Internet-Draft Deprecation of IKEv1 and some algorithms October 2021
Wouters Expires 28 April 2022 [Page]
7296, 8221, 8247 (if approved)
Intended Status:
Standards Track
P. Wouters, Ed.

Deprecation of IKEv1 and obsoleted algorithms


Internet Key Exchange version 1 (IKEv1) is deprecated. Accordingly, IKEv1 has been moved to Historic status. A number of old algorithms that are associated with IKEv1, and not widely implemented for IKEv2 are deprecated as well. This document adds a Status column to the IANA IKEv2 Transform Type registries.

Status of This Memo

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This Internet-Draft will expire on 28 April 2022.

Table of Contents

1. Introduction

IKEv1 [RFC2409] and its related documents for ISAKMP [RFC2408] and IPsec DOI [RFC2407] were obsoleted by IKEv2 [RFC4306] in December 2005. The latest version of IKEv2 at the time of writing was published in 2014 in [RFC7296]. The Internet Key Exchange (IKE) version 2 has replaced version 1 over 15 years ago. IKEv2 has now seen wide deployment and provides a full replacement for all IKEv1 functionality. No new modifications or new algorithms have been accepted for IKEv1 for at least a decade. IKEv2 addresses various issues present in IKEv1, such as IKEv1 being vulnerable to amplification attacks. IKEv1 has been moved to Historic status.

Algorithm implementation requirements and usage guidelines for IKEv2 [RFC8247] and ESP/AH [RFC8223] gives guidance to implementors but limits that guidance to avoid broken or weak algorithms. It does not deprecate algorithms that have aged and are not in use, but leave these algorithms in a state of "MAY be used". This document deprecates those algorithms that are no longer advised but for which there are no known attacks resulting in their earlier deprecation.

2. Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

3. RFC 2409 to Historic

IKEv1 is deprecated. Systems running IKEv1 should be upgraded and reconfigured to run IKEv2. Systems that support IKEv1 but not IKEv2 are most likely also unsuitable candidates for continued operation:

IKEv2 is a more secure protocol than IKEv1. For example, IKEv2 offers more modern cryptographic primitives, proper defense against denial of service attacks, improved authentication via EAP methods, PAKE support and is actively worked on with respect to defending against quantum computer attacks.

IKEv1-only systems should be upgraded or replaced by systems supporting IKEv2. IKEv1 configurations SHOULD NOT be directly translated to IKEv2 configurations without updating the cryptographic algorithms used.

4. IKEv1 feature equivalents for IKEv2

A few notably IKEv1 features are not present in the IKEv2 core specification [RFC7296] but are available for IKEv2 via an additional specification:

4.1. IKEv2 postquantum support

IKEv1 and its way of using Preshared Keys (PSKs) protects against quantum computer based attacks. IKEv2 updated its use of PSK to improve the error reporting, but at the expense of post-quantum security. If post-quantum security is required, these systems should be migrated to use IKEv2 Postquantum Preshared Keys (PPK) [RFC8784]

4.2. IKEv2 Labeled IPsec support

Some IKEv1 implementations support Labeled IPsec, a method to negotiate an addition Security Context selector to the SPD, but this method was never standarized in IKEv1. Those IKEv1 systems that require Labeled IPsec should migrate to an IKEv2 system supporting Labeled IPsec as specified in [draft-ietf-ipsecme-labeled-ipsec].

4.3. IKEv2 Group SA / Multicast support

The Group Domain of Interpretation (GDOI, [RFC6407]) protocol, based on IKEv1 defines the support for Multicast Group SAs. For IKEv2, this work is currently in progress via [draft-ietf-ipsecme-g-ikev2]

5. Deprecating obsolete algorithms

This document deprecates the following algorithms:

6. Security Considerations

There are only security benefits by deprecating IKEv1 for IKEv2.

The deprecated algorithms have long been in disuse and are no longer actively deployed or researched. It presents an unknown security risk that is best avoided. Additionally, these algorithms not being supported in implementations simplifies those implementations and reduces the accidental use of these deprecated algorithms through misconfiguration or downgrade attacks.

7. IANA Considerations

This document instructs IANA to add an additional Status column to the IKEv2 Transform Type registries and mark the following entries as DEPRECATED:

          Transform Type 1 - Encryption Algorithm IDs

          Number    Name                Status
          ------    ---------------     ------
          1         ENCR_DES_IV64       DEPRECATED [this document]
          2         ENCR_DES            DEPRECATED [RFC8247]
          4         ENCR_RC5            DEPRECATED [this document]
          5         ENCR_IDEA           DEPRECATED [this document]
          6         ENCR_CAST           DEPRECATED [this document]
          7         ENCR_BLOWFISH       DEPRECATED [this document]
          8         ENCR_3IDEA          DEPRECATED [this document]
          9         ENCR_DES_IV32       DEPRECATED [this document]
Figure 1

          Transform Type 2 - Pseudorandom Function Transform IDs

          Number    Name                Status
          ------    ------------        ----------
          1         PRF_HMAC_MD5        DEPRECATED [RFC8247]
          1         PRF_HMAC_TIGER      DEPRECATED [this document]
Figure 2

          Transform Type 3 - Integrity Algorithm Transform IDs

          Number    Name                Status
          ------    -----------------   ----------
          1         AUTH_HMAC_MD5_96    DEPRECATED [RFC8247]
          3         AUTH_DES_MAC        DEPRECATED [RFC8247]
          4         AUTH_KPDK_MD5       DEPRECATED [RFC8247]
          6         AUTH_HMAC_MD5_128   DEPRECATED [this document]
          7         AUTH_HMAC_SHA1_160  DEPRECATED [this document]
Figure 3

          Transform Type 4 - Diffie Hellman Group Transform IDs

          Number    Name                           Status
          ------    ----------------------------   ----------
          1         768-bit MODP Group             DEPRECATED [RFC8247]
          22        1024-bit MODP Group with
                    160-bit Prime Order Subgroup   DEPRECATED [RFC8247]
Figure 4

All entries not mentioned here should receive no value in the new Status field.

8. References

8.1. Normative References

Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <>.
Piper, D., "The Internet IP Security Domain of Interpretation for ISAKMP", RFC 2407, DOI 10.17487/RFC2407, , <>.
Maughan, D., Schertler, M., Schneider, M., and J. Turner, "Internet Security Association and Key Management Protocol (ISAKMP)", RFC 2408, DOI 10.17487/RFC2408, , <>.
Harkins, D. and D. Carrel, "The Internet Key Exchange (IKE)", RFC 2409, DOI 10.17487/RFC2409, , <>.
Kaufman, C., Ed., "Internet Key Exchange (IKEv2) Protocol", RFC 4306, DOI 10.17487/RFC4306, , <>.
Weis, B., Rowles, S., and T. Hardjono, "The Group Domain of Interpretation", RFC 6407, DOI 10.17487/RFC6407, , <>.
Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T. Kivinen, "Internet Key Exchange Protocol Version 2 (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, , <>.
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <>.
Esale, S., Torvi, R., Jalil, L., Chunduri, U., and K. Raza, "Application-Aware Targeted LDP", RFC 8223, DOI 10.17487/RFC8223, , <>.
Nir, Y., Kivinen, T., Wouters, P., and D. Migault, "Algorithm Implementation Requirements and Usage Guidance for the Internet Key Exchange Protocol Version 2 (IKEv2)", RFC 8247, DOI 10.17487/RFC8247, , <>.
Fluhrer, S., Kampanakis, P., McGrew, D., and V. Smyslov, "Mixing Preshared Keys in the Internet Key Exchange Protocol Version 2 (IKEv2) for Post-quantum Security", RFC 8784, DOI 10.17487/RFC8784, , <>.

8.2. Informative References

Smyslov, V. and B. Weis, "Group Key Management using IKEv2", Work in Progress, Internet-Draft, draft-ietf-ipsecme-g-ikev2, , <>.
Wouters, P. and S. Prasad, "Labeled IPsec Traffic Selector support for IKEv2", Work in Progress, Internet-Draft, draft-ietf-ipsecme-labeled-ipsec, , <>.

Author's Address

Paul Wouters (editor)