国密sm2 代码实现数字签名

以下是使用Java实现国密SM2数字签名的示例代码：

import org.bouncycastle.crypto.AsymmetricCipherKeyPair;
import org.bouncycastle.crypto.digests.SM3Digest;
import org.bouncycastle.crypto.engines.SM2Engine;
import org.bouncycastle.crypto.generators.ECKeyPairGenerator;
import org.bouncycastle.crypto.params.ECDomainParameters;
import org.bouncycastle.crypto.params.ECKeyGenerationParameters;
import org.bouncycastle.crypto.params.ECPrivateKeyParameters;
import org.bouncycastle.crypto.params.ECPublicKeyParameters;
import org.bouncycastle.crypto.signers.SM2Signer;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.jce.spec.ECParameterSpec;
import org.bouncycastle.util.encoders.Hex;

import java.math.BigInteger;
import java.security.Security;

public class SM2SignDemo {

    public static void main(String[] args) throws Exception {
        Security.addProvider(new BouncyCastleProvider());

        // 生成密钥对
        ECKeyPairGenerator keyPairGenerator = new ECKeyPairGenerator();
        ECKeyGenerationParameters keyGenerationParams = new ECKeyGenerationParameters(
                new ECDomainParameters(SM2Util.SM2_p, SM2Util.SM2_a, SM2Util.SM2_b, SM2Util.SM2_ecparams_G, SM2Util.SM2_n),
                SM2Util.SM2_random);
        keyPairGenerator.init(keyGenerationParams);
        AsymmetricCipherKeyPair keyPair = keyPairGenerator.generateKeyPair();
        ECPrivateKeyParameters privateKey = (ECPrivateKeyParameters) keyPair.getPrivate();
        ECPublicKeyParameters publicKey = (ECPublicKeyParameters) keyPair.getPublic();

        // 签名
        SM2Signer signer = new SM2Signer();
        signer.init(true, privateKey);
        byte[] msg = "Hello, world!".getBytes();
        byte[] z = SM2Util.getSM2Z("1234567812345678".getBytes(), publicKey.getQ());
        signer.update(z, 0, z.length);
        signer.update(msg, 0, msg.length);
        BigInteger[] sig = signer.generateSignature();
        String signature = Hex.toHexString(sig[0].toByteArray()) + Hex.toHexString(sig[1].toByteArray());
        System.out.println("Signature: " + signature);

        // 验证签名
        signer.init(false, publicKey);
        signer.update(z, 0, z.length);
        signer.update(msg, 0, msg.length);
        System.out.println("Signature verification result: " + signer.verifySignature(sig[0], sig[1]));
    }

}

class SM2Util {

    static final BigInteger SM2_p = new BigInteger("FFFFFFFEFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF00000000FFFFFFFFFFFFFFFF", 16);
    static final BigInteger SM2_a = new BigInteger("FFFFFFFEFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF00000000FFFFFFFFFFFFFFFC", 16);
    static final BigInteger SM2_b = new BigInteger("28E9FA9E9D9F5E344D5A9E4BCF6509A7F39789F515AB8F92DDBCBD414D940E93", 16);
    static final BigInteger SM2_n = new BigInteger("FFFFFFFEFFFFFFFFFFFFFFFFFFFFFFFF7203DF6B21C6052B53BBF40939D54123", 16);
    static final BigInteger SM2_h = BigInteger.valueOf(1);
    static final BigInteger SM2_Gx = new BigInteger("32C4AE2C1F1981195F9904466A39C9948FE30BBFF2660BE171F996B8FEEF18EE", 16);
    static final BigInteger SM2_Gy = new BigInteger("BC3736A2F4F6779C59BDCEE36B692153D0A5D10B213A3D89B0C7C5AE0FD36B88", 16);
    static final ECDomainParameters SM2_ecparams_G = new ECDomainParameters(SM2_p, SM2_a, SM2_b, new org.bouncycastle.math.ec.ECPoint.SecP256K1(SM2_p, SM2_a, SM2_b, new BigInteger[]{SM2_Gx, SM2_Gy}, SM2_n, SM2_h));
    static final SM3Digest SM2_256_DIGEST = new SM3Digest();
    static final byte[] SM2_DEFAULT_USER_ID = "1234567812345678".getBytes();
    static final SecureRandom SM2_random = new SecureRandom();

    /**
     * 获取SM2签名中的Z值
     */
    static byte[] getSM2Z(byte[] userId, org.bouncycastle.math.ec.ECPoint userKey) {
        byte[] userIdDigest = new byte[32];
        SM2_256_DIGEST.update(userId, 0, userId.length);
        SM2_256_DIGEST.doFinal(userIdDigest, 0);

        byte[] x = userKey.getXCoord().getEncoded();
        byte[] y = userKey.getYCoord().getEncoded();

        byte[] z = new byte[userIdDigest.length + x.length + y.length];
        System.arraycopy(userIdDigest, 0, z, 0, userIdDigest.length);
        System.arraycopy(x, 0, z, userIdDigest.length, x.length);
        System.arraycopy(y, 0, z, userIdDigest.length + x.length, y.length);

        return z;
    }

}

在上面的示例代码中，我们使用了BouncyCastle库来实现SM2数字签名。其中，`SM2Signer`类用于签名和验签，`ECDomainParameters`类用于定义椭圆曲线参数，`SM3Digest`类用于计算摘要，`SM2Util`类用于定义一些常量和工具方法。

在签名过程中，我们需要先计算出SM2签名中的Z值，然后将Z值和待签名的消息传入`SM2Signer`类中进行签名。签名结果为两个整数，需要将它们转换为十六进制字符串拼接在一起即可得到最终的签名值。

在验签过程中，我们需要使用相同的Z值和待验签的消息来初始化`SM2Signer`类，然后将签名值传入进行验签。如果验签成功，`verifySignature`方法会返回`true`，否则返回`false`。

需要注意的是，以上示例代码仅供参考，实际使用时需要根据具体需求进行修改和优化。