asked on
Encryption/decryption of file
Hi
This question follows on from 21556745.
I used the example question 21556745 in a desktop form fine and it works. However if I use the DLL in a web application I get problems with
A first chance exception of type 'System.FormatException' occurred
The aspx page loads an encrypted textfile then tries to decrypt it to a string.
Here's my code to load a file and then try to decrypt it to a string...
If FileUpload1.HasFile Then
Dim intFileLength As Integer, bytData() As Byte
Dim objStream As System.IO.Stream
intFileLength = FileUpload1.PostedFile.Con
ReDim bytData(intFileLength)
objStream = FileUpload1.PostedFile.Inp
objStream.Read(bytData, 0, intFileLength)
Dim fileContents As String = Encoding.ASCII.GetString(b
'this displays the file contents
Me.TextBox_ReadFromFile.Te
'attempt to decrypt the string
Dim decrypted As String = Crypto.Decrypt(fileContent
'ERROR Happens here...
Me.DecryptedFromFile.Text = fileContents
End If
so....text loads fine but decrypt doesn't work.
However, if I have the following code in design mode
fileContents = "a long string with exactly the same as is in the file being uploaded"
decrypted = Crypto.Decrypt(fileContent
there is no error and the text decrypts fine.
Why would this be happening? Text loaded from a file doesn't decrypted, the same text hard coded into class does - what's the solution? This is a strange one..
Thanks
This question follows on from 21556745.
I used the example question 21556745 in a desktop form fine and it works. However if I use the DLL in a web application I get problems with
A first chance exception of type 'System.FormatException' occurred
The aspx page loads an encrypted textfile then tries to decrypt it to a string.
Here's my code to load a file and then try to decrypt it to a string...
If FileUpload1.HasFile Then
Dim intFileLength As Integer, bytData() As Byte
Dim objStream As System.IO.Stream
intFileLength = FileUpload1.PostedFile.Con
ReDim bytData(intFileLength)
objStream = FileUpload1.PostedFile.Inp
objStream.Read(bytData, 0, intFileLength)
Dim fileContents As String = Encoding.ASCII.GetString(b
'this displays the file contents
Me.TextBox_ReadFromFile.Te
'attempt to decrypt the string
Dim decrypted As String = Crypto.Decrypt(fileContent
'ERROR Happens here...
Me.DecryptedFromFile.Text = fileContents
End If
so....text loads fine but decrypt doesn't work.
However, if I have the following code in design mode
fileContents = "a long string with exactly the same as is in the file being uploaded"
decrypted = Crypto.Decrypt(fileContent
there is no error and the text decrypts fine.
Why would this be happening? Text loaded from a file doesn't decrypted, the same text hard coded into class does - what's the solution? This is a strange one..
Thanks
.NET ProgrammingVisual Basic.NETASP.NET
Last Comment
rwallacej
ASKER
yes it does work however displays blank
its the line
Dim decrypted As String = Crypto.Decrypt(fileContent
that throws exception in the Decrypt method
and returns a blank string/nother
its the line
Dim decrypted As String = Crypto.Decrypt(fileContent
that throws exception in the Decrypt method
and returns a blank string/nother
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ASKER
Hi
Thanks for the feedback;
I don't really have a chance to change the encryption method used. The project I am on is the transfer of a desktop application to a web application, The desktop application has used the above encryption method to save files and users would like files created on the desktop version to open in the new web version
Maybe there's an answer out there !
Thanks for the feedback;
I don't really have a chance to change the encryption method used. The project I am on is the transfer of a desktop application to a web application, The desktop application has used the above encryption method to save files and users would like files created on the desktop version to open in the new web version
Maybe there's an answer out there !
Oh, gotcha. Well, it was worth a shot. Good luck!
ASKER
I've copied the class Crypto.vb across (opposed to using the DLL, there is only one class - see below)
Copying across leads me to the error line:
Dim Buffer As Byte() = Convert.FromBase64String(e
"A first chance exception of type 'System.FormatException' occurred "
Does this help ?
Copying across leads me to the error line:
Dim Buffer As Byte() = Convert.FromBase64String(e
"A first chance exception of type 'System.FormatException' occurred "
Does this help ?
Imports System
Imports System.IO
Imports System.Xml
Imports System.Text
Imports System.Security.Cryptography
Imports System.Windows.Forms
Public Class Crypto
'http://www.experts-exchange.com/Programming/Languages/.NET/Visual_Basic.NET/Q_21556745.html?sfQueryTermInfo=1+obscur+xml
Private Shared DES As New TripleDESCryptoServiceProvider
Private Shared MD5 As New MD5CryptoServiceProvider
Public Shared Function Encrypt(ByVal stringToEncrypt As String, ByVal key As String) As String
DES.Key = MD5.ComputeHash(System.Text.ASCIIEncoding.ASCII.GetBytes(key))
DES.Mode = CipherMode.ECB
Dim DESEncrypt As ICryptoTransform = DES.CreateEncryptor()
Dim Buffer As Byte() = System.Text.ASCIIEncoding.ASCII.GetBytes(stringToEncrypt)
Return Convert.ToBase64String(DESEncrypt.TransformFinalBlock(Buffer, 0, Buffer.Length))
End Function
Public Shared Function Decrypt(ByVal encryptedString As String, ByVal key As String, Optional ByVal displayError As Boolean = True) As String
Try
DES.Key = MD5.ComputeHash(System.Text.ASCIIEncoding.ASCII.GetBytes(key))
DES.Mode = CipherMode.ECB
Dim DESDecrypt As Security.Cryptography.ICryptoTransform = DES.CreateDecryptor()
Dim Buffer As Byte() = Convert.FromBase64String(encryptedString)
Return System.Text.ASCIIEncoding.ASCII.GetString(DESDecrypt.TransformFinalBlock(Buffer, 0, Buffer.Length))
Catch ex As Exception
If displayError Then
MessageBox.Show("Invalid Key", "Decryption Failed", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
End If
System.Diagnostics.Debug.Print("Invalid Key" & vbCrLf & ex.StackTrace)
Return Nothing
End Try
End Function
End Class
ASKER
the error is
Convert.FromBase64String(e
Return System.Text.ASCIIEncoding.
...I'd have thought passing in the same string would be ok...
Convert.FromBase64String(e
Return System.Text.ASCIIEncoding.
...I'd have thought passing in the same string would be ok...
ASKER
changing
bytData(intFileLength)
to be
bytData(intFileLength - 1)
fixed this
bytData(intFileLength)
to be
bytData(intFileLength - 1)
fixed this
Me.TextBox_ReadFromFile.Te