Decryption   

Hi All,

I am trying to take a string that has been encrypted and decrypt it.
Here is the string:   MMP61ubfQt4=


The following code runs, but the result is an empty string at the
end.  Can anyone see what I am doing wrong?


Thanks,
Jeff


   Public Shared Function decryptUser(ByVal userName As String) As
String
        Dim inputInBytes() As Byte =
Convert.FromBase64String(userName)
        Dim key() As Byte = Convert.FromBase64String("ABCDEFG/
LR3t49HgyCUXns9nfCpaAr0q")
        Dim IV() As Byte = Convert.FromBase64String("ABCDEFGlS/U=")
        Dim utf8encoder As UTF8Encoding = New UTF8Encoding
        Dim tdesProvider As TripleDESCryptoServiceProvider = New
TripleDESCryptoServiceProvider


        Dim cryptoTransform As ICryptoTransform =
tdesProvider.CreateDecryptor(key, IV)


        Dim decryptedStream As MemoryStream = New MemoryStream
        Dim cryptStream As CryptoStream = New
CryptoStream(decryptedStream, cryptoTransform,
CryptoStreamMode.Write)
        cryptStream.Write(inputInBytes, 0, inputInBytes.Length)
        cryptStream.FlushFinalBlock()
        decryptedStream.Position = 0


        Dim result(decryptedStream.Length - 1) As Byte
        decryptedStream.Read(result, 0, decryptedStream.Length)
        cryptStream.Close()
        Dim myutf As UTF8Encoding = New UTF8Encoding
        Return myutf.GetString(result)
    End Function

date: Mon, 25 Aug 2008 15:28:55 -0700 (PDT)   author:   Jeff

Re: Decryption   

Where is your encrypt routine. That will make a big difference whether the 
decrypt is correct or not.

-- 
Gregory A. Beamer
MVP, MCP: +I, SE, SD, DBA

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********************************************
| Think outside the box!                               |
********************************************
"Jeff"  wrote in message 
news:dd5c1222-c1eb-4c16-bae2-b4856e1c41b6@i76g2000hsf.googlegroups.com...
> Hi All,
>
> I am trying to take a string that has been encrypted and decrypt it.
> Here is the string:   MMP61ubfQt4=
>
>
> The following code runs, but the result is an empty string at the
> end.  Can anyone see what I am doing wrong?
>
>
> Thanks,
> Jeff
>
>
>   Public Shared Function decryptUser(ByVal userName As String) As
> String
>        Dim inputInBytes() As Byte =
> Convert.FromBase64String(userName)
>        Dim key() As Byte = Convert.FromBase64String("ABCDEFG/
> LR3t49HgyCUXns9nfCpaAr0q")
>        Dim IV() As Byte = Convert.FromBase64String("ABCDEFGlS/U=")
>        Dim utf8encoder As UTF8Encoding = New UTF8Encoding
>        Dim tdesProvider As TripleDESCryptoServiceProvider = New
> TripleDESCryptoServiceProvider
>
>
>        Dim cryptoTransform As ICryptoTransform =
> tdesProvider.CreateDecryptor(key, IV)
>
>
>        Dim decryptedStream As MemoryStream = New MemoryStream
>        Dim cryptStream As CryptoStream = New
> CryptoStream(decryptedStream, cryptoTransform,
> CryptoStreamMode.Write)
>        cryptStream.Write(inputInBytes, 0, inputInBytes.Length)
>        cryptStream.FlushFinalBlock()
>        decryptedStream.Position = 0
>
>
>        Dim result(decryptedStream.Length - 1) As Byte
>        decryptedStream.Read(result, 0, decryptedStream.Length)
>        cryptStream.Close()
>        Dim myutf As UTF8Encoding = New UTF8Encoding
>        Return myutf.GetString(result)
>    End Function

date: Mon, 25 Aug 2008 22:49:54 -0500   author:   Cowboy \(Gregory A. Beamer\) oSpamM

Re: Decryption   

Standard debugging applies i.e. have you put a breakpoint somewhere and 
checked that strings are not empty, streams are written, arrays are not 
empty etc... Here you should find that DecryptedStream.Length is 0 so the 
CryptoStream part is wrong...

According to the doc 
http://msdn.microsoft.com/en-us/library/system.security.cryptography.cryptostream.aspx 
it lloks this is the other way round i.e. you provide an encypted stream to 
the CryptoStream and reading the CryptoStream allows to read decrypted 
data...

What if you try ?

--
Patrice

"Jeff"  a écrit dans le message de groupe de 
discussion : 
dd5c1222-c1eb-4c16-bae2-b4856e1c41b6@i76g2000hsf.googlegroups.com...
> Hi All,
>
> I am trying to take a string that has been encrypted and decrypt it.
> Here is the string:   MMP61ubfQt4=
>
>
> The following code runs, but the result is an empty string at the
> end.  Can anyone see what I am doing wrong?
>
>
> Thanks,
> Jeff
>
>
>   Public Shared Function decryptUser(ByVal userName As String) As
> String
>        Dim inputInBytes() As Byte =
> Convert.FromBase64String(userName)
>        Dim key() As Byte = Convert.FromBase64String("ABCDEFG/
> LR3t49HgyCUXns9nfCpaAr0q")
>        Dim IV() As Byte = Convert.FromBase64String("ABCDEFGlS/U=")
>        Dim utf8encoder As UTF8Encoding = New UTF8Encoding
>        Dim tdesProvider As TripleDESCryptoServiceProvider = New
> TripleDESCryptoServiceProvider
>
>
>        Dim cryptoTransform As ICryptoTransform =
> tdesProvider.CreateDecryptor(key, IV)
>
>
>        Dim decryptedStream As MemoryStream = New MemoryStream
>        Dim cryptStream As CryptoStream = New
> CryptoStream(decryptedStream, cryptoTransform,
> CryptoStreamMode.Write)
>        cryptStream.Write(inputInBytes, 0, inputInBytes.Length)
>        cryptStream.FlushFinalBlock()
>        decryptedStream.Position = 0
>
>
>        Dim result(decryptedStream.Length - 1) As Byte
>        decryptedStream.Read(result, 0, decryptedStream.Length)
>        cryptStream.Close()
>        Dim myutf As UTF8Encoding = New UTF8Encoding
>        Return myutf.GetString(result)
>    End Function

date: Tue, 26 Aug 2008 10:24:42 +0200   author:   Patrice http://www.chez.com/scribe/