Paper 2022/1776 Original: eprint.iacr.org/2022/1776 ↗
Offset-Based BBB-Secure Tweakable Block-ciphers with Updatable Caches
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
- Preprint.
- History
- 2022-12-29: last updated
- 2022-12-29: published
- Short URL
- https://ia.cr/2022/1776
- License
- https://creativecommons.org/licenses/by-nc-sa/4.0/
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}
}