java如何实现SM2加密解密

Java可以使用Bouncy Castle库来实现SM2加密解密。下面是一个示例代码：

import org.bouncycastle.crypto.AsymmetricCipherKeyPair;
import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.engines.SM2Engine;
import org.bouncycastle.crypto.generators.ECKeyPairGenerator;
import org.bouncycastle.crypto.params.ECKeyGenerationParameters;
import org.bouncycastle.crypto.params.ECPrivateKeyParameters;
import org.bouncycastle.crypto.params.ECPublicKeyParameters;
import org.bouncycastle.crypto.params.ParametersWithRandom;
import org.bouncycastle.crypto.util.PrivateKeyFactory;
import org.bouncycastle.crypto.util.PublicKeyFactory;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.util.encoders.Hex;

import java.security.Security;
import java.security.SecureRandom;

public class SM2Example {
    public static void main(String[] args) throws Exception {
        Security.addProvider(new BouncyCastleProvider());

        // 生成密钥对
        ECKeyPairGenerator keyPairGenerator = new ECKeyPairGenerator();
        ECKeyGenerationParameters keyGenerationParameters = new ECKeyGenerationParameters(SM2Util.DOMAIN_PARAMS, new SecureRandom());
        keyPairGenerator.init(keyGenerationParameters);
        AsymmetricCipherKeyPair keyPair = keyPairGenerator.generateKeyPair();

        // 获取公钥和私钥
        ECPublicKeyParameters publicKey = (ECPublicKeyParameters) keyPair.getPublic();
        ECPrivateKeyParameters privateKey = (ECPrivateKeyParameters) keyPair.getPrivate();

        // 加密
        String plaintext = "Hello, SM2!";
        byte[] plaintextBytes = plaintext.getBytes("UTF-8");
        CipherParameters encryptParams = new ParametersWithRandom(publicKey, new SecureRandom());
        SM2Engine encryptEngine = new SM2Engine();
        encryptEngine.init(true, encryptParams);
        byte[] ciphertextBytes = encryptEngine.processBlock(plaintextBytes, 0, plaintextBytes.length);

        // 解密
        CipherParameters decryptParams = new ParametersWithRandom(privateKey, new SecureRandom());
        SM2Engine decryptEngine = new SM2Engine();
        decryptEngine.init(false, decryptParams);
        byte[] decryptedBytes = decryptEngine.processBlock(ciphertextBytes, 0, ciphertextBytes.length);
        String decryptedText = new String(decryptedBytes, "UTF-8");

        System.out.println("Plaintext: " + plaintext);
        System.out.println("Ciphertext: " + Hex.toHexString(ciphertextBytes));
        System.out.println("Decrypted text: " + decryptedText);
    }
}

这段代码使用Bouncy Castle库生成SM2密钥对，然后使用公钥加密明文，私钥解密密文。注意，需要先导入Bouncy Castle库，并且确保密钥对的生成参数`SM2Util.DOMAIN_PARAMS`正确设置。