asked on

encode and discode string type in Delphi

Now i have create a table as loginuser table.I need encode the Password string in delphi and save it into loginuser table.But i don't know what function can do that.But i am so busy that i can write a customer function to encryption that.how to do it well?I need you help.Thanks!
And then i find a encrypt function,but run with something wrong.
error message is : key is out of range .why?
function Encrypt(const S: String; Key: Word): String;
Var
I: byte;
const
C1 = 52845;
C2 = 11719;
Key = 1234;
begin
Result[0] := S[0];
for I := 1 to Length(S) do
begin
Result[I] := char(byte(S[I]) xor (Key shr 8));
Key := (byte(Result[I]) + Key) * C1 + C2;
end;
end;

florisb

download component to do it good and easy... ...check torry's pages f.e.

I used simplistic password functions to code and decode passwords. drop two edits and two button on form and check code if you like. It's enough for some purposes:

(just made a new test, this is not from a project I made....:-)

procedure TForm1.Button2Click(Sender: TObject);
var
s : string;
x,i : integer;
begin
s := edit1.text;
for x := 1 to length(s) do
begin
i := ord(s[x]);
inc(i);
i := 2*i;
dec(i);
s[x] := char(i);
end;
edit2.text := s;
end;

procedure TForm1.Button3Click(Sender: TObject);
var
s : string;
x,i : integer;
begin
s := edit2.text;
for x := 1 to length(s) do
begin
i := ord(s[x]);
inc(i);
i := i div 2;
dec(i);
s[x] := char(i);
end;
edit1.text := s;

end;

Luck,
Floris.

Surme

ASKER

Edited text of question.

Surme

ASKER

Edited text of question.

Surme

ASKER

Thanks Floris.
But you answer is simplistic.
i need a good encrypt way.
Could you answer me again!

ASKER CERTIFIED SOLUTION

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florisb

read your question again, copy-pasted code. Gave error because:
-key is const and you try to change it
-length result not set before filling like array.

Changed it a bit:

function TForm1.Encrypt(S: String): String;
Var
I: byte;
res : string;
C1,C2, Key : Word;
begin
C1 := 52845;
C2 := 11719;
Key := 1234; //

for I := 1 to Length(S) do
begin
res:= res + char(byte(S[I]) xor (Key shr 8));
Key := (byte(Res[I]) + Key) * C1 + C2;
end;
result := res;
end;

procedure TForm1.Button4Click(Sender: TObject);
begin
edit3.text := Encrypt(edit3.text);
end;

seems to work Okee. normal users don;t crack this kind of passwords. Not normal users, well....:-)

craig_capel

if anyone has ever read about how to crack encryption it seems that no way is ever going to be safe, its just a matter of watching how the code is executing, and then just reverse what is happening like this

to encode 564234

blah
blah
blah

9jd883k is the outcome, the "hackers" just reverse the process, so really its only a matter of time, and i am not a hacker just like to know how they get to crack programs in the first place, and has made me wonder about a few things....

Craig C.

Surme

ASKER

Thanks florisb,and then i try your function,but still failure and the same error Msg.When i change key datatype from word into longword.success!

Thanks craig_capel
You say right.

Thanks Dave
Good site you offered.