Core Apps » PixelKnot

App is called SecretBook

Available here - https://chrome.google.com/webstore/detail/secretbook/plglafijddgpenmohgiemalpcfgjjbph

Story - http://www.wired.com/dangerroom/2013/04/secretbook/

Owen Campbell-Moore is the creator. Supervised by Dr. Ker.
http://www.owencampbellmoore.com/
http://www.owencampbellmoore.com/blog/2013/04/hide-secret-messages-in-facebook-photos-using-this-new-chrome-extension/
https://dl.dropboxusercontent.com/u/6853624/secretbook-draft-1.pdf

https://github.com/owencm/js-steg

Uses a
JPEG encoder ported to JavaScript and optimized by Andreas Ritter, www.bytestrom.eu, 11/2009

It appears Facebook reduced to a quality factor of 75% of the image uploaded, so images need to be compressed to that to fit Facebook's quantization matrix. Meaning we might need to integrate a JPEG encoder that reduces file size before we encode images with F5.

His email is owencmoore@gmail.com

Secretbook Instructions

Quickstart

Refresh Facebook. Press ctrl+alt+a while on Facebook to encode a message. Press ctrl+alt+a while looking at a photo to decode a message.

Creating a new secret message

If you've just installed Secretbook then please refresh Facebook before trying to use this extension.

Securely share a password with the friend you wish to communicate secretly with.
While on Facebook press ctrl+alt+a to activate the secret system.
Use the dialogue to create an image. Upload this new image to any album on Facebook or post it on your friend's wall.
Note that sending secret messages via messaging is not yet implemented
Attempt to receive the message from the image you just uploaded in case an error occurred!
Optional: Mention your friend in a comment or the description to ensure they know to check it for a message.
Your friend can now use the password you shared to decode the message.

Receiving a secret message

While looking at an image on Facebook press ctrl+alt+a to activate the secret system.
Enter your shared password to receive the secret message.
Debugging

Please report all bugs to owencmoore@gmail.com.
Help, it says "No message received!" when I put a message in the photo!
Sometimes this happens. Try again with a slightly different message or a new photo!
The message worked but some of the letters are wrong!
Sometimes Facebook's recompression causes an error which can't be fixed by the software. Try a different photo!
Tips and FAQ

How secure is it?
This app is a toy and does NOT provide military grade security. Please do not use it for terrorism or other bad things (you will get caught).
What size image should I use for maximum capacity?
Before encoding, all images are resized to have maximum width and height of 960px and 720px respectively. Therefore any images this size or greater with a 4/3 aspect ratio will have the largest capacity available.
What kinds of photos work best?
High quality photos of 970px-by-720px or greater. Avoid images downloaded from the internet since these may have already been comressed multiple times. Also avoid photos with large flat areas of colour such as sky.
For security purposes, only use photos you have taken yourself and destroy the original copy after creating the new version. Being able to gain access to the original image would greatly help any attacker in decoding your messages.