I guess you're referring to RSA? RSA does not have an international patent,
only a domestic one. This is because publication of the algorigthm was
rushed to prevent a secrecy order from the NSA. US patent law permits you
to apply for a patent up to one year from the date of publication.
International patent law tends to prohibit publication until the patent is
actually approved (certainly until after the patent application is made).
So, because of the forced publication, RSA was not eligible for
international patents.
But this isn't exactly kernel-related...
Stig
PS: Good copyright site: http://www.benedict.com