Cryptology ePrint Archive: Report 2021/1340

TEDT2 - Highly Secure Leakage-resilient TBC-based Authenticated Encryption

Eik List

Abstract: Leakage-resilient authenticated encryption (AE) schemes received considerable attention during the previous decade. Two core security models of bounded and unbounded leakage have evolved, where the latter has been motivated in a very detailed and practice-oriented manner. In that setting, designers often build schemes based on (tweakable) block ciphers due to the small state size, such as the recent two-pass AE scheme TEDT from TCHES 1/2020. TEDT is interesting due to its high security guarantees of O(n - log(n^2))-bit integrity under leakage and similar AE security in the black-box setting. Though, a detail limited it to provide only n/2-bit privacy under leakage. In this work, we extend TEDT to TEDT2 in three aspects with the help of a tweakable block cipher with a 3n-bit tweakey: we (1) adopt the idea from the design team of Romulus of replacing TEDT's previous internal hash function with Naito's MDPH, (2) move the nonce from the hash to the tag-generation function both for more efficiency, and (3) strengthen the security of the encryption to obtain beyond-birthday-bound security also under leakage.

Category / Keywords: secret-key cryptography / Symmetric-key cryptography, authenticated encryption, provable security, leakage resilience

Date: received 5 Oct 2021

Contact author: eik list at uni-weimar de

Available format(s): PDF | BibTeX Citation

Version: 20211005:154438 (All versions of this report)

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