Re: DES ECB Encryption cannot decrypt

From: Per Vestergaard-Laustsen (pvl_at_capto.dk)
Date: 05/09/03 

Date: Fri, 9 May 2003 09:19:05 +0200

Sorry if I make you feel tired, but Base64 does not guarantee that the
characters in the string are converted to the same byte values as I the byte
values I converted from before calling the ActiveX component.

Yes in my excessive efforts to make this work, I have amongst a lot of other
things, tried to call the decryption with only 8 bytes at the time. Normally
I would just write the entire content of PIN to the decryption-stream, which
I have also tried.

I still do not know how the API can make a subjective assessment of the data
feed to it. I would expect that if I feed a wrong encrypted value to the
API, the decrypted value will simply not match the original unencrypted
value.

If you do not know exactly what goes wrong, and can not find out, just say
so. In that case I will just use another product for this task. I need to
move on now. I have a deadline.
"Ivan Medvedev [MS]" <ivanmed@online.microsoft.com> skrev i en meddelelse
news:#HMjJ9XFDHA.2264@TK2MSFTNGP12.phx.gbl...
> Per -
>
> your enctyped value as you show it here is 16 bytes, while it looks like
in
> the decrypting function you only feed 8 bytes to the cryptostream's Write
> method. Also, as I said in my previous post, I would recommend using
Base64
> encoding/decoding to do string <-> byte araay transformations.
> --Ivan
> This posting is provided "AS IS" with no warranties, and confers no
rights.
>
>
> "Per Vestergaard-Laustsen" <pvl@capto.dk> wrote in message
> news:uc0kjfUFDHA.2308@TK2MSFTNGP09.phx.gbl...
> > I am making an ActiveX component, and the application supposed to use it
> > only supports passing arguments as strings. Internally that particular
> > application only uses ASCII format for strings. I need to pass binary
> values
> > to and from the ActiveX component, where each byte can assume all values
> > from 0 to 255 (unsigned char).
> >
> > By the way the crypto API still will not work.
> >
> > I use DES, Mode=ECB. If I have the value to encrypt =
> > '01-47-11-00-00-00-00-00', the Key = 'EE-B7-55-E0-E7-35-B1-74' and IV =
> > '00-00-00-00-00-00-00-00'(since it should not be used when mode=ECB),
then
> > when encrypting I get 'C0-30-76-FF-4D-2C-3C-C5-8B-03-5A-A1-96-FB-9C-3C'.
> >
> > So far so good. But now when I try and decrypt that value, with the same
> Key
> > and IV, I get a bad data error. The Exception thrown has Hresult =
> > &HFFFFFFFF80131430 and _xcode = &HFFFFFFFFE0434F4D.
> >
> > Best regards Per Vestergaard-Laustsen, Denmark
> >
> > Code used :
> >
> > Imports System
> >
> > Imports System.Security.Cryptography 'in order to be able to en- / de-
> crypt
> >
> > Imports System.IO 'in order to use streams or memorystreams
> >
> > Imports System.Object 'in order to be able to create a BinaryReader
> >
> > Imports System.NotSupportedException 'in order to troubleshoot not
> supported
> > exceptions
> >
> > Imports System.Text.UTF8Encoding 'in order to be able to convert between
> > texts and bytearrays
> >
> > <ComClass(Crypto.ClassId, Crypto.InterfaceId, Crypto.EventsId)> _
> >
> > Public Class Crypto
> >
> > #Region "COM GUIDs"
> >
> > ' These GUIDs provide the COM identity for this class
> >
> > ' and its COM interfaces. If you change them, existing
> >
> > ' clients will no longer be able to access the class.
> >
> > Public Const ClassId As String = "E283E523-DDF6-41E5-99FD-D49BEA927F6B"
> >
> > Public Const InterfaceId As String =
> "63468760-BECB-43D0-B001-D656E7D83519"
> >
> > Public Const EventsId As String = "E42A8155-7740-4BE8-BB53-A845E0286A12"
> >
> > #End Region
> >
> > ' A creatable COM class must have a Public Sub New()
> >
> > ' with no parameters, otherwise, the class will not be
> >
> > ' registered in the COM registry and cannot be created
> >
> > ' via CreateObject.
> >
> > Public Sub New()
> >
> > MyBase.New()
> >
> > End Sub
> >
> > Protected Overrides Sub Finalize()
> >
> > MyBase.Finalize()
> >
> > End Sub
> >
> > Dim errPosition As String
> >
> > Dim globalexception As CryptographicException
> >
> > Public Sub test()
> >
> > If "0655" <> decrypt(encrypt("0655", "09689036", "80682702"),
"09689036",
> > "80682702") Then
> >
> > Console.WriteLine("Decrypted : " + decrypt(encrypt("0655", "09689036",
> > "80682702"), "09689036", "80682702"))
> >
> > Console.WriteLine("Unencrypted : " + "0655")
> >
> > End If
> >
> > End Sub
> >
> > Public Function encrypt(ByRef textPIN As String, ByRef textKey As
String,
> > ByRef textInitialValue As String) As String
> >
> > On Error GoTo ErrorHandler
> >
> > errPosition = "In encrypt function"
> >
> > Dim PIN() As Byte
> >
> > Dim Key() As Byte
> >
> > Dim InitialValue() As Byte
> >
> > PIN = GetEncryptKeyByteArray(textPIN)
> >
> > Key = GetEncryptKeyByteArray(textKey)
> >
> > InitialValue = GetEncryptKeyByteArray(textInitialValue)
> >
> > Dim cryptPIN As MemoryStream
> >
> > cryptPIN = New MemoryStream()
> >
> > Dim encryption As ICryptoTransform
> >
> > Dim cryptoService As New
> > System.Security.Cryptography.DESCryptoServiceProvider()
> >
> > 'cryptoService.Mode = CipherMode.ECB
> >
> > encryption = cryptoService.CreateEncryptor(Key, InitialValue)
> >
> > Dim encryptStream As New
> System.Security.Cryptography.CryptoStream(cryptPIN,
> > _
> >
> > encryption, _
> >
> > CryptoStreamMode.Write)
> >
> > encryptStream.Write(PIN, 0, CInt(PIN.Length)) 'encrypt writing to the
> > encryptionstream
> >
> > encryptStream.FlushFinalBlock() 'empty the temporary stream-buffer by
> force
> >
> > encrypt = byte2str(cryptPIN.ToArray())
> >
> > 'close the streams that has been opened
> >
> > encryptStream.Close()
> >
> > cryptPIN.Close()
> >
> > 'destroy the objects that has been created and used
> >
> > cryptPIN = Nothing
> >
> > encryption = Nothing
> >
> > cryptoService = Nothing
> >
> > encryptStream = Nothing
> >
> > Return encrypt
> >
> > ErrorHandler:
> >
> > textPIN = Err.Description
> >
> > textKey = errPosition
> >
> > End Function
> >
> > Public Function decrypt(ByRef textPIN As String, ByRef textKey As
String,
> > ByRef textInitialValue As String) As String
> >
> > 'On Error GoTo ErrorHandler
> >
> > errPosition = "In decrypt function"
> >
> > Dim i As Integer
> >
> > Dim cryptPIN As MemoryStream
> >
> > Dim PIN(15) As Byte
> >
> > Dim Key(7) As Byte
> >
> > Dim InitialValue(7) As Byte
> >
> > PIN = GetDecryptKeyByteArray(textPIN)
> >
> > Key = GetEncryptKeyByteArray(textKey)
> >
> > InitialValue = GetEncryptKeyByteArray(textInitialValue)
> >
> > cryptPIN = New MemoryStream()
> >
> > Dim buffer(1024) As Byte
> >
> > Dim decryption As ICryptoTransform
> >
> > Dim cryptoService As New DESCryptoServiceProvider()
> >
> > 'cryptoService.Mode = CipherMode.ECB
> >
> > decryption = cryptoService.CreateDecryptor(Key, InitialValue)
> >
> > 'the decryption takes place here
> >
> > Dim decryptStream As New CryptoStream(cryptPIN, _
> >
> > decryption, _
> >
> > CryptoStreamMode.Write)
> >
> > 'temp TEST
> >
> > Dim tempArrayOfByte(7) As Byte
> >
> > For i = 0 To 7
> >
> > tempArrayOfByte(i) = PIN(i)
> >
> > Next
> >
> > Try
> >
> > decryptStream.Write(tempArrayOfByte, 0, CInt(tempArrayOfByte.Length))
> > 'encrypt writing to the decryptionstream
> >
> > Catch exception As CryptographicUnexpectedOperationException
> >
> > globalexception = exception
> >
> > GoTo errorhandler
> >
> > End Try
> >
> > Try
> >
> > decryptStream.FlushFinalBlock() 'empty the temporary stream-buffer by
> force
> >
> > Catch exception As CryptographicException
> >
> > globalexception = exception
> >
> > GoTo ErrorHandler
> >
> > End Try
> >
> > 'end temp TEST
> >
> > Try
> >
> > decryptStream.Write(PIN, 0, CInt(PIN.Length)) 'encrypt writing to the
> > decryptionstream
> >
> > Catch exception As CryptographicUnexpectedOperationException
> >
> > globalexception = exception
> >
> > GoTo errorhandler
> >
> > End Try
> >
> > Try
> >
> > decryptStream.FlushFinalBlock() 'empty the temporary stream-buffer by
> force
> >
> > Catch exception As CryptographicException
> >
> > globalexception = exception
> >
> > GoTo ErrorHandler
> >
> > End Try
> >
> > decrypt = byte2str(cryptPIN.ToArray())
> >
> > 'close the streams that has been opened
> >
> > cryptPIN.Close()
> >
> > decryptStream.Close()
> >
> > 'destroy all objects used
> >
> > decryption = Nothing
> >
> > globalexception = Nothing
> >
> > cryptoService = Nothing
> >
> > Return decrypt
> >
> > ErrorHandler:
> >
> > If globalexception.Message = "" Then
> >
> > textPIN = Err.Description
> >
> > textKey = errPosition
> >
> > Else
> >
> > Dim inner As Exception
> >
> > textPIN = globalexception.Message
> >
> > inner = globalexception.InnerException()
> >
> > If Not inner Is Nothing Then
> >
> > textKey = inner.Message
> >
> > End If
> >
> > textInitialValue = globalexception.Source
> >
> > End If
> >
> > End Function
> >
> > Public Function calcXOR(ByVal Arg1 As Integer, ByVal Arg2 As Integer) As
> > Integer
> >
> > calcXOR = Arg1 Xor Arg2
> >
> > Return calcXOR
> >
> > End Function
> >
> > Private Function GetEncryptKeyByteArray(ByVal sPassword As String) As
> Byte()
> >
> > Dim byteTemp(7) As Byte
> >
> > 'sPassword = sPassword.PadRight(8) ' make sure we have 8 chars
> >
> > Dim a, b As String
> >
> > Dim i, n As Integer
> >
> > Dim bPW(7) As Byte
> >
> > n = 0
> >
> > For i = 1 To 22 Step 3
> >
> > a = Asc(Mid(sPassword, i, 1)) - Asc("0")
> >
> > If a > 9 Then a = a - 7
> >
> > If a < 0 Or a > 15 Then
> >
> > Err.Raise(vbObjectError + 513)
> >
> > End If
> >
> > b = Asc(Mid(sPassword, i + 1, 1)) - Asc("0")
> >
> > If b > 9 Then b = b - 7
> >
> > If b < 0 Or b > 15 Then
> >
> > Err.Raise(vbObjectError + 513)
> >
> > End If
> >
> > bPW(n) = a * 16 + b
> >
> > n += 1
> >
> > Next i
> >
> > 'Dim iCharIndex As Integer
> >
> > 'For iCharIndex = 0 To sPassword.Length - 1
> >
> > 'byteTemp(iCharIndex) = Asc(Mid$(sPassword, iCharIndex + 1, 1))
> >
> > 'Next
> >
> > 'byteTemp = UTF8.GetBytes(sPassword)
> >
> > Return bPW
> >
> > End Function
> >
> > Private Function GetDecryptKeyByteArray(ByVal sPassword As String) As
> Byte()
> >
> > Dim byteTemp(15) As Byte
> >
> > ' sPassword = sPassword.PadRight(16) ' make sure we have 16 chars
> >
> > Dim a, b As String
> >
> > Dim i, n As Integer
> >
> > Dim bPW(15) As Byte
> >
> > n = 0
> >
> > For i = 1 To 46 Step 3
> >
> > a = Asc(Mid(sPassword, i, 1)) - Asc("0")
> >
> > If a > 9 Then a = a - 7
> >
> > If a < 0 Or a > 15 Then
> >
> > Err.Raise(vbObjectError + 513)
> >
> > End If
> >
> > b = Asc(Mid(sPassword, i + 1, 1)) - Asc("0")
> >
> > If b > 9 Then b = b - 7
> >
> > If b < 0 Or b > 15 Then
> >
> > Err.Raise(vbObjectError + 513)
> >
> > End If
> >
> > bPW(n) = a * 16 + b
> >
> > n += 1
> >
> > Next i
> >
> > 'Dim iCharIndex As Integer
> >
> > 'For iCharIndex = 0 To sPassword.Length - 1
> >
> > 'byteTemp(iCharIndex) = Asc(Mid$(sPassword, iCharIndex + 1, 1))
> >
> > 'Next
> >
> > 'byteTemp = UTF8.GetBytes(sPassword)
> >
> > Return bPW
> >
> > End Function
> >
> > Private Function byte2str(ByRef bytes() As Byte) As String
> >
> > errPosition = "In byte2str"
> >
> > 'Dim i As Integer
> >
> > 'Dim tmpString As String
> >
> > 'Dim tmpStringOneChar As String
> >
> > 'tmpString = ""
> >
> > 'errPosition = "Before for loop in byte2str"
> >
> > 'For i = 1 To bytes.Length - 1
> >
> > 'tmpStringOneChar = Chr(bytes(i))
> >
> > 'tmpString = tmpString + tmpStringOneChar
> >
> > 'errPosition = "In for loop in byte2str"
> >
> > 'Next
> >
> > 'errPosition = "After for loop in byte2str"
> >
> > 'byte2str = tmpString
> >
> > byte2str = BitConverter.ToString(bytes)
> >
> > errPosition = "Before return from byte2str"
> >
> > Return byte2str
> >
> > End Function
> >
> > Public Function argtest(ByRef bytes As Byte()) As Object
> >
> > Return bytes
> >
> > End Function
> >
> > End Class
> >
> >
>
>

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