In case anyone's interested, I've finally found the source I used for the claim that RC2/RC4 were exportable if the details were kept quiet: "Details about them [RC2 and RC4] have not been published (including by patenting) in order to maintain their special export status". -- RSA FAQ, version 1.0, draft 1e, 14 September 1992, p.40. This makes sense - the NSA wouldn't want the details published to stop non-US non-crippled versions appearing, and I can't really imagine RSADSI volutarily not patenting a new algorithm. Peter.