package org.bouncycastle.crypto.util;import java.io.IOException;import org.bouncycastle.asn1.ASN1OctetString;import org.bouncycastle.asn1.ASN1Sequence;import org.bouncycastle.asn1.DERBitString;import org.bouncycastle.asn1.DERInteger;import org.bouncycastle.asn1.DERObject;import org.bouncycastle.asn1.DERObjectIdentifier;import org.bouncycastle.asn1.DEROctetString;import org.bouncycastle.asn1.oiw.ElGamalParameter;import org.bouncycastle.asn1.oiw.OIWObjectIdentifiers;import org.bouncycastle.asn1.pkcs.DHParameter;import org.bouncycastle.asn1.pkcs.PKCSObjectIdentifiers;import org.bouncycastle.asn1.x509.AlgorithmIdentifier;import org.bouncycastle.asn1.x509.DSAParameter;import org.bouncycastle.asn1.x509.RSAPublicKeyStructure;import org.bouncycastle.asn1.x509.SubjectPublicKeyInfo;import org.bouncycastle.asn1.x509.X509ObjectIdentifiers;import org.bouncycastle.asn1.x9.X962NamedCurves;import org.bouncycastle.asn1.x9.X962Parameters;import org.bouncycastle.asn1.x9.X9ECParameters;import org.bouncycastle.asn1.x9.X9ECPoint;import org.bouncycastle.asn1.x9.X9ObjectIdentifiers;import org.bouncycastle.crypto.params.AsymmetricKeyParameter;import org.bouncycastle.crypto.params.DHParameters;import org.bouncycastle.crypto.params.DHPublicKeyParameters;import org.bouncycastle.crypto.params.DSAParameters;import org.bouncycastle.crypto.params.DSAPublicKeyParameters;import org.bouncycastle.crypto.params.ECDomainParameters;import org.bouncycastle.crypto.params.ECPublicKeyParameters;import org.bouncycastle.crypto.params.ElGamalParameters;import org.bouncycastle.crypto.params.ElGamalPublicKeyParameters;import org.bouncycastle.crypto.params.RSAKeyParameters;/** * Factory to create asymmetric public key parameters for asymmetric ciphers * from range of ASN.1 encoded SubjectPublicKeyInfo objects. */public class PublicKeyFactory{    /**     * Create a public key from the passed in SubjectPublicKeyInfo     *      * @param keyInfo the SubjectPublicKeyInfo containing the key data     * @return the appropriate key parameter     * @throws IOException on an error decoding the key     */    public static AsymmetricKeyParameter createKey(        SubjectPublicKeyInfo    keyInfo)        throws IOException    {        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 params = new DHParameter((ASN1Sequence)keyInfo.getAlgorithmId().getParameters());            DERInteger  derY = (DERInteger)keyInfo.getPublicKey();                        return new DHPublicKeyParameters(derY.getValue(), new DHParameters(params.getP(), params.getG()));        }        else if (algId.getObjectId().equals(OIWObjectIdentifiers.elGamalAlgorithm))        {            ElGamalParameter    params = new ElGamalParameter((ASN1Sequence)keyInfo.getAlgorithmId().getParameters());            DERInteger          derY = (DERInteger)keyInfo.getPublicKey();            return new ElGamalPublicKeyParameters(derY.getValue(), new ElGamalParameters(params.getP(), params.getG()));        }        else if (algId.getObjectId().equals(X9ObjectIdentifiers.id_dsa)                 || algId.getObjectId().equals(OIWObjectIdentifiers.dsaWithSHA1))        {            DSAParameter    params = new DSAParameter((ASN1Sequence)keyInfo.getAlgorithmId().getParameters());            DERInteger      derY = (DERInteger)keyInfo.getPublicKey();            return new DSAPublicKeyParameters(derY.getValue(), new DSAParameters(params.getP(), params.getQ(), params.getG()));        }        else if (algId.getObjectId().equals(X9ObjectIdentifiers.id_ecPublicKey))        {            X962Parameters      params = new X962Parameters((DERObject)keyInfo.getAlgorithmId().getParameters());            ECDomainParameters  dParams = null;                        if (params.isNamedCurve())            {                DERObjectIdentifier oid = (DERObjectIdentifier)params.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)params.getParameters());                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 RuntimeException("algorithm identifier in key not recognised");        }    }}