Hybrid Public Key Encryption
draft-irtf-cfrg-hpke-00

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Last updated 2019-07-04
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Network Working Group                                          R. Barnes
Internet-Draft                                                     Cisco
Intended status: Informational                              K. Bhargavan
Expires: January 4, 2020                                           Inria
                                                           July 03, 2019

                      Hybrid Public Key Encryption
                        draft-irtf-cfrg-hpke-00

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 combination of an asymmetric key encapsulation mechanism
   (KEM), key derivation function (KDF), and authenticated encryption
   with additional data (AEAD) encryption function.  We provide
   instantiations of the scheme using widely-used and efficient
   primitives.

Status of This Memo

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Copyright Notice

   Copyright (c) 2019 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
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   (https://trustee.ietf.org/license-info) in effect on the date of
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   carefully, as they describe your rights and restrictions with respect

Barnes & Bhargavan       Expires January 4, 2020                [Page 1]
Internet-Draft                    HPKE                         July 2019

   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Notation . . . . . . . . . . . . . . . . . . . .   3
   3.  Security Properties . . . . . . . . . . . . . . . . . . . . .   3
   4.  Notation  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   5.  Cryptographic Dependencies  . . . . . . . . . . . . . . . . .   4
     5.1.  DH-Based KEM  . . . . . . . . . . . . . . . . . . . . . .   5
   6.  Hybrid Public Key Encryption  . . . . . . . . . . . . . . . .   6
     6.1.  Creating an Encryption Context  . . . . . . . . . . . . .   7
     6.2.  Encryption to a Public Key  . . . . . . . . . . . . . . .  10
     6.3.  Authentication using a Pre-Shared Key . . . . . . . . . .  10
     6.4.  Authentication using an Asymmetric Key  . . . . . . . . .  11
     6.5.  Authentication using both a PSK and an Asymmetric Key . .  12
     6.6.  Encryption and Decryption . . . . . . . . . . . . . . . .  12
   7.  Algorithm Identifiers . . . . . . . . . . . . . . . . . . . .  13
     7.1.  Key Encapsulation Mechanisms (KEMs) . . . . . . . . . . .  13
     7.2.  Key Derivation Functions (KDFs) . . . . . . . . . . . . .  14
     7.3.  Authentication Encryption with Associated Data (AEAD)
           Functions . . . . . . . . . . . . . . . . . . . . . . . .  14
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  15
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  15
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  15
     10.2.  Informative References . . . . . . . . . . . . . . . . .  15
   Appendix A.  Possible TODOs . . . . . . . . . . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17

1.  Introduction

   "Hybrid" public-key encryption schemes (HPKE) that combine asymmetric
   and symmetric algorithms are 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 cases.  This type of public
   key encryption has many applications in practice, for example:
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