RSA is pretty much the de facto name in public key encryption. They've long held open challenges to programmers to crack their keys going back to 1977 as a means of keeping track of what size key was necessary to maintain security. Currently, it's been a common recommendation that 1024bit keys were still secure and many professional organizations have been brute-force attacking them for years. Some researchers at the University of Michigan have upended previous estimates on the security of a 1024bit key by recovering private keys from encryption hardware in a mere 104 hours. Their method involved a cluster of 81 Pentium 4s working an algorithm designed to detect error fluctuations (PDF) in calculations induced from chip faults. The process was helped along by inducing more faults within the chips by cutting the supplied voltage at key times.