国密算法-SM2

    国密算法是国家密码局制定标准的一系列算法，包括SM1、SM2、SM3、SM4等。其中，SM1是采用硬件实现的，不予讨论；SM2是非对称加密算法；SM3是摘要算法；SM4是对称加密算法。本篇贴出SM2 Java版本实现生成公私钥及加解密、签名验签代码，供大家一起讨论学习，所有的代码实现都是基于BC库来做的。
     BC库是实现加解密算法的基础库，我们首先要在代码里引入BC库

         <dependency>
            <groupId>org.bouncycastle</groupId>
            <artifactId>bcprov-jdk15on</artifactId>
            <version>1.69</version>
        </dependency>

    下面是整个工具类，实现密钥生成，加解密及签名验签功能

import org.apache.commons.codec.binary.Base64;
import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.engines.SM2Engine;
import org.bouncycastle.crypto.params.ECPrivateKeyParameters;
import org.bouncycastle.crypto.params.ECPublicKeyParameters;
import org.bouncycastle.crypto.params.ParametersWithRandom;
import org.bouncycastle.crypto.signers.SM2Signer;
import org.bouncycastle.jcajce.provider.asymmetric.util.ECUtil;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.security.*;
import java.security.spec.ECGenParameterSpec;
import java.security.spec.KeySpec;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

public class Sm2Utils {

    private static Logger log = LoggerFactory.getLogger(Sm2Utils.class);

    /**
     * SM2算法生成密钥对
     *
     * @return 密钥对信息
     */
    public static KeyPair generateSm2KeyPair() {
        try {
            final ECGenParameterSpec sm2Spec = new ECGenParameterSpec("prime256v1");
            final KeyPairGenerator kpg = KeyPairGenerator.getInstance("EC", new BouncyCastleProvider());
            SecureRandom random = new SecureRandom();
            kpg.initialize(sm2Spec, random);
            KeyPair keyPair = kpg.generateKeyPair();
            return keyPair;
        } catch (Exception e) {
            log.error("generate sm2 key pail failed:", e.getMessage(), e);
            throw  new RuntimeException("生成密钥对失败");
        }
    }

    /**
     * sm2公钥加密
     *
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
    public static byte[] encrypt(byte[] data, byte[] key) throws Exception {
        KeySpec keySpec = new X509EncodedKeySpec(key);
        PublicKey publicKey = KeyFactory.getInstance("EC", new BouncyCastleProvider()).generatePublic(keySpec);
        ECPublicKeyParameters parameters = (ECPublicKeyParameters) ECUtil.generatePublicKeyParameter(publicKey);
        CipherParameters pubKeyParameters = new ParametersWithRandom(parameters);
        SM2Engine engine = new SM2Engine(SM2Engine.Mode.C1C2C3);
        engine.init(true, pubKeyParameters);
        return engine.processBlock(data, 0, data.length);
    }

    /**
     * sm2私钥解密
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
    public static byte[] decrypt(byte[] data, byte[] key) throws Exception {
        KeySpec keySpec = new PKCS8EncodedKeySpec(key);
        KeyFactory keyfactory = KeyFactory.getInstance("EC", new BouncyCastleProvider());
        PrivateKey privateKey = keyfactory.generatePrivate(keySpec);
        CipherParameters privateKeyParameters = ECUtil.generatePrivateKeyParameter(privateKey);
        SM2Engine engine = new SM2Engine(SM2Engine.Mode.C1C2C3);
        engine.init(false, privateKeyParameters);
        byte[] byteDate = engine.processBlock(data, 0, data.length);
        return byteDate;
    }

    /**
     * 私钥签名
     * @param data
     * @param key
     * @return
     * @throws Exception
     */

    public static byte[] sign(byte[] data, byte[] key) throws Exception {
        SM2Signer signer = new SM2Signer();
        KeySpec keySpec = new PKCS8EncodedKeySpec(key);
        KeyFactory keyfactory = KeyFactory.getInstance("EC", new BouncyCastleProvider());
        PrivateKey privateKey =  keyfactory.generatePrivate(keySpec);
        ECPrivateKeyParameters keyParameters = (ECPrivateKeyParameters) ECUtil.generatePrivateKeyParameter(privateKey);
        CipherParameters param = new ParametersWithRandom(keyParameters);
        signer.init(true, param);
        signer.update(data, 0, data.length);
        return signer.generateSignature();
    }

    /**
     * 公钥验签
     * @param data
     * @param sign
     * @param key
     * @return
     * @throws Exception
     */
    public static boolean verify(byte[] data, byte[] sign, byte[] key) throws Exception {
        SM2Signer signer = new SM2Signer();
        KeySpec keySpec = new X509EncodedKeySpec(key);
        PublicKey publicKey = KeyFactory.getInstance("EC", new BouncyCastleProvider()).generatePublic(keySpec);
        CipherParameters param =  ECUtil.generatePublicKeyParameter(publicKey);
        signer.init(false, param);
        signer.update(data, 0, data.length);
        return signer.verifySignature(sign);
    }

    public static void main(String[] args) throws Exception {
        KeyPair keyPair = generateSm2KeyPair();//生成密钥
        String publicKey = Base64.encodeBase64String(keyPair.getPublic().getEncoded());
        String privateKey = Base64.encodeBase64String(keyPair.getPrivate().getEncoded());
        System.out.println("sm2公钥=" + publicKey);
        System.out.println("sm2私钥=" + privateKey);
        String plaintext = "test";//明文
        String signature = Base64.encodeBase64String((sign(plaintext.getBytes("utf-8"),keyPair.getPrivate().getEncoded())));
        String ciphertext = Base64.encodeBase64String(encrypt(plaintext.getBytes("utf-8"), Base64.decodeBase64(publicKey)));
        System.out.println("ciphertext: " + ciphertext);
        System.out.println("signature: " + signature);
        boolean result = verify(plaintext.getBytes("utf-8"),Base64.decodeBase64(signature),keyPair.getPublic().getEncoded());
        plaintext = new String(decrypt(Base64.decodeBase64(ciphertext), Base64.decodeBase64(privateKey)), "utf-8");
        System.out.println("plaintext: " + plaintext);
        System.out.println("verify result: " + result);
    }

}