Factoring RSA100

Earlier today I wrote about factoring four 255-bit numbers that I needed for a post. Just out of curiosity, I wanted to see how long it would take to factor RSA 100, the smallest of the factoring challenges posed by RSA Laboratories in 1991. This is a 100-digit (330-bit) number that is the product of two primes.

I used the CADO-NFS software. The software was developed in France, and CADO is a French acronym for Crible Algebrique: Distribution, Optimisation. NFS stands for number field seive, the fastest algorithm for factoring numbers with over 100 digits.

RSA 100 was first factored in 1991 using a few days of compute time on an MP1 MasPar computer, a machine that cost $500,000 at the time, equivalent to around $1,250,000 today.

My effort took about 23 minutes (1376 seconds) on a System 76 Meerkat mini that I paid $600 for in 2022.

The MP1 was about the size of a refrigerator. The Meerkat is about 3'' * 3'' * 1.5''.

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