simple encrypting / decrypting in VB.Net

Question

I\'m trying to figure out how to encrypt / decrypt a string in VB.Net.

I followed the example given here and wrote the following code (below). There\'s a text box,

Answer 1

Your encryption looks mostly correct, but I am not sure if the UTF8 encoding or other settings on the encryption object is throwing you off. Here is the heart of the encryption method that we use, tailored slightly to your code:

' Return the encrypted bytes from the memory stream.
Dim aoBytes As Byte() = Nothing

' Declare the RijndaelManaged object used to encrypt the data.
Using oEncryptor As New RijndaelManaged
    Try
        ' Initialize the encryptor with the specified key and initialization vector
        oEncryptor.Key = KEY_128
        oEncryptor.IV = IV_128

        ' Declare the streams used to encrypt to an in memory array of bytes.
        Using msEncrypt As New MemoryStream
            ' Create the streams used for encryption.
            Using csEncrypt As New CryptoStream(msEncrypt, oEncryptor.CreateEncryptor(), CryptoStreamMode.Write)
                Using swEncrypt As New StreamWriter(csEncrypt)
                    ' Write all data to the stream.
                    swEncrypt.Write(Me.TextBox1.Text)
                End Using

                ' Retrieve the bytes
                aoBytes = msEncrypt.ToArray()
            End Using

        End Using
    Finally
        ' Clear the RijndaelManaged object.
        If oEncryptor IsNot Nothing Then
            oEncryptor.Clear()
        End If
    End Try
End Using

If aoBytes IsNot Nothing Then
    Me.TextBox1.Text = System.Convert.ToBase64String(aoBytes)
Else
    Me.TextBox1.Text = String.Empty
End If

And the decryption is:

Dim sDecryptedValue As String = ""

' Declare the RijndaelManaged object used to encrypt the data.
Using oDecryptor As New RijndaelManaged
    Try
        ' Initialize the encryptor with the specified key and a default initialization vector
        oDecryptor.Key = KEY_128
        oDecryptor.IV = IV_128

        Using msDecrypt As New MemoryStream(System.Convert.FromBase64String(Me.TextBox1.Text))
            ' Create the streams used for encryption.
            Using csDecrypt As New CryptoStream(msDecrypt, oDecryptor.CreateDecryptor(), CryptoStreamMode.Read)
                Using srDecrypt As New StreamReader(csDecrypt)
                    ' Write all data to the stream.
                    sDecryptedValue = srDecrypt.ReadToEnd()
                End Using
            End Using
        End Using
    Finally
        ' Clear the RijndaelManaged object.
        If oDecryptor IsNot Nothing Then
            oDecryptor.Clear()
        End If
    End Try
End Using

Me.TextBox1.Text = sDecryptedValue

One minor difference is that we accept a string key and intializaton vector from the caller and clean them up as follows.

InitializationVector cleanup:

If sInitializationVector.Length > 16 Then
    ' Trim the IV if it is too long
    sInitializationVector = sInitializationVector.Substring(0, 16)
ElseIf sInitializationVector.Length < 16 Then
    ' Pad the IV if it is too short
    sInitializationVector = sInitializationVector.PadRight(16)
End If

oDecryptor.IV = System.Text.Encoding.GetEncoding("ISO-8859-1").GetBytes(sInitializationVector)

Encryption key cleanup:

oDecryptor.Key = GetLegalEncryptionKey(sKey, oDecryptor)

Public Function GetLegalEncryptionKey(ByVal sKey As String, ByVal oEncryptor As RijndaelManaged) As Byte()

Dim sTemp As String

If oEncryptor.LegalKeySizes.Length > 0 Then
    Dim wSize As Integer
    ' key sizes are in bits

    With oEncryptor.LegalKeySizes(0)
        wSize = .MinSize
        Do While sKey.Length * 8 > wSize AndAlso .SkipSize > 0 AndAlso wSize < .MaxSize
            wSize += oEncryptor.LegalKeySizes(0).SkipSize
        Loop
    End With
    Dim wTotalChars As Integer

    wTotalChars = CInt(wSize / 8)
    If sKey.Length > wTotalChars Then
        sTemp = sKey.Substring(0, wTotalChars)
    Else
        sTemp = sKey.PadRight(wTotalChars, " "c)
    End If
Else
    sTemp = sKey
End If

' convert the secret key to byte array
Return System.Text.Encoding.GetEncoding("ISO-8859-1").GetBytes(sTemp)

End Function