pubkey = pub_key;
ASN1EncodableVector content_der = new ASN1EncodableVector();
content_der.add(getKeySpec());
//content_der.add(new SubjectPublicKeyInfo(sigAlg, new RSAPublicKeyStructure(pubkey.getModulus(), pubkey.getPublicExponent()).getDERObject()));
content_der.add(new DERIA5String(challenge));
try
{
content = new DERBitString(new DERSequence(content_der));
}