[RESOLVED] Decrypting (text)File Failure

[Radjesh Klauke]

Ola,

Trying to decrypt a textfile is giving me an error: The input is not a valid Base 64-string as it contains a non-Base 64 character, more then two padding characters, or a non-white space character among the padding characters.

Besides that I also get an exception while debugging: A first chance exception of type 'System.FormatException' occurred in Fenix.exe

When I start the app it opens the file and tries to decrypt it. After decryption the string is send to a label, so I can read it. The codes I used:

'    encrypt the file
    Private Function Encrypt(ByVal strText As String, ByVal strEncrKey As String) As String
        Dim IV() As Byte = {&H12, &H34, &H56, &H78, &H90, &HAB, &HCD, &HEF}
        Try
            Dim bykey() As Byte = System.Text.Encoding.UTF8.GetBytes(strEncrKey)
            Dim InputByteArray() As Byte = System.Text.Encoding.UTF8.GetBytes(strText)
            Dim des As New DESCryptoServiceProvider
            Dim ms As New MemoryStream
            Dim cs As New CryptoStream(ms, des.CreateEncryptor(bykey, IV), CryptoStreamMode.Write)
            cs.Write(InputByteArray, 0, InputByteArray.Length)
            cs.FlushFinalBlock()
            Return Convert.ToBase64String(ms.ToArray())
        Catch ex As Exception
            Return ex.Message
        End Try
    End Function
 
 
    '    decrypt the file
    Private Function Decrypt(ByVal strText As String, ByVal sDecrKey As String) As String
        Dim IV() As Byte = {&H12, &H34, &H56, &H78, &H90, &HAB, &HCD, &HEF}
        Dim inputByteArray(strText.Length) As Byte
        Try
            Dim byKey() As Byte = System.Text.Encoding.UTF8.GetBytes(sDecrKey)
            Dim des As New DESCryptoServiceProvider
            inputByteArray = Convert.FromBase64String(strText)
            Dim ms As New MemoryStream
            Dim cs As New CryptoStream(ms, des.CreateDecryptor(byKey, IV), CryptoStreamMode.Write)
            cs.Write(inputByteArray, 0, inputByteArray.Length)
            cs.FlushFinalBlock()
            Dim encoding As System.Text.Encoding = System.Text.Encoding.UTF8
            Return encoding.GetString(ms.ToArray())
        Catch ex As Exception
            Return ex.Message
        End Try
    End Function
 
'    read the file
 
If File.Exists(Application.StartupPath & "\myfile.file") Then
    decryption_label.Text = Decrypt(Application.StartupPath & "\myfile.file", "passw")
Else
'...

Someone know what could be the issue? Thanks for the help in advance.

[amrita]

You are passsing the file path to decrypt method ..I think you should pass the file content as string to the method., not just the file name.

[Radjesh Klauke]

No, it should be possible, cause I have done it before with the same method and it worked. Just don;t get I why it doesn't work this time. Besides that I need to decrypt the file, can't hardcode it.

[amrita]

You want to decrypt the content of the file , right ? Whatever is written in the file ?

So I think you need to open the file and read the content first and then pass the entire encrypted string to Decrypt method.

[Radjesh Klauke]

You are correct. Stupid that I didn't think of that.

[Radjesh Klauke]

Thanks man. Really stupid of me.