Xor Block Cipher Calculation of 2 Hex Values

[iCracked]

Hello everyone,

I have been trying for some hours now to accomplish my goal. I am trying to use XOR to combine 2 Hex values into 1 hex value of the same length. There exist calculators that accomplish what I need, but they only do it one at a time, and I would like to use excel to perform this function for many values.

I have two hexadecimal values,

Input1:

1747F6001E00DB266F5728FE5257645C

<tbody>
</tbody><colgroup><col></colgroup>

Input2:

1C6262C8DBF510F6554E28EA3BDA58AC

<tbody>
</tbody><colgroup><col></colgroup>

The module I have loaded is:

Option Explicit
Sub test()
'this sub is only present to demonstrate use of the function!
'it is not required to use the function.
Dim r As Range, retVal, sKey As String
sKey = Application.InputBox("Enter your key", "Key entry", "My Key", , , , , 2)
retVal = MsgBox("This is the key you entered:" & vbNewLine & Chr$(34) & sKey & Chr$(34) & vbNewLine & _
        "Please confirm OK or Cancel to exit", vbOKCancel, "Confirm Key")
If retVal = vbCancel Then Exit Sub
For Each r In Sheets("Sheet1").UsedRange
    If r.Interior.ColorIndex = 6 Then
        r.Value = XorC(r.Value, sKey)
    End If
Next r
End Sub


Function XorC(ByVal sData As String, ByVal sKey As String) As String
    Dim l As Long, i As Long, byIn() As Byte, byOut() As Byte, byKey() As Byte
    Dim bEncOrDec As Boolean
    'confirm valid string and key input:
    If Len(sData) = 0 Or Len(sKey) = 0 Then XorC = "Invalid argument(s) used": Exit Function
    'check whether running encryption or decryption (flagged by presence of "xxx" at start of sData):
    If Left$(sData, 3) = "xxx" Then
        bEncOrDec = False   'decryption
        sData = Mid$(sData, 4)
    Else
        bEncOrDec = True   'encryption
    End If
    'assign strings to byte arrays (unicode)
    byIn = sData
    byOut = sData
    byKey = sKey
    l = LBound(byKey)
    For i = LBound(byIn) To UBound(byIn) - 1 Step 2
        byOut(i) = ((byIn(i) + Not bEncOrDec) Xor byKey(l)) - bEncOrDec 'avoid Chr$(0) by using bEncOrDec flag
        l = l + 2
        If l > UBound(byKey) Then l = LBound(byKey)  'ensure stay within bounds of Key
    Next i
    XorC = byOut
    If bEncOrDec Then XorC = "xxx" & XorC  'add "xxx" onto encrypted text
End Function

But this just outputs: 'NAME!'

I have tried other modules suggested, but the output only ever comes out as [][][]nw[]s[] or something unreadable like that.

The expected result is:
0B2594C8C5F5CBD03A190014698D3CF

If anyone can help me, that would be greatly appreciated. Thanks in advance!!

 

[Rick Rothstein]

Missed that, thanks.

Function XorHex(ByVal h1 As String, ByVal h2 As String) As String
  Dim i             As Long

  If Len(h1) > Len(h2) Then h2 = String(Len(h1) - Len(h2), "0") & h2
  If Len(h2) > Len(h1) Then h1 = String(Len(h2) - Len(h1), "0") & h1

  For i = 1 To Len(h1) Step 8
    XorHex = XorHex & Right("0000000" & Hex("&H" & Mid(h1, i, 8) Xor "&H" & Mid(h2, i, 8)), 8)
  Next i
End Function

Row\Col	A​	B​	C​
1​	A000000000000000	0100000000000000	B1: =XorHex(A1,A2)
2​	A100000000000000

I don't think the answer that code produces is correct for these two values...

A000

A10000001

 

[shg]

I should quit while I'm behind

Function XorHex(ByVal h1 As String, ByVal h2 As String) As String
  Dim i             As Long

  If Len(h1) > Len(h2) Then h2 = String(Len(h1) - Len(h2), "0") & h2
  If Len(h2) > Len(h1) Then h1 = String(Len(h2) - Len(h1), "0") & h1

  For i = 1 To Len(h1) Step 8
    XorHex = XorHex & Right("0000000" & Hex("&H" & Mid(h1, i, 8) Xor "&H" & Mid(h2, i, 8)), Len(Mid(h2, i, 8)))
  Next i
End Function

Row\Col	A​	B​	C​
1​	A000	A10000A001	B1: =XorHex(A1,A2)
2​	A10000001

 

[pgc01]

Hi

This last version from shg seems to work fine.

I would just add a statement at the end to remove the leading 0's as they don't usually appear in numbers.


For ex., using MS Windows calculator:

A0100000000 Xor A0200000000 = 300000000

 

[pgc01]

P. S.

I just noticed that the OP left the leading 0 in the example posted, so maybe this could be an option (or don't even bother).

 

[shg]

If desired:

  XorHex = Replace(LTrim(Replace(XorHex, "0", " ")), " ", "0")

 

[FormR]

Cross-posted at How to use Excel to calculate bitwise XOR in hexadecimal format? - Stack Overflow

I do wonder if we'll ever see the OP again, but from this I guess it's unlikely.

@ICracked - If you do come back and can spare a few moments this if worth a read.

Excelguru Help Site - A message to forum cross posters