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Adding a secret key in a program file dynamically, it should not make any side effects on the program - the I had some projects needs to put its own secret key when they needed, and the secret key should not be exist as an alternative file or stored in any secret place in order to have mobility - meaning that application having a secret key should be able to use in any PC/Laptop. The easiest approach can do that is adding an additional information at the end of the binary file, below . |
Below code shows the way to save the necessary secret information in Delphi.
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Following code enables you to hide secret key in a program fileFor your information, if you want to increase the size of the message, you should increase CK_MAX_MSG_LEN below.
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const CK_SINGATURE = '!CK!';
const CK_MAX_MSG_LEN = 1024;
function CKReadPassword(sFileName:string):string;
var
sFile: TFileStream;
lenPWD, lenPWD_old: WORD;
sEncryptedPWD: AnsiString;
buff: PAnsiChar;
begin
GetMem( buff, CK_MAX_MSG_LEN);
ZeroMemory( buff, CK_MAX_MSG_LEN);
if FileExists(sFileName) then begin
lenPWD_old := 0;
sFile := TFileStream.Create( sFileName, fmOpenRead);
if sFile.Handle<>THandle(nil) then begin
sFile.Seek( -4, soFromEnd);
sFile.Read( PAnsiChar(buff)^, 4);
if buff=CK_SINGATURE then
begin
// has master key, so need to erase it
sFile.Seek( -6, soFromEnd);
sFile.Read( lenPwd, 2);
sFile.Seek( -(lenPWD + 6), soFromEnd);
sFile.Read( PAnsIChar(buff)^, lenPWD);
Result := trim(string(buff));
end;
sFile.Destroy;
end;
end;
FreeMem(buff);
end;
function CKUpdatePassword(sFileName, sPWD:String):Boolean;
var
sFile: TFileStream;
lenPWD, lenPWD_old: WORD;
sEncryptedPWD: AnsiString;
buff: PAnsiChar;
begin
GetMem( buff, CK_MAX_MSG_LEN);
ZeroMemory( buff, CK_MAX_MSG_LEN);
if not FileExists(sFileName) then begin
Result := False;
end else begin
lenPWD_old := 0;
sFile := TFileStream.Create( sFileName, fmOpenReadWrite);
if sFile.Handle<>THandle(nil) then begin
sFile.Seek( -4, soFromEnd);
sFile.Read( PAnsiChar(buff)^, 4);
if buff=CK_SINGATURE then
begin
// has master key, so need to erase it
sFile.Seek( -6, soFromEnd);
sFile.Read( lenPwd, 2);
sFile.Seek( -(lenPWD + 6), soFromEnd);
lenPWD_old := lenPWD;
end else sFile.Seek( 0, soFromEnd);
while Length(sPWD)<lenPWD_old do sPWD := sPWD + ' ';
sEncryptedPWD := AnsiString(sPWD);
lenPWD := Length(sEncryptedPWD);
sFile.Write( PAnsiChar(sEncryptedPWD)^, lenPWD);
sFile.Write( lenPWD, 2);
sFile.Write( PAnsiChar(CK_SINGATURE)^, 4);
sFile.Destroy;
Result := True;
end else Result := False;
end;
FreeMem(buff);
end;
procedure TForm1.Button2Click(Sender: TObject);
begin
if not FileExists(eMasterFile.Text) then begin
ShowMessage( 'Please select program file you want');
end else begin
if (CKUpdatePassword( eMasterFile.Text, ePWD.Text)=True) then begin
ShowMessage('Successfully Changed !!');
Close;
end;
end;
end;
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