Hybrid Public Key Encryption
draft-barnes-cfrg-hpke-01

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Last updated 2019-05-23 (latest revision 2019-03-11)
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Network Working Group                                          R. Barnes
Internet-Draft                                                     Cisco
Intended status: Informational                              K. Bhargavan
Expires: September 12, 2019                                        Inria
                                                          March 11, 2019

                      Hybrid Public Key Encryption
                       draft-barnes-cfrg-hpke-01

Abstract

   This document describes a scheme for hybrid public-key encryption
   (HPKE).  This scheme provides authenticated public key encryption of
   arbitrary-sized plaintexts for a recipient public key.  HPKE works
   for any Diffie-Hellman group and has a strong security proof.  We
   provide instantiations of the scheme using standard and efficient
   primitives.

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   Copyright (c) 2019 IETF Trust and the persons identified as the
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Barnes & Bhargavan     Expires September 12, 2019               [Page 1]
Internet-Draft                    HPKE                        March 2019

   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Notation . . . . . . . . . . . . . . . . . . . .   3
   3.  Security Properties . . . . . . . . . . . . . . . . . . . . .   3
   4.  Notation  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   5.  Cryptographic Dependencies  . . . . . . . . . . . . . . . . .   3
     5.1.  DH-Based KEM  . . . . . . . . . . . . . . . . . . . . . .   5
   6.  Hybrid Public Key Encryption  . . . . . . . . . . . . . . . .   5
     6.1.  Encryption to a Public Key  . . . . . . . . . . . . . . .   6
     6.2.  Authentication using a Pre-Shared Key . . . . . . . . . .   7
     6.3.  Authentication using an Asymmetric Key  . . . . . . . . .   8
     6.4.  Encryption and Decryption . . . . . . . . . . . . . . . .   9
   7.  Ciphersuites  . . . . . . . . . . . . . . . . . . . . . . . .  10
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  11
     10.2.  Informative References . . . . . . . . . . . . . . . . .  12
   Appendix A.  Possible TODOs . . . . . . . . . . . . . . . . . . .  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  13

1.  Introduction

   Hybrid public-key encryption (HPKE) is a substantially more efficient
   solution than traditional public key encryption techniques such as
   those based on RSA or ElGamal.  Encrypted messages convey a single
   ciphertext and authentication tag alongside a short public key, which
   may be further compressed.  The key size and computational complexity
   of elliptic curve cryptographic primitives for authenticated
   encryption therefore make it compelling for a variety of use case.
   This type of public key encryption has many applications in practice,
   for example, in PGP [RFC6637] and in the developing Messaging Layer
   Security protocol [I-D.ietf-mls-protocol].

   Currently, there are numerous competing and non-interoperable
   standards and variants for hybrid encryption, including ANSI X9.63
   [ANSI], IEEE 1363a [IEEE], ISO/IEC 18033-2 [ISO], and SECG SEC 1
   [SECG].  Lack of a single standard makes selection and deployment of
   a compatible, cross-platform and ecosystem solution difficult to
   define.  This document defines an HPKE scheme that provides a subset
   of the functions provided by the collection of schemes above, but
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