ISO 18033-2: A Standard for Public-Key Encryption

ISO 18033-2 is standard for public-key encryption. It was published by the ISO in May 2006.

Here are some things that might be of interest:

FCD: Final Committee Draft of December 6, 2004.
The official ISO standard can be purchased for a fee, but the above Final Committee Draft is essentially the same.
A C++ Reference Implementation: unpack the tarball and see the file README.txt.
Preliminary Proposal: a document that gives some of the rationale behind the standard, as well as some preliminary (and by now obsolete) specifications.