Advances in Cryptology — CRYPTO ’85 Proceedings

Volume 218 of the series Lecture Notes in Computer Science pp 403-408


N Using RSA with Low Exponent in a Public Key Network

  • Johan HastadAffiliated withMIT


We consider the problem of solving systems of equations P i(x) ≡ 0 (mod n i) i = 1...k where P i are polynomials of degree d and the n i are distinct relatively prime numbers and x < min n i. We prove that if k > d(d+1)/2 we can recover x in polynomial time provided n i > > 2k. This shows that RSA with low exponent is not a good alternative to use as a public key cryptosystem in a large network. It also shows that a protocol by Broder and Dolev [4] is insecure if RSA with low exponent is used.