Question

这是我的加密类：

public static void encrypt(byte[] file, String password, String fileName, String dir) throws Exception {

    SecureRandom r = new SecureRandom();
    //128 bit IV generated for each file
    byte[] iv = new byte[IV_LENGTH];
    r.nextBytes(iv);
    IvParameterSpec ivspec = new IvParameterSpec(iv);
    SecretKeySpec keySpec = new SecretKeySpec(password.getBytes(), "AES");

    Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
    cipher.init(Cipher.ENCRYPT_MODE, keySpec, ivspec);

    FileOutputStream fos = new FileOutputStream(dir + fileName);
    fos.write(iv);

    CipherOutputStream cos = new CipherOutputStream(fos, cipher);

    // Have to append IV --------

    cos.write(file);

    fos.flush();
    cos.flush();
    cos.close();
    fos.close();
}

这是我的解密方法：

public static void decrypt(byte[] file, String password, String fileName, String dir) throws Exception
{   
    // gets the IV
    int ivIndex = file.length - 16;

    byte[] truncatedFile = Arrays.copyOfRange(file, 0, file.length - 16);

    SecretKeySpec keySpec = new SecretKeySpec(password.getBytes(), "AES");

    Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
    cipher.init(Cipher.DECRYPT_MODE, keySpec, new IvParameterSpec(truncatedFile, ivIndex, 16));

    //IvParameterSpec ivspec = new IvParameterSpec(iv);
    //
    //cipher.init(Cipher.DECRYPT_MODE, keySpec, ivspec);

    FileOutputStream fos = new FileOutputStream(dir + fileName);
    CipherOutputStream cos = new CipherOutputStream(fos, cipher);

    cos.write(file);
    fos.flush();
    cos.flush();
    cos.close();
    fos.close();
}

}

正如您所看到的，我生成了一个16字节长的IV，我已将其附加到加密文件的末尾。这样我就可以将IV用于解密，并且每个文件都有一个独特的IV。我目前收到错误：

java.lang.IllegalArgumentException：对于给定的偏移/长度组合，IV缓冲区太短

除了产生错误的问题，我的逻辑是否正确？这会有用吗？

Answer 1

我生成了一个16字节长的IV，我已将其附加到加密文件的末尾。

不，你没有。你预先 - 它。无论如何，这是一个更好的主意。所以你必须首先阅读它，然后构造你的Cipher和CipherInputStream并解密文件输入流的其余部分。您无需将整个文件读入内存即可实现：

public static void decrypt(File file, String password) throws Exception
{
    byte[] iv = new byte[16];
    DataInputStream dis = new DataInputStream(new FileInputStream(file));
    dis.readFully(iv);

    SecretKeySpec keySpec = new SecretKeySpec(password.getBytes(), "AES");

    Cipher cipher = Cipher.getInstance("AES/CBC/NoPadding");
    cipher.init(Cipher.DECRYPT_MODE, keySpec, new IvParameterSpec(iv));
    CipherInputStream cis = new CipherInputStream(dis, cipher);

    // Now just read plaintext from `cis` and do whatever you want with it.

    cis.close();
}

试图删除我附加到byte []（即IV）的最后16个字节然后解密

1 个答案: