challenge = ((DERIA5String)pkac.getObjectAt(1)).getString();
//this could be dangerous, as ASN.1 decoding/encoding
//could potentially alter the bytes
content = new DERBitString(pkac);
SubjectPublicKeyInfo pubkeyinfo = new SubjectPublicKeyInfo(
(ASN1Sequence)pkac.getObjectAt(0));
X509EncodedKeySpec xspec = new X509EncodedKeySpec(new DERBitString(
pubkeyinfo).getBytes());
keyAlg = pubkeyinfo.getAlgorithmId();
pubkey = KeyFactory.getInstance(keyAlg.getObjectId().getId(), "BC")
.generatePublic(xspec);