如何制作弹性城堡ECPublicKey

Question

我知道曲线名称(SECP256K1)以及EC公钥的X和Y坐标。

如何用它们创建org.bouncycastle.jce.interfaces.ecpublickey？

我读过https://stackoverflow.com/a/29355749/5453873，但是那里的代码使用java.security...而不是org.bouncycastle...，ECPublicKey是org.bouncycastle...中的接口，而不是一个可实例化的类。

Answer 1

这将生成在JCE/JCA中使用的EC公钥。Bouncy Castle提供商可以直接使用这些软件密钥。否则，Bouncy只是用来生成生成公钥所需的参数。

package nl.owlstead.stackoverflow;

import static java.nio.charset.StandardCharsets.US_ASCII;

import java.math.BigInteger;
import java.security.KeyFactory;
import java.security.KeyPairGenerator;
import java.security.Security;
import java.security.interfaces.ECPublicKey;
import java.security.spec.ECGenParameterSpec;
import java.security.spec.ECParameterSpec;
import java.security.spec.ECPoint;
import java.security.spec.ECPublicKeySpec;

import javax.crypto.Cipher;

import org.bouncycastle.jce.ECNamedCurveTable;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.jce.spec.ECNamedCurveParameterSpec;
import org.bouncycastle.jce.spec.ECNamedCurveSpec;
import org.bouncycastle.util.encoders.Hex;

public class ECPublicKeyFactory {

    public static void main(String[] args) throws Exception {

        String name = "secp256r1";

        Security.addProvider(new BouncyCastleProvider());

        // === NOT PART OF THE CODE, JUST GETTING TEST VECTOR ===
        KeyPairGenerator kpg = KeyPairGenerator.getInstance("EC", "BC");
        ECGenParameterSpec ecGenParameterSpec = new ECGenParameterSpec(name);
        kpg.initialize(ecGenParameterSpec);
        ECPublicKey key = (ECPublicKey) kpg.generateKeyPair().getPublic();
        byte[] x = key.getW().getAffineX().toByteArray();
        byte[] y = key.getW().getAffineY().toByteArray();

        // === here the magic happens ===
        KeyFactory eckf = KeyFactory.getInstance("EC");
        ECPoint point = new ECPoint(new BigInteger(1, x), new BigInteger(1, y));
        ECNamedCurveParameterSpec parameterSpec = ECNamedCurveTable.getParameterSpec(name);
        ECParameterSpec spec = new ECNamedCurveSpec(name, parameterSpec.getCurve(), parameterSpec.getG(), parameterSpec.getN(), parameterSpec.getH(), parameterSpec.getSeed());
        ECPublicKey ecPublicKey = (ECPublicKey) eckf.generatePublic(new ECPublicKeySpec(point, spec));
        System.out.println(ecPublicKey.getClass().getName());

        // === test 123 ===
        Cipher ecies = Cipher.getInstance("ECIESwithAES", "BC");
        ecies.init(Cipher.ENCRYPT_MODE, ecPublicKey);
        byte[] ct = ecies.doFinal("owlstead".getBytes(US_ASCII));
        System.out.println(Hex.toHexString(ct));
    }
}

最初，我认为需要一个Bouncy Castle特定的密钥，因此下面的代码生成Bouncy Castle轻量级API中使用的EC公钥。

package nl.owlstead.stackoverflow;

import java.math.BigInteger;
import java.security.KeyPairGenerator;
import java.security.Security;
import java.security.interfaces.ECPublicKey;
import java.security.spec.ECGenParameterSpec;

import org.bouncycastle.asn1.ASN1ObjectIdentifier;
import org.bouncycastle.asn1.x9.ECNamedCurveTable;
import org.bouncycastle.asn1.x9.X9ECParameters;
import org.bouncycastle.crypto.params.ECNamedDomainParameters;
import org.bouncycastle.crypto.params.ECPublicKeyParameters;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.math.ec.ECCurve;
import org.bouncycastle.math.ec.ECPoint;
import org.bouncycastle.util.encoders.Hex;

public class BC_EC_KeyCreator {

    public static void main(String[] args) throws Exception {

        String name = "secp256r1";

        // === NOT PART OF THE CODE, JUST GETTING TEST VECTOR ===
        Security.addProvider(new BouncyCastleProvider());
        KeyPairGenerator kpg = KeyPairGenerator.getInstance("EC", "BC");
        kpg.initialize(new ECGenParameterSpec(name));
        ECPublicKey key = (ECPublicKey) kpg.generateKeyPair().getPublic();
        byte[] x = key.getW().getAffineX().toByteArray();
        byte[] y = key.getW().getAffineY().toByteArray();

        // assumes that x and y are (unsigned) big endian encoded
        BigInteger xbi = new BigInteger(1, x);
        BigInteger ybi = new BigInteger(1, y);
        X9ECParameters x9 = ECNamedCurveTable.getByName(name);
        ASN1ObjectIdentifier oid = ECNamedCurveTable.getOID(name);
        ECCurve curve = x9.getCurve();
        ECPoint point = curve.createPoint(xbi, ybi);
        ECNamedDomainParameters dParams = new ECNamedDomainParameters(oid,
                x9.getCurve(), x9.getG(), x9.getN(), x9.getH(), x9.getSeed());
        ECPublicKeyParameters pubKey = new ECPublicKeyParameters(point, dParams);
        System.out.println(pubKey);

        // some additional encoding tricks
        byte[] compressed = point.getEncoded(true);
        System.out.println(Hex.toHexString(compressed));
        byte[] uncompressed = point.getEncoded(false);
        System.out.println(Hex.toHexString(uncompressed));
    }
}

这很棘手，因为我不想包含任何特定于JCE的代码，而且x9ecParameters不是ecDomainParameters的子类。因此，我使用了从Bouncy Castle代码库的其他地方复制的ecNamedDomainParameters的转换。