用java实现SM4算法

在Java中实现SM4算法，你需要依赖于一些专门库，如Bouncy Castle Crypto或JSSE（Java Secure Socket Extension）。以下是使用Bouncy Castle库的一个简单示例：

import org.bouncycastle.jce.provider.BouncyCastleProvider;
import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;
import java.security.*;
import java.util.Base64;

public class SM4Example {
    static {
        Security.addProvider(new BouncyCastleProvider());
    }

    public static String encrypt(String data, String key) throws Exception {
        SecretKeySpec secretKey = new SecretKeySpec(key.getBytes(), "SM4");
        Cipher cipher = Cipher.getInstance("SM4/CBC/PKCS5Padding", "BC");
        byte[] iv = "0123456789ABCDEF".getBytes();
        cipher.init(Cipher.ENCRYPT_MODE, secretKey, new IvParameterSpec(iv));

        byte[] encryptedData = cipher.doFinal(data.getBytes());
        return Base64.getEncoder().encodeToString(encryptedData);
    }

    public static String decrypt(String encryptedData, String key) throws Exception {
        SecretKeySpec secretKey = new SecretKeySpec(key.getBytes(), "SM4");
        Cipher cipher = Cipher.getInstance("SM4/CBC/PKCS5Padding", "BC");
        byte[] iv = "0123456789ABCDEF".getBytes();
        cipher.init(Cipher.DECRYPT_MODE, secretKey, new IvParameterSpec(iv));

        byte[] decryptedData = cipher.doFinal(Base64.getDecoder().decode(encryptedData));
        return new String(decryptedData);
    }

    public static void main(String[] args) throws Exception {
        // 示例加密和解密
        String message = "Hello, SM4!";
        String key = "0123456789abcdef";
        String encrypted = encrypt(message, key);
        String decrypted = decrypt(encrypted, key);

        System.out.println("Original: " + message);
        System.out.println("Encrypted: " + encrypted);
        System.out.println("Decrypted: " + decrypted);
    }
}

这个例子展示了如何创建一个SM4密钥，设置初始向量，以及执行加密和解密操作。记得替换实际的key和message进行测试。