Java tutorial
package org.bouncycastle.crypto.util; import java.io.IOException; import java.math.BigInteger; import java.util.HashSet; import java.util.Set; import org.bouncycastle.asn1.ASN1Encodable; import org.bouncycastle.asn1.ASN1Integer; import org.bouncycastle.asn1.ASN1ObjectIdentifier; import org.bouncycastle.asn1.ASN1OctetString; import org.bouncycastle.asn1.DERNull; import org.bouncycastle.asn1.DEROctetString; import org.bouncycastle.asn1.cryptopro.CryptoProObjectIdentifiers; import org.bouncycastle.asn1.cryptopro.GOST3410PublicKeyAlgParameters; import org.bouncycastle.asn1.edec.EdECObjectIdentifiers; import org.bouncycastle.asn1.pkcs.PKCSObjectIdentifiers; import org.bouncycastle.asn1.pkcs.RSAPublicKey; import org.bouncycastle.asn1.rosstandart.RosstandartObjectIdentifiers; import org.bouncycastle.asn1.x509.AlgorithmIdentifier; import org.bouncycastle.asn1.x509.DSAParameter; import org.bouncycastle.asn1.x509.SubjectPublicKeyInfo; 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.DSAParameters; import org.bouncycastle.crypto.params.DSAPublicKeyParameters; import org.bouncycastle.crypto.params.ECDomainParameters; import org.bouncycastle.crypto.params.ECGOST3410Parameters; import org.bouncycastle.crypto.params.ECNamedDomainParameters; import org.bouncycastle.crypto.params.ECPublicKeyParameters; import org.bouncycastle.crypto.params.Ed25519PublicKeyParameters; import org.bouncycastle.crypto.params.Ed448PublicKeyParameters; import org.bouncycastle.crypto.params.RSAKeyParameters; import org.bouncycastle.crypto.params.X25519PublicKeyParameters; import org.bouncycastle.crypto.params.X448PublicKeyParameters; /** * Factory to create ASN.1 subject public key info objects from lightweight public keys. */ public class SubjectPublicKeyInfoFactory { private static Set cryptoProOids = new HashSet(5); static { cryptoProOids.add(CryptoProObjectIdentifiers.gostR3410_2001_CryptoPro_A); cryptoProOids.add(CryptoProObjectIdentifiers.gostR3410_2001_CryptoPro_B); cryptoProOids.add(CryptoProObjectIdentifiers.gostR3410_2001_CryptoPro_C); cryptoProOids.add(CryptoProObjectIdentifiers.gostR3410_2001_CryptoPro_XchA); cryptoProOids.add(CryptoProObjectIdentifiers.gostR3410_2001_CryptoPro_XchB); } private SubjectPublicKeyInfoFactory() { } /** * Create a SubjectPublicKeyInfo public key. * * @param publicKey the key to be encoded into the info object. * @return a SubjectPublicKeyInfo representing the key. * @throws java.io.IOException on an error encoding the key */ public static SubjectPublicKeyInfo createSubjectPublicKeyInfo(AsymmetricKeyParameter publicKey) throws IOException { if (publicKey instanceof RSAKeyParameters) { RSAKeyParameters pub = (RSAKeyParameters) publicKey; return new SubjectPublicKeyInfo( new AlgorithmIdentifier(PKCSObjectIdentifiers.rsaEncryption, DERNull.INSTANCE), new RSAPublicKey(pub.getModulus(), pub.getExponent())); } else if (publicKey instanceof DSAPublicKeyParameters) { DSAPublicKeyParameters pub = (DSAPublicKeyParameters) publicKey; DSAParameter params = null; DSAParameters dsaParams = pub.getParameters(); if (dsaParams != null) { params = new DSAParameter(dsaParams.getP(), dsaParams.getQ(), dsaParams.getG()); } return new SubjectPublicKeyInfo(new AlgorithmIdentifier(X9ObjectIdentifiers.id_dsa, params), new ASN1Integer(pub.getY())); } else if (publicKey instanceof ECPublicKeyParameters) { ECPublicKeyParameters pub = (ECPublicKeyParameters) publicKey; ECDomainParameters domainParams = pub.getParameters(); ASN1Encodable params; if (domainParams == null) { params = new X962Parameters(DERNull.INSTANCE); // Implicitly CA } else if (domainParams instanceof ECGOST3410Parameters) { ECGOST3410Parameters gostParams = (ECGOST3410Parameters) domainParams; BigInteger bX = pub.getQ().getAffineXCoord().toBigInteger(); BigInteger bY = pub.getQ().getAffineYCoord().toBigInteger(); params = new GOST3410PublicKeyAlgParameters(gostParams.getPublicKeyParamSet(), gostParams.getDigestParamSet()); int encKeySize; int offset; ASN1ObjectIdentifier algIdentifier; if (cryptoProOids.contains(gostParams.getPublicKeyParamSet())) { encKeySize = 64; offset = 32; algIdentifier = CryptoProObjectIdentifiers.gostR3410_2001; } else { boolean is512 = (bX.bitLength() > 256); if (is512) { encKeySize = 128; offset = 64; algIdentifier = RosstandartObjectIdentifiers.id_tc26_gost_3410_12_512; } else { encKeySize = 64; offset = 32; algIdentifier = RosstandartObjectIdentifiers.id_tc26_gost_3410_12_256; } } byte[] encKey = new byte[encKeySize]; extractBytes(encKey, encKeySize / 2, 0, bX); extractBytes(encKey, encKeySize / 2, offset, bY); try { return new SubjectPublicKeyInfo(new AlgorithmIdentifier(algIdentifier, params), new DEROctetString(encKey)); } catch (IOException e) { return null; } } else if (domainParams instanceof ECNamedDomainParameters) { params = new X962Parameters(((ECNamedDomainParameters) domainParams).getName()); } else { X9ECParameters ecP = new X9ECParameters(domainParams.getCurve(), // TODO Support point compression new X9ECPoint(domainParams.getG(), false), domainParams.getN(), domainParams.getH(), domainParams.getSeed()); params = new X962Parameters(ecP); } // TODO Support point compression byte[] pubKeyOctets = pub.getQ().getEncoded(false); return new SubjectPublicKeyInfo(new AlgorithmIdentifier(X9ObjectIdentifiers.id_ecPublicKey, params), pubKeyOctets); } else if (publicKey instanceof X448PublicKeyParameters) { X448PublicKeyParameters key = (X448PublicKeyParameters) publicKey; return new SubjectPublicKeyInfo(new AlgorithmIdentifier(EdECObjectIdentifiers.id_X448), key.getEncoded()); } else if (publicKey instanceof X25519PublicKeyParameters) { X25519PublicKeyParameters key = (X25519PublicKeyParameters) publicKey; return new SubjectPublicKeyInfo(new AlgorithmIdentifier(EdECObjectIdentifiers.id_X25519), key.getEncoded()); } else if (publicKey instanceof Ed448PublicKeyParameters) { Ed448PublicKeyParameters key = (Ed448PublicKeyParameters) publicKey; return new SubjectPublicKeyInfo(new AlgorithmIdentifier(EdECObjectIdentifiers.id_Ed448), key.getEncoded()); } else if (publicKey instanceof Ed25519PublicKeyParameters) { Ed25519PublicKeyParameters key = (Ed25519PublicKeyParameters) publicKey; return new SubjectPublicKeyInfo(new AlgorithmIdentifier(EdECObjectIdentifiers.id_Ed25519), key.getEncoded()); } else { throw new IOException("key parameters not recognized"); } } private static void extractBytes(byte[] encKey, int size, int offSet, BigInteger bI) { byte[] val = bI.toByteArray(); if (val.length < size) { byte[] tmp = new byte[size]; System.arraycopy(val, 0, tmp, tmp.length - val.length, val.length); val = tmp; } for (int i = 0; i != size; i++) { encKey[offSet + i] = val[val.length - 1 - i]; } } }