不灭的火

加密代码

/**
 * 解密
 *
 * @param content  待解密内容
 * @param password 解密密钥
 * @return
 */
public static byte[] decrypt(byte[] content, String password) {
    try {
        KeyGenerator kgen = KeyGenerator.getInstance("AES");
        kgen.init(128, new SecureRandom(password.getBytes()));
        SecretKey secretKey = kgen.generateKey();
        byte[] enCodeFormat = secretKey.getEncoded();
        SecretKeySpec key = new SecretKeySpec(enCodeFormat, "AES");
        Cipher cipher = Cipher.getInstance("AES");  // 创建密码器
        cipher.init(Cipher.DECRYPT_MODE, key);      // 初始化
        byte[] result = cipher.doFinal(content);
        return result; // 加密
    } catch (NoSuchAlgorithmException e) {
        e.printStackTrace();
    } catch (NoSuchPaddingException e) {
        e.printStackTrace();
    } catch (InvalidKeyException e) {
        e.printStackTrace();
    } catch (IllegalBlockSizeException e) {
        e.printStackTrace();
    } catch (BadPaddingException e) {
        e.printStackTrace();
    }
    return null;
}

解密代码

/**
 * 解密
 *
 * @param content  待解密内容
 * @param password 解密密钥
 * @return
 */
public static byte[] decrypt(byte[] content, String password) {
    try {
        KeyGenerator kgen = KeyGenerator.getInstance("AES");
        kgen.init(128, new SecureRandom(password.getBytes()));
        SecretKey secretKey = kgen.generateKey();
        byte[] enCodeFormat = secretKey.getEncoded();
        SecretKeySpec key = new SecretKeySpec(enCodeFormat, "AES");
        Cipher cipher = Cipher.getInstance("AES");// 创建密码器
        cipher.init(Cipher.DECRYPT_MODE, key);    // 初始化
        byte[] result = cipher.doFinal(content);
        return result; // 加密
    } catch (NoSuchAlgorithmException e) {
        e.printStackTrace();
    } catch (NoSuchPaddingException e) {
        e.printStackTrace();
    } catch (InvalidKeyException e) {
        e.printStackTrace();
    } catch (IllegalBlockSizeException e) {
        e.printStackTrace();
    } catch (BadPaddingException e) {
        e.printStackTrace();
    }
    return null;
}

解密demo

String content = "test";
String password = "12345678";

// 加密
System.out.println("加密前：" + content);
byte[] encryptResult = encrypt(content, password);

try {
    String encryptResultStr = new String(encryptResult,"utf-8");
    
    // 解密
    byte[] decryptResult = decrypt(encryptResultStr.getBytes("utf-8"),password);
    System.out.println("解密后：" + new String(decryptResult));
} catch (UnsupportedEncodingException e) {
    e.printStackTrace();
}

偶尔会报错、抛出异常：

javax.crypto.IllegalBlockSizeException: Input length must be multiple of 16 when decrypting with padded cipher

问题原因：

加密后的byte数组是不能强制转换成字符串的，换言之：字符串和byte数组在这种情况下不是互逆的；

要避免这种情况，我们需要做一些修订，可以考虑将二进制数据转换成十六进制表示

解决方案

二进制转换成16进制

/**
 * 将二进制转换成16进制
 *
 * @param buf 二进制字节数组
 * @return 16进制字符串
 */
private static String parseByte2HexStr(byte[] buf) {
    StringBuilder sb = new StringBuilder();

    for (byte _byte : buf) {
        String hex = Integer.toHexString(_byte & 0xFF);
        if (hex.length() == 1) {
            hex = '0' + hex;
        }
        sb.append(hex.toUpperCase());
    }

    return sb.toString();
}

16进制转换为二进制

/**
 * 将16进制转换为二进制
 *
 * @param hexStr 16进制字符串
 * @return 二进制字节数组
 */
private static byte[] parseHexStr2Byte(String hexStr) {
    if (hexStr.length() < 1) {
        throw new NullPointerException("the param hexStr(String) is blank");
    }

    byte[] result = new byte[hexStr.length() / 2];
    for (int i = 0; i < hexStr.length() / 2; i++) {
        int high = Integer.parseInt(hexStr.substring(i * 2, i * 2 + 1), 16);
        int low = Integer.parseInt(hexStr.substring(i * 2 + 1, i * 2 + 2), 16);
        result[i] = (byte) (high * 16 + low);
    }

    return result;
}

测试结果，问题解决：

String content = "test";
String password = "12345678";

// 加密
System.out.println("加密前：" + content);
byte[] encryptResult = encrypt(content, password);
String encryptResultStr = parseByte2HexStr(encryptResult);
System.out.println("加密后：" + encryptResultStr);

// 解密
byte[] decryptFrom = parseHexStr2Byte(encryptResultStr);
byte[] decryptResult = decrypt(decryptFrom,password);
System.out.println("解密后：" + new String(decryptResult));

参考：https://blog.csdn.net/hbcui1984/article/details/5201247