on top of my head: libgmp (not a crypto library but used by some), libgcrypt, openssl (requires a dynamic engine to do this), libssh2, libmcrypt ... IMHO the u

on top of my head: libgmp (not a crypto library but used by some), libgcrypt, openssl (requires a dynamic engine to do this), libssh2, libmcrypt ... IMHO the user of an encryption library (the developer of a crypto application) should at least be able to ensure that every bit of heap that was touched by the library is zeroed after it was freed.