AKA简单翻译 认证与密钥协商
希望大家与我完善他
Network Working Group A. Niemi
Request for Comments: 3310 Nokia
Category: Informational J. Arkko
V. Torvinen
Ericsson
September 2002
Hypertext Transfer Protocol (HTTP) Digest Authentication
Using Authentication and Key Agreement (AKA)
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved.
Abstract
This memo specifies an Authentication and Key Agreement (AKA) based
one-time password generation mechanism for Hypertext Transfer
Protocol (HTTP) Digest access authentication. The HTTP
Authentication Framework includes two authentication schemes: Basic
and Digest. Both schemes employ a shared secret based mechanism for
access authentication. The AKA mechanism performs user
authentication and session key distribution in Universal Mobile
Telecommunications System (UMTS) networks. AKA is a challenge-
response based mechanism that uses symmetric cryptography.
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Table of Contents
1. Introduction and Motivation . . . . . . . . . . . . . . . . . 2
1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. AKA Mechanism Overview . . . . . . . . . . . . . . . . . . . . 4
3. Specification of Digest AKA . . . . . . . . . . . . . . . . . 5
3.1 Algorithm Directive . . . . . . . . . . . . . . . . . . . . . 5
3.2 Creating a Challenge . . . . . . . . . . . . . . . . . . . . . 6
3.3 Client Authentication . . . . . . . . . . . . . . . . . . . . 7
3.4 Synchronization Failure . . . . . . . . . . . . . . . . . . . 7
3.5 Server Authentication . . . . . . . . . . . . . . . . . . . . 8
4. Example Digest AKA Operation . . . . . . . . . . . . . . . . . 8
5. Security Considerations . . . . . . . . . . . . . . . . . . . 12
5.1 Authentication of Clients using Digest AKA . . . . . . . . . . 13
5.2 Limited Use of Nonce Values . . . . . . . . . . . . . . . . . 13
5.3 Multiple Authentication Schemes and Algorithms . . . . . . . . 14
5.4 Online Dictionary Attacks . . . . . . . . . . . . . . . . . . 14
5.5 Session Protection . . . . . . . . . . . . . . . . . . . . . . 14
5.6 Replay Protection . . . . . . . . . . . . . . . . . . . . . . 15
5.7 Improvements to AKA Security . . . . . . . . . . . . . . . . . 15
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
6.1 Registration Template . . . . . . . . . . . . . . . . . . . . 16
Normative References . . . . . . . . . . . . . . . . . . . . . 16
Informative References . . . . . . . . . . . . . . . . . . . . 16
A. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 17
Full Copyright Statement . . . . . . . . . . . . . . . . . . . 18
1. Introduction and Motivation
The Hypertext Transfer Protocol (HTTP) Authentication Framework,
described in RFC 2617 [2], includes two authentication schemes: Basic
and Digest. Both schemes employ a shared secret based mechanism for
access authentication. The Basic scheme is inherently insecure in
that it transmits user credentials in plain text. The Digest scheme
improves security by hiding user credentials with cryptographic
hashes, and additionally by providing limited message integrity.
The Authentication and Key Agreement (AKA) [6] mechanism performs
authentication and session key distribution in Universal Mobile
Telecommunications System (UMTS) networks. AKA is a challenge-
response based mechanism that uses symmetric cryptography. AKA is
typically run in a UMTS IM Services Identity Module (ISIM), which
resides on a smart card like device that also provides tamper
resistant storage of shared secrets.
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This document specifies a mapping of AKA parameters onto HTTP Digest
authentication. In essence, this mapping enables the usage of AKA as
a one-time password generation mechanism for Digest authentication.
As the Session Initiation Protocol (SIP) [3] Authentication Framework
closely follows the HTTP Authentication Framework, Digest AKA is
directly applicable to SIP as well as any other embodiment of HTTP
Digest.
1.1 Terminology
This chapter explains the terminology(术语) used in this document.
AKA
Authentication and Key Agreement.
认证与键协议。
AuC
Authentication Center. The network element in mobile networks
that can authorize users either in GSM or in UMTS networks.
认证中心，在GSM和UMTS网络中用于验证用户。
AUTN
Authentication Token. A 128 bit value generated by the AuC, which
together with the RAND parameter authenticates the server to the
client.
网络认证令牌。由认证中心产生的128位数值，并从服务器传输给客户的；认证令牌携带着RAND.
AUTS
Authentication Token. A 112 bit value generated by the client
upon experiencing an SQN synchronization failure.
认证令牌。由客户生成的112位数值。
CK
Cipher Key. An AKA session key for encryption.
密钥。
IK
Integrity Key. An AKA session key for integrity check.
完整性校验密钥。
ISIM
IP Multimedia Services Identity Module.
PIN
Personal Identification Number. Commonly assigned passcodes for
use with automatic cash machines, smart cards, etc.
个人识别号。
RAND
Random Challenge. Generated by the AuC using the SQN.
随机口令。认证中心根据SQN产生。
RES
Authentication Response. Generated by the ISIM.
认证响应。客户端产生的。
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SIM
Subscriber Identity Module. GSM counter part for ISIM.
用户ID
SQN
Sequence Number. Both AuC and ISIM maintain the value of the SQN.
UMTS
Universal Mobile Telecommunications System.
通用移动电信系统
XRES
Expected Authentication Response. In a successful authentication
this is equal to RES.
期望认证响应。期望认证响应是保存在服务其端的。如果期望认证响应等于认证响应，则成功认证。
1.2 Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14, RFC 2119 [1].
2. AKA Mechanism Overview
This chapter describes the AKA operation in detail:
1. A shared secret K is established beforehand between the ISIM and
the Authentication Center (AuC). The secret is stored in the
ISIM, which resides on a smart card like, tamper resistant device.
共享密钥K是根据ISIM和AUC预先定义的。他存储于ISIM中，ISIM保存在智能卡中。
2. The AuC of the home network produces an authentication vector AV,
based on the shared secret K and a sequence number SQN. The
authentication vector contains a random challenge RAND, network
authentication token AUTN, expected authentication result XRES, a
session key for integrity check IK, and a session key for
encryption CK.
认证中心根据共享密钥K和序列号产生认证矢量(AV)。认证矢量包含一下信息：
随机口令(RAND)、网络认证令牌(AUTN)、期望认证响应(XRES)、密钥(CK)和完整性密钥(IK)。
3. The authentication vector is downloaded to a server. Optionally,
the server can also download a batch of AVs, containing more than
one authentication vector.
服务器从认证中心下载认证矢量。另外服务器也可以成批的下载认证矢量。
4. The server creates an authentication request, which contains the
random challenge RAND, and the network authenticator token AUTN.
服务器创建认证请求，认证请求中包含了随机口令RAND和网络认证令牌AUTN。
5. The authentication request is delivered to the client.
服务器产生的认证请求发送到客户端。
6. Using the shared secret K and the sequence number SQN, the client
verifies the AUTN with the ISIM. If the verification is
successful, the network has been authenticated. The client then
produces an authentication response RES, using the shared secret K
and the random challenge RAND.
客户端用公共密钥K和序列号(SQN)校验AUTN；校验成功，则证明接入的网络是合法的。
客户端校验网络成功之后，用共享密钥K和随机口令(RAND)产生认证响应(RES)。
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7. The authentication response, RES, is delivered to the server.
客户端发送认证响应(RES)到服务器。
8. The server compares the authentication response RES with the
expected response, XRES. If the two match, the user has been
successfully authenticated, and the session keys, IK and CK, can
be used for protecting further communications between the client
and the server.
服务器比较认证响应(RES)与期望认证响应(XRES)。如果匹配，则用户认证通过.
IK和CK被用于保护将来的通信。
When verifying the AUTN, the client may detect that the sequence
numbers between the client and the server have fallen out of sync.
In this case, the client produces a synchronization parameter AUTS,
using the shared secret K and the client sequence number SQN. The
AUTS parameter is delivered to the network in the authentication
response, and the authentication can be tried again based on
authentication vectors generated with the synchronized sequence
number.
客户端在验证网络认证令牌（AUTN）时获得了序列号。客户端用共享密钥K和获得的序列号来
产生同步认证令牌（AUTS）。同步认证令牌(AUTS)作为认证响应的一个参数被传输到了服务器。
???认证矢量根据序列号再次检验认证信息。???
For a specification of the AKA mechanism and the generation of the
cryptographic parameters AUTN, RES, IK, CK, and AUTS, see reference
3GPP TS 33.102 [6].
3. Specification of Digest AKA
In general, the Digest AKA operation is identical to the Digest
operation in RFC 2617 [2]. This chapter specifies the parts in which
Digest AKA extends the Digest operation. The notation used in the
Augmented BNF definitions for the new and modified syntax elements in
this section is as used in SIP [3], and any elements not defined in
this section are as defined in SIP and the documents to which it
refers.
3.1 Algorithm Directive
In order to direct the client into using AKA for authentication
instead of the standard password system, the RFC 2617 defined
algorithm directive is overloaded in Digest AKA:
AKA取代了通常的密码认证算法；
algorithm = "algorithm" EQUAL ( aka-namespace
/ algorithm-value )
aka-namespace = aka-version "-" algorithm-value
aka-version = "AKAv" 1*DIGIT
algorithm-value = ( "MD5" / "MD5-sess" / token )
algorithm
A string indicating the algorithm used in producing the digest and
the checksum. If the directive is not understood, the nonce
SHOULD be ignored, and another challenge (if one is present)
should be used instead. The default aka-version is "AKAv1".
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Further AKA versions can be specified, with version numbers
assigned by IANA [7]. When the algorithm directive is not
present, it is assumed to be "MD5". This indicates, that AKA is
not used to produce the Digest password.
Example:
algorithm=AKAv1-MD5
If the entropy of the used RES value is limited (e.g., only 32
bits), reuse of the same RES value in authenticating subsequent
requests and responses is NOT RECOMMENDED. Such a RES value
SHOULD only be used as a one-time password, and algorithms such as
"MD5-sess", which limit the amount of material hashed with a
single key, by producing a session key for authentication, SHOULD
NOT be used.
3.2 Creating a Challenge
In order to deliver the AKA authentication challenge to the client in
Digest AKA, the nonce directive defined in RFC 2617 is extended:
nonce目的是发送AKA认证命令到客户端，一下是在RFC2617上扩展的none定义：
nonce = "nonce" EQUAL ( aka-nonce
/ nonce-value )
aka-nonce = LDQUOT aka-nonce-value RDQUOT
aka-nonce-value =
nonce
A parameter, which is populated with the Base64 [4] encoding of
the concatenation of the AKA authentication challenge RAND, the
AKA AUTN token, and optionally some server specific data, as in
Figure 1.
nonce是个参数。他是由RAND、AUTN和服务器的特殊的数据串联，再用Base64编码。（如图1）
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Example:
nonce="MzQ0a2xrbGtmbGtsZm9wb2tsc2tqaHJzZXNy9uQyMzMzMzQK="
0 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| RAND |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| AUTN |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Server Data...
+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Generating the nonce value.
If the server receives a client authentication containing the "auts"
parameter defined in Section 3.4, that includes a valid AKA AUTS
parameter, the server MUST use it to generate a new challenge to the
client. Note that when the AUTS is present, the included "response"
parameter is calculated using an empty password (password of ""),
instead of a RES.
如果服务器收到的客户认证中包含auts参数，并且是有效的AUTS，这时服务器必须用AUTS生成新的客户端口令。
注意：当AUTS存在时，包括的"response"参数用空密码代替RES来计算。
3.3 Client Authentication
When a client receives a Digest AKA authentication challenge, it
extracts the RAND and AUTN from the "nonce" parameter, and assesses
the AUTN token provided by the server. If the client successfully
authenticates the server with the AUTN, and determines that the SQN
used in generating the challenge is within expected range, the AKA
algorithms are run with the RAND challenge and shared secret K.
当客户端接收到AKA认证口令时，客户端从nonce参数中释放出RAND和AUTN，并且评估AUTN。
如果客户端用AUTN成功认证了服务器，并且SQN是在期望的范围内，这时客户端使用RAND和共享密钥K进行AKA运算。
The resulting AKA RES parameter is treated as a "password" when
calculating the response directive of RFC 2617.
运算结果RES被视为计算response时的密码。
3.4 Synchronization Failure（同步失败）
For indicating an AKA sequence number synchronization failure, and to
re-synchronize the SQN in the AuC using the AUTS token, a new
directive is defined for the "digest-response" of the "Authorization"
request header defined in RFC 2617:
AUTS是用于代表AKA序号同步失败和需要重新同步，因此对
头字段Authorization的digest-response参数增加了一个新的描述信息AUTS。
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auts = "auts" EQUAL auts-param
auts-param = LDQUOT auts-value RDQUOT
auts-value =
auts
A string carrying a base64 encoded AKA AUTS parameter. This
directive is used to re-synchronize the server side SQN. If the
directive is present, the client doesn't use any password when
calculating its credentials. Instead, the client MUST calculate
its credentials using an empty password (password of "").
AUTS是用base64编码。指示服务器重新同步SQN。如果AUTS存在，则客户端
不需要使用密码（password）计算证书，计算时密码（password）置为空字符串。
Example:
auts="CjkyMzRfOiwg5CfkJ2UK="
Upon receiving the "auts" parameter, the server will check the
validity of the parameter value using the shared secret K. A valid
AUTS parameter is used to re-synchronize the SQN in the AuC. The
synchronized SQN is then used to generate a fresh authentication
vector AV, with which the client is then re-challenged.
服务器用共享密钥K检查接收的AUTS值的有效性。有效的AUTS用于重新同步AuC的SQN。
用新同步的序列号生成新的认证矢量（AU）。
3.5 Server Authentication
Even though AKA provides inherent mutual authentication with the AKA
AUTN token, mutual authentication mechanisms provided by Digest may
still be useful in order to provide message integrity.
In Digest AKA, the server uses the AKA XRES parameter as "password"
when calculating the "response-auth" of the "Authentication-Info"
header defined in RFC 2617.
在AKA摘要中，服务器在计算头字段Authentication-Info的response-auth参数时，用XRES代替密码（password）。
4. Example Digest AKA Operation
Figure 2 below describes a message flow describing a Digest AKA
process of authenticating a SIP request, namely the SIP REGISTER
request.
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Client Server
| 1) REGISTER |
|------------------------------------------------------>|
| |
| +-----------------------------+
| | Server runs AKA algorithms, |
| | generates RAND and AUTN. |
| +-----------------------------+
| |
| 2) 401 Unauthorized |
| WWW-Authenticate: Digest |
| (RAND, AUTN delivered) |
|<------------------------------------------------------|
| |
+------------------------------------+ |
| Client runs AKA algorithms on ISIM,| |
| verifies AUTN, derives RES | |
| and session keys. | |
+------------------------------------+ |
| |
| 3) REGISTER |
| Authorization: Digest (RES is used) |
|------------------------------------------------------>|
| |
| +------------------------------+
| | Server checks the given RES, |
| | and finds it correct. |
| +------------------------------+
| |
| 4) 200 OK |
| Authentication-Info: (XRES is used) |
|<------------------------------------------------------|
| |
Figure 2: Message flow representing a successful authentication.
1) Initial request
REGISTER sip:home.mobile.biz SIP/2.0
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2) Response containing a challenge
SIP/2.0 401 Unauthorized
WWW-Authenticate: Digest
realm="[email protected]",
nonce="CjPk9mRqNuT25eRkajM09uTl9nM09uTl9nMz5OX25PZz==",
qop="auth,auth-int",
opaque="5ccc069c403ebaf9f0171e9517f40e41",
algorithm=AKAv1-MD5
3) Request containing credentials
REGISTER sip:home.mobile.biz SIP/2.0
Authorization: Digest
username="[email protected]",
realm="[email protected]",
nonce="CjPk9mRqNuT25eRkajM09uTl9nM09uTl9nMz5OX25PZz==",
uri="sip:home.mobile.biz",
qop=auth-int,
nc=00000001,
cnonce="0a4f113b",
response="6629fae49393a05397450978507c4ef1",
opaque="5ccc069c403ebaf9f0171e9517f40e41"
4) Successful response
SIP/2.0 200 OK
Authentication-Info:
qop=auth-int,
rspauth="6629fae49393a05397450978507c4ef1",
cnonce="0a4f113b",
nc=00000001
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Figure 3 below describes a message flow describing a Digest AKA
authentication process, in which there is a synchronization failure.
Client Server
| 1) REGISTER |
|------------------------------------------------------>|
| |
| +-----------------------------+
| | Server runs AKA algorithms, |
| | generates RAND and AUTN. |
| +-----------------------------+
| |
| 2) 401 Unauthorized |
| WWW-Authenticate: Digest |
| (RAND, AUTN delivered) |
|<------------------------------------------------------|
| |
+------------------------------------+ |
| Client runs AKA algorithms on ISIM,| |
| verifies the AUTN, but discovers | |
| that it contains an invalid | |
| sequence number. The client then | |
| generates an AUTS token. | |
+------------------------------------+ |
| |
| 3) REGISTER |
| Authorization: Digest (AUTS is delivered) |
|------------------------------------------------------>|
| |
| +-----------------------+
| | Server performs |
| | re-synchronization |
| | using AUTS and RAND. |
| +-----------------------+
| |
| 4) 401 Unauthorized |
| WWW-Authenticate: Digest |
| (re-synchronized RAND, |
| AUTN delivered) |
|<------------------------------------------------------|
| |
Figure 3: Message flow representing an authentication synchronization
failure.
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1) Initial request
REGISTER sip:home.mobile.biz SIP/2.0
2) Response containing a challenge
SIP/2.0 401 Unauthorized
WWW-Authenticate: Digest
realm="[email protected]",
qop="auth",
nonce="CjPk9mRqNuT25eRkajM09uTl9nM09uTl9nMz5OX25PZz==",
opaque="5ccc069c403ebaf9f0171e9517f40e41",
algorithm=AKAv1-MD5
3) Request containing credentials
REGISTER sip:home.mobile.biz SIP/2.0
Authorization: Digest
username="[email protected]",
realm="[email protected]",
nonce="CjPk9mRqNuT25eRkajM09uTl9nM09uTl9nMz5OX25PZz==",
uri="sip:home.mobile.biz",
qop=auth,
nc=00000001,
cnonce="0a4f113b",
response="4429ffe49393c02397450934607c4ef1",
opaque="5ccc069c403ebaf9f0171e9517f40e41",
auts="5PYxMuX2NOT2NeQ="
4) Response containing a new challenge
SIP/2.0 401 Unauthorized
WWW-Authenticate: Digest
realm="[email protected]",
qop="auth,auth-int",
nonce="9uQzNPbk9jM05Pbl5Pbl5DIz9uTl9uTl9jM0NTHk9uXk==",
opaque="dcd98b7102dd2f0e8b11d0f600bfb0c093",
algorithm=AKAv1-MD5
5. Security Considerations
In general, Digest AKA is vulnerable to the same security threats as
HTTP authentication [2]. This chapter discusses the relevant
exceptions.
一般来说，AKA摘要作为HTTP认证方式是易受完全攻击的。本节讨论相关的异常。
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5.1 Authentication of Clients using Digest AKA
AKA is typically -- though this isn't a theoretical limitation -- run
on an ISIM application that usually resides in a tamper resistant
smart card. Interfaces to the ISIM exist, which enable the host
device to request authentication to be performed on the card.
However, these interfaces do not allow access to the long-term secret
outside the ISIM, and the authentication can only be performed if the
device accessing the ISIM has knowledge of a PIN code, shared between
the user and the ISIM. Such PIN codes are typically obtained from
user input, and are usually required when the device is powered on.
The use of tamper resistant cards with secure interfaces implies that
Digest AKA is typically more secure than regular Digest
implementations, as neither possession of the host device nor Trojan
Horses in the software give access to the long term secret. Where a
PIN scheme is used, the user is also authenticated when the device is
powered on. However, there may be a difference in the resulting
security of Digest AKA, compared to traditional Digest
implementations, depending of course on whether those implementations
cache/store passwords that are received from the user.
5.2 Limited Use of Nonce Values
The Digest scheme uses server-specified nonce values to seed the
generation of the request-digest value. The server is free to
construct the nonce in such a way, that it may only be used from a
particular client, for a particular resource, for a limited period of
time or number of uses, or any other restrictions. Doing so
strengthens the protection provided against, for example, replay
attacks.
Digest AKA limits the applicability of a nonce value to a particular
ISIM. Typically, the ISIM is accessible only to one client device at
a time. However, the nonce values are strong and secure even though
limited to a particular ISIM. Additionally, this requires that the
server is provided with the client identity before an authentication
challenge can be generated. If a client identity is not available,
an additional round trip is needed to acquire it. Such a case is
analogous to an AKA synchronization failure.
A server may allow each nonce value to be used only once by sending a
next-nonce directive in the Authentication-Info header field of every
response. However, this may cause a synchronization failure, and
consequently some additional round trips in AKA, if the same SQN
space is also used for other access schemes at the same time.
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5.3 Multiple Authentication Schemes and Algorithms
In HTTP authentication, a user agent MUST choose the strongest
authentication scheme it understands and request credentials from the
user, based upon that challenge.
In general, using passwords generated by Digest AKA with other HTTP
authentication schemes is not recommended even though the realm
values or protection domains would coincide. In these cases, a
password should be requested from the end-user instead. Digest AKA
passwords MUST NOT be re-used with such HTTP authentication schemes,
which send the password in clear. In particular, AKA passwords MUST
NOT be re-used with HTTP Basic.
The same principle must be applied within a scheme if several
algorithms are supported. A client receiving an HTTP Digest
challenge with several available algorithms MUST choose the strongest
algorithm it understands. For example, Digest with "AKAv1-MD5" would
be stronger than Digest with "MD5".
5.4 Online Dictionary Attacks
Since user-selected passwords are typically quite simple, it has been
proposed that servers should not accept passwords for HTTP Digest,
which are in the dictionary [2]. This potential threat does not
exist in HTTP Digest AKA because the algorithm will use ISIM
originated passwords. However, the end-user must still be careful
with PIN codes. Even though HTTP Digest AKA password requests are
never displayed to the end-user, she will be authenticated to the
ISIM via a PIN code. Commonly known initial PIN codes are typically
installed to the ISIM during manufacturing and if the end-users do
not change them, there is a danger that an unauthorized user may be
able to use the device. Naturally this requires that the
unauthorized user has access to the physical device, and that the
end-user has not changed the initial PIN code. For this reason,
end-users are strongly encouraged to change their PIN codes when they
receive an ISIM.
5.5 Session Protection
Digest AKA is able to generate additional session keys for integrity
(IK) and confidentiality (CK) protection. Even though this document
does not specify the use of these additional keys, they may be used
for creating additional security within HTTP authentication or some
other security mechanism.
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5.6 Replay Protection
AKA allows sequence numbers to be tracked for each authentication,
with the SQN parameter. This allows authentications to be replay
protected even if the RAND parameter happened to be the same for two
authentication requests. More importantly, this offers additional
protection for the case where an attacker replays an old
authentication request sent by the network. The client will be able
to detect that the request is old, and refuse authentication. This
proves liveliness of the authentication request even in the case
where a MitM attacker tries to trick the client into providing an
authentication response, and then replaces parts of the message with
something else. In other words, a client challenged by Digest AKA is
not vulnerable for chosen plain text attacks. Finally, frequent
sequence number errors would reveal an attack where the tamper
resistant card has been cloned and is being used in multiple devices.
The downside of sequence number tracking is that servers must hold
more information for each user than just their long-term secret,
namely the current SQN value. However, this information is typically
not stored in the SIP nodes, but in dedicated authentication servers
instead.
5.7 Improvements to AKA Security
Even though AKA is perceived as a secure mechanism, Digest AKA is
able to improve it. More specifically, the AKA parameters carried
between the client and the server during authentication may be
protected along with other parts of the message by using Digest AKA.
This is not possible with plain AKA.
6. IANA Considerations
This document specifies an aka-version namespace in Section 3.1 which
requires a central coordinating body. The body responsible for this
coordination is the Internet Assigned Numbers Authority (IANA).
The default aka-version defined in this document is "AKAv1".
Following the policies outlined in [5], versions above 1 are
allocated as Expert Review.
Registrations with the IANA MUST include the version number being
registered, including the "AKAv" prefix. For example, a registration
for "AKAv2" would potentially be a valid one, whereas a registration
for "FOOv2" or "2" would not be valid. Further, the registration
MUST include contact information for the party responsible for the
registration.
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As this document defines the default aka-version, the initial IANA
registration for aka-version values will contain an entry for
"AKAv1".
6.1 Registration Template
To: [email protected]
Subject: Registration of a new AKA version
Version identifier:
(Must contain a valid aka-version value,
as described in section 3.1.)
Person & email address to contact for further information:
(Must contain contact information for the
person(s) responsible for the registration.)
Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
Leach, P., Luotonen, A. and L. Stewart, "HTTP Authentication:
Basic and Digest Access Authentication", RFC 2617, June 1999.
[3] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP:
Session Initiation Protocol", RFC 3261, June 2002.
[4] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message Bodies",
RFC 2045, November 1996.
Informative References
[5] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.
[6] 3rd Generation Partnership Project, "Security Architecture
(Release 4)", TS 33.102, December 2001.
[7] http://www.iana.org, "Assigned Numbers".
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Appendix A. Acknowledgements
The authors would like to thank Sanjoy Sen, Jonathan Rosenberg, Pete
McCann, Tao Haukka, Ilkka Uusitalo, Henry Haverinen, John Loughney,
Allison Mankin and Greg Rose.
Authors' Addresses
Aki Niemi
Nokia
P.O. Box 301
NOKIA GROUP, FIN 00045
Finland
Phone: +358 50 389 1644
EMail: [email protected]
Jari Arkko
Ericsson
Hirsalantie 1
Jorvas, FIN 02420
Finland
Phone: +358 40 5079256
EMail: [email protected]
Vesa Torvinen
Ericsson
Joukahaisenkatu 1
Turku, FIN 20520
Finland
Phone: +358 40 7230822
EMail: [email protected]
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RFC 3310 HTTP Digest Authentication Using AKA September 2002
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