Revelation

Aug 28 2005, 09:43 AM

You might know I am a Delphi programmer, and I made this app: Picture Encrypter. It is capable of hiding text in an image by altering the color a little. This change is not visible, so no one will notice. If you want to decrypt the image, load the encrypted image and press decrypt. Then you will have to load the image without the text. If someone else has made an application concerning security/cryptography, don't be afraid to post it!

Download it here.

Code:

 


unit MainUnit;

interface

uses
 SysUtils, Graphics, Forms, Dialogs, ExtCtrls, StdCtrls, ExtDlgs,
 Classes, Controls;

type
 TMainForm = class(TForm)
   BtnDec: TButton;
   BtnEnc: TButton;
   Img1: TImage;
   Img2: TImage;
   TextMem: TMemo;
   LoadBtn: TButton;
   OpenPictureDialog: TOpenPictureDialog;
   SavePictureDialog: TSavePictureDialog;
   OpenPictureDialog2: TOpenPictureDialog;
   ScrollBox1: TScrollBox;
   ScrollBox2: TScrollBox;
   SaveBtn: TButton;
   Label1: TLabel;
   Label2: TLabel;
   procedure BtnDecClick(Sender: TObject);
   procedure BtnEncClick(Sender: TObject);
   procedure LoadBtnClick(Sender: TObject);
   procedure SaveBtnClick(Sender: TObject);
 end;

var
 MainForm: TMainForm;

implementation

uses Math;

{$R *.dfm}

procedure TMainForm.BtnDecClick(Sender: TObject);
var
 x, y: Integer;
 CharMask, AChar: Byte;
begin
 if OpenPictureDialog2.Execute then
 begin
   try
     Img2.Picture.LoadFromFile(OpenPictureDialog2.FileName);
   except
     raise Exception.Create('Error reading bitmap!');
     Exit;
   end;

   TextMem.Clear; // Remove the text
   CharMask := $80; // 128
   AChar := 0;

   with Img2.Picture.Bitmap do
   begin
     for y := 0 to Pred(Height) do
     begin
       for x := 0 to Pred(Width) do
       begin
         if (Img1.Picture.Bitmap.Canvas.Pixels[x, y] <>
           Canvas.Pixels[x, y]) then
           AChar := AChar or CharMask; // Build the character
         CharMask := CharMask shr 1;

         if CharMask = 0 then // If the mask is 0, the decryption of a char is
         begin // completed
           TextMem.Text := TextMem.Text + Char(AChar);
           CharMask := $80;
           AChar := 0;
         end;
       end;
     end;
   end;
 end
 else
   raise Exception.Create('Could not complete the requested action!');
end;

procedure TMainForm.BtnEncClick(Sender: TObject);
var
 x, y, a, b: Integer;
 CharMask: Byte;
begin
 Img2.Picture.Assign(Img1.Picture); // Assign the source to the target image
 x := 0;
 y := 0;

 with Img2.Picture.Bitmap do
 begin
   PixelFormat := pf32bit;

   for a := 1 to Length(TextMem.Text) do
   begin
     CharMask := $80; // 128

     for b := 1 to 8 do // 8 bytes for every letter to be encrypted
     begin
       // Check if the bit in the byte is not a 0
       if (Byte(TextMem.Text[a]) and CharMask <> 0) then
         Canvas.Pixels[x, y] := Canvas.Pixels[x, y] xor $1; // xor the value


       x := Succ(x) mod Width; // Move to the next pixel
       if (x = 0) then
         if y = Height then
         begin
           raise Exception.Create('The text doesn''t fit in the image!');
           Break;
         end
         else
           Inc(y);
       // Move on to the next bit
       CharMask := CharMask shr 1;
     end;

     if B <> 9 then
       Break; // if the exception was created, stop the second loop!
   end;
 end;

 SaveBtn.Enabled := True;
end;

procedure TMainForm.LoadBtnClick(Sender: TObject);
begin
 if OpenPictureDialog.Execute then
 try
   Img1.Picture.LoadFromFile(OpenPictureDialog.FileName);
 except
   raise Exception.Create('Error reading bitmap!');
   Img1.Picture.Bitmap := nil;
 end;

 BtnEnc.Enabled := Img1.Picture.Graphic <> nil;
 BtnDec.Enabled := BtnEnc.Enabled;
end;

procedure TMainForm.SaveBtnClick(Sender: TObject);
begin
 if SavePictureDialog.Execute then
 try
   Img2.Picture.SaveToFile(SavePictureDialog.FileName);
 except
   raise Exception.Create('Error saving bitmap!');
 end;
end;

end.


Revelation

Sep 1 2005, 02:37 PM

It is insecure

Xor-ing isn't a great idea for encryptions if you don't do it multiple times and then hash it or something. Notice when you use the plain text as a key all the chars are spaces.

If you want to make an uncrackable encryption, use a one time pad. This means you add the byte value of every character with the one at the same x-position in the password (this should equal the size of the plain text) and then flip it back to a character.

btw, I will post the source soon.

Code:

 

if Length(PlainText) = Length(Key) then

Revelation

Sep 1 2005, 06:55 PM

Code:

 

if Length(PlainText) = Length(Key) then

or something like that?

Don't make it a byte but a word or whatever that may be in VB.

Code:

 


x := 1;
   for i := 1 to iText do
   begin
     Text := Memo1.Lines.Text[i];
     PW := sPw[x];
     if Sender = Button1 then
       Text := Chr(Ord(Text) + Ord(PW))
     else
       Text := Chr(Ord(Text) - Ord(PW));
     Memo2.Lines.Text := Memo2.Lines.Text + Text;
    Inc(i);
     if x = iPW then x := 1;
   end;


Revelation

Sep 2 2005, 12:47 PM

Nope, it will start all over again from 0. This is not a problem though. If you substract it later, it will go from 0 to 255 .

I see what you mean. Note that this method is insecure and crackable, if you use a char for every plain text char it will be uncrackable.

Try something like this:

Code:

 


x := 1;
   for i := 1 to iText do
   begin
     Text := Memo1.Lines.Text[i];
     PW := sPw[x];
     if Sender = Button1 then
       Text := Chr(Ord(Text) + Ord(PW))
     else
       Text := Chr(Ord(Text) - Ord(PW));
     Memo2.Lines.Text := Memo2.Lines.Text + Text;
    Inc(i);
     if x = iPW then x := 1;
   end;


where x is an integer, Text a string, i an integer, iText the length of the Text, PW a char, sPw the string of the password, iPw the length of the password and memo2 a Memo (something like a richedit).

I made this app once, if the sender is button1 it will encrypt, else decrypt. It will add the ordinal value of the character (the byte) with the password one. If x reaches the length of the password, it will set it back to one. I hope you understand the code