< draft-ietf-emu-rfc5448bis-04.txt   draft-ietf-emu-rfc5448bis-05.txt >
Network Working Group J. Arkko Network Working Group J. Arkko
Internet-Draft V. Lehtovirta Internet-Draft V. Lehtovirta
Obsoletes: 5448 (if approved) V. Torvinen Obsoletes: 5448 (if approved) V. Torvinen
Updates: 4187 (if approved) Ericsson Updates: 4187 (if approved) Ericsson
Intended status: Informational P. Eronen Intended status: Informational P. Eronen
Expires: July 21, 2019 Independent Expires: January 9, 2020 Independent
January 17, 2019 July 8, 2019
Improved Extensible Authentication Protocol Method for 3rd Generation Improved Extensible Authentication Protocol Method for 3GPP Mobile
Authentication and Key Agreement (EAP-AKA') Network Authentication and Key Agreement (EAP-AKA')
draft-ietf-emu-rfc5448bis-04 draft-ietf-emu-rfc5448bis-05
Abstract Abstract
The 3rd Generation Authentication and Key Agreement (AKA) is the The 3GPP Mobile Network Authentication and Key Agreement (AKA) is the
primary authentication mechanism for devices wishing to access mobile primary authentication mechanism for devices wishing to access mobile
networks. RFC 4187 (EAP-AKA) made the use of this mechanism possible networks. RFC 4187 (EAP-AKA) made the use of this mechanism possible
within the Extensible Authentication Protocol (EAP) framework. RFC within the Extensible Authentication Protocol (EAP) framework. RFC
5448 (EAP-AKA') was an improved version of EAP-AKA. 5448 (EAP-AKA') was an improved version of EAP-AKA.
This memo is an update of the specification for EAP-AKA'. This This memo replaces the specification of EAP-AKA'. EAP-AKA' was
version obsoletes RFC 5448. defined in RFC 5448 and updated EAP-AKA RFC 4187. As such this
document obsoletes RFC 5448 and updates RFC 4187.
EAP-AKA' differs from EAP-AKA by providing a key derivation function EAP-AKA' differs from EAP-AKA by providing a key derivation function
that binds the keys derived within the method to the name of the that binds the keys derived within the method to the name of the
access network. The key derivation function has been defined in the access network. The key derivation function has been defined in the
3rd Generation Partnership Project (3GPP). EAP-AKA' allows its use 3rd Generation Partnership Project (3GPP). EAP-AKA' allows its use
in EAP in an interoperable manner. EAP-AKA' is also an algorithm in EAP in an interoperable manner. EAP-AKA' is also an algorithm
update, as it employs SHA-256 instead of SHA-1 as in EAP-AKA. update, as it employs SHA-256 / HMAC-SHA-256 instead of SHA-1 / HMAC-
SHA-1 as in EAP-AKA.
This version of EAP-AKA' specification specifies the protocol This version of EAP-AKA' specification specifies the protocol
behaviour for 5G deployments as well. behaviour for 5G deployments as well.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on July 21, 2019.
This Internet-Draft will expire on January 9, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 33 skipping to change at page 2, line 36
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 5 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 5
3. EAP-AKA' . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. EAP-AKA' . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. AT_KDF_INPUT . . . . . . . . . . . . . . . . . . . . . . 8 3.1. AT_KDF_INPUT . . . . . . . . . . . . . . . . . . . . . . 8
3.2. AT_KDF . . . . . . . . . . . . . . . . . . . . . . . . . 11 3.2. AT_KDF . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.3. Key Derivation . . . . . . . . . . . . . . . . . . . . . 13 3.3. Key Derivation . . . . . . . . . . . . . . . . . . . . . 13
3.4. Hash Functions . . . . . . . . . . . . . . . . . . . . . 15 3.4. Hash Functions . . . . . . . . . . . . . . . . . . . . . 15
3.4.1. PRF' . . . . . . . . . . . . . . . . . . . . . . . . 15 3.4.1. PRF' . . . . . . . . . . . . . . . . . . . . . . . . 15
3.4.2. AT_MAC . . . . . . . . . . . . . . . . . . . . . . . 15 3.4.2. AT_MAC . . . . . . . . . . . . . . . . . . . . . . . 15
3.4.3. AT_CHECKCODE . . . . . . . . . . . . . . . . . . . . 15 3.4.3. AT_CHECKCODE . . . . . . . . . . . . . . . . . . . . 15
4. Bidding Down Prevention for EAP-AKA . . . . . . . . . . . . . 16 3.5. Summary of Attributes for EAP-AKA' . . . . . . . . . . . 16
5. Peer Identities . . . . . . . . . . . . . . . . . . . . . . . 17 4. Bidding Down Prevention for EAP-AKA . . . . . . . . . . . . . 18
5.1. Username Types in EAP-AKA' Identities . . . . . . . . . . 18 4.1. Summary of Attributes for EAP-AKA . . . . . . . . . . . . 19
5. Peer Identities . . . . . . . . . . . . . . . . . . . . . . . 20
5.1. Username Types in EAP-AKA' Identities . . . . . . . . . . 20
5.2. Generating Pseudonyms and Fast Re-Authentication 5.2. Generating Pseudonyms and Fast Re-Authentication
Identities . . . . . . . . . . . . . . . . . . . . . . . 18 Identities . . . . . . . . . . . . . . . . . . . . . . . 21
5.3. Identifier Usage in 5G . . . . . . . . . . . . . . . . . 19 5.3. Identifier Usage in 5G . . . . . . . . . . . . . . . . . 22
5.3.1. Key Derivation . . . . . . . . . . . . . . . . . . . 20 5.3.1. Key Derivation . . . . . . . . . . . . . . . . . . . 23
5.3.2. EAP Identity Response and EAP-AKA' AT_IDENTITY 5.3.2. EAP Identity Response and EAP-AKA' AT_IDENTITY
Attribute . . . . . . . . . . . . . . . . . . . . . . 21 Attribute . . . . . . . . . . . . . . . . . . . . . . 24
6. Exported Parameters . . . . . . . . . . . . . . . . . . . . . 23 6. Exported Parameters . . . . . . . . . . . . . . . . . . . . . 25
7. Security Considerations . . . . . . . . . . . . . . . . . . . 24 7. Security Considerations . . . . . . . . . . . . . . . . . . . 26
7.1. Privacy . . . . . . . . . . . . . . . . . . . . . . . . . 26 7.1. Privacy . . . . . . . . . . . . . . . . . . . . . . . . . 29
7.2. Discovered Vulnerabilities . . . . . . . . . . . . . . . 28 7.2. Discovered Vulnerabilities . . . . . . . . . . . . . . . 30
7.3. Pervasive Monitoring . . . . . . . . . . . . . . . . . . 30 7.3. Pervasive Monitoring . . . . . . . . . . . . . . . . . . 33
7.4. Security Properties of Binding Network Names . . . . . . 30 7.4. Security Properties of Binding Network Names . . . . . . 33
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 31 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 34
8.1. Type Value . . . . . . . . . . . . . . . . . . . . . . . 32 8.1. Type Value . . . . . . . . . . . . . . . . . . . . . . . 35
8.2. Attribute Type Values . . . . . . . . . . . . . . . . . . 32 8.2. Attribute Type Values . . . . . . . . . . . . . . . . . . 35
8.3. Key Derivation Function Namespace . . . . . . . . . . . . 32 8.3. Key Derivation Function Namespace . . . . . . . . . . . . 35
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 35
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 32 9.1. Normative References . . . . . . . . . . . . . . . . . . 35
9.1. Normative References . . . . . . . . . . . . . . . . . . 32 9.2. Informative References . . . . . . . . . . . . . . . . . 37
9.2. Informative References . . . . . . . . . . . . . . . . . 34 Appendix A. Changes from RFC 5448 . . . . . . . . . . . . . . . 41
Appendix A. Changes from RFC 5448 . . . . . . . . . . . . . . . 37 Appendix B. Changes from RFC 4187 to RFC 5448 . . . . . . . . . 41
Appendix B. Changes from RFC 4187 to RFC 5448 . . . . . . . . . 38 Appendix C. Changes from Previous Version of This Draft . . . . 42
Appendix C. Changes from Previous Version of This Draft . . . . 38 Appendix D. Importance of Explicit Negotiation . . . . . . . . . 43
Appendix D. Importance of Explicit Negotiation . . . . . . . . . 39 Appendix E. Test Vectors . . . . . . . . . . . . . . . . . . . . 44
Appendix E. Test Vectors . . . . . . . . . . . . . . . . . . . . 40 Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Appendix F. Contributors . . . . . . . . . . . . . . . . . . . . 44 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 49
Appendix G. Acknowledgments . . . . . . . . . . . . . . . . . . 45 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 49
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 45
1. Introduction 1. Introduction
The 3rd Generation Authentication and Key Agreement (AKA) is the The 3GPP Mobile Network Authentication and Key Agreement (AKA) is the
primary authentication mechanism for devices wishing to access mobile primary authentication mechanism for devices wishing to access mobile
networks. [RFC4187] (EAP-AKA) made the use of this mechanism networks. [RFC4187] (EAP-AKA) made the use of this mechanism
possible within the Extensible Authentication Protocol (EAP) possible within the Extensible Authentication Protocol (EAP)
framework [RFC3748]. framework [RFC3748].
[RFC5448] (EAP-AKA') was an improved version of EAP-AKA. This memo [RFC5448] (EAP-AKA') was an improved version of EAP-AKA. This memo
is an update of the specification for EAP-AKA'. This version replaces the specification of EAP-AKA'. EAP-AKA' was defined in RFC
obsoletes RFC 5448. 5448 and updated EAP-AKA RFC 4187. As such this document obsoletes
RFC 5448 and updates RFC 4187.
EAP-AKA' is commonly implemented in smart phones and network EAP-AKA' is commonly implemented in mobile phones and network
equipment. It can be used for authentication to gain network access equipment. It can be used for authentication to gain network access
via Wireless LAN networks and, with 5G, also directly to mobile via Wireless LAN networks and, with 5G, also directly to mobile
networks. networks.
EAP-AKA' differs from EAP-AKA by providing a different key derivation EAP-AKA' differs from EAP-AKA by providing a different key derivation
function. This function binds the keys derived within the method to function. This function binds the keys derived within the method to
the name of the access network. This limits the effects of the name of the access network. This limits the effects of
compromised access network nodes and keys. EAP-AKA' is also an compromised access network nodes and keys. EAP-AKA' is also an
algorithm update for the used hash functions. algorithm update for the used hash functions.
The EAP-AKA' method employs the derived keys CK' and IK' from the The EAP-AKA' method employs the derived keys CK' and IK' from the
3GPP specification [TS-3GPP.33.402] and updates the used hash 3GPP specification [TS-3GPP.33.402] and updates the used hash
function to SHA-256 [FIPS.180-4]. Otherwise, EAP-AKA' is equivalent function to SHA-256 [FIPS.180-4] and HMAC to HMAC-SHA-256.
to EAP-AKA. Given that a different EAP method type value is used for Otherwise, EAP-AKA' is equivalent to EAP-AKA. Given that a different
EAP-AKA and EAP-AKA', a mutually supported method may be negotiated EAP method type value is used for EAP-AKA and EAP-AKA', a mutually
using the standard mechanisms in EAP [RFC3748]. supported method may be negotiated using the standard mechanisms in
EAP [RFC3748].
Note that any change of the key derivation must be unambiguous to Note that any change of the key derivation must be unambiguous to
both sides in the protocol. That is, it must not be possible to both sides in the protocol. That is, it must not be possible to
accidentally connect old equipment to new equipment and get the accidentally connect old equipment to new equipment and get the
key derivation wrong or attempt to use wrong keys without getting key derivation wrong or attempt to use wrong keys without getting
a proper error message. See Appendix D for further information. a proper error message. See Appendix D for further information.
Note also that choices in authentication protocols should be Note also that choices in authentication protocols should be
secure against bidding down attacks that attempt to force the secure against bidding down attacks that attempt to force the
participants to use the least secure function. See Section 4 for participants to use the least secure function. See Section 4 for
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The rest of this specification is structured as follows. Section 3 The rest of this specification is structured as follows. Section 3
defines the EAP-AKA' method. Section 4 adds support to EAP-AKA to defines the EAP-AKA' method. Section 4 adds support to EAP-AKA to
prevent bidding down attacks from EAP-AKA'. Section 5 specifies prevent bidding down attacks from EAP-AKA'. Section 5 specifies
requirements regarding the use of peer identities, including how how requirements regarding the use of peer identities, including how how
EAP-AKA' identifiers are used in 5G context. Section 6 specifies EAP-AKA' identifiers are used in 5G context. Section 6 specifies
what parameters EAP-AKA' exports out of the method. Section 7 what parameters EAP-AKA' exports out of the method. Section 7
explains the security differences between EAP-AKA and EAP-AKA'. explains the security differences between EAP-AKA and EAP-AKA'.
Section 8 describes the IANA considerations and Appendix A and Section 8 describes the IANA considerations and Appendix A and
Appendix B explains what updates to RFC 5448 EAP-AKA' and RFC 4187 Appendix B explains what updates to RFC 5448 EAP-AKA' and RFC 4187
EAP-AKA have been made in this specification. Appendix D explains EAP-AKA have been made in this specification. Appendix D explains
some of the design rationale for creating EAP-AKA' Finally, some of the design rationale for creating EAP-AKA'. Finally,
Appendix E provides test vectors. Appendix E provides test vectors.
Editor's Note: The publication of this RFC depends on its Editor's Note: The publication of this RFC depends on its
normative references [TS-3GPP.24.302] and [TS-3GPP.33.501] normative references to 3GPP Technical Specifications reaching a
reaching a stable status for Release 15, as indicated by 3GPP. stable status for Release 15, as indicated by 3GPP. The RFC
This is expected to happen shortly. The RFC Editor should check Editor should check with the 3GPP liaisons that a stable version
with the 3GPP liaisons that this has happened. RFC Editor: Please from Release 15 is available and refer to that version. RFC
delete this note upon publication of this specification as an RFC. Editor: Please delete this note upon publication of this
specification as an RFC.
2. Requirements Language 2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
3. EAP-AKA' 3. EAP-AKA'
EAP-AKA' is an EAP method that follows the EAP-AKA specification EAP-AKA' is an EAP method that follows the EAP-AKA specification
[RFC4187] in all respects except the following: [RFC4187] in all respects except the following:
o It uses the Type code 50, not 23 (which is used by EAP-AKA). o It uses the Type code 0x32, not 0x17 (which is used by EAP-AKA).
o It carries the AT_KDF_INPUT attribute, as defined in Section 3.1, o It carries the AT_KDF_INPUT attribute, as defined in Section 3.1,
to ensure that both the peer and server know the name of the to ensure that both the peer and server know the name of the
access network. access network.
o It supports key derivation function negotiation via the AT_KDF o It supports key derivation function negotiation via the AT_KDF
attribute (Section 3.2) to allow for future extensions. attribute (Section 3.2) to allow for future extensions.
o It calculates keys as defined in Section 3.3, not as defined in o It calculates keys as defined in Section 3.3, not as defined in
EAP-AKA. EAP-AKA.
o It employs SHA-256, not SHA-1 [FIPS.180-4] (Section 3.4). o It employs SHA-256 / HMAC-SHA-256, not SHA-1 / HMAC-SHA-1
[FIPS.180-4] (Section 3.4 [RFC2104]).
Figure 1 shows an example of the authentication process. Each Figure 1 shows an example of the authentication process. Each
message AKA'-Challenge and so on represents the corresponding message message AKA'-Challenge and so on represents the corresponding message
from EAP-AKA, but with EAP-AKA' Type code. The definition of these from EAP-AKA, but with EAP-AKA' Type code. The definition of these
messages, along with the definition of attributes AT_RAND, AT_AUTN, messages, along with the definition of attributes AT_RAND, AT_AUTN,
AT_MAC, and AT_RES can be found in [RFC4187]. AT_MAC, and AT_RES can be found in [RFC4187].
Peer Server Peer Server
| EAP-Request/Identity | | EAP-Request/Identity |
|<-------------------------------------------------------| |<-------------------------------------------------------|
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| EAP-Success | | EAP-Success |
|<-------------------------------------------------------| |<-------------------------------------------------------|
Figure 1: EAP-AKA' Authentication Process Figure 1: EAP-AKA' Authentication Process
EAP-AKA' can operate on the same credentials as EAP-AKA and employ EAP-AKA' can operate on the same credentials as EAP-AKA and employ
the same identities. However, EAP-AKA' employs different leading the same identities. However, EAP-AKA' employs different leading
characters than EAP-AKA for the conventions given in Section 4.1.1 of characters than EAP-AKA for the conventions given in Section 4.1.1 of
[RFC4187] for International Mobile Subscriber Identifier (IMSI) based [RFC4187] for International Mobile Subscriber Identifier (IMSI) based
usernames. EAP-AKA' MUST use the leading character "6" (ASCII 36 usernames. EAP-AKA' MUST use the leading character "6" (ASCII 36
hexadecimal) instead of "0" for IMSI-based permanent usernames. All hexadecimal) instead of "0" for IMSI-based permanent usernames, or
other usage and processing of the leading characters, usernames, and 5G-specific identifiers in 5G networks. Identifier usage in 5G is
identities is as defined by EAP-AKA [RFC4187]. For instance, the specified in Section 5.3. All other usage and processing of the
pseudonym and fast re-authentication usernames need to be constructed leading characters, usernames, and identities is as defined by EAP-
so that the server can recognize them. As an example, a pseudonym AKA [RFC4187]. For instance, the pseudonym and fast re-
could begin with a leading "7" character (ASCII 37 hexadecimal) and a authentication usernames need to be constructed so that the server
fast re-authentication username could begin with "8" (ASCII 38 can recognize them. As an example, a pseudonym could begin with a
hexadecimal). Note that a server that implements only EAP-AKA may leading "7" character (ASCII 37 hexadecimal) and a fast re-
not recognize these leading characters. According to Section 4.1.4 authentication username could begin with "8" (ASCII 38 hexadecimal).
of [RFC4187], such a server will re-request the identity via the EAP- Note that a server that implements only EAP-AKA may not recognize
Request/AKA-Identity message, making obvious to the peer that EAP-AKA these leading characters. According to Section 4.1.4 of [RFC4187],
and associated identity are expected. such a server will re-request the identity via the EAP- Request/AKA-
Identity message, making obvious to the peer that EAP-AKA and
associated identity are expected.
3.1. AT_KDF_INPUT 3.1. AT_KDF_INPUT
The format of the AT_KDF_INPUT attribute is shown below. The format of the AT_KDF_INPUT attribute is shown below.
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AT_KDF_INPUT | Length | Actual Network Name Length | | AT_KDF_INPUT | Length | Actual Network Name Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 11, line 29 skipping to change at page 11, line 29
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields are as follows: The fields are as follows:
AT_KDF AT_KDF
This is set to 24. This is set to 24.
Length Length
The length of the attribute, MUST be set to 1. The length of the attribute, calculated as defined in [RFC4187],
Section 8.1. For AT_KDF, the Length field MUST be set to 1.
Key Derivation Function Key Derivation Function
An enumerated value representing the key derivation function that An enumerated value representing the key derivation function that
the server (or peer) wishes to use. Value 1 represents the the server (or peer) wishes to use. Value 1 represents the
default key derivation function for EAP-AKA', i.e., employing CK' default key derivation function for EAP-AKA', i.e., employing CK'
and IK' as defined in Section 3.3. and IK' as defined in Section 3.3.
Servers MUST send one or more AT_KDF attributes in the EAP-Request/ Servers MUST send one or more AT_KDF attributes in the EAP-Request/
AKA'-Challenge message. These attributes represent the desired AKA'-Challenge message. These attributes represent the desired
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alternative, the peer behaves as if AUTN had been incorrect and alternative, the peer behaves as if AUTN had been incorrect and
authentication fails (see Figure 3 of [RFC4187]). The peer fails the authentication fails (see Figure 3 of [RFC4187]). The peer fails the
authentication also if there are any duplicate values within the list authentication also if there are any duplicate values within the list
of AT_KDF attributes (except where the duplication is due to a of AT_KDF attributes (except where the duplication is due to a
request to change the key derivation function; see below for further request to change the key derivation function; see below for further
information). information).
Upon receiving an EAP-Response/AKA'-Challenge with AT_KDF from the Upon receiving an EAP-Response/AKA'-Challenge with AT_KDF from the
peer, the server checks that the suggested AT_KDF value was one of peer, the server checks that the suggested AT_KDF value was one of
the alternatives in its offer. The first AT_KDF value in the message the alternatives in its offer. The first AT_KDF value in the message
from the server is not a valid alternative. If the peer has replied from the server is not a valid alternative since the peer should have
accepted it without further negotiation. If the peer has replied
with the first AT_KDF value, the server behaves as if AT_MAC of the with the first AT_KDF value, the server behaves as if AT_MAC of the
response had been incorrect and fails the authentication. For an response had been incorrect and fails the authentication. For an
overview of the failed authentication process in the server side, see overview of the failed authentication process in the server side, see
Section 3 and Figure 2 of [RFC4187]. Otherwise, the server re-sends Section 3 and Figure 2 of [RFC4187]. Otherwise, the server re-sends
the EAP-Response/AKA'-Challenge message, but adds the selected the EAP-Response/AKA'-Challenge message, but adds the selected
alternative to the beginning of the list of AT_KDF attributes and alternative to the beginning of the list of AT_KDF attributes and
retains the entire list following it. Note that this means that the retains the entire list following it. Note that this means that the
selected alternative appears twice in the set of AT_KDF values. selected alternative appears twice in the set of AT_KDF values.
Responding to the peer's request to change the key derivation Responding to the peer's request to change the key derivation
function is the only legal situation where such duplication may function is the only legal situation where such duplication may
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occurred in the list of AT_KDF attributes. If so, it continues with occurred in the list of AT_KDF attributes. If so, it continues with
processing the received EAP-Request/AKA'-Challenge as specified in processing the received EAP-Request/AKA'-Challenge as specified in
[RFC4187] and Section 3.1 of this document. If not, it behaves as if [RFC4187] and Section 3.1 of this document. If not, it behaves as if
AT_MAC had been incorrect and fails the authentication. If the peer AT_MAC had been incorrect and fails the authentication. If the peer
receives multiple EAP-Request/AKA'-Challenge messages with differing receives multiple EAP-Request/AKA'-Challenge messages with differing
AT_KDF attributes without having requested negotiation, the peer MUST AT_KDF attributes without having requested negotiation, the peer MUST
behave as if AT_MAC had been incorrect and fail the authentication. behave as if AT_MAC had been incorrect and fail the authentication.
Note that the peer may also request sequence number resynchronization Note that the peer may also request sequence number resynchronization
[RFC4187]. This happens after AT_KDF negotiation has already [RFC4187]. This happens after AT_KDF negotiation has already
completed. An AKA'-Synchronization-Failure message is sent as a completed. That is, the EAP-Request/AKA'-Challenge and, possibly,
response to the newly received EAP-Request/AKA'-Challenge (the last the EAP-Response/AKA'-Challenge message are exchanged first to come
message of the AT_KDF negotiation). The AKA'-Synchronization-Failure up with a mutually acceptable key derivation function, and only then
the possible AKA'-Synchronization-Failure message is sent. The AKA'-
Synchronization-Failure message is sent as a response to the newly
received EAP-Request/AKA'-Challenge which is the last message of the
AT_KDF negotiation. Note that if the first proposed KDF is
acceptable, then last message is at the same time the first EAP-
Request/AKA'-Challenge message. The AKA'-Synchronization-Failure
message MUST contain the AUTS parameter as specified in [RFC4187] and message MUST contain the AUTS parameter as specified in [RFC4187] and
a copy the AT_KDF attributes as they appeared in the last message of a copy the AT_KDF attributes as they appeared in the last message of
the AT_KDF negotiation. If the AT_KDF attributes are found to differ the AT_KDF negotiation. If the AT_KDF attributes are found to differ
from their earlier values, the peer and server MUST behave as if from their earlier values, the peer and server MUST behave as if
AT_MAC had been incorrect and fail the authentication. AT_MAC had been incorrect and fail the authentication.
3.3. Key Derivation 3.3. Key Derivation
Both the peer and server MUST derive the keys as follows. Both the peer and server MUST derive the keys as follows.
skipping to change at page 13, line 20 skipping to change at page 13, line 23
In this case, MK is derived and used as follows: In this case, MK is derived and used as follows:
MK = PRF'(IK'|CK',"EAP-AKA'"|Identity) MK = PRF'(IK'|CK',"EAP-AKA'"|Identity)
K_encr = MK[0..127] K_encr = MK[0..127]
K_aut = MK[128..383] K_aut = MK[128..383]
K_re = MK[384..639] K_re = MK[384..639]
MSK = MK[640..1151] MSK = MK[640..1151]
EMSK = MK[1152..1663] EMSK = MK[1152..1663]
Here [n..m] denotes the substring from bit n to m. PRF' is a new Here [n..m] denotes the substring from bit n to m, including bits
pseudo-random function specified in Section 3.4. The first 1664 n and m. PRF' is a new pseudo-random function specified in
bits from its output are used for K_encr (encryption key, 128 Section 3.4. The first 1664 bits from its output are used for
bits), K_aut (authentication key, 256 bits), K_re (re- K_encr (encryption key, 128 bits), K_aut (authentication key, 256
authentication key, 256 bits), MSK (Master Session Key, 512 bits), bits), K_re (re-authentication key, 256 bits), MSK (Master Session
and EMSK (Extended Master Session Key, 512 bits). These keys are Key, 512 bits), and EMSK (Extended Master Session Key, 512 bits).
used by the subsequent EAP-AKA' process. K_encr is used by the These keys are used by the subsequent EAP-AKA' process. K_encr is
AT_ENCR_DATA attribute, and K_aut by the AT_MAC attribute. K_re used by the AT_ENCR_DATA attribute, and K_aut by the AT_MAC
is used later in this section. MSK and EMSK are outputs from a attribute. K_re is used later in this section. MSK and EMSK are
successful EAP method run [RFC3748]. outputs from a successful EAP method run [RFC3748].
IK' and CK' are derived as specified in [TS-3GPP.33.402]. The IK' and CK' are derived as specified in [TS-3GPP.33.402]. The
functions that derive IK' and CK' take the following parameters: functions that derive IK' and CK' take the following parameters:
CK and IK produced by the AKA algorithm, and value of the Network CK and IK produced by the AKA algorithm, and value of the Network
Name field comes from the AT_KDF_INPUT attribute (without length Name field comes from the AT_KDF_INPUT attribute (without length
or padding) . or padding).
The value "EAP-AKA'" is an eight-characters-long ASCII string. It The value "EAP-AKA'" is an eight-characters-long ASCII string. It
is used as is, without any trailing NUL characters. is used as is, without any trailing NUL characters.
Identity is the peer identity as specified in Section 7 of Identity is the peer identity as specified in Section 7 of
[RFC4187]. [RFC4187].
When the server creates an AKA challenge and corresponding AUTN, When the server creates an AKA challenge and corresponding AUTN,
CK, CK', IK, and IK' values, it MUST set the Authentication CK, CK', IK, and IK' values, it MUST set the Authentication
Management Field (AMF) separation bit to 1 in the AKA algorithm Management Field (AMF) separation bit to 1 in the AKA algorithm
skipping to change at page 15, line 7 skipping to change at page 15, line 11
The peer behaves as if the AUTN had been incorrect and MUST fail The peer behaves as if the AUTN had been incorrect and MUST fail
the authentication. the authentication.
If the peer supports a given key derivation function but is unwilling If the peer supports a given key derivation function but is unwilling
to perform it for policy reasons, it refuses to calculate the keys to perform it for policy reasons, it refuses to calculate the keys
and behaves as explained in Section 3.2. and behaves as explained in Section 3.2.
3.4. Hash Functions 3.4. Hash Functions
EAP-AKA' uses SHA-256, not SHA-1 (see [FIPS.180-4]) as in EAP-AKA. EAP-AKA' uses SHA-256 / HMAC-SHA-256, not SHA-1 / HMAC-SHA-1 (see
This requires a change to the pseudo-random function (PRF) as well as [FIPS.180-4] [RFC2104]) as in EAP-AKA. This requires a change to the
the AT_MAC and AT_CHECKCODE attributes. pseudo-random function (PRF) as well as the AT_MAC and AT_CHECKCODE
attributes.
3.4.1. PRF' 3.4.1. PRF'
The PRF' construction is the same one IKEv2 uses (see Section 2.13 of The PRF' construction is the same one IKEv2 uses (see Section 2.13 of
[RFC4306]). The function takes two arguments. K is a 256-bit value [RFC4306]). The function takes two arguments. K is a 256-bit value
and S is an byte string of arbitrary length. PRF' is defined as and S is a byte string of arbitrary length. PRF' is defined as
follows: follows:
PRF'(K,S) = T1 | T2 | T3 | T4 | ... PRF'(K,S) = T1 | T2 | T3 | T4 | ...
where: where:
T1 = HMAC-SHA-256 (K, S | 0x01) T1 = HMAC-SHA-256 (K, S | 0x01)
T2 = HMAC-SHA-256 (K, T1 | S | 0x02) T2 = HMAC-SHA-256 (K, T1 | S | 0x02)
T3 = HMAC-SHA-256 (K, T2 | S | 0x03) T3 = HMAC-SHA-256 (K, T2 | S | 0x03)
T4 = HMAC-SHA-256 (K, T3 | S | 0x04) T4 = HMAC-SHA-256 (K, T3 | S | 0x04)
... ...
skipping to change at page 16, line 20 skipping to change at page 16, line 20
| | | |
| Checkcode (0 or 32 bytes) | | Checkcode (0 or 32 bytes) |
| | | |
| | | |
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Second, the checkcode is a hash value, calculated with SHA-256 Second, the checkcode is a hash value, calculated with SHA-256
[FIPS.180-4], over the data specified in Section 10.13 of [RFC4187]. [FIPS.180-4], over the data specified in Section 10.13 of [RFC4187].
3.5. Summary of Attributes for EAP-AKA'
The following table provides a guide to which attributes may be found
in which kinds of messages, and in what quantity.
Messages are denoted with numbers in parentheses as follows:
(1) EAP-Request/AKA-Identity,
(2) EAP-Response/AKA-Identity,
(3) EAP-Request/AKA-Challenge,
(4) EAP-Response/AKA-Challenge,
(5) EAP-Request/AKA-Notification,
(6) EAP-Response/AKA-Notification,
(7) EAP-Response/AKA-Client-Error
(8) EAP-Request/AKA-Reauthentication,
(9) EAP-Response/AKA-Reauthentication,
(10) EAP-Response/AKA-Authentication-Reject, and
(11) EAP-Response/AKA-Synchronization-Failure.
The column denoted with "E" indicates whether the attribute is a
nested attribute that MUST be included within AT_ENCR_DATA.
In addition:
"0" indicates that the attribute MUST NOT be included in the
message,
"1" indicates that the attribute MUST be included in the message,
"0-1" indicates that the attribute is sometimes included in the
message,
"0+" indicates that zero or more copies of the attribute MAY be
included in the message,
"1+" indicates that there MUST be at least one attribute in the
message but more than one MAY be included in the message, and
"0*" indicates that the attribute is not included in the message
in cases specified in this document, but MAY be included in the
future versions of the protocol.
The attribute table is shown below. The table is largely the same as
in the EAP-AKA attribute table ([RFC4187] Section 10.1), but changes
how many times AT_MAC may appear in EAP-Response/AKA'-Challenge
message as it does not appear there when AT_KDF has to be sent from
the peer to the server. The table also adds the AT_KDF and
AT_KDF_INPUT attributes.
Attribute (1) (2) (3) (4) (5) (6) (7) (8) (9) (10)(11) E
AT_PERMANENT_ID_REQ 0-1 0 0 0 0 0 0 0 0 0 0 N
AT_ANY_ID_REQ 0-1 0 0 0 0 0 0 0 0 0 0 N
AT_FULLAUTH_ID_REQ 0-1 0 0 0 0 0 0 0 0 0 0 N
AT_IDENTITY 0 0-1 0 0 0 0 0 0 0 0 0 N
AT_RAND 0 0 1 0 0 0 0 0 0 0 0 N
AT_AUTN 0 0 1 0 0 0 0 0 0 0 0 N
AT_RES 0 0 0 1 0 0 0 0 0 0 0 N
AT_AUTS 0 0 0 0 0 0 0 0 0 0 1 N
AT_NEXT_PSEUDONYM 0 0 0-1 0 0 0 0 0 0 0 0 Y
AT_NEXT_REAUTH_ID 0 0 0-1 0 0 0 0 0-1 0 0 0 Y
AT_IV 0 0 0-1 0* 0-1 0-1 0 1 1 0 0 N
AT_ENCR_DATA 0 0 0-1 0* 0-1 0-1 0 1 1 0 0 N
AT_PADDING 0 0 0-1 0* 0-1 0-1 0 0-1 0-1 0 0 Y
AT_CHECKCODE 0 0 0-1 0-1 0 0 0 0-1 0-1 0 0 N
AT_RESULT_IND 0 0 0-1 0-1 0 0 0 0-1 0-1 0 0 N
AT_MAC 0 0 1 0-1 0-1 0-1 0 1 1 0 0 N
AT_COUNTER 0 0 0 0 0-1 0-1 0 1 1 0 0 Y
AT_COUNTER_TOO_SMALL 0 0 0 0 0 0 0 0 0-1 0 0 Y
AT_NONCE_S 0 0 0 0 0 0 0 1 0 0 0 Y
AT_NOTIFICATION 0 0 0 0 1 0 0 0 0 0 0 N
AT_CLIENT_ERROR_CODE 0 0 0 0 0 0 1 0 0 0 0 N
AT_KDF 0 0 1+ 0+ 0 0 0 0 0 0 1+ N
AT_KDF_INPUT 0 0 1 0 0 0 0 0 0 0 0 N
4. Bidding Down Prevention for EAP-AKA 4. Bidding Down Prevention for EAP-AKA
As discussed in [RFC3748], negotiation of methods within EAP is As discussed in [RFC3748], negotiation of methods within EAP is
insecure. That is, a man-in-the-middle attacker may force the insecure. That is, a man-in-the-middle attacker may force the
endpoints to use a method that is not the strongest that they both endpoints to use a method that is not the strongest that they both
support. This is a problem, as we expect EAP-AKA and EAP-AKA' to be support. This is a problem, as we expect EAP-AKA and EAP-AKA' to be
negotiated via EAP. negotiated via EAP.
In order to prevent such attacks, this RFC specifies a new mechanism In order to prevent such attacks, this RFC specifies a new mechanism
for EAP-AKA that allows the endpoints to securely discover the for EAP-AKA that allows the endpoints to securely discover the
capabilities of each other. This mechanism comes in the form of the capabilities of each other. This mechanism comes in the form of the
AT_BIDDING attribute. This allows both endpoints to communicate AT_BIDDING attribute. This allows both endpoints to communicate
their desire and support for EAP-AKA' when exchanging EAP-AKA their desire and support for EAP-AKA' when exchanging EAP-AKA
messages. This attribute is not included in EAP-AKA' messages as messages. This attribute is not included in EAP-AKA' messages. It
defined in this RFC. It is only included in EAP-AKA messages. This is only included in EAP-AKA messages. (Those messages are protected
is based on the assumption that EAP-AKA' is always preferable (see with the AT_MAC attribute.) This approach is based on the assumption
Section 7). If during the EAP-AKA authentication process it is that EAP-AKA' is always preferable (see Section 7). If during the
discovered that both endpoints would have been able to use EAP-AKA', EAP-AKA authentication process it is discovered that both endpoints
the authentication process SHOULD be aborted, as a bidding down would have been able to use EAP-AKA', the authentication process
attack may have happened. SHOULD be aborted, as a bidding down attack may have happened.
The format of the AT_BIDDING attribute is shown below. The format of the AT_BIDDING attribute is shown below.
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AT_BIDDING | Length |D| Reserved | | AT_BIDDING | Length |D| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields are as follows: The fields are as follows:
skipping to change at page 17, line 4 skipping to change at page 19, line 14
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AT_BIDDING | Length |D| Reserved | | AT_BIDDING | Length |D| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The fields are as follows: The fields are as follows:
AT_BIDDING AT_BIDDING
This is set to 136. This is set to 136.
Length Length
The length of the attribute, MUST be set to 1. The length of the attribute, calculated as defined in [RFC4187],
Section 8.1. For AT_BIDDING, the Length MUST be set to 1.
D D
This bit is set to 1 if the sender supports EAP-AKA', is willing This bit is set to 1 if the sender supports EAP-AKA', is willing
to use it, and prefers it over EAP-AKA. Otherwise, it should be to use it, and prefers it over EAP-AKA. Otherwise, it should be
set to zero. set to zero.
Reserved Reserved
This field MUST be set to zero when sent and ignored on receipt. This field MUST be set to zero when sent and ignored on receipt.
skipping to change at page 17, line 35 skipping to change at page 19, line 47
authentication (see Figure 3 of [RFC4187]). A peer not supporting authentication (see Figure 3 of [RFC4187]). A peer not supporting
EAP-AKA' will simply ignore this attribute. In all cases, the EAP-AKA' will simply ignore this attribute. In all cases, the
attribute is protected by the integrity mechanisms of EAP-AKA, so it attribute is protected by the integrity mechanisms of EAP-AKA, so it
cannot be removed by a man-in-the-middle attacker. cannot be removed by a man-in-the-middle attacker.
Note that we assume (Section 7) that EAP-AKA' is always stronger than Note that we assume (Section 7) that EAP-AKA' is always stronger than
EAP-AKA. As a result, there is no need to prevent bidding "down" EAP-AKA. As a result, there is no need to prevent bidding "down"
attacks in the other direction, i.e., attackers forcing the endpoints attacks in the other direction, i.e., attackers forcing the endpoints
to use EAP-AKA'. to use EAP-AKA'.
4.1. Summary of Attributes for EAP-AKA
The appearance of the AT_BIDDING attribute in EAP-AKA exchanges is
shown below, using the notation from Section 3.5:
Attribute (1) (2) (3) (4) (5) (6) (7) (8) (9) (10)(11) E
AT_BIDDING 0 0 1 0 0 0 0 0 0 0 0 N
5. Peer Identities 5. Peer Identities
EAP-AKA' peer identities are as specified in [RFC4187] Section 4.1, EAP-AKA' peer identities are as specified in [RFC4187] Section 4.1,
with the addition of some requirements specified in this section. with the addition of some requirements specified in this section.
EAP-AKA' includes optional identity privacy support that can be used EAP-AKA' includes optional identity privacy support that can be used
to hide the cleartext permanent identity and thereby make the to hide the cleartext permanent identity and thereby make the
subscriber's EAP exchanges untraceable to eavesdroppers. EAP-AKA' subscriber's EAP exchanges untraceable to eavesdroppers. EAP-AKA'
can also use the privacy friendly identifiers specified for 5G can also use the privacy friendly identifiers specified for 5G
networks. networks.
skipping to change at page 21, line 6 skipping to change at page 23, line 24
If the AT_KDF_INPUT parameter contains the prefix "5G:", the AT_KDF If the AT_KDF_INPUT parameter contains the prefix "5G:", the AT_KDF
parameter has the value 1, and this authentication is not a fast re- parameter has the value 1, and this authentication is not a fast re-
authentication, then the peer identity used in the key derivation authentication, then the peer identity used in the key derivation
MUST be the 5G SUPI for the peer. This rule applies to all full EAP- MUST be the 5G SUPI for the peer. This rule applies to all full EAP-
AKA' authentication processes, even if the peer sent some other AKA' authentication processes, even if the peer sent some other
identifier at a lower layer or as a response to an EAP Identity identifier at a lower layer or as a response to an EAP Identity
Request or if no identity was sent. Request or if no identity was sent.
The identity MUST also be represented in the exact correct format for The identity MUST also be represented in the exact correct format for
the key derivation formula to produce correct results. For the SUPI, the key derivation formula to produce correct results. In 5G, this
this format is as defined Section 5.3.1.1. identifier is the SUPI. The SUPI format is as defined
Section 5.3.1.1.
In all other cases, the following applies: In all other cases, the following applies:
The identity used in the key derivation formula MUST be exactly The identity used in the key derivation formula MUST be exactly
the one sent in EAP-AKA' AT_IDENTITY attribute, if one was sent, the one sent in EAP-AKA' AT_IDENTITY attribute, if one was sent,
regardless of the kind of identity that it may have been. If no regardless of the kind of identity that it may have been. If no
AT_IDENTITY was sent, the identity MUST be the exactly the one AT_IDENTITY was sent, the identity MUST be the exactly the one
sent in the generic EAP Identity exchange, if one was made. sent in the generic EAP Identity exchange, if one was made.
Again, the identity MUST be used exactly as sent. Again, the identity MUST be used exactly as sent.
skipping to change at page 21, line 31 skipping to change at page 23, line 50
In this case, the used identity MUST be the identity most recently In this case, the used identity MUST be the identity most recently
communicated by the peer to the network, again regardless of what communicated by the peer to the network, again regardless of what
type of identity it may have been. type of identity it may have been.
5.3.1.1. Format of the SUPI 5.3.1.1. Format of the SUPI
A SUPI is either an IMSI or a Network Access Identifier [RFC4282]. A SUPI is either an IMSI or a Network Access Identifier [RFC4282].
When used in EAP-AKA', the format of the SUPI MUST be as specified in When used in EAP-AKA', the format of the SUPI MUST be as specified in
[TS-3GPP.23.003] Section 28.7.2, with the semantics defined in [TS-3GPP.23.003] Section 28.7.2, with the semantics defined in
[TS-3GPP.23.003] Section 2.2B. Also, in contrast to [RFC5448], in 5G [TS-3GPP.23.003] Section 2.2A. Also, in contrast to [RFC5448], in 5G
EAP-AKA' does not use the "0" or "6" prefix in front of the entire EAP-AKA' does not use the "0" or "6" prefix in front of the entire
IMSI. IMSI.
For instance, if the IMSI is 234150999999999 (MCC = 234, MNC = 15), For instance, if the IMSI is 234150999999999 (MCC = 234, MNC = 15),
the NAI format for the SUPI takes the form: the NAI format for the SUPI takes the form:
234150999999999@nai.5gc.mnc015.mcc234.3gppnetwork.org 234150999999999@nai.5gc.mnc015.mcc234.3gppnetwork.org
5.3.2. EAP Identity Response and EAP-AKA' AT_IDENTITY Attribute 5.3.2. EAP Identity Response and EAP-AKA' AT_IDENTITY Attribute
skipping to change at page 22, line 8 skipping to change at page 24, line 28
When the EAP peer is connecting to a 5G access network and uses the When the EAP peer is connecting to a 5G access network and uses the
5G Non-Access Stratum (NAS) protocol [TS-3GPP.24.501], the EAP server 5G Non-Access Stratum (NAS) protocol [TS-3GPP.24.501], the EAP server
is in a 5G network. The EAP identity exchanges are generally not is in a 5G network. The EAP identity exchanges are generally not
used in this case, as the identity is already made available on used in this case, as the identity is already made available on
previous link layer exchanges. previous link layer exchanges.
In this situation, the EAP server SHOULD NOT request an additional In this situation, the EAP server SHOULD NOT request an additional
identity from the peer. If the peer for some reason receives EAP- identity from the peer. If the peer for some reason receives EAP-
Request/Identity or EAP-Request/AKA-Identity messages, the peer Request/Identity or EAP-Request/AKA-Identity messages, the peer
should behave as follows. behaves as follows.
Receive EAP-Request/Identity Receive EAP-Request/Identity
In this case, the peer SHOULD respond with a EAP-Response/Identity In this case, the peer MUST respond with a EAP-Response/Identity
containing the privacy-friendly 5G identifier, the SUCI. The SUCI containing the privacy-friendly 5G identifier, the SUCI. The SUCI
SHOULD be represented as specified in Section 5.3.2.1. MUST be represented as specified in Section 5.3.2.1.
EAP-Request/AKA-Identity with AT_PERMANENT_REQ EAP-Request/AKA-Identity with AT_PERMANENT_REQ
For privacy reasons, the peer should follow a "conservative" For privacy reasons, the peer MUST follow a "conservative" policy
policy and terminate the authentication exchange rather than risk and terminate the authentication exchange rather than risk
revealing its permanent identity. revealing its permanent identity.
The peer SHOULD respond with EAP-Response/AKA-Client-Error with The peer MUST respond with EAP-Response/AKA-Client-Error with the
the client error code 0, "unable to process packet". client error code 0, "unable to process packet".
EAP-Request/AKA-Identity with AT_FULLAUTH_REQ EAP-Request/AKA-Identity with AT_FULLAUTH_REQ
In this case, the peer SHOULD respond with a EAP-Response/AKA- In this case, the peer MUST respond with a EAP-Response/AKA-
Identity containing the SUCI. The SUCI SHOULD be represented as Identity containing the SUCI. The SUCI MUST be represented as
specified in Section 5.3.2.1. specified in Section 5.3.2.1.
EAP-Request/AKA-Identity with AT_ANY_ID_REQ EAP-Request/AKA-Identity with AT_ANY_ID_REQ
If the peer supports fast re-authentication and has a fast re- If the peer supports fast re-authentication and has a fast re-
authentication identity available, the peer SHOULD respond with authentication identity available, the peer SHOULD respond with
EAP-Response/AKA-Identity containing the fast re-authentication EAP-Response/AKA-Identity containing the fast re-authentication
identity. Otherwise the peer SHOULD respond with a EAP-Response/ identity. Otherwise the peer MUST respond with a EAP-Response/
AKA-Identity containing the SUCI, and SHOULD represent the SUCI as AKA-Identity containing the SUCI, and MUST represent the SUCI as
specified in Section 5.3.2.1. specified in Section 5.3.2.1.
Similarly, if the peer is communicating over a non-3GPP network but Similarly, if the peer is communicating over a non-3GPP network but
carrying EAP inside 5G NAS protocol, it MUST assume that the EAP carrying EAP inside 5G NAS protocol, it MUST assume that the EAP
server is in a 5G network, and again employ the SUCI within EAP. server is in a 5G network, and again employ the SUCI within EAP.
Otherwise, the peer SHOULD employ IMSI, SUPI, or a NAI as it is Otherwise, the peer SHOULD employ IMSI, SUPI, or a NAI as it is
configured to use. configured to use.
5.3.2.1. Format of the SUCI 5.3.2.1. Format of the SUCI
skipping to change at page 23, line 26 skipping to change at page 25, line 45
For the Profile <A> protection scheme: For the Profile <A> protection scheme:
type0.rid678.schid1.hnkey27.ecckey<ECC ephemeral public key>. type0.rid678.schid1.hnkey27.ecckey<ECC ephemeral public key>.
cip<encryption of 0999999999>.mac<MAC tag value>@nai.5gc. cip<encryption of 0999999999>.mac<MAC tag value>@nai.5gc.
mnc015.mcc234.3gppnetwork.org mnc015.mcc234.3gppnetwork.org
6. Exported Parameters 6. Exported Parameters
The EAP-AKA' Session-Id is the concatenation of the EAP Type Code The EAP-AKA' Session-Id is the concatenation of the EAP Type Code
(50, one byte) with the contents of the RAND field from the AT_RAND (0x32, one byte) with the contents of the RAND field from the AT_RAND
attribute, followed by the contents of the AUTN field in the AT_AUTN attribute, followed by the contents of the AUTN field in the AT_AUTN
attribute: attribute:
Session-Id = 50 || RAND || AUTN Session-Id = 0x32 || RAND || AUTN
When using fast re-authentication, the EAP-AKA' Session-Id is the When using fast re-authentication, the EAP-AKA' Session-Id is the
concatenation of the EAP Type Code (50) with the contents of the concatenation of the EAP Type Code (0x32) with the contents of the
NONCE_S field from the AT_NONCE_S attribute, followed by the contents NONCE_S field from the AT_NONCE_S attribute, followed by the contents
of the MAC field from the AT_MAC attribute from EAP-Request/AKA- of the MAC field from the AT_MAC attribute from EAP-Request/AKA-
Reauthentication: Reauthentication:
Session-Id = 50 || NONCE_S || MAC Session-Id = 0x32 || NONCE_S || MAC
The Peer-Id is the contents of the Identity field from the The Peer-Id is the contents of the Identity field from the
AT_IDENTITY attribute, using only the Actual Identity Length bytes AT_IDENTITY attribute, using only the Actual Identity Length bytes
from the beginning. Note that the contents are used as they are from the beginning. Note that the contents are used as they are
transmitted, regardless of whether the transmitted identity was a transmitted, regardless of whether the transmitted identity was a
permanent, pseudonym, or fast EAP re-authentication identity. If no permanent, pseudonym, or fast EAP re-authentication identity. If no
AT_IDENTITY attribute was exchanged, the exported Peer-Id is the AT_IDENTITY attribute was exchanged, the exported Peer-Id is the
identity provided from the EAP Identity Response packet. If no EAP identity provided from the EAP Identity Response packet. If no EAP
Identity Response was provided either, the exported Peer-Id is null Identity Response was provided either, the exported Peer-Id is null
string (zero length). string (zero length).
skipping to change at page 24, line 32 skipping to change at page 27, line 4
The negotiation mechanism allows changing the offered key The negotiation mechanism allows changing the offered key
derivation function, but the change is visible in the final EAP- derivation function, but the change is visible in the final EAP-
Request/AKA'-Challenge message that the server sends to the peer. Request/AKA'-Challenge message that the server sends to the peer.
This message is authenticated via the AT_MAC attribute, and This message is authenticated via the AT_MAC attribute, and
carries both the chosen alternative and the initially offered carries both the chosen alternative and the initially offered
list. The peer refuses to accept a change it did not initiate. list. The peer refuses to accept a change it did not initiate.
As a result, both parties are aware that a change is being made As a result, both parties are aware that a change is being made
and what the original offer was. and what the original offer was.
Mutual authentication Mutual authentication
Under the SHA-256 assumption, the properties of EAP-AKA' are at Under the SHA-256 assumption, the properties of EAP-AKA' are at
least as good as those of EAP-AKA in this respect. Refer to least as good as those of EAP-AKA in this respect. Refer to
[RFC4187], Section 12 for further details. [RFC4187], Section 12 for further details.
Integrity protection Integrity protection
Under the SHA-256 assumption, the properties of EAP-AKA' are at Under the SHA-256 assumption, the properties of EAP-AKA' are at
least as good (most likely better) as those of EAP-AKA in this least as good (most likely better) as those of EAP-AKA in this
respect. Refer to [RFC4187], Section 12 for further details. The respect. Refer to [RFC4187], Section 12 for further details. The
only difference is that a stronger hash algorithm, SHA-256, is only difference is that a stronger hash algorithm and keyed MAC,
used instead of SHA-1. SHA-256 / HMAC-SHA-256, is used instead of SHA-1 / HMAC-SHA-1.
Replay protection Replay protection
Under the SHA-256 assumption, the properties of EAP-AKA' are at Under the SHA-256 assumption, the properties of EAP-AKA' are at
least as good as those of EAP-AKA in this respect. Refer to least as good as those of EAP-AKA in this respect. Refer to
[RFC4187], Section 12 for further details. [RFC4187], Section 12 for further details.
Confidentiality Confidentiality
The properties of EAP-AKA' are exactly the same as those of EAP- The properties of EAP-AKA' are exactly the same as those of EAP-
AKA in this respect. Refer to [RFC4187], Section 12 for further AKA in this respect. Refer to [RFC4187], Section 12 for further
details. details.
Key derivation Key derivation
EAP-AKA' supports key derivation with an effective key strength EAP-AKA' supports key derivation with an effective key strength
against brute force attacks equal to the minimum of the length of against brute force attacks equal to the minimum of the length of
the derived keys and the length of the AKA base key, i.e., 128 the derived keys and the length of the AKA base key, i.e., 128
bits or more. The key hierarchy is specified in Section 3.3. bits or more. The key hierarchy is specified in Section 3.3.
skipping to change at page 27, line 15 skipping to change at page 29, line 33
RECOMMENDED. RECOMMENDED.
As discussed in Section 5.3, when authenticating to a 5G network, As discussed in Section 5.3, when authenticating to a 5G network,
only the 5G SUCI identifier should be used. The use of pseudonyms in only the 5G SUCI identifier should be used. The use of pseudonyms in
this situation is at best limited. In fact, the re-use of the same this situation is at best limited. In fact, the re-use of the same
pseudonym multiple times will result in a tracking opportunity for pseudonym multiple times will result in a tracking opportunity for
observers that see the pseudonym pass by. To avoid this, the peer observers that see the pseudonym pass by. To avoid this, the peer
and server need to follow the guidelines given in Section 5.2. and server need to follow the guidelines given in Section 5.2.
When authenticating to a 5G network, per Section 5.3.1, both the EAP- When authenticating to a 5G network, per Section 5.3.1, both the EAP-
AKA' peer and server need employ permanent identifier, SUPI, as an AKA' peer and server need to employ the permanent identifier, SUPI,
input to key derivation. However, this use of the SUPI is only as an input to key derivation. However, this use of the SUPI is only
internal and the SUPI need not be communicated in EAP messages. SUCI internal. As such, the SUPI need not be communicated in EAP
MUST NOT be communicated in EAP-AKA' when authenticating to a 5G messages. Therefore, SUPI MUST NOT be communicated in EAP-AKA' when
network. authenticating to a 5G network.
While the use of SUCI in 5G networks generally provides identity While the use of SUCI in 5G networks generally provides identity
privacy, this is not true if the null-scheme encryption is used to privacy, this is not true if the null-scheme encryption is used to
construct the SUCI (see [TS-3GPP.23.501] Annex C). The use of this construct the SUCI (see [TS-3GPP.23.501] Annex C). The use of this
scheme turns the use of SUCI equivalent to the use of SUPI or IMSI. scheme turns the use of SUCI equivalent to the use of SUPI or IMSI.
The use of the null scheme is NOT RECOMMENDED where identity privacy The use of the null scheme is NOT RECOMMENDED where identity privacy
is important. is important.
The use of fast re-authentication identities when authenticating to a The use of fast re-authentication identities when authenticating to a
5G network does not have the same problems as the use of pseudonyms, 5G network does not have the same problems as the use of pseudonyms,
skipping to change at page 29, line 46 skipping to change at page 32, line 17
the impacts in such situations. These are discussed further in the impacts in such situations. These are discussed further in
Section 7.3. Section 7.3.
Arapinis et al ([Arapinis2012]) describe an attack that uses the AKA Arapinis et al ([Arapinis2012]) describe an attack that uses the AKA
resynchronization protocol to attempt to detect whether a particular resynchronization protocol to attempt to detect whether a particular
subscriber is on a given area. This attack depends on the ability of subscriber is on a given area. This attack depends on the ability of
the attacker to have a false base station on the given area, and the the attacker to have a false base station on the given area, and the
subscriber performing at least one authentication between the time subscriber performing at least one authentication between the time
the attack is set up and run. the attack is set up and run.
Finally, while this is not a problem with the protocol itself, bad Borgaonkar et al discovered that the AKA resynchronization protocol
implementations may not produce pseudonym usernames or fast re- may also be used to predict the authentication frequency of a
authentication identities in a manner that is sufficiently secure. subscribers if non-time-based SQN generation scheme is used
Recommendations from Section 5.2 need to be followed to avoid this. [Borgaonkar2018]. The attacker can force the re-use of the keystream
that is used to protect the SQN in the AKA resynchronization
protocol. The attacker then guesses the authentication frequency
based on the lowest bits of two XORed SQNs. The researchers' concern
was that the authentication frequency would reveal some information
about the phone usage behavior, e.g., number of phone calls made or
number of SMS messages sent. However, phone calls and SMS messages
are just some of the many potential triggers for authentication. For
instance, various mobility events and the amount of mobile data sent
or received can also trigger authentication. As a result, while some
amount of information may be derived about the activity level on a
particular phone in some cases, the linkage to specific activities is
not direct. The impact of the attack is also different depending on
whether time or non-time-based SQN generation scheme is used.
Similar attacks are possible outside AKA in the cellular paging
protocols where the attacker can simply send application layer data,
short messages or make phone calls to the intended victim and observe
the air-interface (e.g., [Kune2012] and [Shaik2016]). Hussain et.
al. demonstrated a slightly more sophisticated version of the attack
that exploits the fact that 4G paging protocol uses the IMSI to
calculate the paging timeslot [Hussain2019]. As this attack is
outside AKA, it does not impact EAP-AKA'.
Finally, bad implementations of EAP-AKA' may not produce pseudonym
usernames or fast re-authentication identities in a manner that is
sufficiently secure. While it is not a problem with the protocol
itself, recommendations from Section 5.2 need to be followed to avoid
this.
7.3. Pervasive Monitoring 7.3. Pervasive Monitoring
As required by [RFC7258], work on IETF protocols needs to consider As required by [RFC7258], work on IETF protocols needs to consider
the effects of pervasive monitoring and mitigate them when possible. the effects of pervasive monitoring and mitigate them when possible.
As described Section 7.2, after the publication of RFC 5448, new As described Section 7.2, after the publication of RFC 5448, new
information has come to light regarding the use of pervasive information has come to light regarding the use of pervasive
monitoring techniques against many security technologies, including monitoring techniques against many security technologies, including
AKA-based authentication. AKA-based authentication.
skipping to change at page 32, line 7 skipping to change at page 35, line 7
domains or devices using the same technology. domains or devices using the same technology.
8. IANA Considerations 8. IANA Considerations
IANA should update the Extensible Authentication Protocol (EAP) IANA should update the Extensible Authentication Protocol (EAP)
Registry and the EAP-AKA and EAP-SIM Parameters so that entries Registry and the EAP-AKA and EAP-SIM Parameters so that entries
pointing to RFC 5448 will point to this RFC instead. pointing to RFC 5448 will point to this RFC instead.
8.1. Type Value 8.1. Type Value
EAP-AKA' has the EAP Type value 50 in the Extensible Authentication EAP-AKA' has the EAP Type value 0x32 in the Extensible Authentication
Protocol (EAP) Registry under Method Types. Per Section 6.2 of Protocol (EAP) Registry under Method Types. Per Section 6.2 of
[RFC3748], this allocation can be made with Designated Expert and [RFC3748], this allocation can be made with Designated Expert and
Specification Required. Specification Required.
8.2. Attribute Type Values 8.2. Attribute Type Values
EAP-AKA' shares its attribute space and subtypes with EAP-SIM EAP-AKA' shares its attribute space and subtypes with EAP-SIM
[RFC4186] and EAP-AKA [RFC4187]. No new registries are needed. [RFC4186] and EAP-AKA [RFC4187]. No new registries are needed.
However, a new Attribute Type value (23) in the non-skippable range However, a new Attribute Type value (23) in the non-skippable range
skipping to change at page 32, line 45 skipping to change at page 35, line 45
Value Description Reference Value Description Reference
--------- ---------------------- ------------------------------- --------- ---------------------- -------------------------------
0 Reserved [RFC Editor: Refer to this RFC] 0 Reserved [RFC Editor: Refer to this RFC]
1 EAP-AKA' with CK'/IK' [RFC Editor: Refer to this RFC] 1 EAP-AKA' with CK'/IK' [RFC Editor: Refer to this RFC]
2-65535 Unassigned 2-65535 Unassigned
9. References 9. References
9.1. Normative References 9.1. Normative References
[Note] Editors, "All 3GPP references should be updated to the
latest Release 15 version before publishing.".
[TS-3GPP.23.003] [TS-3GPP.23.003]
3GPP, "3rd Generation Partnership Project; Technical 3GPP, "3rd Generation Partnership Project; Technical
Specification Group Core Network and Terminals; Numbering, Specification Group Core Network and Terminals; Numbering,
addressing and identification (Release 15)", 3GPP Draft addressing and identification (Release 15)", 3GPP Draft
Technical Specification 23.003, September 2018. Technical Specification 23.003, June 2019.
[TS-3GPP.23.501] [TS-3GPP.23.501]
3GPP, "3rd Generation Partnership Project; Technical 3GPP, "3rd Generation Partnership Project; Technical
Specification Group Services and System Aspects; 3G Specification Group Services and System Aspects; 3G
Security; Security architecture and procedures for 5G Security; Security architecture and procedures for 5G
System; (Release 15)", 3GPP Technical Specification System; (Release 15)", 3GPP Technical Specification
23.501, September 2018. 23.501, June 2019.
[TS-3GPP.24.302] [TS-3GPP.24.302]
3GPP, "3rd Generation Partnership Project; Technical 3GPP, "3rd Generation Partnership Project; Technical
Specification Group Core Network and Terminals; Access to Specification Group Core Network and Terminals; Access to
the 3GPP Evolved Packet Core (EPC) via non-3GPP access the 3GPP Evolved Packet Core (EPC) via non-3GPP access
networks; Stage 3; (Release 15)", 3GPP Draft Technical networks; Stage 3; (Release 15)", 3GPP Draft Technical
Specification 24.302, September 2018. Specification 24.302, June 2019.
[TS-3GPP.24.501] [TS-3GPP.24.501]
3GPP, "3rd Generation Partnership Project; Technical 3GPP, "3rd Generation Partnership Project; Technical
Specification Group Core Network and Terminals; Access to Specification Group Core Network and Terminals; Access to
the 3GPP Evolved Packet Core (EPC) via non-3GPP access the 3GPP Evolved Packet Core (EPC) via non-3GPP access
networks; Stage 3; (Release 15)", 3GPP Draft Technical networks; Stage 3; (Release 15)", 3GPP Draft Technical
Specification 24.501, September 2018. Specification 24.501, June 2019.
[TS-3GPP.33.102] [TS-3GPP.33.102]
3GPP, "3rd Generation Partnership Project; Technical 3GPP, "3rd Generation Partnership Project; Technical
Specification Group Services and System Aspects; 3G Specification Group Services and System Aspects; 3G
Security; Security architecture (Release 15)", 3GPP Draft Security; Security architecture (Release 15)", 3GPP Draft
Technical Specification 33.102, June 2018. Technical Specification 33.102, December 2018.
[TS-3GPP.33.402] [TS-3GPP.33.402]
3GPP, "3GPP System Architecture Evolution (SAE); Security 3GPP, "3GPP System Architecture Evolution (SAE); Security
aspects of non-3GPP accesses (Release 15)", 3GPP Draft aspects of non-3GPP accesses (Release 15)", 3GPP Draft
Technical Specification 33.402, June 2018. Technical Specification 33.402, June 2018.
[TS-3GPP.33.501] [TS-3GPP.33.501]
3GPP, "3rd Generation Partnership Project; Technical 3GPP, "3rd Generation Partnership Project; Technical
Specification Group Services and System Aspects; 3G Specification Group Services and System Aspects; 3G
Security; Security architecture and procedures for 5G Security; Security architecture and procedures for 5G
System (Release 15)", 3GPP Draft Technical Specification System (Release 15)", 3GPP Draft Technical Specification
33.501, September 2018. 33.501, June 2019.
[FIPS.180-4] [FIPS.180-4]
National Institute of Standards and Technology, "Secure National Institute of Standards and Technology, "Secure
Hash Standard", FIPS PUB 180-4, August 2015, Hash Standard", FIPS PUB 180-4, August 2015,
<https://nvlpubs.nist.gov/nistpubs/FIPS/ <https://nvlpubs.nist.gov/nistpubs/FIPS/
NIST.FIPS.180-4.pdf>. NIST.FIPS.180-4.pdf>.
[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed- [RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104, Hashing for Message Authentication", RFC 2104,
DOI 10.17487/RFC2104, February 1997, <https://www.rfc- DOI 10.17487/RFC2104, February 1997, <https://www.rfc-
skipping to change at page 34, line 41 skipping to change at page 37, line 41
Writing an IANA Considerations Section in RFCs", BCP 26, Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017, RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>. <https://www.rfc-editor.org/info/rfc8126>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
9.2. Informative References 9.2. Informative References
[NoteAlso]
Editors, "All 3GPP references should be updated to the
latest Release 15 version before publishing.".
[TS-3GPP.35.208] [TS-3GPP.35.208]
3GPP, "3rd Generation Partnership Project; Technical 3GPP, "3rd Generation Partnership Project; Technical
Specification Group Services and System Aspects; 3G Specification Group Services and System Aspects; 3G
Security; Specification of the MILENAGE Algorithm Set: An Security; Specification of the MILENAGE Algorithm Set: An
example algorithm set for the 3GPP authentication and key example algorithm set for the 3GPP authentication and key
generation functions f1, f1*, f2, f3, f4, f5 and f5*; generation functions f1, f1*, f2, f3, f4, f5 and f5*;
Document 4: Design Conformance Test Data (Release 14)", Document 4: Design Conformance Test Data (Release 14)",
3GPP Technical Specification 35.208, March 2017. 3GPP Technical Specification 35.208, October 2018.
[FIPS.180-1] [FIPS.180-1]
National Institute of Standards and Technology, "Secure National Institute of Standards and Technology, "Secure
Hash Standard", FIPS PUB 180-1, April 1995, Hash Standard", FIPS PUB 180-1, April 1995,
<http://www.itl.nist.gov/fipspubs/fip180-1.htm>. <http://www.itl.nist.gov/fipspubs/fip180-1.htm>.
[FIPS.180-2] [FIPS.180-2]
National Institute of Standards and Technology, "Secure National Institute of Standards and Technology, "Secure
Hash Standard", FIPS PUB 180-2, August 2002, Hash Standard", FIPS PUB 180-2, August 2002,
<http://csrc.nist.gov/publications/fips/fips180-2/ <http://csrc.nist.gov/publications/fips/fips180-2/
skipping to change at page 36, line 40 skipping to change at page 39, line 40
editor.org/info/rfc6973>. editor.org/info/rfc6973>.
[RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an [RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May
2014, <https://www.rfc-editor.org/info/rfc7258>. 2014, <https://www.rfc-editor.org/info/rfc7258>.
[I-D.arkko-eap-aka-pfs] [I-D.arkko-eap-aka-pfs]
Arkko, J., Norrman, K., and V. Torvinen, "Perfect-Forward Arkko, J., Norrman, K., and V. Torvinen, "Perfect-Forward
Secrecy for the Extensible Authentication Protocol Method Secrecy for the Extensible Authentication Protocol Method
for Authentication and Key Agreement (EAP-AKA' PFS)", for Authentication and Key Agreement (EAP-AKA' PFS)",
draft-arkko-eap-aka-pfs-03 (work in progress), October draft-arkko-eap-aka-pfs-04 (work in progress), January
2018. 2019.
[Heist2015] [Heist2015]
Scahill, J. and J. Begley, "The great SIM heist", February Scahill, J. and J. Begley, "The great SIM heist", February
2015, in https://firstlook.org/theintercept/2015/02/19/ 2015, in https://firstlook.org/theintercept/2015/02/19/
great-sim-heist/ . great-sim-heist/ .
[MT2012] Mjolsnes, S. and J-K. Tsay, "A vulnerability in the UMTS [MT2012] Mjolsnes, S. and J-K. Tsay, "A vulnerability in the UMTS
and LTE authentication and key agreement protocols", and LTE authentication and key agreement protocols",
October 2012, in Proceedings of the 6th international October 2012, in Proceedings of the 6th international
conference on Mathematical Methods, Models and conference on Mathematical Methods, Models and
skipping to change at page 37, line 33 skipping to change at page 40, line 33
Basin, D., Dreier, J., Hirsch, L., Radomirovic, S., Sasse, Basin, D., Dreier, J., Hirsch, L., Radomirovic, S., Sasse,
R., and V. Stettle, "A Formal Analysis of 5G R., and V. Stettle, "A Formal Analysis of 5G
Authentication", August 2018, arXiv:1806.10360. Authentication", August 2018, arXiv:1806.10360.
[Arapinis2012] [Arapinis2012]
Arapinis, M., Mancini, L., Ritter, E., Ryan, M., Golde, Arapinis, M., Mancini, L., Ritter, E., Ryan, M., Golde,
N., and R. Borgaonkar, "New Privacy Issues in Mobile N., and R. Borgaonkar, "New Privacy Issues in Mobile
Telephony: Fix and Verification", October 2012, CCS'12, Telephony: Fix and Verification", October 2012, CCS'12,
Raleigh, North Carolina, USA. Raleigh, North Carolina, USA.
[Borgaonkar2018]
Borgaonkar, R., Hirschi, L., Park, S., and A. Shaik, "New
Privacy Threat on 3G, 4G, and Upcoming 5G AKA Protocols",
2018 in IACR Cryptology ePrint Archive.
[Kune2012]
Kune, D., Koelndorfer, J., and Y. Kim, "Location leaks on
the GSM air interface", 2012 in the proceedings of NDSS
'12 held 5-8 February, 2012 in San Diego, California.
[Shaik2016]
Shaik, A., Seifert, J., Borgaonkar, R., Asokan, N., and V.
Niemi, "Practical attacks against privacy and availability
in 4G/LTE mobile communication systems", 2012 in the
proceedings of NDSS '16 held 21-24 February, 2016 in San
Diego, California.
[Hussain2019]
Hussain, S., Echeverria, M., Chowdhury, O., Li, N., and E.
Bertino, "Privacy Attacks to the 4G and 5G Cellular Paging
Protocols Using Side Channel Information", in the
Proceedings of NDSS '19, held 24-27 February, 2019, in San
Diego, California.
Appendix A. Changes from RFC 5448 Appendix A. Changes from RFC 5448
The changes consist first of all, referring to a newer version of The changes consist first of all, referring to a newer version of
[TS-3GPP.24.302]. The new version includes an updated definition of [TS-3GPP.24.302]. The new version includes an updated definition of
the Network Name field, to include 5G. the Network Name field, to include 5G.
Secondly, identifier usage for 5G has been specified in Section 5.3. Secondly, identifier usage for 5G has been specified in Section 5.3.
Also, the requirements on generating pseudonym usernames and fast re- Also, the requirements on generating pseudonym usernames and fast re-
authentication identities have been updated from the original authentication identities have been updated from the original
definition in RFC 5448, which referenced RFC 4187. See Section 5. definition in RFC 5448, which referenced RFC 4187. See Section 5.
skipping to change at page 38, line 12 skipping to change at page 41, line 38
The security, privacy, and pervasive monitoring considerations have The security, privacy, and pervasive monitoring considerations have
been updated or added. See Section 7. been updated or added. See Section 7.
The references to [RFC2119], [RFC5226], [FIPS.180-1] and [FIPS.180-2] The references to [RFC2119], [RFC5226], [FIPS.180-1] and [FIPS.180-2]
have been updated to their most recent versions and language in this have been updated to their most recent versions and language in this
document changed accordingly. Similarly, references to all 3GPP document changed accordingly. Similarly, references to all 3GPP
technical specifications have been updated to their 5G (Release 15) technical specifications have been updated to their 5G (Release 15)
versions or otherwise most recent version when there has not been a versions or otherwise most recent version when there has not been a
5G-related update. 5G-related update.
Finally, a number of editorial clarifications have been made. Finally, a number of clarifications have been made, including a
summary of where attributes may appear.
Appendix B. Changes from RFC 4187 to RFC 5448 Appendix B. Changes from RFC 4187 to RFC 5448
The changes to RFC 4187 relate only to the bidding down prevention The changes to RFC 4187 relate only to the bidding down prevention
support defined in Section 4. In particular, this document does not support defined in Section 4. In particular, this document does not
change how the Master Key (MK) is calculated in RFC 4187 (it uses CK change how the Master Key (MK) is calculated in RFC 4187 (it uses CK
and IK, not CK' and IK'); neither is any processing of the AMF bit and IK, not CK' and IK'); neither is any processing of the AMF bit
added to RFC 4187. added to RFC 4187.
Appendix C. Changes from Previous Version of This Draft Appendix C. Changes from Previous Version of This Draft
skipping to change at page 39, line 21 skipping to change at page 43, line 5
when referring to AT_KDF values vs. AT_KDF attribute number, provided when referring to AT_KDF values vs. AT_KDF attribute number, provided
guidance on random number generation, clarified the dangers relating guidance on random number generation, clarified the dangers relating
to the use of permanent user identities such as IMSIs, aligned the to the use of permanent user identities such as IMSIs, aligned the
key derivation function/mechanism terminology, aligned the key key derivation function/mechanism terminology, aligned the key
derivation/generation terminology, aligned the octet/byte derivation/generation terminology, aligned the octet/byte
terminology, clarified the text regarding strength of SHA-256, added terminology, clarified the text regarding strength of SHA-256, added
some cross references between sections, instructed IANA to change some cross references between sections, instructed IANA to change
registries to point to this RFC rather than RFC 5448, and changed registries to point to this RFC rather than RFC 5448, and changed
Pasi's listed affiliation. Pasi's listed affiliation.
The -05 version of the draft corrected the Section 7.1 statement that
SUCI must not be communicated in EAP-AKA'; this statement was meant
to say SUPI must not be communicated. That was a major bug, but
hopefully one that previous readers understood was a mistake!
The -05 version also changed keyword strengths for identifier
requests in different cases in a 5G network, to match the 3GPP
specifications (see Section 5.3.2.
Tables of where attributes may appear has been added to the -05
version of the document, see Section 3.5 and Section 4.1. The tables
are based on the original table in RFC 4187.
Other changes in the -05 version included the following:
o The attribute appearance table entry for AT_MAC in EAP-Response/
AKA-Challenge has been specified to be 0-1 because it does not
appear when AT_KDF has to be sent; this was based on implementor
feedback.
o Added information about attacks against the re-synchronization
protocol and other attacks recently discussed in academic
conferences.
o Clarified length field calculations and the AT_KDF negotiation
procedure.
o The treatment of AT_KDF attribute copy in the EAP-Response/AKA'-
Synchronization-Failure message was clarified in Section 3.2.
o Updated and added several references
o Switched to use of hexadecimal for EAP Type Values for consistency
with other documents.
o Made editorial clarifications to a number places in the document.
Appendix D. Importance of Explicit Negotiation Appendix D. Importance of Explicit Negotiation
Choosing between the traditional and revised AKA key derivation Choosing between the traditional and revised AKA key derivation
functions is easy when their use is unambiguously tied to a functions is easy when their use is unambiguously tied to a
particular radio access network, e.g., Long Term Evolution (LTE) as particular radio access network, e.g., Long Term Evolution (LTE) as
defined by 3GPP or evolved High Rate Packet Data (eHRPD) as defined defined by 3GPP or evolved High Rate Packet Data (eHRPD) as defined
by 3GPP2. There is no possibility for interoperability problems if by 3GPP2. There is no possibility for interoperability problems if
this radio access network is always used in conjunction with new this radio access network is always used in conjunction with new
protocols that cannot be mixed with the old ones; clients will always protocols that cannot be mixed with the old ones; clients will always
know whether they are connecting to the old or new system. know whether they are connecting to the old or new system.
skipping to change at page 44, line 47 skipping to change at page 48, line 47
MSK: c6d3 a6e0 ceea 951e b20d 74f3 2c30 61d0 MSK: c6d3 a6e0 ceea 951e b20d 74f3 2c30 61d0
680a 04b0 b086 ee87 00ac e3e0 b95f a026 680a 04b0 b086 ee87 00ac e3e0 b95f a026
83c2 87be ee44 4322 94ff 98af 26d2 cc78 83c2 87be ee44 4322 94ff 98af 26d2 cc78
3bac e75c 4b0a f7fd feb5 511b a8e4 cbd0 3bac e75c 4b0a f7fd feb5 511b a8e4 cbd0
EMSK: 7fb5 6813 838a dafa 99d1 40c2 f198 f6da EMSK: 7fb5 6813 838a dafa 99d1 40c2 f198 f6da
cebf b6af ee44 4961 1054 02b5 08c7 f363 cebf b6af ee44 4961 1054 02b5 08c7 f363
352c b291 9644 b504 63e6 a693 5415 0147 352c b291 9644 b504 63e6 a693 5415 0147
ae09 cbc5 4b8a 651d 8787 a689 3ed8 536d ae09 cbc5 4b8a 651d 8787 a689 3ed8 536d
Appendix F. Contributors Contributors
The test vectors in Appendix C were provided by Yogendra Pal and The test vectors in Appendix C were provided by Yogendra Pal and
Jouni Malinen, based on two independent implementations of this Jouni Malinen, based on two independent implementations of this
specification. specification.
Jouni Malinen provided suggested text for Section 6. John Mattsson Jouni Malinen provided suggested text for Section 6. John Mattsson
provided much of the text for Section 7.1. Karl Norrman was the provided much of the text for Section 7.1. Karl Norrman was the
source of much of the information in Section 7.2. source of much of the information in Section 7.2.
Appendix G. Acknowledgments Acknowledgments
The authors would like to thank Guenther Horn, Joe Salowey, Mats The authors would like to thank Guenther Horn, Joe Salowey, Mats
Naslund, Adrian Escott, Brian Rosenberg, Laksminath Dondeti, Ahmad Naslund, Adrian Escott, Brian Rosenberg, Laksminath Dondeti, Ahmad
Muhanna, Stefan Rommer, Miguel Garcia, Jan Kall, Ankur Agarwal, Jouni Muhanna, Stefan Rommer, Miguel Garcia, Jan Kall, Ankur Agarwal, Jouni
Malinen, John Mattsson, Jesus De Gregorio, Brian Weis, Russ Housley, Malinen, John Mattsson, Jesus De Gregorio, Brian Weis, Russ Housley,
Alfred Hoenes, Anand Palanigounder, and Mohit Sethi for their in- Alfred Hoenes, Anand Palanigounder, Michael Richardsson, Marcus Wong,
depth reviews and interesting discussions in this problem space. Kalle Jarvinen, Daniel Migault, and Mohit Sethi for their in-depth
reviews and interesting discussions in this problem space.
Authors' Addresses Authors' Addresses
Jari Arkko Jari Arkko
Ericsson Ericsson
Jorvas 02420 Jorvas 02420
Finland Finland
Email: jari.arkko@piuha.net Email: jari.arkko@piuha.net
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