3.1.9 NetscapeSPKI objects 
NetscapeSPKI objects have the following methods:
- b64_encode()
- 
Return a base64-encoded string representation of the object.
- get_pubkey()
- 
Return the public key of object.
- set_pubkey(key)
- 
Set the public key of the object to key.
- sign(key, digest_name)
- 
Sign the NetscapeSPKI object using the given key and
digest_name.  digest_name must be a string describing a digest
algorithm supported by OpenSSL (by EVP_get_digestbyname, specifically).  For
example, "md5" or "sha1".
- verify(key)
- 
Verify the NetscapeSPKI object using the given key.