C＃Rijandel文件解密填充无效，无法删除

Question

i want to encrypt file from single file stream but i got this error when decryption padding is invalid and cannot be removed but Encryption and Decryption method has same padding if i set padding.Zeros does not encrypt file

  private static readonly byte[] SALT = new byte[] { 0x26, 0xdc, 0xff, 0x00, 0xad, 0xed, 0x7a, 0xee, 0xc5, 0xfe, 0x07, 0xaf, 0x4d, 0x08, 0x22, 0x3c };
    Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes("TestKey", SALT);
    public bool EncryptFileP(string Path)
    {
        FileInfo IOF = new FileInfo(Path);
        WRStream = new FileStream(Path, FileMode.Open);

        CryptoStream cryptoStream;
        Rijndael rijndael = Rijndael.Create();

        rijndael.Key = pdb.GetBytes(16);
        rijndael.IV = pdb.GetBytes(16);

        rijndael.Mode = CipherMode.CBC;
        rijndael.Padding = PaddingMode.PKCS7;

        cryptoStream = new CryptoStream(WRStream, rijndael.CreateEncryptor(), CryptoStreamMode.Write);

        cryptoStream.Close();
        WRStream.Close();

        return true;
    }
    public bool DecryptFileP(string Path)
    {
        FileInfo IOF = new FileInfo(Path);
        WRStream = new FileStream(Path, FileMode.Open);

        CryptoStream cryptoStream;
        Rijndael rijndael = Rijndael.Create();

        rijndael.Key = pdb.GetBytes(16);
        rijndael.IV = pdb.GetBytes(16);

        rijndael.Mode = CipherMode.CBC;
        rijndael.Padding = PaddingMode.PKCS7;

        cryptoStream = new CryptoStream(WRStream, rijndael.CreateDecryptor(), CryptoStreamMode.Write);

        cryptoStream.Close(); //error! padding is invalid and cannot be removed 
        WRStream.Close();


        return true;
    }

Answer 1

Looks to me like you are missing reading and writing from the streams you are creating.

At some point to encrypt a file, you will need to write the plaint-text data you want to encrypt to cryptoStream in your EncryptFileP , and similarly, when you decrypt you need to read back out of cryptoStream in DecryptFileP . These streams won't encrypt/decrypt a file in place like it appears you are trying to do

Answer 2

You have to instantiate Rfc2898DeriveBytes separately for encryption and decryption, because it is stateful. Move Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes("TestKey", SALT); into EncryptFileP and DecryptFileP .

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Security hints:

The IV must be unpredictable (read: random). Don't use a static IV, because that makes the cipher deterministic and therefore not semantically secure. An attacker who observes ciphertexts can determine when the same message prefix was sent before. The IV is not secret, so you can send it along with the ciphertext. Usually, it is simply prepended to the ciphertext and sliced off before decryption.

It is better to authenticate your ciphertexts so that attacks like a padding oracle attack are not possible. This can be done with authenticated modes like GCM or EAX, or with an encrypt-then-MAC scheme.