International Association for Cryptologic Research

International Association
for Cryptologic Research


Paper: Indifferentiable Authenticated Encryption

Manuel Barbosa
Pooya Farshim
DOI: 10.1007/978-3-319-96884-1_7 (login may be required)
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Presentation: Slides
Conference: CRYPTO 2018
Abstract: We study Authenticated Encryption with Associated Data (AEAD) from the viewpoint of composition in arbitrary (single-stage) environments. We use the indifferentiability framework to formalize the intuition that a “good” AEAD scheme should have random ciphertexts subject to decryptability. Within this framework, we can then apply the indifferentiability composition theorem to show that such schemes offer extra safeguards wherever the relevant security properties are not known, or cannot be predicted in advance, as in general-purpose crypto libraries and standards.We show, on the negative side, that generic composition (in many of its configurations) and well-known classical and recent schemes fail to achieve indifferentiability. On the positive side, we give a provably indifferentiable Feistel-based construction, which reduces the round complexity from at least 6, needed for blockciphers, to only 3 for encryption. This result is not too far off the theoretical optimum as we give a lower bound that rules out the indifferentiability of any construction with less than 2 rounds.
Video from CRYPTO 2018
  title={Indifferentiable Authenticated Encryption},
  booktitle={Advances in Cryptology – CRYPTO 2018},
  series={Lecture Notes in Computer Science},
  author={Manuel Barbosa and Pooya Farshim},