A team at the German Federal Agency for Information Technology Security
(BSI) recently announced the factorization of the 193-digit number known as
RSA-640. The team responsible for this factorization is the same one that
previously factored the 174-digit number known as RSA-576 and the 200-digit
number known as RSA-200. While RSA-640 has slightly fewer digits than the
previously factored RSA-200, its factorization carries the additional
benefit of a cash reward of $20,000 awarded by RSA Laboratories as part of
RSA’s program to encourage research into computational number theory and
the practical difficulty of factoring large integers.