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

ePrint Report: Offset-Based BBB-Secure Tweakable Block-ciphers with Updatable Caches

Arghya Bhattacharjee, Ritam Bhaumik, Mridul Nandi

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 block ciphers eprint report