DES

[fiazhnd]

Hi, guys, i want to decrypt DES in Pascal is there any example to learn, decrypting the ciphertext with the key?

[taazz]

there are 2 3rd party libraries that can help you with cryptography.
1) dcpcrypt http://wiki.lazarus.freepascal.org/DCPcrypt
2) Lockbox https://sourceforge.net/projects/tplockbox/?source=directory

both support des as far as I remember.
Take your pick.

[Thaddy]

Yup, both of these do the job.
But note DES is not considered a good or safe algorithm to use. I have seen Delphi code that can break DES: so that may be an alternative decrypt method... (Google for it...) Also, I wrote koldes.pas but that relies slightly on the KOL unit and is not considered for beginners.

[fiazhnd]

This code work for me perfectly 
However, i need a little help this key and Target is already define in script what if i want  to get "Key" from Edit1 and "Target" from Edit2

Mannually Enter Value in Edit1 and Edit2
Key: AA78BFB9A479B496
Target: 85104868F071C1F2
 

Code: Pascal  [Select][+][-]

1. procedure TForm1.Button1Click(Sender: TObject);
2. const
3.   Key: array [1..8] of Byte = (
4.     $12,$34,$56,$78,$90,$AB,$CD,$EF,
5.   );
6.   Target: array [1..8] of Byte = (
7.     $12,$34,$56,$78,$90,$AB,$CD,$EF
8.   );
9. var
10.   Result: array [1..8] of Byte;
11.   S: String;
12.   B: Byte;
13. begin
14.   FillByte(Result[1],SizeOf(Result),0);
15.   DCP_3des1.Init(Key,Length(Key) * 8,nil);
16.   DCP_3des1.EncryptECB(Target,Result);
17.   S := '';
18.   for B in Result do
19.     S := S + HexStr(B,2);
20.   Edit1.Caption := S;
21.   DCP_3des1.Reset;
22. end;

[fiazhnd]

I try But no luck yet any suggestion will be highly regarded

Code: Pascal  [Select][+][-]

1. procedure TForm1.Button3Click(Sender: TObject);
2. var
3.     Result: array [1..8] of Byte;
4.     Key,Target: Int64;
5.     S: String;
6.     B: Byte;
7.     Key1,Target1: String;
8.   begin
9.     Key := StrToInt64('$'+Edit1.Text);
10.     Key1:=  IntToHex(Key,8);
11.     Target:= StrToInt64('$'+Edit2.Text);
12.     Target1:=IntToHex(Target,8);
13.     FillByte(Result[1],SizeOf(Result),0);
14.     DCP_des1.Init(Key1,Length(Key1) * 8,nil);
15.     DCP_des1.DecryptECB(Target1,Result);
16.     S := '';
17.     for B in Result do
18.       S := S + HexStr(B,2);
19.     Edit3.Text := S;
20.     DCP_des1.Reset;
21.   end;

But Face following error
Invalid Key Size;
In File 'dcpcrypt.pas' at line 406;             

[Thaddy]

Your first code uses 3DES, not DES... Are you sure you want triple DES (3DES) ? because that is completely different from (the second code) DES?

[fiazhnd]

My original code is in reply #4, before was only to indicate that found a useful example.
I use DCP_des1 it converts to DES and provides an accurate result.

Now my issue is a Key size which acquires from Tedit.

For Sake of clarity, the below code gives correct DES result 10119803B3FFA5D0. But want to use "Key" and "Target" from TEdit.

Code: Pascal  [Select][+][-]

1. procedure TForm1.Button1Click(Sender: TObject);
2. const
3.   Key: array [1..8] of Byte = (
4.     $83,$10,$48,$68,$D0,$71,$C1,$B2
5.   );
6.   Target: array [1..8] of Byte = (
7.    $7C,68,$F7,$D1,$74,$08,$75,$0A  
8.   );
9. var
10.   Result: array [1..8] of Byte;
11.   S: String;
12.   B: Byte;
13. begin
14.   FillByte(Result[1],SizeOf(Result),0);
15.   DCP_des1.Init(Key,Length(Key) * 8,nil);
16.   DCP_des1.DecryptECB(Target,Result);
17.   S := '';
18.   for B in Result do
19.     S := S + HexStr(B,2);
20.   Edit1.Caption := S;
21.   DCP_3des1.Reset;
22. end;
23.  

[fiazhnd]

Code: Pascal  [Select][+][-]

1. Key: array [1..8] of Byte;

How Can i convert this string into Byte, Any Help guys........
   

Code: Pascal  [Select][+][-]

1. Key[1]:= (StrToInt('$'+Edit1.Text[1]+Edit1.Text[2]);
2.     showmessage(IntToStr(Key[1]));
3.     Key[2]:= StrToInt('$'+Edit1.Text[3]+Edit1.Text[4]);
4.     Key[3]:= StrToInt('$'+Edit1.Text[5]+Edit1.Text[6]);
5.     Key[4]:= StrToInt('$'+Edit1.Text[7]+Edit1.Text[8]);
6.     Key[5]:= StrToInt('$'+Edit1.Text[9]+Edit1.Text[10]);
7.     Key[6]:= StrToInt('$'+Edit1.Text[11]+Edit1.Text[12]);
8.     Key[7]:= StrToInt('$'+Edit1.Text[13]+Edit1.Text[14]);
9.     Key[8]:= StrToInt('$'+Edit1.Text[15]+Edit1.Text[16]);
10.  

[taazz]

why are you using strtoint? most of the times a simple type cast is what is needed. what are the context of edit1.text?

[fiazhnd]

thank you for your reply Mr. taazz;

In Edit1.Text i have value obtain from hex file 83104868D071C1B2.

Required following value like this;

Code: Pascal  [Select][+][-]

1.     Key[1]:= $83;
2.     Key[2]:= $10;
3.     Key[3]:= $48;
4.     Key[4]:= $68;
5.     Key[5]:= $D0;
6.     Key[6]:= $71;
7.     Key[7]:= $C1;
8.     Key[8]:= $B2;
9.  

i was try to convert to byte thats using strtoints

[taazz]

thank you for your reply Mr. taazz;

In Edit1.Text i have value obtain from hex file 83104868D071C1B2.

Required following value like this;

Code: Pascal  [Select][+][-]

1.     Key[1]:= $83;
2.     Key[2]:= $10;
3.     Key[3]:= $48;
4.     Key[4]:= $68;
5.     Key[5]:= $D0;
6.     Key[6]:= $71;
7.     Key[7]:= $C1;
8.     Key[8]:= $B2;
9.  

i was try to convert to byte thats using strtoints

that looks ok what is the result of the conversion? what the showmessage show?

[fiazhnd]

I think i am not able to explain well let me try again sir,

I have value 83104868D071C1B2 in Edit1 which i acquired from Hex file, what i want sir to convert value from Edit1 in the following shape;

Code: Pascal  [Select][+][-]

1.     Key[1]:= $83;
2.     Key[2]:= $10;
3.     Key[3]:= $48;
4.     Key[4]:= $68;
5.     Key[5]:= $D0;
6.     Key[6]:= $71;
7.     Key[7]:= $C1;
8.     Key[8]:= $B2;
9.  

So that's why i was trying to convert into byte  as above;

Code: Pascal  [Select][+][-]

1. Key[1]:= IntToStr('$'+Edit1.Text[1]+Edit1.Text[2]);

[Thaddy]

 DCP_3des1.Reset;?

[taazz]

I think i am not able to explain well let me try again sir,

I have value 83104868D071C1B2 in Edit1 which i acquired from Hex file, what i want sir to convert value from Edit1 in the following shape;

Code: Pascal  [Select][+][-]

1.     Key[1]:= $83;
2.     Key[2]:= $10;
3.     Key[3]:= $48;
4.     Key[4]:= $68;
5.     Key[5]:= $D0;
6.     Key[6]:= $71;
7.     Key[7]:= $C1;
8.     Key[8]:= $B2;
9.  

So that's why i was trying to convert into byte  as above;

Code: Pascal  [Select][+][-]

1. Key[1]:= IntToStr('$'+Edit1.Text[1]+Edit1.Text[2]);

start lazarus and selecct the menu project\NEw Project on the dialog select simple program then copy paste the code below execute it and paste the results here.

Code: Pascal  [Select][+][-]

1. program Project1;
2.  
3. uses sysutils;
4.  
5. const
6.   cKey : array [1..8] of Byte = ($83,$10,$48,$68,$D0,$71,$C1,$B2);
7.   cStr : string = '83104868D071C1B2';
8. var
9.   sKey : array[1..8] of Byte;// absolute cKey;
10.   vCntr :Integer;
11. begin
12.   sKey[1] := StrToInt('$' + cStr[01] + cStr[02]);
13.   sKey[2] := StrToInt('$' + cStr[03] + cStr[04]);
14.   sKey[3] := StrToInt('$' + cStr[05] + cStr[06]);
15.   sKey[4] := StrToInt('$' + cStr[07] + cStr[08]);
16.   sKey[5] := StrToInt('$' + cStr[09] + cStr[10]);
17.   sKey[6] := StrToInt('$' + cStr[11] + cStr[12]);
18.   sKey[7] := StrToInt('$' + cStr[13] + cStr[14]);
19.   sKey[8] := StrToInt('$' + cStr[15] + cStr[16]);
20.   writeln('cstr : ', cStr[1], cStr[2], ',', cStr[3], cStr[4], ',', cStr[5], cStr[6], ',',cStr[7], cStr[8], ',',
21.                      cStr[9], cStr[10],',', cStr[11],cStr[12],',', cStr[13],cStr[14],',',cStr[15],cStr[16] );
22.   WriteLn('sKey : ', IntToHex(sKey[1], 2),',', IntToHex(sKey[2], 2),',', IntToHex(sKey[3], 2),',', IntToHex(sKey[4],2), ',',
23.                      IntToHex(sKey[5], 2),',', IntToHex(sKey[6], 2),',', IntToHex(sKey[7], 2),',', IntToHex(sKey[8],2) );
24.   ReadLn;
25. end.
26.  

You should get something along the lines of

Code: Text  [Select][+][-]

1. cstr : 83,10,48,68,D0,71,C1,B2
2. sKey : 83,10,48,68,D0,71,C1,B2

[howardpc]

If you want direct conversion from the Text of a TEdit to an array of byte you could use this function

Code: Pascal  [Select][+][-]

1. type
2.   TOctByteArray = array[1..8] of Byte;
3.   Ts2 = string[2];
4.  
5. function ConvertEditTextToOctByte(anEdit: TEdit): TOctByteArray;
6.  
7.   function IsValidHexStr: Boolean;
8.   var
9.     c: Char;
10.   begin
11.     for c in anEdit.Text do
12.       if not (c in ['0'..'9','A'..'F','a'..'f']) then
13.         Exit(False);
14.     Result:=True;
15.   end;
16.  
17.   function StrToHex(s: Ts2): Byte;
18.  
19.     function GetValue(c: Char): Byte;
20.     begin
21.       if c in ['0'..'9'] then
22.         Exit(Ord(c) - 48)
23.       else if c in ['A'..'F'] then
24.         Exit(Ord(c) - 55)
25.       else if c in ['a'..'f'] then
26.         Exit(Ord(c) - 87)
27.       else Assert(True,'Error in hex string value');
28.     end;
29.   begin
30.     Exit(GetValue(s[2]) + 16*GetValue(s[1]));
31.   end;
32.  
33. var
34.   i: Integer;
35.   s: Ts2;
36. begin
37.   if not (Assigned(anEdit) and (Length(anEdit.Text)=16) and IsValidHexStr) then
38.     ShowMessage('Invalid text to convert')
39.   else
40.     for i:=Low(TOctByteArray) to High(TOctByteArray) do begin
41.       s:=Copy(anEdit.Text, Pred(i*2), 2);
42.       Result[i]:=StrToHex(s);
43.     end;
44. end;