如何制作充气城堡 ECPublicKey

Question

我知道曲线名称 (secp256k1) 以及 EC public 键的 X 和 Y 坐标。

如何用它们制作 org.bouncycastle.jce.interfaces.ECPublicKey？

我读过但那里的代码使用 java.security... 而不是 org.bouncycastle... 并且 ECPublicKey 是 org.bouncycastle... 中的接口而不是可实例化的 class .

Answer 1

使用 Bouncy Castle 生成 ECPublicKey

这会生成 JCE/JCA 中使用的 EC public 密钥。 Bouncy Castle 提供商可以直接使用这些软件密钥。否则 Bouncy 仅用于生成生成 public 密钥所需的参数。

package nl.owlstead.Whosebug;

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));
    }
}

正在生成 Bouncy Castle ECPublicKeyParameters

最初我认为需要一个 Bouncy Castle 特定的密钥，所以下面的代码生成了在 Bouncy Castle 轻量级 API.

中使用的 EC public 密钥

package nl.owlstead.Whosebug;

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));
    }
}

这主要是棘手的，因为我不想包含任何 JCE 特定代码，并且 X9ECParameters 不是 ECDomainParameters 的子类。所以我使用了从 Bouncy Castle 代码库的其他地方复制的 ECNamedDomainParameters 的转换。

Answer 2

在后面的代码中，encoded 包含 0x04 后跟 32 个字节的 X，然后是 32 个字节的 Y。

或者，它可以包含 0x02 或 0x03（取决于 Y 的符号）后跟 32 个字节的 X。

public static ECPublicKey decodeKey(byte[] encoded) throws InvalidKeySpecException, NoSuchAlgorithmException, NoSuchProviderException{
    ECNamedCurveParameterSpec params = ECNamedCurveTable.getParameterSpec("secp256k1");
    KeyFactory fact = KeyFactory.getInstance("ECDSA", "BC");
    ECCurve curve = params.getCurve();
    java.security.spec.EllipticCurve ellipticCurve = EC5Util.convertCurve(curve, params.getSeed());
    java.security.spec.ECPoint point = ECPointUtil.decodePoint(ellipticCurve, encoded);
    java.security.spec.ECParameterSpec params2 =EC5Util.convertSpec(ellipticCurve, params);
    java.security.spec.ECPublicKeySpec keySpec = new java.security.spec.ECPublicKeySpec(point,params2);
    return (ECPublicKey) fact.generatePublic(keySpec);
}

Answer 3

ECUtil 已经提供

ECPublicKeyParameters bcecPublicKey =(ECPublicKeyParameters) ECUtil.generatePublicKeyParameter(kp.getPublic());
ECPrivateKeyParameters bcecPrivateKey = (ECPrivateKeyParameters) ECUtil.generatePrivateKeyParameter(kp.getPrivate());

Answer 4

不使用 KeyFactory 的 Thomas 答案的较短变体是：

public static ECPublicKey decodeKey(byte[] encoded) {
  ECNamedCurveParameterSpec params = ECNamedCurveTable.getParameterSpec("secp256k1");
  ECPublicKeySpec keySpec = new ECPublicKeySpec(params.getCurve().decodePoint(encoded), params);
  return new BCECPublicKey("ECDSA", keySpec, BouncyCastleProvider.CONFIGURATION);
}

我假设encoded是由BCECPublicKey.getQ().getEncoded(bool)得到的，即它是一个字节0x2-0x4后跟[=20=]点的一个或两个仿射坐标secp256k1.

如何制作充气城堡 ECPublicKey

How to make a Bouncy Castle ECPublicKey

java

cryptography

bouncycastle

使用 Bouncy Castle 生成 ECPublicKey

正在生成 Bouncy Castle ECPublicKeyParameters