Synthetic IV (SIV) for non-AES ciphers and MACs
draft-madden-generalised-siv-00

Document Type Active Internet-Draft (individual)
Last updated 2018-11-22
Stream (None)
Intended RFC status (None)
Formats plain text xml pdf html bibtex
Stream Stream state (No stream defined)
Consensus Boilerplate Unknown
RFC Editor Note (None)
IESG IESG state I-D Exists
Telechat date
Responsible AD (None)
Send notices to (None)
Network Working Group                                          N. Madden
Internet-Draft                                                 ForgeRock
Intended status: Informational                         November 22, 2018
Expires: May 26, 2019

            Synthetic IV (SIV) for non-AES ciphers and MACs
                    draft-madden-generalised-siv-00

Abstract

   This document specifies how the Synthetic Initialization Vector (SIV)
   block cipher mode of operation can be adapted to non-AES ciphers and
   message authentication codes (MACs), with block sizes and MAC tag
   sizes other than 128 bits.  Concrete instantiations are defined using
   the XChaCha20 nonce-extended stream cipher combined with HMAC-SHA256.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on May 26, 2019.

Copyright Notice

   Copyright (c) 2018 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.

Madden                    Expires May 26, 2019                  [Page 1]
Internet-Draft               Generalised SIV               November 2018

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Terminology  . . . . . . . . . . . . . . . .   2
     1.2.  Motivation  . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  The Generic SIV Construction  . . . . . . . . . . . . . . . .   3
     2.1.  Encryption  . . . . . . . . . . . . . . . . . . . . . . .   4
     2.2.  Decryption  . . . . . . . . . . . . . . . . . . . . . . .   5
     2.3.  Generalised S2V . . . . . . . . . . . . . . . . . . . . .   5
     2.4.  AES-SIV . . . . . . . . . . . . . . . . . . . . . . . . .   7
   3.  XChaCha20-HMAC-SHA256-SIV . . . . . . . . . . . . . . . . . .   8
   4.  IANA considerations . . . . . . . . . . . . . . . . . . . . .   9
     4.1.  AEAD_XCHACHA20_SIV_HMAC_SHA256  . . . . . . . . . . . . .   9
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     6.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   Appendix A.  Test Vectors . . . . . . . . . . . . . . . . . . . .  12
     A.1.  Nonce-Based Authenticated Encryption Example  . . . . . .  12
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  14

1.  Introduction

   The Synthetic Initialization Vector (SIV) block cipher mode of
   operation [RFC5297] provides either deterministic authenticated
   encryption (DAE) or nonce-reuse misuse-resistant authenticated
   encryption (MRAE) [DAE].  It was originally specified for the
   combination of AES-CMAC for authenticity and AES-CTR for
   confidentiality.  The 128-bit AES-CMAC tag is used as the 128-bit
   (synthetic) IV for AES-CTR.  This document show how to apply SIV mode
   to ciphers and MACs with IV and tag lengths other than 128 bits,
   including where the IV and tag length may differ.

1.1.  Requirements Terminology

   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 [RFC8174] when, and only when, they appear in all capitals, as
   shown here.

1.2.  Motivation

   Common IV-based authenticated encryption modes of operation require a
   unique IV (or nonce) to be provided on each call to the encryption
   function with the same key.  If an IV is reused, either by accident
   or through malicious action, then some combination of the
   confidentiality and/or authenticity properties is usually lost.  For

Madden                    Expires May 26, 2019                  [Page 2]
Show full document text