CryptoDB
Indifferentiability of the Sponge Construction with a Restricted Number of Message Blocks
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| Abstract: | The sponge construction is a popular method for hashing. Quickly after its introduction, the sponge was proven to be tightly indifferentiable from a random oracle up to ≈ 2c/2 queries, where c is the capacity. However, this bound is not tight when the number of message blocks absorbed is restricted to ℓ < ⌈ c / 2(b−c) ⌉ + 1 (but still an arbitrary number of blocks can be squeezed). In this work, we show that this restriction leads to indifferentiability from a random oracle up to ≈ min { 2b/2, max { 2c/2, 2b−ℓ×(b−c) }} queries, where b > c is the permutation size. Depending on the parameters chosen, this result allows to have enhanced security or to absorb at a larger rate for applications that require a fixed-length input hash function. |
BibTeX
@article{tosc-2023-33059,
title={Indifferentiability of the Sponge Construction with a Restricted Number of Message Blocks},
journal={IACR Transactions on Symmetric Cryptology},
publisher={Ruhr-Universität Bochum},
volume={2023, Issue 1},
pages={224-243},
url={https://tosc.iacr.org/index.php/ToSC/article/view/10313},
doi={10.46586/tosc.v2023.i1.224-243},
author={Charlotte Lefevre},
year=2023
}