public static AsymmetricKeyParameter CreateKey(SubjectPublicKeyInfo keyInfo)
{
AlgorithmIdentifier algId = keyInfo.getAlgorithmId();
if (algId.getObjectId().Equals(PKCSObjectIdentifiers.rsaEncryption) ||
algId.getObjectId().Equals(X509ObjectIdentifiers.id_ea_rsa))
{
RSAPublicKeyStructure pubKey = new RSAPublicKeyStructure((ASN1Sequence)keyInfo.getPublicKey());
return(new RSAKeyParameters(false, pubKey.getModulus(), pubKey.getPublicExponent()));
}
else if (algId.getObjectId().Equals(PKCSObjectIdentifiers.dhKeyAgreement) ||
algId.getObjectId().Equals(X9ObjectIdentifiers.dhpublicnumber))
{
DHParameter para = new DHParameter((ASN1Sequence)keyInfo.getAlgorithmId().getParameters());
DERInteger derY = (DERInteger)keyInfo.getPublicKey();
return(new DHPublicKeyParameters(derY.getValue(), new DHParameters(para.getP(), para.getG())));
}
else if (algId.getObjectId().Equals(OIWObjectIdentifiers.elGamalAlgorithm))
{
ElGamalParameter para = new ElGamalParameter((ASN1Sequence)keyInfo.getAlgorithmId().getParameters());
DERInteger derY = (DERInteger)keyInfo.getPublicKey();
return(new ElGamalPublicKeyParameters(derY.getValue(), new ElGamalParameters(para.getP(), para.getG())));
}
else if (algId.getObjectId().Equals(X9ObjectIdentifiers.id_dsa) ||
algId.getObjectId().Equals(OIWObjectIdentifiers.dsaWithSHA1))
{
DSAParameter para = new DSAParameter((ASN1Sequence)keyInfo.getAlgorithmId().getParameters());
DERInteger derY = (DERInteger)keyInfo.getPublicKey();
return(new DSAPublicKeyParameters(derY.getValue(), new DSAParameters(para.getP(), para.getQ(), para.getG())));
}
else if (algId.getObjectId().Equals(X9ObjectIdentifiers.id_ecPublicKey))
{
X962Parameters para = new X962Parameters((ASN1Object)keyInfo.getAlgorithmId().getParameters());
ECDomainParameters dParams = null;
if (para.isNamedCurve())
{
DERObjectIdentifier oid = (DERObjectIdentifier)para.getParameters();
X9ECParameters ecP = X962NamedCurves.getByOID(oid);
dParams = new ECDomainParameters(
ecP.getCurve(),
ecP.getG(),
ecP.getN(),
ecP.getH(),
ecP.getSeed());
}
else
{
X9ECParameters ecP = new X9ECParameters((ASN1Sequence)para.getParameters().toASN1Object());
dParams = new ECDomainParameters(
ecP.getCurve(),
ecP.getG(),
ecP.getN(),
ecP.getH(),
ecP.getSeed());
}
DERBitString bits = keyInfo.getPublicKeyData();
byte[] data = bits.getBytes();
ASN1OctetString key = new DEROctetString(data);
X9ECPoint derQ = new X9ECPoint(dParams.getCurve(), key);
return(new ECPublicKeyParameters(derQ.getPoint(), dParams));
}
else
{
throw new Exception("algorithm identifier in key not recognised");
}
}