RSA/Rabin least significant bits are 1-2- + 1/poly(log N) secure

  • Authors:
  • Benny Chor;Oded Goldreich

  • Affiliations:
  • -;-

  • Venue:
  • Proceedings of CRYPTO 84 on Advances in cryptology
  • Year:
  • 1985

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Abstract

We prove that RSA least significant bit is 1/2 + 1/logc N secure, for any constant c (where N is the RSA modulus). This means that an adversary, given the ciphertext, cannot guess the least significant bit of the plaintext with probability better than 1/2 + 1/logc N unless he can break RSA.Our proof technique is strong enough to give, with slight modifications, the following related results: (1) The log log N least significant bits are simultaneously 1/2 + 1/logc N secure. (2) The above also holds for Rabin's encryption function.Our results imply that Rabin/RSA encryption can be directly used for pseudo random bits generation, provided that factoring/inverting RSA is hard.