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Steganography III - Change only one Bit per Pixel

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3 Apr 2004CPOL1 min read 208.9K   5.8K   64   52
An article about hiding each byte of a message bit-by-bit in eight pixels.

Sample Image - steganodotnet3.png

Introduction

The application described in the last article Steganography II always added visible noise to the carrier bitmaps. This article is about splitting the bytes and hiding each bit in a different pixel. The hidden message is really invisible, because only the lowest bit of one color component is changed.

Background

Before reading this, you should have read at least part one, Steganography - Hiding messages in the Noise of a Picture. This article uses the application described in part one and two, but you don't need the features added in part two to understand this one.

End of the rainbow

Replacing a whole byte of a RGB color produces a rainbow pattern. This is how a white image (all pixels just white) looks like after hiding a text message:

typical colour noise

On a colorful photo, these rainbow pixels may be alright. In grayscale mode, the same message in the same picture looks like this:

typical grayscale noise

As you can see, too many bits of the pixels have been changed. Now, we’re going to spread each byte over eight pixels and make the rainbow disappear.

Get and set bits

spreading a byte over eight pixels

For each byte of the message, we have to:

  1. Grab a pixel.
  2. Get the first bit of the message byte.
  3. Get one color component of the pixel.
  4. Get the first bit from the color component.
  5. If the color-bit is different from the message-bit, set/reset it.
  6. Do the same for the other seven bits.

The C#-functions for getting and setting single bits are simple:

C#
private static bool GetBit(byte b, byte position){
	return ((b & (byte)(1 << position)) != 0);
}

private static byte SetBit(byte b, byte position, bool newBitValue){
	byte mask = (byte)(1 << position);
	if(newBitValue){
		return (byte)(b | mask);
	}else{
		return (byte)(b & ~mask);
	}
}

The rest of the code has not changed much. Hiding works like that now...

hide a message

...and extraction works like that:

extract a message

That's enough text for today. If you want to know the details, you should download the source.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


Written By
Software Developer
Germany Germany
Corinna lives in Hanover/Germany and works as a C# developer.

Comments and Discussions

 
GeneralRe: image hiding Pin
M.Arulraj10-Dec-08 0:41
M.Arulraj10-Dec-08 0:41 
GeneralRe: image hiding Pin
wwwwaaaalla7-Mar-10 6:46
wwwwaaaalla7-Mar-10 6:46 
QuestionCan anybody have the Base Paper for this Steganograhy -III Pin
pvprasad12-Apr-08 5:39
pvprasad12-Apr-08 5:39 
GeneralRe: Can anybody have the Base Paper for this Steganograhy -III Pin
Corinna John12-Apr-08 7:24
Corinna John12-Apr-08 7:24 
Generalimplementation USB Token Pin
Parneyan19-Jun-07 18:19
Parneyan19-Jun-07 18:19 
GeneralSteganografy in java Pin
rafaelvecchio9-May-06 2:51
rafaelvecchio9-May-06 2:51 
GeneralRe: Steganografy in java Pin
Corinna John9-May-06 5:45
Corinna John9-May-06 5:45 
GeneralSteganografy in java Pin
rafaelvecchio9-May-06 2:46
rafaelvecchio9-May-06 2:46 
Hi, I need implementation in java using image GIF ...
I need to help ..
Please

Rafa
GeneralRe: Steganografy in java Pin
andre.fiap.br22-Mar-07 10:44
andre.fiap.br22-Mar-07 10:44 
GeneralRe: Steganografy in java Pin
chaitumad24-May-09 19:50
chaitumad24-May-09 19:50 
GeneralRe: Steganografy in java Pin
andre.fiap.br25-May-09 7:32
andre.fiap.br25-May-09 7:32 
GeneralVC6++ HELP HOW Pin
cnncnn18-Aug-04 20:20
cnncnn18-Aug-04 20:20 
GeneralProblem with PNG Image Pin
lonelywind198221-Jun-04 22:09
lonelywind198221-Jun-04 22:09 
GeneralRe: Problem with PNG Image Pin
Corinna John22-Jun-04 20:31
Corinna John22-Jun-04 20:31 
GeneralSetting pixel in Bitmap Object Pin
Alexsander Antunes4-Mar-04 6:23
professionalAlexsander Antunes4-Mar-04 6:23 
GeneralRe: Setting pixel in Bitmap Object Pin
Corinna John4-Mar-04 20:16
Corinna John4-Mar-04 20:16 
GeneralRe: Setting pixel in Bitmap Object Pin
chaitumad24-May-09 19:50
chaitumad24-May-09 19:50 
GeneralGetBit/SetBit Pin
jmueller4-Nov-03 21:24
jmueller4-Nov-03 21:24 
GeneralRe: GetBit/SetBit Pin
Corinna John5-Nov-03 9:20
Corinna John5-Nov-03 9:20 
GeneralRe: GetBit/SetBit Pin
jmueller5-Nov-03 9:30
jmueller5-Nov-03 9:30 
GeneralRe: GetBit/SetBit Pin
Corinna John5-Nov-03 9:35
Corinna John5-Nov-03 9:35 
GeneralRe: GetBit/SetBit Pin
Corinna John4-Apr-04 21:56
Corinna John4-Apr-04 21:56 
Generalavi file Pin
unitecsoft6-Oct-03 8:25
unitecsoft6-Oct-03 8:25 
GeneralRe: avi file Pin
Corinna John6-Oct-03 19:38
Corinna John6-Oct-03 19:38 
GeneralRe: avi file Pin
Corinna John25-Oct-03 5:52
Corinna John25-Oct-03 5:52 

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