sentences:  As of the end of 2007, thanks to the constant decline in memory prices, the ready availability of multi-core 64-bit computers, and the availability of the efficient sieving code (developed by Thorsten Kleinjung of the Bonn group) via ggnfs and of robust open-source software such as msieve for the finishing stages, special-form numbers of up to 750 bits and general-form numbers of up to about 520 bits can be factored in a few months on a few PCs by a single person without any special mathematical experience.These bounds increase to about 950 and 600 if it were possible to secure the collaboration of a few dozen PCs for sieving; currently the amount of memory and the CPU power of a single machine for the finishing stage are equal barriers to progress.In 2009, Benjamin Moody factored a 512-bit RSA key used to sign the TI-83 graphing calculator using software found on the internet; this eventually led to the Texas Instruments signing key controversy.