X25519Kyber768Draft00 hybrid post-quantum key agreement

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Table of Contents

1. Introduction

2. Conventions and Definitions

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 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶

3. Construction

We instantiate draft-ietf-tls-hybrid-design-06 with X25519 [rfc7748] and Kyber768Draft00 [kyber]. The latter is Kyber as submitted to round 3 of the NIST PQC process [KyberV302].¶

For the client's share, the key_exchange value contains the concatenation of the client's X25519 ephemeral share (32 bytes) and the client's Kyber768Draft00 public key (1184 bytes). The resulting key_exchange value is 1216 bytes in length.¶

For the server's share, the key_exchange value contains the concatenation of the server's X25519 ephemeral share (32 bytes) and the Kyber768Draft00 ciphertext (1088 bytes) returned from encapsulation for the client's public key. The resulting key_exchange value is 1120 bytes in length.¶

The shared secret is calculated as the concatenation of the X25519 shared secret (32 bytes) and the Kyber768Draft00 shared secret (32 bytes). The resulting shared secret value is 64 bytes in length.¶

4. Security Considerations

For TLS 1.3, this concatenation approach provides a secure key exchange if either component key exchange methods (X25519 or Kyber768Draft00) are secure [hybrid].¶

5. IANA Considerations

This document requests/registers a new entry to the TLS Named Group (or Supported Group) registry, according to the procedures in Section 6 of [tlsiana].¶

Value:

0x6399 (please)¶

Description:

X25519Kyber768Draft00¶

DTLS-OK:

Y¶

Recommended:

N¶

Reference:

This document¶

Comment:

Pre-standards version of Kyber768¶

Appendix A. Change log

• RFC Editor's Note: Please remove this section prior to publication of a final version of this document.¶

Authors' Addresses