AEAD Key Usage Limits in OSCORE
draft-hoeglund-core-oscore-key-limits-00

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CoRE Working Group                                           R. Hoeglund
Internet-Draft                                                 M. Tiloca
Updates: 8613 (if approved)                                      RISE AB
Intended status: Standards Track                       February 19, 2021
Expires: August 23, 2021

                    AEAD Key Usage Limits in OSCORE
                draft-hoeglund-core-oscore-key-limits-00

Abstract

   Object Security for Constrained RESTful Environments (OSCORE) uses
   AEAD algorithms to ensure confidentiality and integrity of exchanged
   messages.  Due to known issues allowing forgery attacks against AEAD
   algorithms, limits should be followed on the number of times a
   specific key is used for encryption or decryption.  This document
   defines how two peers using OSCORE must take these limits into
   account and what steps they must take to preserve the security of
   their communications.  Therefore, this document updates RFC8613.

Status of This Memo

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   This Internet-Draft will expire on August 23, 2021.

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Hoeglund & Tiloca        Expires August 23, 2021                [Page 1]
Internet-Draft       AEAD Key Usage Limits in OSCORE       February 2021

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Problem Overview  . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Limits for 'q' and 'v'  . . . . . . . . . . . . . . . . .   4
   3.  Additional Information in the Security Context  . . . . . . .   4
   4.  OSCORE Messages Processing  . . . . . . . . . . . . . . . . .   5
     4.1.  Protecting a Request or a Response  . . . . . . . . . . .   5
     4.2.  Verifying a Request or a Response . . . . . . . . . . . .   6
   5.  Methods for Rekeying OSCORE . . . . . . . . . . . . . . . . .   6
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   7
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   Object Security for Constrained RESTful Environments (OSCORE)
   [RFC8613] provides end-to-end protection of CoAP [RFC7252] messages
   at the application-layer, ensuring message confidentiality and
   integrity, replay protection, as well as binding of response to
   request between a sender and a recipient.

   In particular, OSCORE uses AEAD algorithms to provide confidentiality
   and integrity of messages exchanged between two peers.  Due to known
   issues allowing forgery attacks against AEAD algorithms, limits
   should be followed on the number of times a specific key is used to
   perform encryption or decryption [I-D.irtf-cfrg-aead-limits].

   Should these limits be exceeded, an adversary may break the security
   properties of the AEAD algorithm, such as message confidentiality and
   integrity, e.g. by performing a message forgery attack.  The original
   OSCORE specification [RFC8613] does not consider such limits.

   This document updates [RFC8613] and defines when a peer must stop
   using an OSCORE Security Context shared with another peer, due to the
   reached key usage limits.  When this happens, the two peers have to
   establish a new Security Context with new keying material, in order