Gif Steganography

What is Steganography?

Imagine you want to send a secret message. You will encode your message and send it. By doing this, you still risk attracting the attention of those who will see it pass. You sent a secret message, but you didn't do it secretly!

To send it discreetly, you have to hide your message inside another message, of an innocuous aspect this one. It's Steganography!

How does it work?

Generally steganography algorithms slightly modify the pixels of an image in such a way that the human eye does not see any difference (modification of the LSB, manipulation of the DCTs...). However, for a computer, this difference compared to the original image, is visible.

This application uses GIF images because they have a property that allows to produce a new image with pixels strictly identical to the original and a completely standard structure. Nothing is added, no pixels are modified!

What messages can be camouflaged?

In addition to a text message, you can embed any file.

The size of the messages does not depend on the dimensions of the image, but only on the number of colors used and the number of animations in the image. Thus, an animated GIF image, even of a few pixels, with 5 images in 256 colors can store a message of about one kilobyte (or more if the message can be compressed)!

Data is compressed (DEFLATE mode) to increase storage capacity. You can also limit yourself to 64 characters in the message to increase its size by 33%.

If the message is too big, the application can extend or add color tables automatically to increase the storage capacity (the image nevertheless remains in accordance with the GIF standard). Note however that if it is not necessary to add palettes, the size of the file created is practically unchanged, which makes the image all the less suspicious!

What security for the message?

For added security, messages are encrypted with 256-bit AES (GCM mode) with a cryptographic key generated by a PBKDF2 algorithm (16,000 iterations) from a password.

Can we share these images?

The images produced being completely 'normal', you can send them by any means without the message being altered, provided of course that the file format is not modified (for example in mp4 video as with WhatsApp). On the other hand, the message will generally be destroyed if the image is edited.

Personal Data

Your personal data is preserved because all the processing is carried out entirely on your device, no data is transmitted to an external server. No account is required.