Home/ Questions/Q 66771
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-05-10T19:09:20+00:00

I’m writing a password encryption routine. I’ve written the below app to illustrate my

  • 0

I’m writing a password encryption routine. I’ve written the below app to illustrate my problem. About 20% of the time, this code works as expected. The rest of the time, the decryption throws a cryptographic exception – ‘The data is invalid’.

I believe the problem is in the encryption portion, because the decryption portion works the same every time. That is, if the encryption routine yields a value that the decryption routine can decrypt, it can always decrypt it. But if the encryption routine yields a value that chokes the decryption routine, it always chokes. So the decrypt routine is consistent; the encrypt routine is not.

I suspect my use of Unicode encoding is incorrect, but I’ve tried others with the same result.

What am I doing wrong?

using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Text; using System.Windows.Forms; using System.Security.Cryptography;  namespace DataProtectionTest {     public partial class Form1 : Form     {         private static readonly byte[] entropy = { 1, 2, 3, 4, 1, 2, 3, 4 };         private string password;         public Form1()         {             InitializeComponent();         }          private void btnEncryptIt_Click(object sender, EventArgs e)         {             Byte[] pw = Encoding.Unicode.GetBytes(textBox1.Text);             Byte[] encryptedPw = ProtectedData.Protect(pw, entropy, DataProtectionScope.LocalMachine);             password = Encoding.Unicode.GetString(encryptedPw);              }          private void btnDecryptIt_Click(object sender, EventArgs e)         {             Byte[] pwBytes = Encoding.Unicode.GetBytes(password);             try             {                 Byte[] decryptedPw = ProtectedData.Unprotect(pwBytes, entropy, DataProtectionScope.LocalMachine);                 string pw = Encoding.Unicode.GetString(decryptedPw);                 textBox2.Text = pw;             }             catch (CryptographicException ce)             {                 textBox2.Text = ce.Message;             }         }     } }
Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. On the advice of a colleague, I opted for Convert.ToBase64String. Works well. Corrected program below.

    using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Text; using System.Windows.Forms; using System.Security.Cryptography;  namespace DataProtectionTest {     public partial class Form1 : Form     {         private static readonly byte[] entropy = { 1, 2, 3, 4, 1, 2, 3, 4 };         private string password;         public Form1()         {             InitializeComponent();         }          private void btnEncryptIt_Click(object sender, EventArgs e)         {             Byte[] pw = Encoding.Unicode.GetBytes(textBox1.Text);             Byte[] encryptedPw = ProtectedData.Protect(pw, entropy, DataProtectionScope.LocalMachine);             //password = Encoding.Unicode.GetString(encryptedPw);                    password = Convert.ToBase64String(encryptedPw);         }          private void btnDecryptIt_Click(object sender, EventArgs e)         {             //Byte[] pwBytes = Encoding.Unicode.GetBytes(password);             Byte[] pwBytes = Convert.FromBase64String(password);             try             {                 Byte[] decryptedPw = ProtectedData.Unprotect(pwBytes, entropy, DataProtectionScope.LocalMachine);                 string pw = Encoding.Unicode.GetString(decryptedPw);                 textBox2.Text = pw;             }             catch (CryptographicException ce)             {                 textBox2.Text = ce.Message;             }         }     } }
    • 0