Question

I have created a TripleDes class like that :

class TripleDes_Crypto
{
    // Key Lenght must be 24
    string Key = string.Empty;
    // IV Lenght must be 8
    string IV = string.Empty;

public TripleDes_Crypto(string KEY, string IV)
{
    this.Key = KEY;
    this.IV = IV;
}

public string Encrypt(string Data)
{
    byte[] key = Encoding.ASCII.GetBytes(Key);
    byte[] iv = Encoding.ASCII.GetBytes(IV);
    byte[] data = Encoding.ASCII.GetBytes(Data);
    byte[] enc = new byte[0];

    TripleDES tdes = TripleDES.Create();
    tdes.IV = iv;
    tdes.Key = key;
    tdes.Mode = CipherMode.CBC;
    tdes.Padding = PaddingMode.Zeros;

    // encryption
    ICryptoTransform ict = tdes.CreateEncryptor();
    enc = ict.TransformFinalBlock(data, 0, data.Length);

    return ASCIIEncoding.ASCII.GetString(enc);
}

public string Decrypt(string Data)
{
    byte[] key = Encoding.ASCII.GetBytes(Key);
    byte[] iv = Encoding.ASCII.GetBytes(IV);
    byte[] data = Encoding.ASCII.GetBytes(Data);
    byte[] dec = new byte[0];

    TripleDES tdes = TripleDES.Create();
    tdes.IV = iv;
    tdes.Key = key;
    tdes.Mode = CipherMode.CBC;
    tdes.Padding = PaddingMode.Zeros;

    // decryption
    ICryptoTransform ict = tdes.CreateDecryptor();
    dec = ict.TransformFinalBlock(data, 0, data.Length);

    return ASCIIEncoding.ASCII.GetString(dec);
}

}

And i used :

    private void button1_Click(object sender, EventArgs e)
    {
        TripleDes_Crypto tdes = new TripleDes_Crypto("passwordDR0wSS@P6660juht", "password");
        File.WriteAllText(@"encrypted", tdes.Encrypt("Hey TEST DATA"));
        MessageBox.Show(tdes.Decrypt(File.ReadAllText(@"encrypted")));
    }

Well the encryption method works fine but the decryption method is the problem as when i use decrypt it generates some random data while it should output : Hey TEST DATA.

Thanks for help in advance.

Answer 1

These are your problem:

return ASCIIEncoding.ASCII.GetString(enc);
...
byte[] data = Encoding.ASCII.GetBytes(Data);

You’re treating encrypted data as if it were ASCII text. It’s not. You’re losing data.

To represent arbitrary binary data without loss in text, you should almost always use Base64:

return Convert.ToBase64String(enc);
...
byte[] data = Convert.FromBase64String(Data);

Additionally, I’d suggest using something other than ASCII to convert key/iv text into bytes – and also follow .NET naming conventions for parameters.