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Steganography as a Windows 8.1 RT (metro) app.

Hide your secret-eyes-only text in pictures!

Hide Text in Images with PicStealth

Real Steganography

Steganography is the art and science of hiding information by embedding messages within others. Steganography works by replacing bits of useless or unused data in a picture with bits of different, invisible information.

This “unused data” are the least significant bits (LSBs) in the image pixels. The LSB is the bit that when flipped from 0 to 1 or from 1 to 0, then no significant change will occur on the total value; meaning no (optical) significant change will occur to the picture.

Fake Steganography

There are other apps that claim to provide Steganography while in fact they don’t!  Those apps simply create a large file, containg the picture at position 1 followed by one or more files.  Such pseudo-steganography can be easily de-coded.  In fact, that’s nothing more than a ZIP file (without compression)   🙂

Size of Hidden Text

Assume that the image is 1000 pixels width by 800 pixels height, then we’ll have 1000 x 800 x 3 = 2.400.000 LSBs. The pixels are multiplied by 3 because each pixel has 3 elements (red, green, blue).  And as each character of our message to hide can be represented by 8 bits, then that image can hide 2.400.000 / 8 = 300.000 characters!

PNG Output

The picture containing the hidden message will be saved as an PNG image.  JPEG is a lossy format. The pixels and the hidden data would be be significantly altered when saving as JPEG.  This would result in an “disturbed” image.


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