Cryptology ePrint Archive: Report 2004/296

Designs of Efficient Secure Large Hash Values

Mridul Nandi

Abstract: A double length hash function is a 2n-bit hash function based on an n-bit compression function. To increase the security level, designs of good double length hash functions are important. In this paper we construct a class of maximally secure double length hash functions in random oracle model based on some good permutations. This class contains recently proposed double length hash functions. We also propose an efficient double length hash function and study its security level in the random oracle model. We prove that any attack algorithm in the random oracle model needs \Omega(2^n/(s^2n^s)) time complexity, where $s$ is some parameter related to the rate of the hash function. Thus there is a trade-off between the efficiency and security. We use the notion of computable message to make the security analysis of proposed hash functions. We also see that the security analysis of hash functions based on random permutations and hash functions based on random functions are very much related.

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Date: received 10 Nov 2004, last revised 20 Apr 2005

Contact author: mridul_r at isical ac in

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Version: 20050420:125956 (All versions of this report)

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