JISE

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Journal of Information Science and Engineering, Vol. 27 No. 4, pp. 1315-1327

Preimage Attack on Reduced DHA-256

JINMIN ZHONG AND XUEJIA LAI
Department of Computer Science and Engineering
Shanghai Jiao Tong University
Shanghai, 200240 P.R. China

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 an attack on 35-step DHA-256. The attack finds pseudo-preimage and preimage of 35-step DHA-256 with the time complexity of 2²⁴⁰ and 2²⁴⁹compression function operations, respectively, and 2¹⁶ x 11 words memory. To the best of our knowledge, this is the first paper that analyzes the preimage resistance of DHA-256.

Keywords: DHA-256, meet-in-the-middle, pseudo-preimage, preimage, hash function

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