Offset-Based BBB-Secure Tweakable Block-ciphers with Updatable Caches

Arghya Bhattacharjee; Ritam Bhaumik; Mridul Nandi

Paper 2022/1776

Offset-Based BBB-Secure Tweakable Block-ciphers with Updatable Caches

Arghya Bhattacharjee, Indian Statistical Institute

Ritam Bhaumik

, French Institute for Research in Computer Science and Automation

Mridul Nandi

, Indian Statistical Institute

Abstract

A nonce-respecting tweakable blockcipher is the building-block for the OCB authenticated encryption mode. An XEX-based TBC is used to process each block in OCB. However, XEX can provide at most birthday bound privacy security, whereas in Asiacrypt 2017, beyond-birthday-bound (BBB) forging security of OCB3 was shown by Bhaumik and Nandi. In this paper we study how at a small cost we can construct a nonce-respecting BBB-secure tweakable blockcipher. We propose the OTBC-3 construction, which maintains a cache that can be easily updated when used in an OCB-like mode. We show how this can be used in a BBB-secure variant of OCB with some additional keys and a few extra blockcipher calls but roughly the same amortised rate.

Metadata

Available format(s): PDF
Category: Secret-key cryptography
Publication info: Published elsewhere. Indocrypt 2022
Keywords: OCB tweakable block-cipher authenticated encryption updatable offsets beyond-birthday-bound security
Contact author(s): bhattacharjeearghya29 @ gmail com
ritam bhaumik @ epfl ch
mridul nandi @ gmail com
History: 2022-12-31: approved; 2022-12-29: received; See all versions
Short URL: https://ia.cr/2022/1776
License: CC BY-NC-SA

BibTeX

@misc{cryptoeprint:2022/1776,
      author = {Arghya Bhattacharjee and Ritam Bhaumik and Mridul Nandi},
      title = {Offset-Based {BBB}-Secure Tweakable Block-ciphers with Updatable Caches},
      howpublished = {Cryptology {ePrint} Archive, Paper 2022/1776},
      year = {2022},
      url = {https://eprint.iacr.org/2022/1776}
}