Advances in Cryptology — CRYPTO’ 93

Volume 773 of the series Lecture Notes in Computer Science pp 166-174


On the factorization of RSA-120

  • T. DennyAffiliated withLehrstuhl Prof. Buchmann, Fachbereich Informatik, Uníversität des Saarlandes
  • , B. DodsonAffiliated withDepartment of Mathematics, Lehigh University
  • , A. K. LenstraAffiliated withMRE-2Q334, Bellcore
  • , M. S. ManasseAffiliated withDEC SRC


We present data concerning the factorization of the 120-digit number RSA-120, which we factored on July 9, 1993, using the quadratic sieve method. The factorization took approximately 825 MIPS years and was completed within three months real time. At the time of writing RSA-120 is the largest integer ever factored by a general purpose factoring algorithm. We also present some conservative extrapolations to estimate the difficulty of factoring even larger numbers, using either the quadratic sieve method or the number field sieve, and discuss the issue of the crossover point between these two methods.