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Short Non-Malleable Codes from Related-Key Secure Block Ciphers
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| Abstract: | A non-malleable code is an unkeyed randomized encoding scheme that offers the strong guarantee that decoding a tampered codeword either results in the original message, or in an unrelated message. We consider the simplest possible construction in the computational split-state model, which simply encodes a message m as k||Ek(m) for a uniformly random key k, where E is a block cipher. This construction is comparable to, but greatly simplifies over, the one of Kiayias et al. (ACM CCS 2016), who eschewed this simple scheme in fear of related-key attacks on E. In this work, we prove this construction to be a strong non-malleable code as long as E is (i) a pseudorandom permutation under leakage and (ii) related-key secure with respect to an arbitrary but fixed key relation. Both properties are believed to hold for “good” block ciphers, such as AES-128, making this non-malleable code very efficient with short codewords of length |m|+2τ (where τ is the security parameter, e.g., 128 bits), without significant security penalty. |
BibTeX
@article{tosc-2018-28402,
title={Short Non-Malleable Codes from Related-Key Secure Block Ciphers},
journal={IACR Trans. Symmetric Cryptol.},
publisher={Ruhr-Universität Bochum},
volume={2018, Issue 1},
pages={336-352},
url={https://tosc.iacr.org/index.php/ToSC/article/view/854},
doi={10.13154/tosc.v2018.i1.336-352},
author={Serge Fehr and Pierre Karpman and Bart Mennink},
year=2018
}