Zipography

Steganography with zip archives: hide a blob of data within an archive. For typical file archivers (7-zip, WinRAR, File Roller, &c) or file managers (Windows Explorer), the blob is invisible.

$ gem install zipography

Limitations:

• single blob only (but you can just add another .zip as a blob);
• doesn't work w/ zip64 files (this means 4GB max for an archive+blob combo);
• corrupts zip spec v6.2+ files that use central directory encryption;
• memory hungry, for it's just a toy, not a serious spy tool.

Usage

Say we have a .zip that contains 2 files:

$ du orig.zip
12K     orig.zip

$ bsdtar tf orig.zip
The Celebrated Jumping Frog of Calaveras County.txt
What You Want.txt

Inject a picture into the archive:

$ zipography-inject orig.zip blob1.png > 1.zip

It it visible? No:

$ bsdtar tf 1.zip
The Celebrated Jumping Frog of Calaveras County.txt
What You Want.txt

$ du 1.zip
30K     1.zip

(unzip -l prints the same, but in a much verbose form.)

Check if we have the picture in the archive:

$ zipography-info 1.zip
Payload size:    18313
Adler32:         0x6812d9f
Version:         1
Valid:           true

Extract it:

$ zipography-extract 1.zip > 1.png
$ xdg-open !$

How does it work?

A blob is injected after a file section right before the 1st central directory header. After that, a pointer in an end of central directory record is updated to compensate the shift of the central directory header.

License

MIT.