SM4加密算法实现java代码示例

以下是SM4加密算法的Java代码示例：

import org.bouncycastle.crypto.BlockCipher;
import org.bouncycastle.crypto.BufferedBlockCipher;
import org.bouncycastle.crypto.engines.SM4Engine;
import org.bouncycastle.crypto.modes.CBCBlockCipher;
import org.bouncycastle.crypto.paddings.PaddedBufferedBlockCipher;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.crypto.params.ParametersWithIV;
import org.bouncycastle.util.encoders.Hex;

import java.nio.charset.StandardCharsets;
import java.security.SecureRandom;

public class SM4Util {

    private static final int KEY_LENGTH = 16;
    private static final int IV_LENGTH = 16;

    /**
     * 生成随机密钥
     *
     * @return 随机密钥的十六进制字符串表示
     */
    public static String generateKey() {
        byte[] key = new byte[KEY_LENGTH];
        SecureRandom random = new SecureRandom();
        random.nextBytes(key);
        return Hex.toHexString(key);
    }

    /**
     * 加密
     *
     * @param plainText 明文
     * @param key       密钥的十六进制字符串表示
     * @return 密文的十六进制字符串表示
     */
    public static String encrypt(String plainText, String key) throws Exception {
        byte[] keyBytes = Hex.decode(key);
        byte[] ivBytes = new byte[IV_LENGTH];
        SecureRandom random = new SecureRandom();
        random.nextBytes(ivBytes);

        BlockCipher engine = new SM4Engine();
        BufferedBlockCipher cipher = new PaddedBufferedBlockCipher(new CBCBlockCipher(engine));
        cipher.init(true, new ParametersWithIV(new KeyParameter(keyBytes), ivBytes));

        byte[] input = plainText.getBytes(StandardCharsets.UTF_8);
        byte[] output = new byte[cipher.getOutputSize(input.length)];
        int outputLen = cipher.processBytes(input, 0, input.length, output, 0);
        outputLen += cipher.doFinal(output, outputLen);

        byte[] result = new byte[IV_LENGTH + outputLen];
        System.arraycopy(ivBytes, 0, result, 0, IV_LENGTH);
        System.arraycopy(output, 0, result, IV_LENGTH, outputLen);

        return Hex.toHexString(result);
    }

    /**
     * 解密
     *
     * @param cipherText 密文的十六进制字符串表示
     * @param key        密钥的十六进制字符串表示
     * @return 明文
     */
    public static String decrypt(String cipherText, String key) throws Exception {
        byte[] keyBytes = Hex.decode(key);
        byte[] input = Hex.decode(cipherText);

        byte[] ivBytes = new byte[IV_LENGTH];
        System.arraycopy(input, 0, ivBytes, 0, IV_LENGTH);

        BlockCipher engine = new SM4Engine();
        BufferedBlockCipher cipher = new PaddedBufferedBlockCipher(new CBCBlockCipher(engine));
        cipher.init(false, new ParametersWithIV(new KeyParameter(keyBytes), ivBytes));

        byte[] output = new byte[cipher.getOutputSize(input.length - IV_LENGTH)];
        int outputLen = cipher.processBytes(input, IV_LENGTH, input.length - IV_LENGTH, output, 0);
        outputLen += cipher.doFinal(output, outputLen);

        return new String(output, 0, outputLen, StandardCharsets.UTF_8);
    }
}