Too Much Crypto

Jean-Philippe Aumasson

Paper 2019/1492

Too Much Crypto

Jean-Philippe Aumasson, Taurus SA, Switzerland

Abstract

We show that many symmetric cryptography primitives would not be less safe with significantly fewer rounds. To support this claim, we review the cryptanalysis progress in the last 20 years, examine the reasons behind the current number of rounds, and analyze the risk of doing fewer rounds. Advocating a rational and scientific approach to round numbers selection, we propose revised number of rounds for AES, BLAKE2, ChaCha, and SHA-3, which offer more consistent security margins across primitives and make them much faster, without increasing the security risk.

Note: Presented at Real-World Crypto 2020. April 4, 2023: New version updated the link to the NCC report. May 24, 2021: New version fixed a calculus error (see https://twitter.com/laughinghan/status/1394844992531689476) and adds a few lines to the conclusion.

Metadata

Available format(s): PDF
Category: Secret-key cryptography
Publication info: Preprint.
Keywords: cryptanalysis AES BLAKE2 ChaCha SHA-3
Contact author(s): jeanphilippe aumasson @ gmail com
History: 2023-04-04: last of 5 revisions; 2019-12-30: received; See all versions
Short URL: https://ia.cr/2019/1492
License: CC BY

BibTeX

@misc{cryptoeprint:2019/1492,
      author = {Jean-Philippe Aumasson},
      title = {Too Much Crypto},
      howpublished = {Cryptology ePrint Archive, Paper 2019/1492},
      year = {2019},
      note = {\url{https://eprint.iacr.org/2019/1492}},
      url = {https://eprint.iacr.org/2019/1492}
}