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c#encryptionbitmapdata-hiding
Abby
Abby

Reputation: 101

Open encrypted image as Bitmap C#

I need to perform data hiding in encrypted image. To perform data hiding i need to have bitmap Image. But i don't know how to save the image as bitmap.

Below is my encryption code.

public void EncryptFile(string source, string destination)
{
    string sKey = "super545";
    FileStream fsInput = new FileStream(source, FileMode.Open, FileAccess.Read);

    FileStream fsEncrypted = new FileStream(destination, FileMode.Create, FileAccess.Write);

    DESCryptoServiceProvider DES = new DESCryptoServiceProvider();
    DES.Key = ASCIIEncoding.ASCII.GetBytes(sKey);
    DES.IV = ASCIIEncoding.ASCII.GetBytes(sKey);
    ICryptoTransform desencrypt = DES.CreateEncryptor();
    CryptoStream cryptostream = new CryptoStream(fsEncrypted, desencrypt, CryptoStreamMode.Write);
    byte[] bytearrayinput = new byte[fsInput.Length - 1];

    fsInput.Read(bytearrayinput, 0, bytearrayinput.Length);
    cryptostream.Write(bytearrayinput, 0, bytearrayinput.Length);
    cryptostream.Close();
    fsInput.Close();
    fsEncrypted.Close();
}

This is called like:

EncryptFile(originalimage, output);

output is a string variable with the path to store the encrypted image.

How can I call the function to run the encryption?

I receive the error the parameter is invalid when i hit this line:

Bitmap bitmap3 = new Bitmap(output);

Upvotes: 0

Views: 1226

Answers (1)

DarkSquirrel42
DarkSquirrel42

Reputation: 10267

I guess what you are trying to do is pretty close to this:

public void EncryptFile(string source, string destination)
{
    string sKey = "super545";
    FileStream fsInput = new FileStream(source, FileMode.Open, FileAccess.Read);

    FileStream fsEncrypted = new FileStream(destination, FileMode.Create, FileAccess.Write);

    //Consider to use something else, DES is dead
    DESCryptoServiceProvider DES = new DESCryptoServiceProvider();

    //use some key derivation function like pbkdf2 instead
    DES.Key = ASCIIEncoding.ASCII.GetBytes(sKey);

    //should be random, may be fixed ONLY for testing purposes
    DES.IV = ASCIIEncoding.ASCII.GetBytes(sKey);

    ICryptoTransform desencrypt = DES.CreateEncryptor();
    CryptoStream cryptostream = new CryptoStream(fsEncrypted, desencrypt, CryptoStreamMode.Write);

    //byte[] bytearrayinput = new byte[fsInput.Length - 1]; // what do you need that big buffer for anyways?
    //fsInput.Read(bytearrayinput, 0, bytearrayinput.Length);
    //cryptostream.Write(bytearrayinput, 0, bytearrayinput.Length);

    byte[] headerBuffer = new byte[54]; // buffer for our bmp header ... without any color tables or masks

    //No need for lots of checks in a proof of concept
    fsInput.Read(headerBuffer, 0, headerBuffer.Length);
    var biCompression = BitConverter.ToInt32(headerBuffer, 30); //get biComp from header

    if (biCompression != 0 && biCompression != 3)
    {
        throw new Exception("Compression is not in the correct format");
    }

    //The buffer is copied without any encryption
    fsEncrypted.Write(headerBuffer, 0, headerBuffer.Length);

    //copy the rest and encrypt it ... don't care about color tables and masks for now
    //and let's just hope plaintext and ciphertext have the right size
    fsInput.CopyTo(cryptostream);

    cryptostream.Close();
    fsInput.Close();
    fsEncrypted.Close();
}

Upvotes: 2

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