XChaCha: eXtended-nonce ChaCha and AEAD_XChaCha20_Poly1305
draft-arciszewski-xchacha-03

Document Type Replaced Internet-Draft (cfrg RG)
Last updated 2018-12-18
Replaced by draft-irtf-cfrg-xchacha
Stream IRTF
Intended RFC status (None)
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Expired & archived
pdf htmlized bibtex
Stream IRTF state Replaced
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Document shepherd No shepherd assigned
IESG IESG state Replaced by draft-irtf-cfrg-xchacha
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at
https://www.ietf.org/archive/id/draft-arciszewski-xchacha-03.txt

Abstract

The eXtended-nonce ChaCha cipher construction (XChaCha) allows for ChaCha-based ciphersuites to accept a 192-bit nonce with similar guarantees to the original construction, except with a much lower probability of nonce misuse occurring. This enables XChaCha constructions to be stateless, while retaining the same security assumptions as ChaCha. This document defines XChaCha20, which uses HChaCha20 to convert the key and part of the nonce into a subkey, which is in turn used with the remainder of the nonce with ChaCha20 to generate a pseudorandom keystream (e.g. for message encryption). This document also defines AEAD_XChaCha20_Poly1305, a variant of [RFC7539] that utilizes the XChaCha20 construction in place of ChaCha20.

Authors

Scott Arciszewski (security@paragonie.com)

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)