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 code shows the way to save the necessary secret information in Delphi. For your information, if you want to increase the size of the message, you should increase the value of CK_MAX_MSG_LEN below.
const CK_SINGATURE = '!CK!';
const CK_MAX_MSG_LEN = 1024*8;
function CKReadPassword(sFileName:string):string;
var
lenPWD: WORD;
buff: PAnsiChar;
sFile: TFileStream;
sEncryptedPWD: AnsiString;
begin
GetMem( buff, CK_MAX_MSG_LEN);
ZeroMemory( buff, CK_MAX_MSG_LEN);
if FileExists(sFileName) then begin
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);
if (lenPWD>CK_MAX_MSG_LEN) then begin
// Too long encrypted password
Result := False
end else begin
sFile.Write( PAnsiChar(sEncryptedPWD)^, lenPWD);
sFile.Write( lenPWD, 2);
sFile.Write( PAnsiChar(CK_SINGATURE)^, 4);
Result := True;
end;
sFile.Destroy;
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;
Below code provides better secure way to store secret key
uses IdCoder, IdCoderMIME, IdGlobal;
.
.
.
const CK_SINGATURE = '!CK!';
const CK_SINGATURE_KEY = 'ChunKang';
const CK_MAX_MSG_LEN = 1024*8;
const CK_ENC_VAR_RANGE=10;
function CKEncrypt(const Source:string; Salt:string): string;
var
i, lenSalt, key, keyWeight: Word;
InString: string;
begin
Result := '';
if (Salt = '') then begin
Result := Source;
end else begin
InString := TIdEncoderMIME.EncodeString(Source, IndyTextEncoding_UTF8);
lenSalt := Length(Salt);
keyWeight := 0;
for i := 1 to lenSalt do keyWeight := keyWeight + ord(Salt[i]);
keyWeight := keyWeight mod CK_ENC_VAR_RANGE;
for i := 1 to Length(InString) do
begin
key := ( ord(Salt[(i mod lenSalt) + 1]) mod CK_ENC_VAR_RANGE);
Result := Result + CHAR(Byte(InString[i]) + key - keyWeight);
end;
end;
end;
function CKDecrypt(const InString:string; Salt:string): string;
var
i, lenSalt, key, keyWeight: Word;
Target: string;
begin
if (Salt = '') then begin
Target := InString;
end else begin
lenSalt := Length(Salt);
keyWeight := 0;
for i := 1 to lenSalt do keyWeight := keyWeight + ord(Salt[i]);
keyWeight := keyWeight mod CK_ENC_VAR_RANGE;
Target := '';
for i := 1 to Length(InString) do
begin
key := ( ord(Salt[(i mod lenSalt) + 1]) mod CK_ENC_VAR_RANGE);
Target := Target + CHAR(Byte(InString[i]) - key + keyWeight);
end;
Result := TIdDecoderMIME.DecodeString(Target, IndyTextEncoding_UTF8);
end;
end;
function CKReadPassword(sFileName:string):string;
var
lenPWD: WORD;
buff: PAnsiChar;
tmp: AnsiString;
sFile: TFileStream;
sEncryptedPWD: AnsiString;
begin
GetMem( buff, CK_MAX_MSG_LEN);
ZeroMemory( buff, CK_MAX_MSG_LEN);
if FileExists(sFileName) then begin
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);
tmp := ansiString(string(buff));
tmp := CKDecrypt( tmp, CK_SINGATURE_KEY);
Result := Trim(tmp);
end;
sFile.Destroy;
end;
end;
FreeMem(buff);
end;
function CKUpdatePassword(sFileName, sPWD:String):Boolean;
var
buff: PAnsiChar;
sFile: TFileStream;
lenPWD, lenPWD_old: WORD;
sEncryptedPWD: AnsiString;
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 := CKEncrypt(sPWD, CK_SINGATURE_KEY);
lenPWD := Length(sEncryptedPWD);
if (lenPWD>CK_MAX_MSG_LEN) then begin
// too long message length
Result := False;
end else begin
sFile.Write( PAnsiChar(sEncryptedPWD)^, lenPWD);
sFile.Write( lenPWD, 2);
sFile.Write( PAnsiChar(CK_SINGATURE)^, 4);
Result := True;
end;
sFile.Destroy;
end else Result := False;
end;
FreeMem(buff);
end;
procedure Test;
begin
CKUpdatePassword( "c:\foo.exe", "hello kitty");
ShowMessage( CKReadPassword( "c:\foo.exe"));
end;