Public key support, analogous to that provided by RSAREF. Suggested by
Dan Egnor. Signatures are done now, but RSA encryption is still
More feedback modes, in order of decreasing priority: CBC-MAC, OFB,
and CFB. Suggested by Rafael 'Dido' Sevilla. References:
Valgrind reports errors on the des-compat test program. Investigate.
The make rules for building position independent *_p.o files doesn't
get dependencies right.