“Apart from its practical implications, the factorization is a scientific breakthrough: 25 years ago, 512-bit numbers (about 155 decimals) were thought virtually impossible to factor. Estimates based on the then-fastest known algorithms and computers predicted a CPU time of more than 50 billion (50 000 000 000) years. The factored number, indicated by RSA-155, was taken from the "RSA Challenge List", which is used as a yardstick for the security of the RSA cryptosystem.”