Xor on string--help me please

[gaya3_k]

hi,
in my program i am Xor ing 3 strings , i am taking each character in the strings and Xor ing their ASCII values
but manually if i do Xor operation i am getting a different answer,
Can someone tell me how this result is coming,
x="7CA674" first string
lenx=len(x)

y="17767F" Second string
leny=len(y)

z="251270" Third string
lenz=len(z)

and my code is

For l = 1 To Len(x)

l Mid$(x, l, 1) = (Asc(Mid$(x, l, 1)) Xor Asc(Mid$(y,leny , 1)) Xor Asc(Mid$(z, lenz, 1)))

Next l
and my result is
x = 376456

[gaya3_k]

hi,
in my program i am Xor ing 3 strings , i am taking each character in the strings and Xor ing their ASCII values
but manually if i do Xor operation i am getting a different answer,
Can someone tell me how this result is coming,
x="7CA674" first string
lenx=len(x)

y="17767F" Second string
leny=len(y)

z="251270" Third string
lenz=len(z)

and my code is

Originally Posted by gaya3_k

For l = 1 To Len(x)

l Mid$(x, l, 1) = (Asc(Mid$(x, l, 1)) Xor Asc(Mid$(y,leny , 1)) Xor Asc(Mid$(z, lenz, 1)))

Next l

and my result is
x = 376456

[dglienna]

Bitwise operations can only be executed on BYTE data types. You'd have to convert.

CBYTE() might help

[gaya3_k]

Thanks alot for your reply,

Can u please tell me exactly what CBYTE will do to solve my problem.

Gayathri.k

[dglienna]

Each character is has a byte code. You can't use a part of a character, unless you convert it to a byte

Take a look at this link:
http://msdn.microsoft.com/en-us/libr...8VS.80%29.aspx

[WoF]

No, no.
You can xor integers as well as ASC values.
The problem is in the expression

 Mid$(x, l, 1) = (Asc(Mid$(x, l, 1)) Xor Asc(Mid$(y,leny , 1)) Xor Asc(Mid$(z, lenz, 1)))

Look what you are doing: from the y string and the z string you are always taking only ever the last character.
Make it so:

 Mid$(x, l, 1) = (Asc(Mid$(x, l, 1)) Xor Asc(Mid$(y,l , 1)) Xor Asc(Mid$(z, l, 1)))

l is the loop variable which increments with every step in the for loop. leny and lenz are constantly pointing the last character of y and z.

[gaya3_k]

thanks alot for your reply,
my exact code is

Private Sub XORIt(ByRef data As String, ByRef key As String, ByRef Y As String)
    Dim l As Long
    Dim lonLenKey As Long, lonKeyPos, lonLenTime, lonTmePos As Long
    Dim key_file As String
    key_file = "input\key.txt"
    
    lonLenKey = Len(key)
    
    For l = 1 To Len(data)
    
        lonKeyPos = lonKeyPos + 1
               If lonKeyPos > lonLenKey Then lonKeyPos = 1
        Mid$(data, l, 1) = (Asc(Mid$(data, l, 1)) Xor Asc(Mid$(key, lonKeyPos, 1)))
          
    Next l
    
    lonLenTime = Len(Y)
    For l = 1 To Len(data)
    
       
        lonTmePos = lonTmePos + 1
        If lonTmePos > lonLenTime Then lonKeyPos = 1
        Mid$(data, l, 1) = (Asc(Mid$(data, l, 1)) Xor Asc(Mid$(Y, lonTmePos, 1)))
          
    Next l
    
      
    
    Close #55
     Open key_file For Output As #55
     Print #55, Hex(data)
     Close #55
    
    
End Sub

what i am doing is ,each time my key,data and time will be different values taken from a text file as a string.
say for example,
data value is "7CA674"
key is "17767FA"
time is "25127000"

i will take the length of each string and i will do the xor operation, till the length of least string

my result for these value is 376456
Please someone justify this answer.

I am not getting how this result is coming


Thanks in advance,
Gayathri.K

[WoF]

No, I'm getting a different result. Let me show you how I did it:

Private Sub XORTest()
'data Value Is "7CA674"
'key is "17767FA"
'time is "25127000"
'result is 376456

  Dim dat$, key$, tim$ 'the strings
  Dim ld%, lk%, lt%, lm1%, lmin% 'being the lengths and minimum
  Dim i%, res$
  
  dat = "7CA674"
  key = "17767FA"
  tim = "25127000"
  
  ld = Len(dat)
  lk = Len(key)
  lt = Len(tim)
  
  'get the minimum in 2 steps for better overview
  lm1 = IIf(ld < lk, ld, lk)
  lmin = IIf(lt < lm1, lt, lm1)
  'lmin is now the shortest length
  
  For i = 1 To lmin
    res = res + Chr$(Asc(Mid$(dat, i, 1)) Xor Asc(Mid$(key, i, 1)) Xor Asc(Mid$(tim, i, 1)))
  Next
  MsgBox res
    
End Sub

The result is "4AG27B". I'm quite confident of the result.
I get the min length of all three strings, then in a loop I xor the ASC values of corresponding characters in same positions and add the Chr$() of the resultin value to the resulting string res$.
I'm confident, because I use a similar algorithm to xor strings for simple encoding.

Let me hint, that you are making a common error.

   Dim lonLenKey As Long, lonKeyPos, lonLenTime, lonTmePos As Long

lonKeyPos and lonLenTime wont be long. You have to declare As Long for every variable individually. Without it, it becomaes a variant.
If lazy for writing, you can use the shortcuts
Dim a&, b&, c&, d$, i%
a, b, and c become Long, d becomes string and i% will be integer.

Also you don't need longs for this. Integer is sufficient.

[gaya3_k]

Hi WoF
Thanks alot yar..............
I will try out as u said...
And will tell you

THANKS,
Gayathri.k