Padding-based forgeries in the mode XOCB

Jean Liénardy

Paper 2023/637

Padding-based forgeries in the mode XOCB

Jean Liénardy

, Royal Military Academy

Abstract

In this note, we identify a minor flaw in the design of the XOCB mode, presented at Eurocrypt '23. This vulnerability enables trivial tag forgeries and arises from the padding applied to messages. We examine the security proof and pinpoint the presence of the flaw within it. Furthermore, we propose a simple fix for this issue, drawing upon the features of OCB3, and discuss the implications of this modification on the proof of security.

Metadata

Available format(s): PDF
Category: Cryptographic protocols
Publication info: Preprint.
Keywords: Authenticated Encryption Forgery OCB XOCB
Contact author(s): jean lienardy @ mil be
History: 2023-05-08: approved; 2023-05-04: received; See all versions
Short URL: https://ia.cr/2023/637
License: CC BY

BibTeX

@misc{cryptoeprint:2023/637,
      author = {Jean Liénardy},
      title = {Padding-based forgeries in the mode {XOCB}},
      howpublished = {Cryptology {ePrint} Archive, Paper 2023/637},
      year = {2023},
      url = {https://eprint.iacr.org/2023/637}
}