Re: Encryption / string encoding

From: Rich Bernstein (rab38_at_cornell.edu)
Date: 05/22/03 

Date: Thu, 22 May 2003 14:39:50 -0400

Looks like you're leaving off the last byte of data in the byte array during
decryption. Change "EncryptedStream.Length - 1" in DecryptStream to
"EncryptedStream.Length". 

--
-Rich
"Sparky" <mark.smith@nospam.farmade.com> wrote in message
news:#lytGgHIDHA.612@TK2MSFTNGP11.phx.gbl...
> Hi
>
> I'm using Visual Studio Magazines Crypto class, as described in Jan 2003.
> The problem that I'm having is that I am encrypting a string, and then at
a
> later date decrypting the string. If I debug.print the decrypted string,
it
> is correct but has no end quote displayed.
>
> ie. in the output window, rather than "hello" being displayed, "hello is
> displayed. It looks like the string is now longer than it ought to be but
> has funny characters appended to the end. This affects webservices,. ie. I
> can't pass the string, and also affects sql as I can't use that string in
an
> sql statement. I have tried Trim'ming etc but to no avail. All I want is
my
> original string back....
>
> I've pasted below the encryption / decrption code. I think it's just a
case
> of doing something like Convert.ToString (although that doesn't work but I
> suspect something similar will!)
>
> Any help much appreciated!
>
> Mark
>
>
> ==========================
>  Public Function DecryptString(ByVal EncryptedString As String) As String
>   If mbKeyIsSet Then
>    Return _DecryptString(EncryptedString, True)
>   Else
>    Throw New Exception(mksKeyNotSetException)
>   End If
>  End Function
>
>
>  Private Function _DecryptString(ByVal EncryptedString As String, ByVal
> Base64 As Boolean) As String
>   Try
>    'put string in byte array depending on Base64 flag
>    Dim byteArray() As Byte
>    If Base64 Then
>     byteArray = Convert.FromBase64String(EncryptedString)
>    Else
>     byteArray = BytesFromString(EncryptedString)
>    End If
>    'create the streams, decrypt and return a string
>    Dim msEnc As New MemoryStream(byteArray)
>    Dim msPlain As MemoryStream = DecryptStream(msEnc)
>    Return BytesToString(msPlain.GetBuffer)
>   Catch ex As Exception
>    'Debug.WriteLine("_DecryptString Error: " & ex.ToString)
>    'Return String.Empty
>    cFmsException.ThrowFMS(Me.GetType.FullName, ex)
>   End Try
>  End Function
>
>  Private Function BytesToString(ByVal byteArray() As Byte) As String
>   Return (New UnicodeEncoding).GetString(byteArray)
>   'Return (New ASCIIEncoding).GetString(byteArray)
>  End Function
>
>
>
>  'encrypt a string - wrapper without Base64 flag (True by default)
>  Public Function EncryptString(ByVal PlainText As String) As String
>   If mbKeyIsSet Then
>    Return _EncryptString(PlainText, True)
>   Else
>    Throw New Exception(mksKeyNotSetException)
>   End If
>  End Function
>
>
>  Private Function _EncryptString(ByVal PlainText As String, ByVal Base64
As
> Boolean) As String
>   Try
>    'put string in byte array
>    Dim byteArray() As Byte = BytesFromString(PlainText)
>    'create streams and encrypt
>    Dim msPlain As New MemoryStream(byteArray)
>    Dim msEnc As MemoryStream = EncryptStream(msPlain)
>    'return string depending on Base64 flag
>    If Base64 Then
>     Return Convert.ToBase64String(msEnc.ToArray)
>    Else
>     Return BytesToString(msEnc.ToArray)
>    End If
>   Catch ex As Exception
>    'Debug.WriteLine("_EncryptString Error: " & ex.ToString)
>    'Return String.Empty
>    cFmsException.ThrowFMS(Me.GetType.FullName, ex)
>   End Try
>  End Function
>
>
>  Public Function EncryptStream(ByVal PlainStream As MemoryStream) As
> MemoryStream
>   If mbKeyIsSet Then
>    Try
>     'open stream for encrypted data
>     Dim encStream As New MemoryStream
>     'create Crypto Service Provider, set key, transform and crypto stream
>     Dim oCSP As New RijndaelManaged
>     oCSP.Key = mbytKey
>     oCSP.IV = mbytIV
>     Dim ct As ICryptoTransform = oCSP.CreateEncryptor()
>     Dim cs As CryptoStream = New CryptoStream(encStream, ct,
> CryptoStreamMode.Write)
>     'get input stream into byte array
>     Dim byteArray() As Byte = PlainStream.ToArray()
>     'write input bytes to crypto stream and close up
>     cs.Write(byteArray, 0, CType(PlainStream.Length, Integer))
>     cs.FlushFinalBlock()
>     cs.Close()
>     Return encStream
>    Catch ex As Exception
>     'Debug.WriteLine("EncryptStream Error: " & ex.ToString)
>     'Return Stream.Null
>     cFmsException.ThrowFMS(Me.GetType.FullName, ex)
>    End Try
>   Else
>    Throw New Exception(mksKeyNotSetException)
>   End If
>  End Function
>
>
> Public Function DecryptStream(ByVal EncryptedStream As MemoryStream) As
> MemoryStream
>   If mbKeyIsSet Then
>    Try
>     'create Crypto Service Provider, set key, transform and crypto stream
>     Dim oCSP As New RijndaelManaged
>     oCSP.Key = mbytKey
>     oCSP.IV = mbytIV
>     Dim ct As ICryptoTransform = oCSP.CreateDecryptor()
>     Dim cs As CryptoStream = New CryptoStream(EncryptedStream, ct,
> CryptoStreamMode.Read)
>     'get bytes from encrypted stream
>     Dim byteArray(CType(EncryptedStream.Length - 1, Integer)) As Byte
>     Dim iBytesIn As Integer = cs.Read(byteArray, 0,
> CType(EncryptedStream.Length, Integer))
>     cs.Close()
>     'create and write the decrypted output stream
>     Dim plainStream As New MemoryStream
>     plainStream.Write(byteArray, 0, iBytesIn)
>     Return plainStream
>    Catch ex As Exception
>     'Debug.WriteLine("DecryptStream Error: " & ex.ToString)
>     'Return Stream.Null
>     cFmsException.ThrowFMS(Me.GetType.FullName, ex)
>    End Try
>   Else
>    Throw New Exception(mksKeyNotSetException)
>   End If
>  End Function
>
>

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