I think we're talking about two different encryption algorithms. The RSA public key algorithm is the one discussed in the article. The distributed.net challenge is RC5, which I don't think has a ...

RC6, a cryptographic algorithm, is specified as RC6-w/r/b, where w is word size, r is the number of rounds and b is the length of encryption key in bytes. RC6 is the successor to RC5. It is one of the ...