Cryptology ePrint Archive: Report 2003/089

Efficient Public Key Generation for Multivariate Cryptosystems

Christopher Wolf

Abstract: Asymmetric cryptographic systems using multivariate polynomials over finite fields have been proposed several times since the 1980s. Although some of them have been successfully broken, the area is still vital and promises interesting algorithms with low computational costs, short message, and signature sizes.

In this paper, we present two novel strategies ``base transformation" and ``adapted evaluation" for the generation of the public key in such schemes. We demonstrate both at the example of the Hidden Field Equations (HFE) system and outline how they can be adapted to similar systems.

In addition, we compare the running time of the previously known technique ``polynomial interpolation" with our new developments both from a theoretical perspective and by empirical studies. These experiments confirm our theoretical studies, namely, base transformation is faster than polynomial interpolation. Especially the first step is $O(n^2)$ while it is $O(n^4)$ for polynomial interpolation where $n$ denotes the number of variables. Moreover, the running time of polynomial interpolation is approximately 30\% higher than for base transformation.

Category / Keywords: implementation / public-key cryptography, implementation, complexity theory, implementation, public-key cryptography, HFE, Hidden Field Equations

Publication Info: This is a preliminary version of the article ``Efficient public key generation for HFE and variations." In Cryptographic Algorithms and Their Uses 2004, pages 78--93. Dawson, Klimm, editors, QUT University, 2004.

Date: received 5 May 2003, last revised 6 Aug 2005

Contact author: Christopher Wolf at esat kuleuven ac be

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Version: 20050806:144941 (All versions of this report)

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