Tight Security of TNT: Reinforcing Khairallah's Birthday-bound Attack

Ashwin Jha; Mridul Nandi; Abishanka Saha

Paper 2023/1233

Tight Security of TNT: Reinforcing Khairallah's Birthday-bound Attack

Ashwin Jha

, CISPA Helmholtz Center for Information Security, Saarbrücken, Germany

Mridul Nandi

, Indian Statistical Institute, Kolkata, India

Abishanka Saha, Indian Statistical Institute, Kolkata, India

Abstract

In a recent paper, Khairallah demonstrated a birthday-bound attack on TNT, thereby invalidating its (beyond-the-birthday-bound) CCA security claims. In this short note, we reestablish a birthday-bound CCA security bound for TNT. Furthermore, using a minor variant of Khairallah's attack, we show that our security bound is tight. We provide a rigorous and complete attack advantage calculations to further enhance the confidence in Khairallah's proposed attack strategy.

Note: See [Cryptology ePrint Archive: Report 2023/1272] that appeared on August 24, 2023, which combines and extends the findings of [Cryptology ePrint Archive: Report 2023/1212] (by Khairallah), and this report.

Metadata

Available format(s): PDF
Category: Secret-key cryptography
Publication info: Preprint.
Keywords: TNT LRW1 tight security birthday-bound attack
Contact author(s): ashwin jha @ cispa de
mridul nandi @ gmail com
sahaa 1993 @ gmail com
History: 2023-08-24: revised; 2023-08-14: received; See all versions
Short URL: https://ia.cr/2023/1233
License: CC BY-NC-SA

BibTeX

@misc{cryptoeprint:2023/1233,
      author = {Ashwin Jha and Mridul Nandi and Abishanka Saha},
      title = {Tight Security of TNT: Reinforcing Khairallah's Birthday-bound Attack},
      howpublished = {Cryptology ePrint Archive, Paper 2023/1233},
      year = {2023},
      note = {\url{https://eprint.iacr.org/2023/1233}},
      url = {https://eprint.iacr.org/2023/1233}
}