Encryption using rijndael

Question

I'm quite new in programming .I wrote the below code in order to prompt the user for a password to encrypting a file, But it just work when the length of password is 8, What can I do on order to accepting any number of characters for the password?

 string pass = textBox2.Text.ToString();
            string password = @"" + pass + ""; 
            UnicodeEncoding UE = new UnicodeEncoding();
            byte[] key = UE.GetBytes(password);


            FileStream fsCrypt = new FileStream(@"c:\\users\\new", FileMode.Create);
            name = fsCrypt.Name;
            RijndaelManaged RMCrypto = new RijndaelManaged();

            CryptoStream cs = new CryptoStream(fsCrypt,
                RMCrypto.CreateEncryptor(key, key),
                CryptoStreamMode.Write);

            FileStream fsIn = new FileStream(filename, FileMode.Open);

            int data;
            while ((data = fsIn.ReadByte()) != -1)
                cs.WriteByte((byte)data);

Answer 1

You need a function that is going to get a valid key length for Rijndael from your password, and at the moment, your use of UnicodeEncoding.GetBytes is only going to give this for certain discrete lengths of password, as you've discovered.

You should use another function to get a key from your password - perhaps take the byte array you have generated, and run a cryptographic hash function like SHA1 on it. SHA1 will give you a 128 bit length, like your 8 character passwords currently do, but regardless of the length of the password.