Triple DES Blues

[gchq]

Hi there

There is no problem encypting and decrypting a credit card number, but whilst encrypting the expiry date seems to work it blows out on decryption with "Invalid length for a Base-64 char array"

Any ideas?

Here is the code - the keys are generated from a 40+ string held on another database (ReturnKey)....

Private Function IV_192()
        Dim vKey As String = ReturnKey()
        
        'Make the IV Key
        Dim ss1 As String = Left(vKey, 10)
        Dim ss2 As String = Right(vKey, 25)
        Dim ss3 As String = ss1 & ss2

        Dim vIV_192() As Byte = Encoding.ASCII.GetBytes(ss3.ToCharArray)
        Return vIV_192
    End Function


    Private Function KEY_192()
        Dim vKey As String = ReturnKey()
        
        'Make the key
        Dim s1 As String = Left(vKey, 30)
        Dim s2 As String = Right(vKey, 5)
        Dim s3 As String = s1 & s2
        ' Hash this
        vKey = EncryptVariable(s3)
        Dim vKEY_192() As Byte = Encoding.ASCII.GetBytes(vKey.ToCharArray)
        Return vKEY_192
    End Function


    'TRIPLE DES encryption
    Private Function EncryptTripleDES(ByVal value As String) As String
        If value <> "" Then
            Dim cryptoProvider As TripleDESCryptoServiceProvider = _
                New TripleDESCryptoServiceProvider()
            Dim ms As MemoryStream = New MemoryStream()
            Dim cs As CryptoStream = _
                New CryptoStream(ms, cryptoProvider.CreateEncryptor(KEY_192(), IV_192), _
                    CryptoStreamMode.Write)
            Dim sw As StreamWriter = New StreamWriter(cs)

            sw.Write(value)
            sw.Flush()
            cs.FlushFinalBlock()
            ms.Flush()

            'convert back to a string
            Return Convert.ToBase64String(ms.GetBuffer(), 0, ms.Length)
        Else
            Return "Error"
        End If
    End Function


    'TRIPLE DES decryption
    Private Function DecryptTripleDES(ByVal value As String) As String
        
        If value <> "" Then
            Dim cryptoProvider As TripleDESCryptoServiceProvider = _
                New TripleDESCryptoServiceProvider()
            value = value.Replace(" ", "+")
            'convert from string to byte array
            Dim buffer As Byte() = Convert.FromBase64String(value)
            Dim ms As MemoryStream = New MemoryStream(buffer)
            Dim cs As CryptoStream = _
                New CryptoStream(ms, cryptoProvider.CreateDecryptor(KEY_192, IV_192), _
                    CryptoStreamMode.Read)
            Dim sr As StreamReader = New StreamReader(cs)

            Return sr.ReadToEnd()
        Else
            Return "Error"
        End If
    End Function

Function EncryptVariable(ByVal vName As String)
        Dim vEncryptName As String
        Dim Ue As New UnicodeEncoding()
        Dim ByteSourceText() As Byte = Ue.GetBytes(vName)
        Dim MD5 As New MD5CryptoServiceProvider()
        Dim ByteHash() As Byte = MD5.ComputeHash(ByteSourceText)
        Dim vComp As String = Convert.ToBase64String(ByteHash)
        vEncryptName = vComp
        Return vEncryptName
    End Function

[gchq]

Ooops - the DB column was set to varchar(6) from the original mmyyyy format! The encrypted string was being truncated! Now it works as it should!

[PRR]

One suggestion would be use of

System.Text.Encoding.UTF8.GetBytes();

instead of

System.Text.Encoding.ACSII.GetBytes();