[Resource Topic] 2011/591: A Unified Framework for Small Secret Exponent Attack on RSA

Welcome to the resource topic for 2011/591

Title:
A Unified Framework for Small Secret Exponent Attack on RSA

Authors: Noboru Kunihiro, Naoyuki Shinohara, Tetsuya Izu

Abstract:

We address a lattice based method on small secret exponent attack on RSA scheme. Boneh and Durfee reduced the attack into finding small roots of a bivariate modular equation: x(N+1+y)+1 ¥equiv 0 mod e), where N is an RSA moduli and e is the RSA public key. Boneh and Durfee proposed a lattice based algorithm for solving the problem. When the secret exponent d is less than N^{0.292}, their method breaks RSA scheme. Since the lattice used in the analysis is not full-rank, the analysis is not easy. Bl¥"omer and May gave an alternative algorithm. Although their bound d ¥leq N^{0.290} is worse than Boneh–Durfee result, their method used a full rank lattice. However, the proof for their bound is still complicated. Herrmann and May gave an elementary proof for the Boneh–Durfee’s bound: d ¥leq N^{0.292}. In this paper, we first give an elementary proof for achieving the bound of Bl¥"omer–May: d ¥leq N^{0.290}. Our proof employs unravelled linearization technique introduced by Herrmann and May and is rather simpler than Bl¥"omer–May’s proof. Then, we provide a unified framework to construct a lattice that are used for solving the problem, which includes two previous method: Herrmann–May and Bl¥"omer–May methods as a special case. Furthermore, we prove that the bound of Boneh–Durfee: d ¥leq N^{0.292} is still optimal in our unified framework.

ePrint: https://eprint.iacr.org/2011/591

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