A polynomial time attack on RSA with private CRT-exponents smaller than N0.073

  • Authors:
  • Ellen Jochemsz;Alexander May

  • Affiliations:
  • Department of Mathematics and Computer Science, TU Eindhoven, Eindhoven, The Netherlands;Faculty of Computer Science, TU Darmstadt, Darmstadt, Germany

  • Venue:
  • CRYPTO'07 Proceedings of the 27th annual international cryptology conference on Advances in cryptology
  • Year:
  • 2007

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Abstract

Wiener's famous attack on RSA with d N0.25 shows that using a small d for an efficient decryption process makes RSA completely insecure. As an alternative, Wiener proposed to use the Chinese Remainder Theorem in the decryption phase, where dp = d mod (p - 1) and dq = d mod (q - 1) are chosen significantly smaller than p and q. The parameters dp, dq are called private CRT-exponents. Since Wiener's proposal in 1990, it has been a challenging open question whether there exists a polynomial time attack on small private CRT-exponents. In this paper, we give an affirmative answer to this question, and show that a polynomial time attack exists if dp and dq are smaller than N0.073.