JAVA 将 AES key 、初始化 vector 和数据从加密文件中分离出来，并在加密过程中使用这 3 种组合

Question

我已经创建了结合 AES 加密、intilizatio vector 和原始数据的加密文件。所以我的加密文件包含以上 3 个加密形式的元素。现在，在解密过程中，我再次陷入分离所有这 3 个元素的困境，此外，我必须使用在加密过程中生成的解密过程中硬编码的 AES key 长度。

public static void encrypt() throws Exception {

        // RSA with ECB mode
        Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
        cipher.init(Cipher.ENCRYPT_MODE, generatePublicKey(readKeysFromFile("My_public.pub")));

        // AES key generator
        KeyGenerator kgen = KeyGenerator.getInstance("AES");
        kgen.init(128, srandom);
        SecretKey skey = kgen.generateKey();

        // Initialization vector 16 byte
        byte[] iv = new byte[128/8];
        srandom.nextBytes(iv);
        IvParameterSpec ivspec = new IvParameterSpec(iv);

        try (FileOutputStream out = new FileOutputStream("dataFile" + ".enc")) {
            {
                byte[] b = cipher.doFinal(skey.getEncoded());
                out.write(b);
                System.err.println("AES Key Length: " + b.length);
            }

            out.write(iv);
            System.err.println("IV Length: " + iv.length);

            Cipher ci = Cipher.getInstance("AES/CBC/PKCS5Padding");
            ci.init(Cipher.ENCRYPT_MODE, skey, ivspec);

            File inputDataFile = new File("dataFile.xml");
            try (DataInputStream in = new DataInputStream(new FileInputStream(inputDataFile))) {
                byte[] buffer = new byte[(int)inputDataFile.length()];
                in.readFully(buffer);
                in.close();
                byte[] encryptedData = ci.doFinal(buffer);
                out.write(encryptedData);
                out.close();
            }
        }

    }


public static void decryptRSAAES() throws Exception {

        Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
        cipher.init(Cipher.DECRYPT_MODE, generatePrivateKey(readKeysFromFile("My_private.key")));

        File file2 = new File("dataFile.enc");
        RandomAccessFile raf = new RandomAccessFile(file2, "r");

        // length of AES key 
        byte[] c = new byte[384];

        // read the AES key from file
        raf.read(c, 0 , 384);
        byte[] fileContent = Files.readAllBytes(file2.toPath());
        byte[] keyb = cipher.doFinal(c);
        SecretKeySpec skey = new SecretKeySpec(keyb, "AES");

        // read the initializatoin vector
        byte[] iv = new byte[128/8];
        raf.seek(384);
        raf.read(iv);
        IvParameterSpec ivspec = new IvParameterSpec(iv);

        raf.seek(400);

        Cipher ci = Cipher.getInstance("AES/CBC/PKCS5Padding");
        ci.init(Cipher.DECRYPT_MODE, skey, ivspec);
        try (FileOutputStream out = new FileOutputStream("decryptedFileTest"+".xml")){

            byte[] decryptedData = ci.doFinal(fileContent);
            out.write(decryptedData);
            out.close();
            //processDecryptFile(ci, in, out);
        }
    }

实际结果:使用 AES key 和原始纯数据创建解密文件

预期结果:在输出中仅写入原始纯数据，删除 AES 和初始化 vector 。

Answer 1

让我们简化一下并使用 Java 的 InputStream 中新提供的功能类(class):

public static void encrypt(RSAPublicKey publicKey) throws Exception {

    try (FileOutputStream out = new FileOutputStream("dataFile" + ".enc")) {

        // --- RSA using PKCS#1 v1.5 padding
        Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);

        // --- AES key generator
        KeyGenerator kgen = KeyGenerator.getInstance("AES");
        kgen.init(128);
        SecretKey skey = kgen.generateKey();

        // --- write encrypted AES key
        byte[] encryptedSKey = cipher.doFinal(skey.getEncoded());
        out.write(encryptedSKey);

        // --- Initialization vector 16 byte
        SecureRandom srandom = new SecureRandom();
        byte[] iv = new byte[128/8];
        srandom.nextBytes(iv);
        IvParameterSpec ivspec = new IvParameterSpec(iv);

        // --- write IV
        out.write(iv);


        // --- initialize AES cipher
        Cipher ci = Cipher.getInstance("AES/CBC/PKCS5Padding");
        ci.init(Cipher.ENCRYPT_MODE, skey, ivspec);

        // --- convert file by copying to memory
        try (FileInputStream in = new FileInputStream("dataFile.xml")) {
            byte[] buffer = in.readAllBytes();
            byte[] encryptedData = ci.doFinal(buffer);
            out.write(encryptedData);
        }
    }
}


public static void decrypt(RSAPrivateKey privateKey) throws Exception {

    try (FileInputStream in = new FileInputStream("dataFile" + ".enc")) {

        // --- RSA using PKCS#1 v1.5 padding
        Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
        cipher.init(Cipher.DECRYPT_MODE, privateKey);

        // --- read encrypted AES key
        byte[] encryptedSKey = in.readNBytes(determineEncryptionSizeInBytes(privateKey));

        byte[] decryptedSKey = cipher.doFinal(encryptedSKey);
        SecretKey skey = new SecretKeySpec(decryptedSKey, "AES");

        // --- Initialization vector 16 byte
        byte[] iv = in.readNBytes(128 / Byte.SIZE);
        IvParameterSpec ivspec = new IvParameterSpec(iv);

        // --- initialize AES cipher
        Cipher ci = Cipher.getInstance("AES/CBC/PKCS5Padding");
        ci.init(Cipher.DECRYPT_MODE, skey, ivspec);

        // --- convert file by copying to memory
        File outputDataFile = new File("dataFile.xml2");
        try (FileOutputStream out = new FileOutputStream(outputDataFile)) {
            byte[] buffer = in.readAllBytes();
            byte[] decryptedData = ci.doFinal(buffer);
            out.write(decryptedData);
        }
    }
}

private static int determineEncryptionSizeInBytes(RSAPrivateKey privateKey) {
    return (privateKey.getModulus().bitLength() + Byte.SIZE - 1) / Byte.SIZE;
}

public static void main(String[] args) throws Exception {
    KeyPairGenerator kpg = KeyPairGenerator.getInstance("RSA");
    kpg.initialize(384 * Byte.SIZE);
    KeyPair pair = kpg.generateKeyPair();
    encrypt((RSAPublicKey) pair.getPublic());
    decrypt((RSAPrivateKey) pair.getPrivate());
}

正如您所看到的，代码现在更像是镜像。我只是复制了加密代码，然后对其进行了更改。正如您所看到的，它现在通过依赖 InputStream#readAllBytes() 使用更少的类。 (自 Java 9 起)和 InputStream#readNBytes() (自 Java 11 起)。

请注意，您通常希望使用较小的缓冲区流文件。由于整个明文和密文当前都在缓冲，您的应用程序使用的内存比所需的多得多。要使用流加密数据，您可以依靠 CipherInputStream和CipherOutputStream .

不用说异常处理需要改进，我只是简单地研究了解决您当前问题的最佳方法。当您让事情正常运转时(让事情正常运转、让事情正确、让事情优化)，请再看一下它。