[Resource Topic] 2021/1469: New Indifferentiability Security Proof of MDPH Hash Function

Welcome to the resource topic for 2021/1469

Title:
New Indifferentiability Security Proof of MDPH Hash Function

Authors: Chun Guo, Tetsu Iwata, Kazuhiko Minematsu

Abstract:

MDPH is a double-block-length hash function proposed by Naito at Latincrypt 2019.This is a combination of Hirose’s compression function and the domain extender called Merkle-Damg\r{a}rd with permutation (MDP). When instantiated with an n-bit block cipher, Naito proved that this achieves the (nearly) optimal indifferentiable security bound of O(n-\log n)-bit security. In this paper, we first point out that the proof of the claim contains a gap, which is related to the definition of the simulator in simulating the decryption of the block cipher. We then show that the proof can be fixed. We introduce a new simulator that addresses the issue, showing that MDPH retains its (nearly) optimal indifferentiable security bound of O(n-\log n)-bit security.

ePrint: https://eprint.iacr.org/2021/1469

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