[Solved] ASP.Net Error: invalid length for Base-64 char array or string

Hi nauna,

The length of a base64 encoded string is always a multiple of 4.

So while decrypting, the string is not a valid base 64 char array, so the error.

I have created a sample as per your shared code. Please refer sample below.

HTML

<u>Encrypt</u>
<br />
Enter text:
<br />
<asp:TextBox ID="txtOriginal" runat="server"></asp:TextBox>
<asp:Button ID="btnEncrypt" runat="server" Text="Encrypt" OnClick="Encrypt" /><br />
<br />
Encrypted Text:
<asp:Label ID="lblEncryptedText" runat="server"></asp:Label><br />
<br />
<u>Decrypt</u>
<br />
Enter Encrypted Text:
<br />
<asp:TextBox ID="txtDecrypt" runat="server"></asp:TextBox>
<asp:Button ID="btnDecrypt" runat="server" Text="Decrupt" OnClick="Decrypt" /><br />
<br />
Original Text:
<asp:Label ID="lblDecryptedText" runat="server"></asp:Label>

Namespaces

using System.IO;
using System.Text;
using System.Security.Cryptography;

Code

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        txtOriginal.Text = GenerateRandomNo();
    }
}

private Random _random = new Random();

public string GenerateRandomNo()
{
    return _random.Next(0, 9999).ToString("D4");
}

protected void Encrypt(object sender, EventArgs e)
{
    lblEncryptedText.Text = this.Encrypt(txtOriginal.Text.Trim());
}

public string Encrypt(string clearText)
{
    string EncryptionKey = "MAKV2SPBNI99212";
    byte[] clearBytes = Encoding.Unicode.GetBytes(clearText);
    using (Aes encryptor = Aes.Create())
    {
        Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes(EncryptionKey, new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });
        encryptor.Key = pdb.GetBytes(32);
        encryptor.IV = pdb.GetBytes(16);
        using (MemoryStream ms = new MemoryStream())
        {
            using (CryptoStream cs = new CryptoStream(ms, encryptor.CreateEncryptor(), CryptoStreamMode.Write))
            {
                cs.Write(clearBytes, 0, clearBytes.Length);
                cs.Close();
            }
            clearText = Convert.ToBase64String(ms.ToArray());
        }
    }
    return clearText;
}

protected void Decrypt(object sender, EventArgs e)
{
    lblDecryptedText.Text = this.Decrypt(txtDecrypt.Text.Trim());
}

public string Decrypt(string cipherText)
{
    string EncryptionKey = "MAKV2SPBNI99212";
    byte[] cipherBytes = Convert.FromBase64String(cipherText);
    using (Aes encryptor = Aes.Create())
    {
        Rfc2898DeriveBytes pdb = new Rfc2898DeriveBytes(EncryptionKey, new byte[] { 0x49, 0x76, 0x61, 0x6e, 0x20, 0x4d, 0x65, 0x64, 0x76, 0x65, 0x64, 0x65, 0x76 });
        encryptor.Key = pdb.GetBytes(32);
        encryptor.IV = pdb.GetBytes(16);
        using (MemoryStream ms = new MemoryStream())
        {
            using (CryptoStream cs = new CryptoStream(ms, encryptor.CreateDecryptor(), CryptoStreamMode.Write))
            {
                cs.Write(cipherBytes, 0, cipherBytes.Length);
                cs.Close();
            }
            cipherText = Encoding.Unicode.GetString(ms.ToArray());
        }
    }
    return cipherText;
}

Screenshot