Hidden Files in images

[PhoenixRose]

I found a tutuorial on how to hide files using the following command in windows

copy /b file.txt + image.jpg newfimage.jpg

The file in now inside the image and can only be see by winrar or w/e program you are using to archive.

How can one do this in Linux?

[rcgreen]

You're looking for the cat command.


cat file.txt image.jpg > newfimage.jpg

[kahoona]

You're looking for the cat command.


cat file.txt image.jpg > newfimage.jpg

How do you get the "file.txt" back out of "newfimage.jpg"?

[kakariko81280]

Perhaps it isn't a text file you're after.

I've heard of something similar, but it used a zip file and a gif image. The reasoning runs something like gif file have their size defined at the start and the displaying app will discard anything after the point defined by this length. Zip files on the other hand define their length at the end and will discard anything before the eof - length.

The upshot of this is if you cat a gif and a zip together (in that order) you can open it in an image program/embed it in a web page/whatever and it will behave like an image. Open it in winzip/unzip/ark and it will decompress the zip.

As far as stenography is concerned this is a neat trick but it's a definite case of security through obscurity.

Of course all of this may well be irrelevant because txt files have no header information. For what you are describing you will need to read the jpeg header and then read from the end of the jpeg onwards. Or else just open it in a hex editor.

Chris...

[Viswanathan]

Hi,

Maybe if you just want a simple text file to be hidden into a picture, you can simply use

cat a.txt b.jpg > c.jpg

When you want to see the text, you can rather open the "c.jpg" file in the "vim" editor (or any other text editor for that case). Your text file will be in the first few lines of the .jpg file.

Regards
Visu