Re: Need help decrypting

From: Valery Pryamikov (valery_at_harper.no)
Date: 02/23/05 

Date: Wed, 23 Feb 2005 00:21:43 +0100

Just a brief look (not checking anyting else): in your encrypt function you
derive bytes from "passwd" password, while in your decrypt function you use
"pa[]ss!!wo//dd".

-Valery.
http://www.harper.no/valery

"Steve Long" <Steve_Noneya@NoSpam.com> wrote in message
news:%23$4F0oPGFHA.2032@tk2msftngp13.phx.gbl...
> Hello,
> I'm wondering if somebody can help me figure out how to decrypt data. I
> seem
> to be able to encrypt data but have not been able to decrypt the very data
> that I've encrypted. I know it's because I'm just not understanding the
> whole process but I'm obviously just not getting it. Here's the encryption
> function I'm using:
>
> Private Sub Encryptpwd()
> Dim cdk As PasswordDeriveBytes = New PasswordDeriveBytes("passwd",
> Nothing)
> Dim iv() As Byte = {0, 0, 0, 0, 0, 0, 0, 0}
> Dim key() As Byte = cdk.CryptDeriveKey("RC2", "SHA1", 128, iv)
>
> Console.WriteLine(key.Length * 8)
> ' Set up an RC2 object to encrypt with the derived key
> Dim rc2 As RC2CryptoServiceProvider = New RC2CryptoServiceProvider
> rc2.Key = key
> Dim b() As Byte = {21, 22, 23, 24, 25, 26, 27, 28}
> rc2.IV = b
> Dim plaintext() As Byte = Encoding.UTF8.GetBytes("iiMap")
> Dim ms As New MemoryStream
> Dim cs As CryptoStream = New CryptoStream(ms, rc2.CreateEncryptor(),
> _
> CryptoStreamMode.Write)
> cs.Write(plaintext, 0, plaintext.Length)
> cs.Close()
> Dim result() As Byte = ms.ToArray()
> Dim asc As New ASCIIEncoding
> txtResult.Text = asc.GetString(result)
> ms.Close()
> End Sub
>
> When I try to decrypt the text that's in txtResult.Text, my result is
> always
> and empty string:
>
> Private Sub Decryptpwd()
> Dim cdk As PasswordDeriveBytes = New
> PasswordDeriveBytes("pa[]ss!!wo//dd", Nothing)
> Dim iv() As Byte = {0, 0, 0, 0, 0, 0, 0, 0}
> Dim key() As Byte = cdk.CryptDeriveKey("RC2", "SHA1", 128, iv)
>
> Console.WriteLine(key.Length * 8)
> ' Set up an RC2 object to encrypt with the derived key
> Dim rc2 As RC2CryptoServiceProvider = New RC2CryptoServiceProvider
> rc2.Key = key
> Dim b() As Byte = {21, 22, 23, 24, 25, 26, 27, 28}
> rc2.IV = b
> Dim plaintext() As Byte = Encoding.UTF8.GetBytes(txtResult.Text)
>
> Dim ms As New MemoryStream
> Dim cs As CryptoStream = New CryptoStream(ms, rc2.CreateDecryptor(),
> _
> CryptoStreamMode.Write)
> cs.Write(plaintext, 0, plaintext.Length)
> Dim result(plaintext.Length - 1) As Byte
> ms.Read(result, 0, result.Length - 1)
> Dim asc As New ASCIIEncoding
> txtDecrypt.Text = asc.GetString(result)
> cs.Close()
> ms.Close()
> End Sub
>
> I would very much appreciate someone setting me straight on this issue.
> Thanks in advance
> Steve
>
>
>

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