Implicit Initialization Vector (IV) for Counter-Based Ciphers in Encapsulating Security Payload (ESP)
RFC 8750
Document | Type | RFC - Proposed Standard (March 2020; No errata) | |
---|---|---|---|
Authors | Daniel Migault , Tobias Guggemos , Yoav Nir | ||
Last updated | 2020-03-11 | ||
Replaces | draft-mglt-ipsecme-diet-esp-iv-generation, draft-mglt-ipsecme-implicit-iv, draft-mglt-6lo-aes-implicit-iv | ||
Stream | Internent Engineering Task Force (IETF) | ||
Formats | plain text html xml pdf htmlized (tools) htmlized bibtex | ||
Reviews | |||
Stream | WG state | Submitted to IESG for Publication | |
Document shepherd | Tero Kivinen | ||
Shepherd write-up | Show (last changed 2019-03-11) | ||
IESG | IESG state | RFC 8750 (Proposed Standard) | |
Action Holders |
(None)
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Consensus Boilerplate | Yes | ||
Telechat date | |||
Responsible AD | Alexey Melnikov | ||
Send notices to | Tero Kivinen <kivinen@iki.fi> | ||
IANA | IANA review state | IANA OK - Actions Needed | |
IANA action state | RFC-Ed-Ack |
Internet Engineering Task Force (IETF) D. Migault Request for Comments: 8750 Ericsson Category: Standards Track T. Guggemos ISSN: 2070-1721 LMU Munich Y. Nir Dell Technologies March 2020 Implicit Initialization Vector (IV) for Counter-Based Ciphers in Encapsulating Security Payload (ESP) Abstract Encapsulating Security Payload (ESP) sends an initialization vector (IV) in each packet. The size of the IV depends on the applied transform and is usually 8 or 16 octets for the transforms defined at the time this document was written. When used with IPsec, some algorithms, such as AES-GCM, AES-CCM, and ChaCha20-Poly1305, take the IV to generate a nonce that is used as an input parameter for encrypting and decrypting. This IV must be unique but can be predictable. As a result, the value provided in the ESP Sequence Number (SN) can be used instead to generate the nonce. This avoids sending the IV itself and saves 8 octets per packet in the case of AES-GCM, AES-CCM, and ChaCha20-Poly1305. This document describes how to do this. Status of This Memo This is an Internet Standards Track document. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 7841. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at https://www.rfc-editor.org/info/rfc8750. Copyright Notice Copyright (c) 2020 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction 2. Requirements Notation 3. Terminology 4. Implicit IV 5. IKEv2 Initiator Behavior 6. IKEv2 Responder Behavior 7. Security Considerations 8. IANA Considerations 9. References 9.1. Normative References 9.2. Informative References Acknowledgements Authors' Addresses 1. Introduction Counter-based AES modes of operation such as AES-CCM [RFC4309] and AES-GCM [RFC4106] require the specification of a nonce for each ESP packet. The same applies for ChaCha20-Poly1305 [RFC7634]. Currently, this nonce is generated thanks to the initialization vector (IV) provided in each ESP packet [RFC4303]. This practice is designated in this document as "explicit IV". In some contexts, such as the Internet of Things (IoT), it may be preferable to avoid carrying the extra bytes associated to the IV and instead generate it locally on each peer. The local generation of the IV is designated in this document as "implicit IV". The size of this IV depends on the specific algorithm, but all of the algorithms mentioned above take an 8-octet IV. This document defines how to compute the IV locally when it is implicit. It also specifies how peers agree with the Internet Key Exchange version 2 (IKEv2) [RFC7296] on using an implicit IV versus an explicit IV. This document limits its scope to the algorithms mentioned above. Other algorithms with similar properties may later be defined to use similar mechanisms. This document does not consider AES-CBC [RFC3602], as AES-CBC requires the IV to be unpredictable. Deriving it directly from the packet counter as described below is insecure, as mentioned in Section 6 of [RFC3602], and has led to real-world chosen plaintext attacks such as BEAST [BEAST]. This document does not consider AES-CTR [RFC3686], as it focuses on the recommended Authenticated Encryption with Associated Data (AEAD) suites provided in [RFC8221]. 2. Requirements Notation 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 allShow full document text