Gmp-ecm is a free implementation of the elliptic curve method (ecm) for integer factorization.
the original purpose of the ecmnet project was to make richard brent's prediction true, i.e. to find a factor of 50 digits or more by ecm. this goal was attained on september 14, 1998, when conrad curry found a 53-digit factor of 2^677-1 c150 using george woltman's mprime program. the new goal of ecmnet is now to find other large factors by ecm, mainly by contributing to the cunningham project, most likely the longest, ongoing computational project in history according to bob silverman. a new record was set by nik lygeros and michel mizony, who found in december 1999 a prime factor of 54 digits using gmp-ecm.
see http://www.loria.fr/~zimmerma/records/ecmnet.html for more information about ecmnet.