Internet Engineering Task Force Y. Hori
Internet-Draft Saga University
Intended status: Informational T. Uehara
Expires: May 5, 2016 Ritsumeikan University
November 2, 2015

Use of KCipher-2 with Poly1305 in Transport Layer Security


This document describes the use of the KCipher-2 stream cipher with Poly1305 in Transport Layer Security (TLS) protocols version 1.2 and Datagram Transport Layer Security (DTLS) protocols. KCipher-2 is a stream cipher with a 128-bit key and a 128-bit initialization vector, which provides fast, efficient encryption and decryption.

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Table of Contents

1. Introduction

This document describes the use of the KCipher-2 [RFC7008] in the Transport Layer Security (TLS) version 1.2 [RFC5246] protocol, as well as in the Datagram Transport Layer Security (DTLS) version 1.2 [RFC6347], or any later versions.

Cryptographic operations used in TLS can be categorized in five ways: digital signing, stream cipher encryption, block cipher encryption, authenticated encryption with additional data encryption, and public key encryption [RFC5246]. This document defines the cipher suites to use KCipher-2 for stream cipher encryption in TLS. KCipher-2 is a fast, secure stream cipher algorithm as well as ChaCha20 [ChaCha20].

1.1. KCipher2

KCipher-2 is a stream cipher algorithm with a 128-bit key and a 128-bit initialization vector (IV). The algorithm and other properties are described in [SECRYPT]. KCipher-2 has been evaluated by the cryptographic technique evaluation project for the Japanese e-Government [CRYPTREC]. KCipher-2 also has been submitted to another international standardization body [ISO18033].

1.2. Poly1305 Authenticator

Poly1305 [POLY1305] is a Wegman-Carter, one-time authenticator designed by D. J. Bernstein. In details, Poly1305 is described in Section 2.5 and 2.6 of [RFC7539] .

1.3. Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].

2. Cipher Suites Values

The following are proposed identifiers and values for the cipher suites of TLS.

    CipherSuite TLS_ECDHE_RSA_WITH_KCIPHER2_128_POLY1305   = { TBD, TBD };
    CipherSuite TLS_ECDHE_ECDSA_WITH_KCIPHER2_128_POLY1305 = { TBD, TBD };
    CipherSuite TLS_DHE_RSA_WITH_KCIPHER2_128_POLY1305     = { TBD, TBD };

3. Cipher Suite Definitions

3.1. Key Exchange

The DHE_RSA, ECDHE_RSA, and ECDHE_ECDSA key exchanges are performed as defined in [RFC5246] and [RFC4496].

3.2. Cipher

The KCIPHER2_128 cipher suites use KCipher-2 with a 128-bit key and a 128-bit initialization vector.

3.3. Pseudorandom Function

For the cipher suites in this document, [RFC2104] based on SHA-256 is used for TLS PseudoRandom Function (PRF) [RFC5246] with SHA-256 is used as the PRF.

3.4. AEAD Construction

KCIPHER2_128_POLY1305 is an authenticated encryption with additional data algorithm. The KCipher-2 and Poly1305 [POLY1305]primitives are combined into an AEAD.

4. Security Considerations

As of the time this document was written, we are not aware of any attack on KCipher-2. No security vulnerabilities have been identified in the security evaluations by the KCipher-2 developers and other independent institutions [SECRYPT], [CRYPTREC10], and [KDDI].

Poly1305 is designed to ensure that forged messages are rejected with a probability of 1-(n/2^102) for a 16*n byte message, even after sending 2^64 legitimate messages.

5. IANA Considerations

IANA is requested to allocate the following numbers in the TLS Cipher Suite Registry:

    CipherSuite TLS_ECDHE_RSA_WITH_KCIPHER2_128_POLY1305   = { TBD, TBD };
    CipherSuite TLS_ECDHE_ECDSA_WITH_KCIPHER2_128_POLY1305 = { TBD, TBD };
    CipherSuite TLS_DHE_RSA_WITH_KCIPHER2_128_POLY1305     = { TBD, TBD };

6. Acknowledgements

Thanks to Marshall Rose for developing the XML2RFC format.

Thanks to Shinsaku Kiyomoto who is an author of draft-kiyomoto-kcipher2-tls-01.txt.

7. References

7.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC4496] Stecher, M. and A. Barbir, "Open Pluggable Edge Services (OPES) SMTP Use Cases", RFC 4496, DOI 10.17487/RFC4496, May 2006.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/RFC5246, August 2008.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, January 2012.
[RFC7008] Kiyomoto, S. and W. Shin, "A Description of the KCipher-2 Encryption Algorithm", RFC 7008, DOI 10.17487/RFC7008, August 2013.
[RFC7539] Nir, Y. and A. Langley, "ChaCha20 and Poly1305 for IETF Protocols", RFC 7539, DOI 10.17487/RFC7539, May 2015.

7.2. Informative References

[ChaCha20] Bernstein, D., "ChaCha, a variant of Salsa20", January 2008.
[CRYPTREC] CRYPTREC (Cryptography Research and Evaluation Committees),
[CRYPTREC10] Bogdanov, A., Preneel, B. and V. Rijmen, "Security Evaluation of the K2 Stream Cipher", 2010.
[ISO18033] International Organization for Standardization, "Information technology - Security techniques - Encryption algorithms - Part 4: Stream ciphers", ISO/IEC 18033-4, December 2011.
[KDDI] Roy, B., "Evaluation of the Word-Oriented Stream Cipher: K2", 2009.
[POLY1305] Bernstein, D., "The Poly1305-AES message-authentication code.", March 2005.
[RFC2104] Krawczyk, H., Bellare, M. and R. Canetti, "HMAC: Keyed-Hashing for Message Authentication", RFC 2104, DOI 10.17487/RFC2104, February 1997.
[SECRYPT] Kiyomoto, S., Tanaka, T. and K. Sakurai, "K2: A Stream Cipher Algorithm Using Dynamic Feedback Control", 2007.

Authors' Addresses

Yoshiaki Hori Saga University 1 Honjo Saga-shi, Saga 840-8502 JP Phone: +81-952-28-8982 EMail:
Tetsutaro Uehara Ritsumeikan University 1-1-1 Noji-higashi Kusatsu-shi, Shiga 525-8577 JP Phone: +81-77-599-4357 EMail: