Monday, November 4, 2013

Using social media comment streams

It is very simple to imagine that one can use social media to send covert messages. One can use steganography through images one shares... But that's too simple for us :)

As a start, let us imagine two friends. They can do the following:
 - On a popular page, that they are both members of, they can either use OMG, or LOL in a comment. The first means a 0 bit, the second means a 1 bit.
They can definitely communicate, but its take a lot of time to send a secret message. But... with all the omg, and lol's that are all over the place, no one will notice... I guess.

Imagine these two individuals were absolute geeks and they still need to send a secret message. They can do the following:
 - Each will own a set of n users.
- They will "like" the same m communities (Google +) or Pages (Facebook)
- They will share a dictionary of k words, split into b sub-groups.

Each comment one of them sends on one of these pages is basically a number of bits. To know the number of bits, let us see how many options each of them can send. The number of different messages is:
  (using one of n users) * (send on one of the m pages) * (a comment using one word out of one of the b different parts of their dictionary) = n * m * b
  So, the number of bits will be:
   log2(n*m*b) = log2(n) + log2(m) + log2(b)

For typical numbers:
  16 users, 32 different pages, and 128 different parts of the dictionary...
They can send 4+5+7 = 16 bits. Two characters by every comment they send.... Not bad.