Class: BmpCrypt

Screenshots:

File	Role	Description
`ScreenShot.jpg`	Screen	Screenshot

Supplied by:

Name:	Chao-Chyuan Shih `<e-mail contact>`
Published packages:	2
Country:	United States - PHP professionals from United States looking for PHP jobs
Home page:	`http://www.elgorithms.com/`

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Innovation Award:

PHP Programming Innovation award nominee

April 2005
Number 3

Some sites use digital watermark techniques to mark their images in order to notice when the images are being used without permission by other sites.

However, this does not stop people from cleaning the visible marks and still show them without asking permission or giving proper credit to the original owners. This fact makes it difficult to take legal action.

An alternative solution consists in adding information to the image files that does not show in the image itself. Later, that information could be used to detect and prove that the images files were stollen.

This class provides a solution for encrypting and embedding in image files that can be used later to demonstrate the real origin of the images.

Manuel Lemos

Groups:

	Graphics	Colors, images, charts and picture formats	View top rated classes
	Cryptography	Encrypting, decrypting and hashing data	View top rated classes

Detailed description:

BmpCrypt is a class that uses the steganography technique to hide encrypted data within a bitmap image (.BMP).

This class can hide the data very well in 24 or 32 bit RGB images.

The class could be used to hide the data in indexed color images, for instance of 256 colors, but that would require adding a few functions to deal with the modifications to the color palette.

This class implements 4 levels of bit stream encoding. Each level uses an increasing number of bits per each byte in the RGB pixel table. Therefore, the higher level of encoding will hold more bytes of data in the bitmap image.

The class comes with a Web base example that shows how to decrypt an encrypted JPEG out of a BMP file and displays the output image.

There is also an example script that shows how to use the class to encrypt and decrupt data from the command line.

Applications that use this class:

No application links were specified for this class.

If you know an application of this package, send a message to the author to add a link here.

Files:

File	Role	Description
`BmpCrypt_Class.php`	Class	BmpCrypt
`BmpCrypt_CmdLine_Example.php`	Example	Command Line Example
`Decrypt_Webpage_Example.php`	Example	Web Page Example
`Dog.bmp`	Photo	Sample Image
`Horse.jpg`	Photo	Sample Image
`HorseInDog.bmp`	Output	Sample Output
`readme.txt`	Doc.	Read Me

Download all files: bmpcrypt.tar.gz bmpcrypt.zip

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