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Context-Committing Security of Leveled Leakage-Resilient AEAD

Authors:
Chandranan Dhar , Indian Statistical Institute, Kolkata, India
Jordan Ethan , CISPA Helmholtz Center for Information Security, Saarbrücken, Germany
Ravindra Jejurikar , Cryptography Research Centre, Technology Innovation Institute, Abu Dhabi, UAE
Mustafa Khairallah , Dept. of Electrical and Information Technology, Lund University, Lund, Sweden
Eik List , Nanyang Technological University, Singapore, Singapore
Sougata Mandal , Institute for Advancing Intelligence, TCG CREST, Kolkata, India; Ramakrishna Mission Vivekananda Educational and Research Institute, Kolkata, India
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DOI: 10.46586/tosc.v2024.i2.348-370
URL: https://tosc.iacr.org/index.php/ToSC/article/view/11634
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Abstract: During recent years, research on authenticated encryption has been thriving through two highly active and practically motivated research directions: provable leakage resilience and key- or context-commitment security. However, the intersection of both fields had been overlooked until very recently. In ToSC 1/2024, Struck and Weishäupl studied generic compositions of encryption schemes and message authentication codes for building committing leakage-resilient schemes. They showed that, in general, Encrypt-then-MAC (EtM) and MAC-then-Encrypt (MtE) are not committing while Encrypt-and-MAC (EaM) is, under plausible and weak assumptions on the components. However, real-world schemes are rarely strict blackbox constructions. Instead, while various leakage-resilient schemes follow blueprints inspired by generic compositions, they often tweak them for security or efficiency.In this paper, we study two blueprints, the first one based on EtM for one of the strongest possible levels of leakage resilience. The second one is a single-pass framework based on leveled implementations. We show that, with a careful selection of the underlying primitives such as with identical encryption and authentication keys and a collision-resistant PRF as the MAC, these blueprints are committing. Our results do not contradict the results by Struck and Weishäupl since we pose more, but practically-motivated, requirements on the components. We demonstrate the practical relevance of our results by showing that our results on those blueprints allow us to easily derive proofs that several state-of-the-art leakage-resilient schemes are indeed committing, including TEDT and its descendants TEDT2 and Romulus-T, as well as the single-pass scheme Triplex.
BibTeX
@article{tosc-2024-34386,
  title={Context-Committing Security of Leveled Leakage-Resilient AEAD},
  journal={IACR Transactions on Symmetric Cryptology},
  publisher={Ruhr-Universität Bochum},
  volume={024 No. 2},
  pages={348-370},
  url={https://tosc.iacr.org/index.php/ToSC/article/view/11634},
  doi={10.46586/tosc.v2024.i2.348-370},
  author={Chandranan Dhar and Jordan Ethan and Ravindra Jejurikar and Mustafa Khairallah and Eik List and Sougata Mandal},
  year=2024
}