java - AES 使用相同的 IV 进行加密和解密

Question

我的代码存在一些问题，我没有使用相同的 IV 进行加密和解密。我知道为了正确地做到这一点，我必须在数据之前将 IV 写入我的输出文件，但是我正在努力实现这一点。谁能帮我解决这个问题吗？

再次编辑代码以显示完整范围

public class TestFileEncryption {
    private static void mainCrypto(int cipherMode, File inputFile, File outputFile) throws Exception{
        //Let the user enter the key they wish to use
        Key secretKey = new SecretKeySpec(UITest.getStoreKey().getBytes(), UITest.getSendAlg()); //Generates a key based on the default keysize for the specified algorithm

        //Generate an Initialization Vector (IV)
        final int ALG_KEYLENGTH = UITest.getStoreKey().length(); //Change this as desired for the security level you want
        byte[] iv = new byte[ALG_KEYLENGTH]; //Save the IV bytes or send it in plaintext with the encrypted data so you can decrypt the data later
        SecureRandom prng = new SecureRandom(); //Use SecureRandom to generate random bits. The size of the IV matches the blocksize of the cipher
        prng.nextBytes(iv); //Construct the appropriate IvParameterSpec object for the data to pass to Cipher's init() method

        //Create a Cipher by specifying the following parameters: Alg name, Mode (CBC), Padding (PKC7/PKCS5)
        Cipher cipherForEncryption = Cipher.getInstance(UITest.getSendAlg() + "/CBC/PKCS5PADDING"); // Must specify the mode explicitly as most JCE providers default to ECB mode

        //Initialize the Cipher for Encryption
        cipherForEncryption.init(cipherMode, secretKey, new IvParameterSpec(iv));

        //Declare / Initialize the Data, Convert the Input to Bytes and encrypt or decrypt using doFinal.
        FileInputStream inputStream = new FileInputStream(inputFile);
        byte[] inputBytes = new byte[(int) inputFile.length() - ALG_KEYLENGTH];
        inputStream.read(iv);
        inputStream.read(inputBytes);
        byte[] outputBytes = cipherForEncryption.doFinal(inputBytes);
        FileOutputStream outputStream = new FileOutputStream(outputFile);
        outputStream.write(iv);
        outputStream.write(outputBytes);
        inputStream.close();
        outputStream.close();
    }

    public static void encrypt(File inputFile, File outputFile) throws Exception {
        mainCrypto(Cipher.ENCRYPT_MODE, inputFile, outputFile); //ENC_MODE = Constant used to initialize cipher to encryption mode.
    }

    public static void decrypt(File inputFile, File outputFile) throws Exception {
        mainCrypto(Cipher.DECRYPT_MODE, inputFile, outputFile); //ENC_MODE = Constant used to initialize cipher to encryption mode.
    }

    public static void main(String[] args) {}
}

Answer 1

只是扩展@Javier的答案。

看起来您想使用相同的方法进行加密和解密(取决于模式)，但是处理 IV 方面存在差异。

您生成了一个随机 IV，然后用(纯)输入的输入覆盖它，最后将其写入输出(无论它是解密的)。

所以你要区分模式是否为

• 加密 - 生成 IV 并在密文之前写入输出
• 解密 - 从输入中读取 IV 并用于解密，但不写入输出

类似的东西:

private void encrypt(File inputFile, File outputFile)  {
    //Declare / Initialize the Data, Convert the Input to Bytes and encrypt or decrypt using doFinal.
    FileInputStream inputStream = new FileInputStream(inputFile);
    byte[] inputBytes = new byte[(int) inputFile.length()];
    byte[] iv = new byte[16]; // 16 for AES-CBC
    SecureRandom prng = new SecureRandom(); //Use SecureRandom to generate random bits. The size of the IV matches the blocksize of the cipher
    prng.nextBytes(iv); //Construct the appropriate IvParameterSpec object for the data to pass to Cipher's init() method

    //Create a Cipher by specifying the following parameters: Alg name, Mode (CBC), Padding (PKC7/PKCS5)
    Cipher cipherForEncryption = Cipher.getInstance(UITest.getSendAlg() + "/CBC/PKCS5PADDING"); // Must specify the mode explicitly as most JCE providers default to ECB mode

    //Initialize the Cipher for Encryption
    cipherForEncryption.init(cipherMode, secretKey, new IvParameterSpec(iv));      
        inputStream.read(inputBytes);
        byte[] outputBytes = cipherForEncryption.doFinal(inputBytes);
        FileOutputStream outputStream = new FileOutputStream(outputFile);
        outputStream.write(iv);
        outputStream.write(outputBytes);
        outputStream.flush();
        inputStream.close();
        outputStream.close();
    }
}

private void decrypt(File inputFile, File outputFile) {
    //Declare / Initialize the Data, Convert the Input to Bytes and encrypt or decrypt using doFinal.
    FileInputStream inputStream = new FileInputStream(inputFile);
    byte[] inputBytes = new byte[(int) inputFile.length()-16];
    byte[] iv = new byte[16]; // 16 for AES-CBC

    //Create a Cipher by specifying the following parameters: Alg name, Mode (CBC), Padding (PKC7/PKCS5)
    Cipher cipherForEncryption = Cipher.getInstance(UITest.getSendAlg() + "/CBC/PKCS5PADDING"); // Must specify the mode explicitly as most JCE providers default to ECB mode

    //Initialize the Cipher for Encryption
    cipherForEncryption.init(cipherMode, secretKey, new IvParameterSpec(iv));      
    inputStream.read(iv);
    inputStream.read(inputBytes);
    byte[] outputBytes = cipherForEncryption.doFinal(inputBytes);
    FileOutputStream outputStream = new FileOutputStream(outputFile);
    outputStream.write(outputBytes);
    outputStream.flush();
    inputStream.close();
    outputStream.close();
}

为了省略一些细节，也许您可​​以直接使用 Java CipherOutputStream 和 CiptherInputStream，并且实现将为您处理这些细节(如果您不关心确切的格式)。

接下来您缺少的是身份验证标签，至少是保证密文完整性的明文哈希。 (这称为认证加密)