X-Git-Url: http://git.silcnet.org/gitweb/?a=blobdiff_plain;f=doc%2Fdraft-riikonen-silc-ke-auth-00.nroff;fp=doc%2Fdraft-riikonen-silc-ke-auth-00.nroff;h=0000000000000000000000000000000000000000;hb=f9d9c92fcc179ff82ae7aa5f724440215f194827;hp=18d604b32e6890695d407114ce0c4b8fac886983;hpb=e7b6c157b80152bf9fb9266e6bdd93f9fb0db776;p=crypto.git diff --git a/doc/draft-riikonen-silc-ke-auth-00.nroff b/doc/draft-riikonen-silc-ke-auth-00.nroff deleted file mode 100644 index 18d604b3..00000000 --- a/doc/draft-riikonen-silc-ke-auth-00.nroff +++ /dev/null @@ -1,1055 +0,0 @@ -.pl 10.0i -.po 0 -.ll 7.2i -.lt 7.2i -.nr LL 7.2i -.nr LT 7.2i -.ds LF Riikonen -.ds RF FORMFEED[Page %] -.ds CF -.ds LH INTERNET-DRAFT -.ds RH 13 September 2000 -.ds CH -.na -.hy 0 -.in 0 -.nf -Network Working Group P. Riikonen -INTERNET-DRAFT -draft-riikonen-silc-ke-auth-00.txt 13 September 2000 -Expires: 13 May 2001 - -.in 3 - -.ce 2 -SILC Key Exchange and Authentication Protocols - - -.ti 0 -Status of this Memo - -This document is an Internet-Draft and is in full conformance with -all provisions of Section 10 of RFC 2026. Internet-Drafts are -working documents of the Internet Engineering Task Force (IETF), its -areas, and its working groups. Note that other groups may also -distribute working documents as Internet-Drafts. - -Internet-Drafts are draft documents valid for a maximum of six months -and may be updated, replaced, or obsoleted by other documents at any -time. It is inappropriate to use Internet-Drafts as reference -material or to cite them other than as "work in progress." - -The list of current Internet-Drafts can be accessed at -http://www.ietf.org/ietf/1id-abstracts.txt - -The list of Internet-Draft Shadow Directories can be accessed at -http://www.ietf.org/shadow.html - -The distribution of this memo is unlimited. - - -.ti 0 -Abstract - -This memo describes two protocols used 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 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 -(pre-shared- secret) or public key (and certificate). - - - -.ti 0 -Table of Contents - -.nf -1 Introduction .................................................. 2 -2 SILC Key Exchange Protocol .................................... 3 - 2.1 Key Exchange Payloads ..................................... 3 - 2.1.1 Key Exchange Start Payload .......................... 4 - 2.1.2 Key Exchange 1 Payload .............................. 7 - 2.1.3 Key Exchange 2 Payload .............................. 9 - 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 - 2.4.2 diffie-hellman-group2 ............................... 14 - 2.5 Key Exchange Status Types ................................. 14 -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 - 3.3 Connection Authentication Status Types .................... 19 -4 Security Considerations ....................................... 19 -5 References .................................................... 19 -6 Author's Address .............................................. 20 - - -.ti 0 -List of Figures - -.nf -Figure 1: Key Exchange Start Payload -Figure 2: Key Exchange 1 Payload -Figure 3: Key Exchange 2 Payload -Figure 4: Connection Auth Payload - - -.ti 0 -1 Introduction - -This memo describes two protocols used 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 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 -(pre-shared- secret) or public key (and certificate). - -The basis of secure SILC session requires strong and secure key exchange -protocol and authentication. The authentication protocol is entirely -secured and no authentication data is ever sent in the network without -encrypting and authenticating it first. Thus, authentication protocol -may be used only after the key exchange protocol has been successfully -completed. - -This document refers constantly to other SILC protocol specification -Internet Drafts that are a must read for those who wants to understand -the function of these protocols. The most important references are -the Secure Internet Live Conferencing, Protocol Specification [SILC1] -and SILC Packet Protocol [SILC2] Internet Drafts. - -The protocol is intended to be used with the SILC protocol thus it -does not define own framework that could be used. The framework is -provided by the SILC protocol. - - -.ti 0 -2 SILC Key Exchange Protocol - -SILC Key Exchange Protocol (SKE) is used to exchange shared secret -between connecting entities. The result of this protocol is a key -material used to secure the communication channel. The protocol uses -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 protocol does not claim any conformance -to any of these protocols, they were merely used as a reference when -designing this protocol. - -The purpose of SILC Key Exchange protocol is to create session keys to -be used in current SILC session. The keys are valid only for some period -of time (usually an hour) or at most until the session ends. These keys -are used to protect packets like commands, command replies and other -communication between two entities. If connection is server to server -connection, the keys are used to protect all traffic between those -servers. In client connections usually all the packets are protected -with this key except channel messages; channels has their own keys and -they are not exchanged with this protocol. - - -.ti 0 -2.1 Key Exchange Payloads - -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. - - -.ti 0 -2.1.1 Key Exchange Start Payload - -Key exchange between two entities always begins with a -SILC_PACKET_KEY_EXCHANGE packet containing Key Exchange Start Payload. -When performing key exchange between client and server, the client sends -Key Exchange Start Payload to server filled with all security properties -that the client supports. Server then checks if it supports the security -properties. - -It then sends a Key Exchange Start Payload to client filled with security -properties it selected from the payload client originally sent. The -payload sent by server must include only one chosen property per list. - -When performing key exchange between server and server, the server who -is contacting sends the Key Exchange Start Payload with security property -list it supports to the other server. The contacted party then chooses -the preferred properties same way as previously described. It then -replies with the properties it wanted same way as previously described. - -The Key Exchange Start Payload is used to tell connecting entities what -security properties and algorithms should be used in the communication. -If perfect forward secrecy (PFS) is not desired (PFS is undefined by -default) Key Exchange Start Payload is sent only once per session, thus, -for example, re-keying will not cause sending of a new payload. If PFS -is desired, re-keying will always cause new key exchange thus causes -sending of a new Key Exchange Start Payload. - -When performing first key exchange this payload is never encrypted, as -there are no existing keys to encrypt it with. If performing re-keying -(PFS was selected) this payload is encrypted with the existing key and -encryption algorithm. - -Cookie is also send in this payload. Cookie is used to uniform the -payload so that none of the key exchange parties cannot determine this -payload before hand. 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 -not include spaces (` '). - - - - - - - -.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 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -| RESERVED | Flags | Payload Length | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -| | -+ + -| | -+ Cookie + -| | -+ + -| | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -| Version String Length | | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + -| | -~ Version String ~ -| | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -| Key Exchange Grp Length | | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + -| | -~ Key Exchange Groups ~ -| | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -| PKCS Alg Length | | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + -| | -~ PKCS Algorithms ~ -| | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -| Encryption Alg Length | | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + -| | -~ Encryption Algorithms ~ -| | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -| Hash Alg Length | | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + -| | -~ Hash Algorithms ~ -| | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -| Compression Alg Length | | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + -| | -~ Compression Algorithms ~ -| | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -.in 3 - -.ce -Figure 1: Key Exchange Start Payload - - - -.in 6 -o RESERVED (1 byte) - Reserved field. Sender fills this with - zeroes (0). - -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. - - No flags 0x00 - - In this case the field is ignored. - - No Reply 0x01 - - If set the receiver of the payload does not reply to - the packet. - - PFS 0x02 - - Perfect Forward Secrecy (PFS) to be used in the - key exchange protocol. If not set, re-keying - is performed using the old key. When PFS is used, - re-keying and creating new keys for any particular - purpose will cause new key exchange. - - Rest of the flags are reserved for the future and - must not be set. - -o Payload Length (2 bytes) - Length of the entire Key Exchange - Start payload, not including any other field. - -o Cookie (16 bytes) - Cookie that uniforms this payload so - that each of the party cannot determine the payload before - hand. - -o Version String Length (2 bytes) - The length of the Version - String field, not including any other field. - -o Version String (variable length) - Indicates the version of - the sender of this payload. Initiator sets this when sending - the payload and responder sets this when it replies by sending - this payload. See [SILC1] for definition of the version - string format. - -o Key Exchange Grp Length (2 bytes) - The length of the - key exchange group list, not including any other field. - -o Key Exchange Group (variable length) - The list of - key exchange groups. See the section 2.1.2 SILC Key Exchange - Groups for definitions of these groups. - -o PKCS Alg Length (2 bytes) - The length of the PKCS algorithms - list, not including any other field. - -o PKCS Algorithms (variable length) - The list of PKCS - algorithms. - -o Encryption Alg Length (2 bytes) - The length of the encryption - algorithms list, not including any other field. - -o Encryption Algorithms (variable length) - The list of - encryption algorithms. - -o Hash Alg Length (2 bytes) - The length of the Hash algorithms - list, not including any other field. - -o Hash Algorithms (variable length) - The list of Hash algorithms. - -o Compression Alg Length (2 bytes) - The length of the - compression algorithms list, not including any other field. - -o Compression Algorithms (variable length) - The list of - compression algorithms. -.in 3 - - -.ti 0 -2.1.2 Key Exchange 1 Payload - -Key Exchange 1 Payload is used to deliver computed public data from -initiator to responder. This data is used to compute the shared secret, -later by all parties. Key Exchange 1 Payload is only sent after the -SILC_PACKET_KEY_EXCHANGE packet and the Key Exchange Start Payload has -been processed by all the parties. - -This payload sends the initiator's public key to the responder. Responder -may need the public key in which case it should be checked to be trusted -by the responder. - -The payload may only be sent with SILC_PACKET_KEY_EXCHANGE_1 packet. -It must not be sent in any other packet type. Following diagram -represent the Key Exchange 1 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 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -| Public Key Length | Public Key Type | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -| | -~ Public Key of the Host (or certificate) ~ -| | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -| Public Data Length | | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + -| | -~ Public Data (e = g ^ x mod p) ~ -| | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -.in 3 - -.ce -Figure 2: Key Exchange 1 Payload - - -.in 6 -o Public Key Length (2 bytes) - The length of the Public Key - (or certificate) field, not including any other field. - -o Public Key Type (2 bytes) - The public key (or certificate) - type. This field indicates the type of the public key in - the packet. Following types are defined: - - 1 SILC style public key (mandatory) - 2 SSH2 style public key (optional) - 3 X.509 Version 3 certificate (optional) - 4 OpenPGP certificate (optional) - 5 SPKI certificate (optional) - - The only required type to support is type number 1. See - [SILC1] for the SILC public key specification. See - SSH public key specification in [SSH-TRANS]. See X.509v3 - 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. - -o Public Data Length (2 bytes) - The length of the public - data computed by the responder, not including any other - field. - -o Public Data (variable length) - The public data to be - sent to the responder. See section 2.2 Key Exchange - Procedure for detailed description how this field is - computed. This value is binary encoded. -.in 3 - - -.ti 0 -2.1.3 Key Exchange 2 Payload - -Key Exchange 2 Payload is used to deliver public key, computed public -data and signature from responder to initiator. Initiator uses these -public parts of the key exchange protocol to compute the shared secret. - -The payload may only be sent with SILC_PACKET_KEY_EXCHANGE_2 packet. -It must not be sent in any other packet type. Following diagram -represent the Key Exchange 2 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 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -| Public Key Length | Public Key Type | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -| | -~ Public Key of the Host (or certificate) ~ -| | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -| Public Data Length | | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + -| | -~ Public Data (f = g ^ y mod p) ~ -| | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -| Signature Length | | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + -| | -~ Signature Data ~ -| | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -.in 3 - -.ce -Figure 3: Key Exchange 2 Payload - - - -.in 6 -o Public Key Length (2 bytes) - The length of the Public Key - (or certificate) field, not including any other field. - -o Public Key Type (2 bytes) - The public key (or certificate) - type. This field indicates the type of the public key in - the packet. See previous sections for defined public key - types. - -o Public Key of the host (variable length) - The public - key of the sender (or its certificate). This is verified - by the receiver of the packet. The type of this field - is indicated by previous Public Key Type field. - -o Public Data Length (2 bytes) - The length of the public - data computed by the responder, not including any other - field. - -o Public Data (variable length) - The public data computed - by the responder. See section 2.2 Key Exchange Procedure - for detailed description how this field is computed. This - value is binary encoded. - -o Signature Length (2 bytes) - The length of the signature, - not including any other field. - -o Signature Data (variable length) - The signature signed - by the responder. 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. - - -.ti 0 -2.2 Key Exchange Procedure - -The key exchange begins by sending SILC_PACKET_KEY_EXCHANGE packet with -Key Exchange Start Payload to select the security properties to be used -in the key exchange and later in the communication. - -After Key Exchange Start Payload has been processed by both of the -parties the protocol proceeds as follows: - - -Setup: p is a large and public safe prime. This is one of the - Diffie Hellman groups. q is order of subgroup (largest - prime factor of p). g is a generator and is defined - along with the Diffie Hellman group. - - 1. Initiator generates a random number x, where 1 < x < q, - and computes e = g ^ x mod p. The result e is then - encoded into Key Exchange 1 Payload and sent - to the responder. - - - 2. Responder generates a random number y, where 1 < y < q, - and computes f = g ^ y mod p. It then computes the - shared secret KEY = e ^ y mod p, and, a hash value - HASH = hash(Key Exchange Start Payload data | Host public - key (or certificate) | e | f | KEY). It then signs - the HASH value with its private key resulting a signature - SIGN. - - It then encodes its public key (or certificate), f and - SIGN into Key Exchange 2 Payload and sends it to the - initiator. - - - 3. Initiator verifies that the public key provided in - the payload is authentic, or if certificates are used - it verifies the certificate. 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 - practical reasons on many environments. For long term - use this is never desirable, in which case certificates - would be the preferred method to use). - - Initiator then computes the shared secret KEY = - f ^ x mod p, and, a hash value HASH in the same way as - responder did in phase 2. It then verifies the - signature SIGN from the payload with the hash value - 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 failed. Any other packets must -not be sent or accepted during the key exchange except the -SILC_PACKET_KEY_EXCHANGE_*, SILC_PACKET_DISCONNECT, SILC_PACKET_FAILURE -and/or SILC_PACKET_SUCCESS packets. - -The result of this protocol is a shared secret key material KEY and -a hash value HASH. The key material itself is not fit to be used as -a key, it needs to be processed further to derive the actual keys to be -used. The key material is also used to produce other security parameters -later used in the communication. See section 2.3 Processing the Key -Material for detailed description how to process the key material. - -After the keys are processed the protocol is ended by sending the -SILC_PACKET_SUCCESS packet. Both entities send this packet to -each other. After this both parties will start using the new keys. - - - -.ti 0 -2.3 Processing the Key Material - -Key Exchange protocol produces secret shared key material KEY. This -key material is used to derive the actual keys used in the encryption -of the communication channel. The key material is also used to derive -other security parameters used in the communication. Key Exchange -protocol produces a hash value HASH as well. This is used in the key -deriving process as a session identifier. - -Keys are derived from the key material as follows: - -.in 6 -Sending Initial Vector (IV) = hash(0 | KEY | HASH) -Receiving Initial Vector (IV) = hash(1 | KEY | HASH) -Sending Encryption Key = hash(2 | KEY | HASH) -Receiving Encryption Key = hash(3 | KEY | HASH) -HMAC Key = hash(4 | KEY | HASH) -.in 3 - - -The Initial Vector (IV) is used in the encryption when doing for -example CBC mode. As many bytes as needed are taken from the start of -the hash output for IV. Sending IV is for sending key and receiving IV -is for receiving key. For receiving party, the receiving IV is actually -sender's sending IV, and, the sending IV is actually sender's receiving -IV. Initiator uses IV's as they are (sending IV for sending and -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: - -.in 6 -K1 = hash(2 | KEY | HASH) -K2 = hash(KEY | K1) -K3 = hash(KEY | K1 | K2) ... - -Sending Encryption Key = K1 | K2 | K3 ... - - -K1 = hash(3 | KEY | HASH) -K2 = hash(KEY | K1) -K3 = hash(KEY | K1 | K2) ... - -Receiving Encryption Key = K1 | K2 | K3 ... -.in 3 - - -The key is distributed by hashing the previous hash with the original -key material. The final key is a concatenation of the hash values. -For Receiving Encryption Key the procedure is equivalent. Sending key -is used only for encrypting data to be sent. The receiving key is used -only to decrypt received data. For receiving party, the receive key is -actually sender's sending key, and, the sending key is actually sender's -receiving key. Initiator uses generated keys as they are (sending key -for sending and receiving key for sending). - -The HMAC key is used to create MAC values to packets in the communication -channel. As many bytes as needed are taken from the start of the 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 -sending the SILC_PACKET_SUCCESS packet. - - -.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 -negotiated to be used in the connection with Key Exchange Start Payload -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 doesn't have to be the first on the list). - - -.ti 0 -2.4.1 diffie-hellman-group1 - -The length of this group is 1024 bits. This is mandatory group. -The prime is 2^1024 - 2^960 - 1 + 2^64 * { [2^894 pi] + 129093 }. - -Its decimal value is - -.in 6 -179769313486231590770839156793787453197860296048756011706444 -423684197180216158519368947833795864925541502180565485980503 -646440548199239100050792877003355816639229553136239076508735 -759914822574862575007425302077447712589550957937778424442426 -617334727629299387668709205606050270810842907692932019128194 -467627007 -.in 3 - -Its hexadecimal value is - -.in 6 -FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1 -29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD -EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245 -E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED -EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE65381 -FFFFFFFF FFFFFFFF -.in 3 - - -The generator used with this prime is g = 2. The group order q is -(p - 1) / 2. - -This group was taken from the OAKLEY specification. - - -.ti 0 -2.4.2 diffie-hellman-group2 - -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 - -.in 6 -241031242692103258855207602219756607485695054850245994265411 -694195810883168261222889009385826134161467322714147790401219 -650364895705058263194273070680500922306273474534107340669624 -601458936165977404102716924945320037872943417032584377865919 -814376319377685986952408894019557734611984354530154704374720 -774996976375008430892633929555996888245787241299381012913029 -459299994792636526405928464720973038494721168143446471443848 -8520940127459844288859336526896320919633919 -.in 3 - -Its hexadecimal value is - -.in 6 -FFFFFFFF FFFFFFFF C90FDAA2 2168C234 C4C6628B 80DC1CD1 -29024E08 8A67CC74 020BBEA6 3B139B22 514A0879 8E3404DD -EF9519B3 CD3A431B 302B0A6D F25F1437 4FE1356D 6D51C245 -E485B576 625E7EC6 F44C42E9 A637ED6B 0BFF5CB6 F406B7ED -EE386BFB 5A899FA5 AE9F2411 7C4B1FE6 49286651 ECE45B3D -C2007CB8 A163BF05 98DA4836 1C55D39A 69163FA8 FD24CF5F -83655D23 DCA3AD96 1C62F356 208552BB 9ED52907 7096966D -670C354E 4ABC9804 F1746C08 CA237327 FFFFFFFF FFFFFFFF -.in 3 - -The generator used with this prime is g = 2. The group order q is -(p - 1) / 2. - -This group was taken from the OAKLEY specification. - - -.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 -status types to human readable error message. All types except the -SILC_SKE_STATUS_OK type must be sent in SILC_PACKET_FAILURE packet. -Following status types are defined: - -.in 6 -0 SILC_SKE_STATUS_OK - - Protocol were exeucted succesfully. - - -1 SILC_SKE_STATUS_ERROR - - Unknown error occured. No specific error type is defined. - - -2 SILC_SKE_STATUS_BAD_PAYLOAD - - Provided KE payload were malformed or included bad fields. - - -3 SILC_SKE_STATUS_UNSUPPORTED_GROUP - - None of the provided groups were supported. - - -4 SILC_SKE_STATUS_UNSUPPORTED_CIPHER - - None of the provided ciphers were supported. - - -5 SILC_SKE_STATUS_UNSUPPORTED_PKCS - - None of the provided public key algorithms were supported. - - -6 SILC_SKE_STATUS_UNSUPPORTED_HASH_FUNCTION - - None of the provided hash functions were supported. - - -7 SILC_SKE_STATUS_UNSUPPORTED_PUBLIC_KEY - - Provided public key type is not supported. - - -8 SILC_SKE_STATUS_INCORRECT_SIGNATURE - - Provided signature was incorrect. -.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. -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 -protocol all traffic in the connection authentication protocol is -encrypted with the exchanged keys. - -The protocol is started by the connecting party by sending -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 must -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 -connecting party already knows the mandatory authentication method -sending the request is not necessary. - -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 -executed; the authentication data just is empty indicating no -authentication is required. - -If authentication method is passphrase the authentication data is -plaintext passphrase. As the payload is entirely encrypted it is safe -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 -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 -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 -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. - - - -.ti 0 -3.1 Connection Auth Payload - -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. - -The payload may only be sent with SILC_PACKET_CONNECTION_AUTH packet. -It must not be sent in any other packet type. Following diagram -represent the Connection Auth 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 -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -| Payload Length | Connection Type | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -| | -~ Authentication Data ~ -| | -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -.in 3 - -.ce -Figure 4: Connection Auth Payload - - -.in 6 -o Payload Length (2 bytes) - Length of the entire 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. - -o Authentication Data (variable length) - The actual - authentication data. Contents of this depends on the - authentication method known by both parties. If no - authentication is required this field does not exist. -.in 3 - - -.ti 0 -3.2 Connection Authentication Types - -SILC supports two authentication types to be used in the connection -authentication protocol; passphrase or public key based authentication. -Following sections defines the authentication methods. See [SILC2] -for defined numerical authentication method types. - - -.ti 0 -3.2.1 Passphrase Authentication - -Passphrase authentication or pre-shared-key base authentication is -simply an authentication where the party that wants to authenticate -itself to the other end sends the passphrase that is required by -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 -sent to the sender and the protocol execution fails. - -This is required authentication method to be supported by all SILC -implementations. - - -.ti 0 -3.2.2 Public Key Authentication - -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, -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 -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 -implementations. - - -.ti 0 -3.3 Connection Authentication Status Types - -This section defines all connection authentication 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_AUTH_STATUS_OK type must be sent in SILC_PACKET_FAILURE packet. -Following status types are defined: - -0 SILC_AUTH_OK - - Protocol was executed succesfully. - - -1 SILC_AUTH_FAILED - - Authentication failed. - - -.ti 0 -4 Security Considerations - -Security is central to the design of this protocol, and these security -considerations permeate the specification. - - -.ti 0 -5 References - -[SILC1] Riikonen, P., "Secure Internet Live Conferencing (SILC), - Protocol Specification", Internet Draft, June 2000. - -[SILC2] Riikonen, P., "SILC Packet Protocol", Internet Draft, - June 2000. - -[IRC] Oikarinen, J., and Reed D., "Internet Relay Chat Protocol", - RFC 1459, May 1993. - -[SSH-TRANS] Ylonen, T., et al, "SSH Transport Layer Protocol", - Internet Draft. - -[PGP] Callas, J., et al, "OpenPGP Message Format", RFC 2440, - November 1998. - -[SPKI] Ellison C., et al, "SPKI Certificate Theory", RFC 2693, - September 1999. - -[PKIX-Part1] Housley, R., et al, "Internet X.509 Public Key - Infrastructure, Certificate and CRL Profile", RFC 2459, - January 1999. - -[Schneier] Schneier, B., "Applied Cryptography Second Edition", - John Wiley & Sons, New York, NY, 1996. - -[Menezes] Menezes, A., et al, "Handbook of Applied Cryptography", - CRC Press 1997. - -[OAKLEY] Orman, H., "The OAKLEY Key Determination Protocol", - RFC 2412, November 1998. - -[ISAKMP] Maughan D., et al, "Internet Security Association and - Key Management Protocol (ISAKMP)", RFC 2408, November - 1998. - -[IKE] Harkins D., and Carrel D., "The Internet Key Exhange - (IKE)", RFC 2409, November 1998. - -[HMAC] Krawczyk, H., "HMAC: Keyed-Hashing for Message - Authentication", RFC 2104, February 1997. - - -.ti 0 -6 Author's Address - -.nf -Pekka Riikonen -Kasarmikatu 11 A4 -70110 Kuopio -Finland - -EMail: priikone@poseidon.pspt.fi - -This Internet-Draft expires 13 May 2001 -