修改Java代码以支持AES128和AES256

Question

我在git hub上找到了AES加密和解密的代码如下：

public static String encrypt(String plainText, String key) throws Exception {
    byte[] clean = plainText.getBytes();

    // Generating IV.
        int ivSize = 16;
        byte[] iv = new byte[ivSize];
        SecureRandom random = new SecureRandom();
        random.nextBytes(iv);
        IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);

    // Hashing key.
        MessageDigest digest = MessageDigest.getInstance("SHA-256");
        digest.update(key.getBytes("UTF-8"));
        byte[] keyBytes = new byte[16];
        System.arraycopy(digest.digest(), 0, keyBytes, 0, keyBytes.length);
        SecretKeySpec secretKeySpec = new SecretKeySpec(keyBytes, "AES");

    // Encrypt.
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, ivParameterSpec);
        byte[] encrypted = cipher.doFinal(clean);

    // Combine IV and encrypted part.
        byte[] encryptedIVAndText = new byte[ivSize + encrypted.length];
        System.arraycopy(iv, 0, encryptedIVAndText, 0, ivSize);
        System.arraycopy(encrypted, 0, encryptedIVAndText, ivSize, encrypted.length);

    return new String(Base64.getEncoder().encode(encryptedIVAndText));
}

// decrypt method
public static String decrypt(String encrypted, String key) throws Exception {
    int ivSize = 16;
    int keySize = 16;

    byte[] encryptedIvTextBytes = Base64.getDecoder().decode(encrypted);
    // Extract IV.
        byte[] iv = new byte[ivSize];
        System.arraycopy(encryptedIvTextBytes, 0, iv, 0, iv.length);
        IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);

    // Extract encrypted part.
        int encryptedSize = encryptedIvTextBytes.length - ivSize;
        byte[] encryptedBytes = new byte[encryptedSize];
        System.arraycopy(encryptedIvTextBytes, ivSize, encryptedBytes, 0, encryptedSize);

    // Hash key.
        byte[] keyBytes = new byte[keySize];
        MessageDigest md = MessageDigest.getInstance("SHA-256");
        md.update(key.getBytes());
        System.arraycopy(md.digest(), 0, keyBytes, 0, keyBytes.length);
        SecretKeySpec secretKeySpec = new SecretKeySpec(keyBytes, "AES");

    // Decrypt.
        Cipher cipherDecrypt = Cipher.getInstance("AES/CBC/PKCS5Padding");
        cipherDecrypt.init(Cipher.DECRYPT_MODE, secretKeySpec, ivParameterSpec);
        byte[] decrypted = cipherDecrypt.doFinal(encryptedBytes);

    return new String(decrypted);
}

我发现java通过密钥大小确定aes算法128或256的信息，所以我修改了上面的代码，将“keySize”的固定值更改为key.length() 如下：

public static String encryptAes(String plainText, String key){
    byte[] clean = plainText.getBytes();
    String str = null;
    int keyLen = key.length();

    try{
        // Generating IV.
        int ivSize = 16;
        byte[] iv = new byte[ivSize];
        SecureRandom random = new SecureRandom();
        random.nextBytes(iv);
        IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);

    // Hashing key.
        MessageDigest digest = MessageDigest.getInstance("SHA-256");
        digest.update(key.getBytes("UTF-8"));
        byte[] keyBytes = new byte[keyLen];
        System.arraycopy(digest.digest(), 0, keyBytes, 0, keyBytes.length);
        SecretKeySpec secretKeySpec = new SecretKeySpec(keyBytes, "AES");

    // Encrypt.
        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, ivParameterSpec);
        byte[] encrypted = cipher.doFinal(clean);

    // Combine IV and encrypted part.
        byte[] encryptedIVAndText = new byte[ivSize + encrypted.length];
        System.arraycopy(iv, 0, encryptedIVAndText, 0, ivSize);
        System.arraycopy(encrypted, 0, encryptedIVAndText, ivSize, encrypted.length);
        str = new String(Base64.getEncoder().encode(encryptedIVAndText));
    }
    catch (Exception e) {
        // TODO: handle exception
        System.out.println("Error");
    }
    return str;
}

public static String decryptAes(String encrypted, String key){
    int ivSize = 16;
    int keySize = key.length();
    String str = null;

    try{
        byte[] encryptedIvTextBytes = Base64.getDecoder().decode(encrypted);
        // Extract IV.
        byte[] iv = new byte[ivSize];
        System.arraycopy(encryptedIvTextBytes, 0, iv, 0, iv.length);
        IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);

    // Extract encrypted part.
        int encryptedSize = encryptedIvTextBytes.length - ivSize;
        byte[] encryptedBytes = new byte[encryptedSize];
        System.arraycopy(encryptedIvTextBytes, ivSize, encryptedBytes, 0, encryptedSize);

    // Hash key.
        byte[] keyBytes = new byte[keySize];
        MessageDigest md = MessageDigest.getInstance("SHA-256");
        md.update(key.getBytes());
        System.arraycopy(md.digest(), 0, keyBytes, 0, keyBytes.length);
        SecretKeySpec secretKeySpec = new SecretKeySpec(keyBytes, "AES");

    // Decrypt.
        Cipher cipherDecrypt = Cipher.getInstance("AES/CBC/PKCS5Padding");
        cipherDecrypt.init(Cipher.DECRYPT_MODE, secretKeySpec, ivParameterSpec);
        byte[] decrypted = cipherDecrypt.doFinal(encryptedBytes);
    
        str = new String(decrypted);
    }
    catch (Exception e) {
        // TODO: handle exception
        System.out.println("Error");
    }
    return str;
}

这里是 Main 和 input

public static void main (String[] args){

    String txtInput = "11700000108";

    String key256 = "SxKFF2Kunz7tjyUZ4sb7TzzZBR83e8FL"; //length of key will be fixed as 32
    String cipher256 = encryptAes(txtInput, key256);
    System.out.println("CipherAes256: " + cipher256);

    String key128 = "RfZVnF76FshjN46e"; //length of key will be fixed as 16
    String cipher128 = encryptAes(txtInput, key128);
    System.out.println("CipherAes128: " + cipher128);
}

但 cipher256 和 cipher128 的结果长度相同（本例中为 44 个字符）我不确定是否需要进行任何进一步的更改。 请给我建议，谢谢。