Nonces are Noticed: AEAD Revisited

Mihir Bellare; Ruth Ng; Björn Tackmann

Paper 2019/624

Nonces are Noticed: AEAD Revisited

Mihir Bellare, Ruth Ng, and Björn Tackmann

Abstract

We draw attention to a gap between theory and usage of nonce-based symmetric encryption, under which the way the former treats nonces can result in violation of privacy in the latter. We bridge the gap with a new treatment of nonce-based symmetric encryption that modifies the syntax (decryption no longer takes a nonce), upgrades the security goal (asking that not just messages, but also nonces, be hidden) and gives simple, efficient schemes conforming to the new definitions. We investigate both basic security (holding when nonces are not reused) and advanced security (misuse resistance, providing best-possible guarantees when nonces are reused).

Note: Added credits and citations. Proofs overhauled and simplified. GCM result improved, dropping blockcipher assumption from strong PRP to PRF. Decomposition theorem generalized. Significant changes over prior full version.

Metadata

Available format(s): PDF
Category: Secret-key cryptography
Publication info: A major revision of an IACR publication in CRYPTO 2019
Keywords: Nonce Authenticated Encryption Symmetric Encryption GCM
Contact author(s): mihir @ eng ucsd edu
ring @ eng ucsd edu
bta @ zurich ibm com
History: 2019-11-12: revised; 2019-06-03: received; See all versions
Short URL: https://ia.cr/2019/624
License: CC BY

BibTeX

@misc{cryptoeprint:2019/624,
      author = {Mihir Bellare and Ruth Ng and Björn Tackmann},
      title = {Nonces are Noticed: {AEAD} Revisited},
      howpublished = {Cryptology {ePrint} Archive, Paper 2019/624},
      year = {2019},
      url = {https://eprint.iacr.org/2019/624}
}