-is performed outside the SILC network. The server and router must not
+is performed outside the SILC network. The server and router MUST NOT
send this payload.
-The sender may tell the receiver of this payload the hostname and the
+The sender MAY tell the receiver of this payload the hostname and the
port where the SKE protocol is running in the sender's end. The
-receiver may then initiate the SKE negotiation with the sender. The
-sender may also optionally not to include the hostname and the port
-of its SKE protocol. In this case the receiver may reply to the
+receiver MAY then initiate the SKE negotiation with the sender. The
+sender MAY also optionally not to include the hostname and the port
+of its SKE protocol. In this case the receiver MAY reply to the
request by sending the same payload filled with the receiver's hostname
-and the port where the SKE protocol is running. The sender may then
+and the port where the SKE protocol is running. The sender MAY then
initiate the SKE negotiation with the receiver.
The payload may only be sent with SILC_PACKET_KEY_AGREEMENT packet.
-It must not be sent in any other packet type. The following diagram
+It MUST NOT be sent in any other packet type. The following diagram
represents the Key Agreement Payload.
.in 6
-o Hostname Length (2 bytes) - Indicates the length of the Hostname
- field.
+o Hostname Length (2 bytes) - Indicates the length of the
+ Hostname field.
o Hostname (variable length) - The hostname or IP address where
- the SKE protocol is running. The sender may fill this field
+ the SKE protocol is running. The sender MAY fill this field
when sending the payload. If the receiver sends this payload
as reply to the request it must fill this field.
o Port (4 bytes) - The port where the SKE protocol is bound.
- The sender may fill this field when sending the payload. If
+ The sender MAY fill this field when sending the payload. If
the receiver sends this payload as reply to the request it
- must fill this field. This is a 32 bit MSB first order value.
+ MUST fill this field. This is a 32 bit MSB first order value.
.in 3
Cell Routers payload is used by router to notify its primary router what
other routers exist in the cell. The other routers are considered to be
backup routers and one of them will come active only in the case of
-failure of the primary router. Normal server can send this packet if it
-is acting as backup router. Client must not send this packet. To send
+failure of the primary router. Normal server MAY send this packet if it
+is acting as backup router. Client MUST NOT send this packet. To send
more than one backup router set the List flag and assemble the payloads
as list.
The payload may only be sent with SILC_PACKET_CELL_ROUTERS packet. It
-must not be sent in any other packet type. The Following diagram
+MUST NOT be sent in any other packet type. The Following diagram
represents the Cell Routers Payload.
cases. Computed MAC of the packet must not be encrypted.
Decryption process in these cases are straightforward. The receiver
-of the packet must first decrypt the SILC Packet header, or some parts
+of the packet MUST first decrypt the SILC Packet header, or some parts
of it, usually first 16 bytes of it. Then the receiver checks the
packet type from the decrypted part of the header and can determine
how the rest of the packet must be decrypted. If the packet type is
-any of the special cases described in The following sections the packet
+any of the special cases described in the following sections the packet
decryption is special. If the packet type is not among those special
-packet types rest of the packet may be decrypted with the same key.
+packet types rest of the packet can be decrypted with the same key.
Also, note that two bytes of the SILC Packet header are not encrypted
thus it must be noticed in the decryption process by starting the
encrypted with that key. As in normal case, the header is encrypted
with the key of the next receiver of the packet, who ever that might
be. Note that in this case the encrypted data area is not touched
-at all; it must not be re-encrypted with the session key.
+at all; it MUST NOT be re-encrypted with the session key.
-Receiver of a channel message, who ever that is, is required to decrypt
+Receiver of a channel message, who ever that is, is REQUIRED to decrypt
the SILC Packet header to be able to even recognize the packet to be as
channel message. This is same procedure as for normal SILC packets.
As the receiver founds the packet to be channel message, rest of the
the channel. See section 2.7 Packet Padding Generation for more
information about padding on special packets.
-If the receiver of the channel message is router who is routing the
-message to another router then it must decrypt the Channel Message
+If the receiver of the channel message is router which is routing the
+message to another router then it MUST decrypt the Channel Message
payload. Between routers (that is, between cells) channel messages
are protected with session keys shared between the routers. This
causes another special packet processing for channel messages. If
the channel message is received from another router then the entire
-packet, including Channel Message payload, is encrypted with the
+packet, including Channel Message payload, MUST be encrypted with the
session key shared between the routers. In this case the packet
decryption process is as with normal SILC packets. Hence, if the
router is sending channel message to another router the Channel
-Message payload must have been decrypted and must be re-encrypted
+Message payload MUST have been decrypted and MUST be re-encrypted
with the session key shared between the another router. In this
case the packet encryption is as with any normal SILC packet.
different processing of channel messages with router to router
connection is because channel keys are cell specific. All cells has
their own channel keys thus the channel message traveling from one
-cell to another must be protected as it would be any normal SILC
+cell to another MUST be protected as it would be any normal SILC
packet.
If the SILC_CMODE_PRIVKEY channel mode has been set for the channel
then the router cannot decrypt the packet as it does not know the
-private key. In this case the entire packet is encrypted with the
-session key and sent to the router. The router receiving the packet
-must check the channel mode and decrypt the packet accordingly.
+private key. In this case the entire packet MUST be encrypted with
+the session key and sent to the router. The router receiving the
+packet MUST check the channel mode and decrypt the packet accordingly.
.ti 0
In this case the private message encryption and decryption process is
equivalent to normal packet encryption and decryption.
-However, private messages can be protected with private message key
+However, private messages MAY be protected with private message key
which causes the packet to be special packet. The procedure in this
case is very much alike to channel packets. The actual private message
is encrypted with the private message key and other parts of the
2.7 Packet Padding Generation
Padding is needed in the packet because the packet is encrypted. It
-must always be multiple by eight (8) or multiple by the size of the
+MUST always be multiple by eight (8) or multiple by the size of the
cipher's block size, which ever is larger. The padding is always
encrypted.
are calculated as follows:
.in 6
-padding length = 16 - ((packet length - 2) % 16)
+padding length = 16 - ((packet length - 2) mod 16)
.in 3
The 16 is the maximum padding allowed in SILC packet. Two (2) is
subtracted from the true length of the packet because two (2) bytes
is not encrypted in SILC Packet Header, see section 2.2 SILC Packet
-Header. Those two bytes that are not encrypted must not be calculated
+Header. Those two bytes that are not encrypted MUST NOT be calculated
to the padding length.
-For special packets the padding calculation may be different as special
+For special packets the padding calculation MAY be different as special
packets may be encrypted differently. In these cases the encrypted
-data area must already be multiple by the block size thus in this case
+data area MUST already be multiple by the block size thus in this case
the padding is calculated only for SILC Packet Header, not for any
other area of the packet. The same algorithm works in this case as
well, except that the `packet length' is now the SILC Packet Header
length. In this case, as well, two (2) is subtracted from the
length.
-The padding must be random data, preferably, generated by
+The padding MUST be random data, preferably, generated by
cryptographically strong random number generator.
.ti 0
2.8 Packet Compression
-SILC Packets may be compressed. In this case the data payload area
-is compressed and all other areas of the packet must remain as they
+SILC Packets MAY be compressed. In this case the data payload area
+is compressed and all other areas of the packet MUST remain as they
are. After compression is performed for the data area, the length
-field of Packet Header must be set to the compressed length of the
+field of Packet Header MUST be set to the compressed length of the
data.
-The compression must always be applied before encryption. When
-the packet is received and decrypted the data area must be decompressed.
-Note that the true sender of the packet must apply the compression and
-the true receiver of the packet must apply the decompression. Any
-server or router en route must not decompress the packet.
-
+The compression MUST always be applied before encryption. When
+the packet is received and decrypted the data area MUST be decompressed.
+Note that the true sender of the packet MUST apply the compression and
+the true receiver of the packet MUST apply the decompression. Any
+server or router en route MUST NOT decompress the packet.
.ti 0
2.9 Packet Sending
-The sender of the packet must assemble the SILC Packet Header with
-correct values. It must set the Source ID of the header as its own
-ID, unless it is forwarding the packet. It must also set the Destination
+The sender of the packet MUST assemble the SILC Packet Header with
+correct values. It MUST set the Source ID of the header as its own
+ID, unless it is forwarding the packet. It MUST also set the Destination
ID of the header to the true destination. If the destination is client
it will be Client ID, if it is server it will be Server ID and if it is
channel it will be Channel ID.
-If the sender wants to compress the packet it must apply the
-compression now. Sender must also compute the padding as described
-in above sections. Then sender must compute the MAC of the packet.
+If the sender wants to compress the packet it MUST apply the
+compression now. Sender MUST also compute the padding as described
+in above sections. Then sender MUST compute the MAC of the packet.
-Then sender encrypts the packet as has been described in above
+Then sender MUST encrypt the packet as has been described in above
sections according whether the packet is normal packet or special
-packet. The computed MAC must not be encrypted.
+packet. The computed MAC MUST NOT be encrypted.
.ti 0
2.10 Packet Reception
-On packet reception the receiver must check that all fields in the
-SILC Packet Header are valid. It must check the flags of the
-header and act accordingly. It must also check the MAC of the packet
-and if it is to be failed the packet must be discarded. Also if the
-header of the packet includes any bad fields the packet must be
+On packet reception the receiver MUST check that all fields in the
+SILC Packet Header are valid. It MUST check the flags of the
+header and act accordingly. It MUST also check the MAC of the packet
+and if it is to be failed the packet MUST be discarded. Also if the
+header of the packet includes any bad fields the packet MUST be
discarded.
See above sections on the decryption process of the received packet.
-The receiver must also check that the ID's in the header are valid
-ID's. Unsupported ID types or malformed ID's must cause packet
+The receiver MUST also check that the ID's in the header are valid
+ID's. Unsupported ID types or malformed ID's MUST cause packet
rejection. The padding on the reception is always ignored.
-The receiver must also check the packet type and start parsing the
+The receiver MUST also check the packet type and start parsing the
packet according to the type. However, note the above sections on
special packet types and their parsing.
Routing is quite simple as every packet tells the true origin and the
true destination of the packet.
-It is still recommended for routers that has several routing connections
+It is still RECOMMENDED for routers that has several routing connections
to create route cache for those destinations that has faster route than
the router's primary route. This information is available for the router
when other router connects to the router. The connecting party then
are created to a cell its information is broadcasted to all routers
in the network. Channel ID's are based on router's ID thus it is easy
to create route cache based on these informations. If faster route for
-destination does not exist in router's route cache the packet must be
+destination does not exist in router's route cache the packet MUST be
routed to the primary route (default route).
-For server who receives a packet to be routed to its locally connected
-client the server must check whether the particular packet type is
+For server which receives a packet to be routed to its locally connected
+client the server MUST check whether the particular packet type is
allowed to be routed to the client. Not all packets may be sent by
some odd entity to client that is indirectly connected to the sender.
See section 2.3 SILC Packet Types and paragraph about indirectly connected
.ti 0
2.12 Packet Broadcasting
-SILC packets may be broadcasted in SILC network. However, only router
+SILC packets MAY be broadcasted in SILC network. However, only router
server may send or receive broadcast packets. Client and normal server
-must not send broadcast packets and they must ignore broadcast packets
+MUST NOT send broadcast packets and they MUST ignore broadcast packets
if they receive them. Broadcast packets are sent by setting Broadcast
flag to the SILC packet header.
Broadcasting packets means that the packet is sent to all routers in
the SILC network, except to the router that sent the packet. The router
-receiving broadcast packet must send the packet to its primary route.
-The fact that SILC routers may have several router connections may
+receiving broadcast packet MUST send the packet to its primary route.
+The fact that SILC routers may have several router connections can
cause problems, such as race conditions inside the SILC network, if
-care is not taken when broadcasting packets. Router must not send
+care is not taken when broadcasting packets. Router MUST NOT send
the broadcast packet to any other route except to its primary route.
If the primary route of the router is the original sender of the packet
-the packet must not be sent to the primary route. This may happen
+the packet MUST NOT be sent to the primary route. This may happen
if router has several router connections and some other router uses
the router as its primary route.
4 References
[SILC1] Riikonen, P., "Secure Internet Live Conferencing (SILC),
- Protocol Specification", Internet Draft, June 2000.
+ Protocol Specification", Internet Draft, April 2001.
[SILC3] Riikonen, P., "SILC Key Exchange and Authentication
- Protocols", Internet Draft, June 2000.
+ Protocols", Internet Draft, April 2001.
+
+[SILC4] Riikonen, P., "SILC Commands", Internet Draft, April 2001.
[IRC] Oikarinen, J., and Reed D., "Internet Relay Chat Protocol",
RFC 1459, May 1993.
[PKCS1] Kalinski, B., and Staddon, J., "PKCS #1 RSA Cryptography
Specifications, Version 2.0", RFC 2437, October 1998.
+[RFC2119] Bradner, S., "Key Words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
+
.ti 0
5 Author's Address
EMail: priikone@poseidon.pspt.fi
-This Internet-Draft expires 6 Jun 2001
+This Internet-Draft expires XX October 2001
\ No newline at end of file
projects / silc.git / commitdiff