How to hide files in JPEG pictures | Hacker News Reader

How to hide files in JPEG pictures

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11 pointsgrrow9 comments

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This makeahistory site is spam. All the articles are copied from other sites. This one was copied and pasted from:

http://www.online-tech-tips.com/computer-tips/hide-file-in-p...

The images are even hotlinked from the original.

Further, the poster, grrow, had made no comments. They just post links to makeahistory "articles".

First: I wonder if all jpeg viewers accept the "new file", I guess some will choke on the altered files.

Second: If this works it might be possible to distribute hidden files through profile pictures (one facebook and friends) :) I'm glad I never store original jpegs in my web projects, but rather saved processed versions (resized etc).

1. Most of them work, yes (especially all browsers).

2. Bookchan uses that method to distribute ebooks. People simply post the book cover picture with the ebook attached in .rar on an imageboard. (eg. http://bookchan.wikidot.com/mario-puzo)

This works most of the time because jpg files are decoded from the first byte until the last byte of the image. Any bytes after need not be inspected. Zip/rar are decompressed from the last byte going backwards. Again stopping as the final byte of the archive is seen.

The inverse operation being base64 encoding: http://en.wikipedia.org/wiki/Base64 (meaning you can use it to store a JPEG in text rather than text in a JPEG, among other uses)

Base64 has proven to be a great source of amusement for me. Free picture-mail on my cellphone without paying for it. Harassing my still-learning brother. ("hey, run this python script.", has a GIF file stored in the source in base64, pops it up in a tkinter window.)

There's a nifty app somewhere that allows you to print files to paper, not base64, but something else, I forget the name though...

There are more sophisticated steganograpic tools out there for this purpose; Wikipedia has a good writeup on it: http://en.wikipedia.org/wiki/Steganography

Several years ago Neils Provos wrote several papers and tools for detecting this content: http://www.citi.umich.edu/u/provos/stego/

If you're interested in more research on image steganography, Hany Farid and Jessica Fridrich are writing great papers about it.

Something similar was the goal ofthe Underhanded C contest a while back. The goal was to be able black out a portion of an image while maintaining the data or "leaky redaction". http://underhanded.xcott.com/?p=8

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