Cryptology ePrint Archive: Report 2009/552

Preimage Attacks on Reduced DHA-256

Jinmin Zhong and Xuejia Lai

Abstract: DHA-256 (Double Hash Algorithm) was proposed at the Cryptographic Hash Workshop hosted by NIST in November 2005. DHA-256 is a dedicated hash function with output length of 256 bits and 64 steps of operations designed to enhance SHA-256 security. In this paper, we show two attacks on reduced DHA-256. The first attack finds one-block second preimage and preimage of 26-step DHA-256 with time complexity of 2^{223.82} compression function operations and 2^{32} x 9 words memory. The second attack finds pseudo-preimage and preimage of 35-step DHA-256 with time complexity of 2^{239.63} and 2^{248.82} compression function operations, respectively, and 2^{16} x 11 words memory. To the best of our knowledge, this is the first paper that analyzes second pre-image resistance and preimage resistance of DHA-256.

Category / Keywords: DHA-256, meet-in-the-middle, second preimage, preimage, hash function

Date: received 10 Nov 2009

Contact author: zjm_new at sjtu edu cn

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Version: 20091117:211803 (All versions of this report)

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