Exploiting crc with function

[Team dz]

Hi  all

Exploiting crc with function
I am working on a algorithm, despite all attempts, I did not reach a result
Does anyone of the members correct me where I am wrong or amend the algorithm for me

I want to modify the code to calculate the value of the checksum

Checksum calculates the sum for a 2-byte checksum

These are some values to show how the function or algorithm is calculated



[/quote]

Code: Pascal  [Select][+][-]

1.  function CRC(Data: AnsiString): UInt16;
2. var
3.  i,j,Sum,f : Integer;
4. begin
5.  Sum := $0000;
6.  for i := 1 to Length(Data) do
7.  
8.  
9.  begin
10.  
11.   Sum := Sum xor Ord(Data[i]);
12.   for j := 1 to 8 do
13.   begin
14.  
15.    f := Sum and $0001 ;
16.    Sum := Sum shr 1;
17.    if f = 1 then Sum := Sum xor $FFFF ;
18.    Sum:=sum;
19.   end;
20.  
21.  end;
22.  Result := UInt16(Sum);
23. end;
24.  

 Edit2.Text := IntToHex(CRC(Edit1.Text), 4);




Value  :35E01A00     crc  is  4A16

4ED8FFFFFFFF
4F4C00000000
8E8C00000001
CE8D00000002
0F4D00000003
4E8F00000004
8F4F00000005
CF4E00000006
0E8E00000007
4E8A00000008
8F4A00000009
CF4B0000000A
0E8B0000000B
4F490000000C
8E890000000D
CE880000000E
0F480000000
4E8000000010
8F4000000011


4A1635E01A00

[Thaddy]

I worked on crc16 some years ago.
See here: https://forum.lazarus.freepascal.org/index.php/topic,38279.msg259533.html#msg259533
Note there is a crc16 in hashes, I believe.

(Silly me, I wrote them - but forgot - and all are there in crc16.pas )

[Thaddy]

Did that help you?
These are all known standards known to me.

The original is here:
https://forum.lazarus.freepascal.org/index.php?action=dlattach;topic=38279.0;attach=22540