XOR and String

[Adriano]

Hello,

I have the following string headers:

Header 1, 2, 3, 4:

1.00TJ123456PPC
00000000DLGLGN
00000001TXBEG
Login:user=a, pswd=a"

As written in documentation, the checksum is "a negative value of the result
of an exclusive or operation of 'Header1 + Header2 + Header3 + Header4' in
32-digit format". The result is something like B8DEA5DC (8 digit hex.)
I would really appreciate if someone could help me on that, by examples,
anyhow.

Thanks in advance,
Adrano.

[=?UTF-8?B?R8O2cmFuIEFuZGVyc3Nvbg==?=]

Re: XOR and String

Adriano wrote:

Hello,
>
I have the following string headers:
>
Header 1, 2, 3, 4:
>
1.00TJ123456PPC
00000000DLGLGN
00000001TXBEG
Login:user=a, pswd=a"
>
As written in documentation, the checksum is "a negative value of the
result of an exclusive or operation of 'Header1 + Header2 + Header3 +
Header4' in 32-digit format". The result is something like B8DEA5DC (8
digit hex.)
I would really appreciate if someone could help me on that, by examples,
anyhow.
>
Thanks in advance,
Adrano.

I don't know what kind of format the documentation is meaning. I
searched for "32-digit format", and the few occurances that I found were
either totally unrelated or typos. It's possible that there is some 32
bit format, that would correspond with the format of the checksum, but
there is no logical way to interpret the strings as 32 bit values.

You have to find out how the text is interpreted as numbers, and how the
numbers are arranged and calculated.

Using an 8 bit character encoding, you can decode each character to an 8
bit value, but you have to arrange them into some larger entities. If
you simply xor the character codes and then add the result from each
header, you end up with a 10 bit number, not the 32 bit number needed to
fill up the 8 digit hexadecimal representation.

--
Göran Andersson
_____

http://www.guffa.com

[James Hahn]

Re: XOR and String

One possible procedure that makes partial sense for that description is:

Working from the start of each header, take one character from each string,
Combine them into a 32 bit value (ie, 4 characters at 8 bits each by bitwise
concatenation - left to right). Then XOR each 32-bit value. The strings are
assumed to be left-aligned, and missing characters are assumed to have a bit
value of zero.

The following Sub implements the above rule

Note that I have not attempted to work out what "a negative value of the
result" might mean. Does it mean the two's complement, or is it simply
confirming tha tthe result could be a negative number? You will need to get
some actual examples of headers and checksums then do a bitwise comparison
to the results of this operation to see what 'negative value' might mean
(assuming, of course, that this process correctly implements what the rest
of the description means).

Dim a(3) As String
Dim v(3) As Byte
a(0) = TextBox1.Text
a(1) = TextBox2.Text
a(2) = TextBox3.Text
a(3) = TextBox4.Text
Dim flag = True
Dim k As Integer = 0
While flag
flag = False
For i = 0 To 3
v(i) = 0
If a(i) <"" Then
flag = True
v(i) = BitConverter.Ge tBytes(CChar(a( i)))(0)
a(i) = a(i).Substring( 1)
End If
Next
If flag Then
k = k Xor BitConverter.To Int32(v, 0)
End If
End While
TextBox5.Text = Hex(k).PadLeft( 8, "0")


"Adriano" <adriano@mail.i twrote in message
news:%23lg0wZ4M JHA.5696@TK2MSF TNGP03.phx.gbl. ..

Hello,
>
I have the following string headers:
>
Header 1, 2, 3, 4:
>
1.00TJ123456PPC
00000000DLGLGN
00000001TXBEG
Login:user=a, pswd=a"
>
As written in documentation, the checksum is "a negative value of the
result of an exclusive or operation of 'Header1 + Header2 + Header3 +
Header4' in 32-digit format". The result is something like B8DEA5DC (8
digit hex.)
I would really appreciate if someone could help me on that, by examples,
anyhow.
>
Thanks in advance,
Adrano.

[Adriano]

Re: XOR and String

To get a whole picture please see http://www.epay.tj/img/MML-Packets.jpg

Regards
Adriano


"Adriano" <adriano@mail.i twrote in message
news:%23lg0wZ4M JHA.5696@TK2MSF TNGP03.phx.gbl. ..

Hello,
>
I have the following string headers:
>
Header 1, 2, 3, 4:
>
1.00TJ123456PPC
00000000DLGLGN
00000001TXBEG
Login:user=a, pswd=a"
>
As written in documentation, the checksum is "a negative value of the
result of an exclusive or operation of 'Header1 + Header2 + Header3 +
Header4' in 32-digit format". The result is something like B8DEA5DC (8
digit hex.)
I would really appreciate if someone could help me on that, by examples,
anyhow.
>
Thanks in advance,
Adrano.

[Adriano]

Re: XOR and String

Hello James,

Many thanks for your reply. I tried your example, but it does not produce
the correct checksum. Maybe I was wrong in explaining situation, sorry for
my bad English! See what they gave me for checking if I'm generating correct
packet and checkum:
2008-09-30 11:35:00 `SC`00541.00TJ1 23456PPC 00000000DLGLGN
00000001TXBEG Login:user=mmlo s, pswd=osmp 9afb81c7
Complete description of the packet is here:

http://www.epay.tj/img/MML-Packets.jpg

The packet I created seems okay, remote server is responding, now I get
"checksum error".
I'd really appreciate if you could help me to solve this headache.

Thanks in advance,
Adriano


"James Hahn" <jhahn@yahoo.co mwrote in message
news:OOIzL78MJH A.4600@TK2MSFTN GP06.phx.gbl...

One possible procedure that makes partial sense for that description is:
>
Working from the start of each header, take one character from each
string, Combine them into a 32 bit value (ie, 4 characters at 8 bits each
by bitwise concatenation - left to right). Then XOR each 32-bit value.
The strings are assumed to be left-aligned, and missing characters are
assumed to have a bit value of zero.
>
The following Sub implements the above rule
>
Note that I have not attempted to work out what "a negative value of the
result" might mean. Does it mean the two's complement, or is it simply
confirming tha tthe result could be a negative number? You will need to
get some actual examples of headers and checksums then do a bitwise
comparison to the results of this operation to see what 'negative value'
might mean (assuming, of course, that this process correctly implements
what the rest of the description means).
>
Dim a(3) As String
Dim v(3) As Byte
a(0) = TextBox1.Text
a(1) = TextBox2.Text
a(2) = TextBox3.Text
a(3) = TextBox4.Text
Dim flag = True
Dim k As Integer = 0
While flag
flag = False
For i = 0 To 3
v(i) = 0
If a(i) <"" Then
flag = True
v(i) = BitConverter.Ge tBytes(CChar(a( i)))(0)
a(i) = a(i).Substring( 1)
End If
Next
If flag Then
k = k Xor BitConverter.To Int32(v, 0)
End If
End While
TextBox5.Text = Hex(k).PadLeft( 8, "0")
>
>
"Adriano" <adriano@mail.i twrote in message
news:%23lg0wZ4M JHA.5696@TK2MSF TNGP03.phx.gbl. ..

>Hello,
>>
>I have the following string headers:
>>
>Header 1, 2, 3, 4:
>>
>1.00TJ123456PP C
>00000000DLGL GN
>00000001TXBE G
>Login:user=a , pswd=a"
>>
>As written in documentation, the checksum is "a negative value of the
>result of an exclusive or operation of 'Header1 + Header2 + Header3 +
>Header4' in 32-digit format". The result is something like B8DEA5DC (8
>digit hex.)
>I would really appreciate if someone could help me on that, by examples,
>anyhow.
>>
>Thanks in advance,
>Adrano.

>

[James Hahn]

Re: XOR and String

I think you have sufficient example code to solve the problem. What you now
need is a proper description of the algorithm. The description provided at
the page you have referenced is not a complete description by any means. As
mentioned, I have no idea what "a negative value of the result" might mean,
and that's obviously going to be important in getting the correct answer.
Also, it is purely guesswork that my bit concatenation is what is meant by
"'Header1 + Header2 + Header3 + Header4' in 32-digit format".

Without a proper specification of the problem it's not possible to provide a
comprehensive answer.

"Adriano" <adriano@mail.i twrote in message
news:%23%23ZCwb BNJHA.276@TK2MS FTNGP02.phx.gbl ...

Hello James,
>
Many thanks for your reply. I tried your example, but it does not produce
the correct checksum. Maybe I was wrong in explaining situation, sorry for
my bad English! See what they gave me for checking if I'm generating
correct packet and checkum:
2008-09-30 11:35:00 `SC`00541.00TJ1 23456PPC 00000000DLGLGN
00000001TXBEG Login:user=mmlo s, pswd=osmp 9afb81c7
Complete description of the packet is here:

http://www.epay.tj/img/MML-Packets.jpg

The packet I created seems okay, remote server is responding, now I get
"checksum error".
I'd really appreciate if you could help me to solve this headache.
>
Thanks in advance,
Adriano
>
>
"James Hahn" <jhahn@yahoo.co mwrote in message
news:OOIzL78MJH A.4600@TK2MSFTN GP06.phx.gbl...

>One possible procedure that makes partial sense for that description is:
>>
>Working from the start of each header, take one character from each
>string, Combine them into a 32 bit value (ie, 4 characters at 8 bits each
>by bitwise concatenation - left to right). Then XOR each 32-bit value.
>The strings are assumed to be left-aligned, and missing characters are
>assumed to have a bit value of zero.
>>
>The following Sub implements the above rule
>>
>Note that I have not attempted to work out what "a negative value of the
>result" might mean. Does it mean the two's complement, or is it simply
>confirming tha tthe result could be a negative number? You will need to
>get some actual examples of headers and checksums then do a bitwise
>comparison to the results of this operation to see what 'negative value'
>might mean (assuming, of course, that this process correctly implements
>what the rest of the description means).
>>
> Dim a(3) As String
> Dim v(3) As Byte
> a(0) = TextBox1.Text
> a(1) = TextBox2.Text
> a(2) = TextBox3.Text
> a(3) = TextBox4.Text
> Dim flag = True
> Dim k As Integer = 0
> While flag
> flag = False
> For i = 0 To 3
> v(i) = 0
> If a(i) <"" Then
> flag = True
> v(i) = BitConverter.Ge tBytes(CChar(a( i)))(0)
> a(i) = a(i).Substring( 1)
> End If
> Next
> If flag Then
> k = k Xor BitConverter.To Int32(v, 0)
> End If
> End While
> TextBox5.Text = Hex(k).PadLeft( 8, "0")
>>
>>
>"Adriano" <adriano@mail.i twrote in message
>news:%23lg0wZ4 MJHA.5696@TK2MS FTNGP03.phx.gbl ...

>>Hello,
>>>
>>I have the following string headers:
>>>
>>Header 1, 2, 3, 4:
>>>
>>1.00TJ123456P PC
>>00000000DLGLG N
>>00000001TXB EG
>>Login:user= a, pswd=a"
>>>
>>As written in documentation, the checksum is "a negative value of the
>>result of an exclusive or operation of 'Header1 + Header2 + Header3 +
>>Header4' in 32-digit format". The result is something like B8DEA5DC (8
>>digit hex.)
>>I would really appreciate if someone could help me on that, by examples,
>>anyhow.
>>>
>>Thanks in advance,
>>Adrano.

>>

>

[Clive Lumb]

Re: XOR and String

This is the sort of thing that drives me crazy...

So I did it for you.

I just had to fudge the result by "-1" to get it right, probably something
to do with how the two's-complement is used.

Note the the input strings have to be padded with spaces to conform to the
packet description. The spaces have been removed here by Outlook express
(GRRR)

Have fun working out how it works.

Public Class Form1
Dim MessageHeader As String = "1.00TJ123456PP C " '20 bytes
Dim SessionHeader As String = "00000000DL GLGN " '18 bytes
Dim TransactionHead er As String = "00000001TX BEG " '18 bytes
Dim OpInfo As String = "Login:user=mml os, pswd=osmp " 'N bytes, where N
is a multiple of 4 (probably pad it to 4 byte boundary?)
Dim targetChecksum As String = "9afb81c7"

Private Sub Button1_Click(B yVal sender As System.Object, ByVal e As
System.EventArg s) Handles Button1.Click
Dim MessageForXOR As String
Dim Hash As String
MessageForXOR = MessageHeader & SessionHeader & TransactionHead er &
OpInfo
If MessageForXOR.L ength \ 4 <MessageForXOR. Length / 4 Then
MessageBox.Show ("Incorrect length") 'Message is not a multiple
of 4 bytes
Else
Hash = CalcHash(Messag eForXOR, 4)
MsgBox(Hash)
End If
End Sub

Private Function CalcHash(ByVal StringToHash As String, ByVal Bytes As
Int16) As String
Dim I As Integer
Dim J As Integer
Dim Dummy As Int32
Dim Result As Int32
Dim temp As Int32
If Bytes 4 Then Return "overflow"
For I = 0 To Len(StringToHas h) - 1 Step Bytes 'step along the string
in chunks of Bytes
Dummy = 0
For J = Bytes - 1 To 0 Step -1 ' Build a "Bytes" long
representation of the chunk
' extract the byte we're interested in
temp = Asc(StringToHas h.Substring(I + (Bytes - J - 1), 1))
' shift bits to left
temp = temp << 8 * J
' add to running total for this block
Dummy = Dummy + temp
Next J
If I = 0 Then ' first block, noting to xor with
Result = Dummy
Else ' subsequent blocks, xor with running hash for the message
Result = Result Xor Dummy
End If
Next I
Result = -Result - 1 'take the negative
Return Conversion.Hex( Result)
End Function
End Class

[Adriano]

Re: XOR and String

Thank you very much Clive!

I really appreciate your help, that's really working!!!

Adriano


"Clive Lumb" <clumb2@gratuit _en_anglais.fr. invalidwrote in message
news:ez9ZBIRNJH A.276@TK2MSFTNG P02.phx.gbl...

This is the sort of thing that drives me crazy...
>
So I did it for you.
>
I just had to fudge the result by "-1" to get it right, probably something
to do with how the two's-complement is used.
>
Note the the input strings have to be padded with spaces to conform to the
packet description. The spaces have been removed here by Outlook express
(GRRR)
>
Have fun working out how it works.
>
Public Class Form1
Dim MessageHeader As String = "1.00TJ123456PP C " '20 bytes
Dim SessionHeader As String = "00000000DL GLGN " '18 bytes
Dim TransactionHead er As String = "00000001TX BEG " '18 bytes
Dim OpInfo As String = "Login:user=mml os, pswd=osmp " 'N bytes, where N
is a multiple of 4 (probably pad it to 4 byte boundary?)
Dim targetChecksum As String = "9afb81c7"
>
Private Sub Button1_Click(B yVal sender As System.Object, ByVal e As
System.EventArg s) Handles Button1.Click
Dim MessageForXOR As String
Dim Hash As String
MessageForXOR = MessageHeader & SessionHeader & TransactionHead er &
OpInfo
If MessageForXOR.L ength \ 4 <MessageForXOR. Length / 4 Then
MessageBox.Show ("Incorrect length") 'Message is not a multiple
of 4 bytes
Else
Hash = CalcHash(Messag eForXOR, 4)
MsgBox(Hash)
End If
End Sub
>
Private Function CalcHash(ByVal StringToHash As String, ByVal Bytes As
Int16) As String
Dim I As Integer
Dim J As Integer
Dim Dummy As Int32
Dim Result As Int32
Dim temp As Int32
If Bytes 4 Then Return "overflow"
For I = 0 To Len(StringToHas h) - 1 Step Bytes 'step along the
string in chunks of Bytes
Dummy = 0
For J = Bytes - 1 To 0 Step -1 ' Build a "Bytes" long
representation of the chunk
' extract the byte we're interested in
temp = Asc(StringToHas h.Substring(I + (Bytes - J - 1), 1))
' shift bits to left
temp = temp << 8 * J
' add to running total for this block
Dummy = Dummy + temp
Next J
If I = 0 Then ' first block, noting to xor with
Result = Dummy
Else ' subsequent blocks, xor with running hash for the message
Result = Result Xor Dummy
End If
Next I
Result = -Result - 1 'take the negative
Return Conversion.Hex( Result)
End Function
End Class
>

[=?ISO-8859-1?Q?G=F6ran_Andersson?=]

Re: XOR and String

Clive Lumb wrote:

This is the sort of thing that drives me crazy...
>
So I did it for you.
>
I just had to fudge the result by "-1" to get it right, probably something
to do with how the two's-complement is used.
>
Note the the input strings have to be padded with spaces to conform to the
packet description. The spaces have been removed here by Outlook express
(GRRR)
>
Have fun working out how it works.
>
Public Class Form1
Dim MessageHeader As String = "1.00TJ123456PP C " '20 bytes
Dim SessionHeader As String = "00000000DL GLGN " '18 bytes
Dim TransactionHead er As String = "00000001TX BEG " '18 bytes
Dim OpInfo As String = "Login:user=mml os, pswd=osmp " 'N bytes, where N
is a multiple of 4 (probably pad it to 4 byte boundary?)
Dim targetChecksum As String = "9afb81c7"
>
Private Sub Button1_Click(B yVal sender As System.Object, ByVal e As
System.EventArg s) Handles Button1.Click
Dim MessageForXOR As String
Dim Hash As String
MessageForXOR = MessageHeader & SessionHeader & TransactionHead er &
OpInfo
If MessageForXOR.L ength \ 4 <MessageForXOR. Length / 4 Then
MessageBox.Show ("Incorrect length") 'Message is not a multiple
of 4 bytes
Else
Hash = CalcHash(Messag eForXOR, 4)
MsgBox(Hash)
End If
End Sub
>
Private Function CalcHash(ByVal StringToHash As String, ByVal Bytes As
Int16) As String
Dim I As Integer
Dim J As Integer
Dim Dummy As Int32
Dim Result As Int32
Dim temp As Int32
If Bytes 4 Then Return "overflow"
For I = 0 To Len(StringToHas h) - 1 Step Bytes 'step along the string
in chunks of Bytes
Dummy = 0
For J = Bytes - 1 To 0 Step -1 ' Build a "Bytes" long
representation of the chunk
' extract the byte we're interested in
temp = Asc(StringToHas h.Substring(I + (Bytes - J - 1), 1))
' shift bits to left
temp = temp << 8 * J
' add to running total for this block
Dummy = Dummy + temp
Next J
If I = 0 Then ' first block, noting to xor with
Result = Dummy
Else ' subsequent blocks, xor with running hash for the message
Result = Result Xor Dummy
End If
Next I
Result = -Result - 1 'take the negative
Return Conversion.Hex( Result)
End Function
End Class
>

Nice work. :)

Let's clean up the code a bit. Making it always put four bytes in an int
makes the code simpler. Initialising the result removes the need to
check if it's the first block.

Private Function CalcHash(ByVal stringToHash As String) As String
' get character codes into an array
Dim chars As Byte() = Encoding.ASCII. GetBytes(string ToHash)
Dim result As Integer = 0
'step along the string in chunks of bytes
For i As Integer = 0 To chars.Length - 1 Step 4
' get 4 bytes as an int and xor into the result
result = result Xor BitConverter.To Int32(chars, i)
Next
' get the negative result, no idea where the extra -1 comes from
result = -result - 1
' make sure that the resulting string is always 8 hex digits
Return result.ToString ("x8")
End Function

--
Göran Andersson
_____

http://www.guffa.com

[Clive Lumb]

Re: XOR and String


"Göran Andersson" <guffa@guffa.co ma écrit dans le message de news:
%23bE$H5dNJHA.4 116@TK2MSFTNGP0 2.phx.gbl...

Clive Lumb wrote:

>This is the sort of thing that drives me crazy...
>>
>So I did it for you.
>>
>I just had to fudge the result by "-1" to get it right, probably
>something to do with how the two's-complement is used.
>>
>Note the the input strings have to be padded with spaces to conform to
>the packet description. The spaces have been removed here by Outlook
>express (GRRR)
>>
>Have fun working out how it works.
>>
>Public Class Form1
> Dim MessageHeader As String = "1.00TJ123456PP C " '20 bytes
> Dim SessionHeader As String = "00000000DL GLGN " '18 bytes
> Dim TransactionHead er As String = "00000001TX BEG " '18 bytes
> Dim OpInfo As String = "Login:user=mml os, pswd=osmp " 'N bytes, where
>N is a multiple of 4 (probably pad it to 4 byte boundary?)
> Dim targetChecksum As String = "9afb81c7"
>>
> Private Sub Button1_Click(B yVal sender As System.Object, ByVal e As
>System.EventAr gs) Handles Button1.Click
> Dim MessageForXOR As String
> Dim Hash As String
> MessageForXOR = MessageHeader & SessionHeader & TransactionHead er
>& OpInfo
> If MessageForXOR.L ength \ 4 <MessageForXOR. Length / 4 Then
> MessageBox.Show ("Incorrect length") 'Message is not a
>multiple of 4 bytes
> Else
> Hash = CalcHash(Messag eForXOR, 4)
> MsgBox(Hash)
> End If
> End Sub
>>
> Private Function CalcHash(ByVal StringToHash As String, ByVal Bytes
>As Int16) As String
> Dim I As Integer
> Dim J As Integer
> Dim Dummy As Int32
> Dim Result As Int32
> Dim temp As Int32
> If Bytes 4 Then Return "overflow"
> For I = 0 To Len(StringToHas h) - 1 Step Bytes 'step along the
>string in chunks of Bytes
> Dummy = 0
> For J = Bytes - 1 To 0 Step -1 ' Build a "Bytes" long
>representati on of the chunk
> ' extract the byte we're interested in
> temp = Asc(StringToHas h.Substring(I + (Bytes - J - 1),
>1))
> ' shift bits to left
> temp = temp << 8 * J
> ' add to running total for this block
> Dummy = Dummy + temp
> Next J
> If I = 0 Then ' first block, noting to xor with
> Result = Dummy
> Else ' subsequent blocks, xor with running hash for the
>message
> Result = Result Xor Dummy
> End If
> Next I
> Result = -Result - 1 'take the negative
> Return Conversion.Hex( Result)
> End Function
>End Class

>
Nice work. :)
>
Let's clean up the code a bit. Making it always put four bytes in an int
makes the code simpler. Initialising the result removes the need to check
if it's the first block.
>
Private Function CalcHash(ByVal stringToHash As String) As String
' get character codes into an array
Dim chars As Byte() = Encoding.ASCII. GetBytes(string ToHash)
Dim result As Integer = 0
'step along the string in chunks of bytes
For i As Integer = 0 To chars.Length - 1 Step 4
' get 4 bytes as an int and xor into the result
result = result Xor BitConverter.To Int32(chars, i)
Next
' get the negative result, no idea where the extra -1 comes from
result = -result - 1
' make sure that the resulting string is always 8 hex digits
Return result.ToString ("x8")
End Function
>
--
Göran Andersson
_____
http://www.guffa.com

Nicely done Göran,
After I had posted I was wondering how to grab 4 bytes at a time (I'm fairly
new to .Net), now I know.