KangarooTwelve
draft-viguier-kangarootwelve-00
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Internet Research Task Force (IRTF) B. Viguier
Internet-Draft Radboud University
Intended status: Informational June 14, 2017
Expires: December 16, 2017
KangarooTwelve
draft-viguier-kangarootwelve-00
Abstract
This document defines the KangarooTwelve eXtendable Output Function
(XOF), a hash function with arbitrary output length. It provides an
efficient and secure hashing primitive, which is able to exploit the
parallelism of the implementation in a scalable way. It uses tree
hashing over a round-reduced version of SHAKE128 as underlying
primitive.
This document builds up on the definitions of the permutations and of
the sponge construction in [FIPS 202], and is meant to serve as a
stable reference and an implementation guide.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 16, 2017.
Copyright Notice
Copyright (c) 2017 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
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
Viguier Expires December 16, 2017 [Page 1]
Internet-Draft KangarooTwelve June 2017
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions . . . . . . . . . . . . . . . . . . . . . . . 3
2. Specifications . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Inner function: F . . . . . . . . . . . . . . . . . . . . 4
2.2. Tree hashing over F . . . . . . . . . . . . . . . . . . . 5
2.3. right_encode( x ) . . . . . . . . . . . . . . . . . . . . 7
3. Test vectors . . . . . . . . . . . . . . . . . . . . . . . . 7
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
6.1. Normative References . . . . . . . . . . . . . . . . . . 10
6.2. Informative References . . . . . . . . . . . . . . . . . 10
Appendix A. Pseudo code . . . . . . . . . . . . . . . . . . . . 11
A.1. Keccak-p[1600] over 12 rounds . . . . . . . . . . . . . . 11
A.2. Inner function F . . . . . . . . . . . . . . . . . . . . 12
A.3. KangarooTwelve . . . . . . . . . . . . . . . . . . . . . 13
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction
This document defines the KangarooTwelve eXtendable Output Function
(XOF) [K12], i.e. a generalization of a hash function that can return
arbitrary output length. KangarooTwelve is based on a Keccak-p
permutation specified in [FIPS202] and aims at higher speed than
SHAKE and SHA-3.
The SHA-3 functions process data in a serial manner and unable to
optimally exploit parallelism available in modern CPU architectures.
KangarooTwelve splits the input message in fragments and applies an
inner hash function F on each of them separately. It then applies F
again on the concatenation of the digests. It makes use of Sakura
coding for ensuring soundness of the tree hashing mode [SAKURA]. The
inner hash function F is a sponge function and uses a round-reduced
version of the permutation used in Keccak. Its security builds up on
the scrutiny that Keccak has received since its publication
[KECCAK_CRYPTANALYSIS].
Viguier Expires December 16, 2017 [Page 2]
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