Usage Limits on AEAD Algorithms
draft-irtf-cfrg-aead-limits-01

Document Type Active Internet-Draft (cfrg RG)
Authors Felix Günther  , Martin Thomson  , Christopher Wood 
Last updated 2020-09-20
Replaces draft-wood-cfrg-aead-limits
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Intended RFC status Informational
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Network Working Group                                         F. Günther
Internet-Draft                                                ETH Zurich
Intended status: Informational                                M. Thomson
Expires: 24 March 2021                                           Mozilla
                                                               C.A. Wood
                                                              Cloudflare
                                                       20 September 2020

                    Usage Limits on AEAD Algorithms
                     draft-irtf-cfrg-aead-limits-01

Abstract

   An Authenticated Encryption with Associated Data (AEAD) algorithm
   provides confidentiality and integrity.  Excessive use of the same
   key can give an attacker advantages in breaking these properties.
   This document provides simple guidance for users of common AEAD
   functions about how to limit the use of keys in order to bound the
   advantage given to an attacker.  It considers limits in both single-
   and multi-user settings.

Discussion Venues

   This note is to be removed before publishing as an RFC.

   Source for this draft and an issue tracker can be found at
   https://github.com/chris-wood/draft-wood-cfrg-aead-limits
   (https://github.com/chris-wood/draft-wood-cfrg-aead-limits).

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 24 March 2021.

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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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Requirements Notation . . . . . . . . . . . . . . . . . . . .   4
   3.  Notation  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Calculating Limits  . . . . . . . . . . . . . . . . . . . . .   6
   5.  Single-User AEAD Limits . . . . . . . . . . . . . . . . . . .   7
     5.1.  AEAD_AES_128_GCM and AEAD_AES_256_GCM . . . . . . . . . .   7
       5.1.1.  Confidentiality Limit . . . . . . . . . . . . . . . .   7
       5.1.2.  Integrity Limit . . . . . . . . . . . . . . . . . . .   8
     5.2.  AEAD_CHACHA20_POLY1305  . . . . . . . . . . . . . . . . .   8
     5.3.  AEAD_AES_128_CCM  . . . . . . . . . . . . . . . . . . . .   8
       5.3.1.  Confidentiality Limit . . . . . . . . . . . . . . . .   9
       5.3.2.  Integrity Limit . . . . . . . . . . . . . . . . . . .   9
     5.4.  AEAD_AES_128_CCM_8  . . . . . . . . . . . . . . . . . . .   9
   6.  Multi-User AEAD Limits  . . . . . . . . . . . . . . . . . . .   9
     6.1.  AEAD_AES_128_GCM and AEAD_AES_256_GCM . . . . . . . . . .  10
       6.1.1.  Authenticated Encryption Security Limit . . . . . . .  10
       6.1.2.  Confidentiality Limit . . . . . . . . . . . . . . . .  10
       6.1.3.  Integrity Limit . . . . . . . . . . . . . . . . . . .  10
     6.2.  AEAD_CHACHA20_POLY1305, AEAD_AES_128_CCM, and
           AEAD_AES_128_CCM_8  . . . . . . . . . . . . . . . . . . .  11
       6.2.1.  AEAD_CHACHA20_POLY1305  . . . . . . . . . . . . . . .  11
       6.2.2.  AEAD_AES_128_CCM and AEAD_AES_128_CCM_8 . . . . . . .  11
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  14

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