From what I understand, steganography works if an observer (Carl) cannot tell that transmission of covert data is taking place between Alice and Bob. The proposed method results in an RTP bitstream that does not hold the payload advertised in its headers -- the audio is compressed using a more efficient codec than advertised in the packet headers, and the extra space is used to carry the "hidden" payload; Alice and Bob agree beforehand on the audio codec to use.

Now if Carl wants to eavesdrop on the conversation by hijacking (or owning) an intermediary network node, he would get corrupted audio data when trying to decode the packets with the (fake) advertised codec. Wouldn't this be a strong indication that covert communication is taking place?

You have to use common sense to NOT INTENTIONALLY PUT YOUR FINGERS OR BODY IN A GIGANTIC MOVING METAL DEVICE.

Funny personal story about this: a few years ago, I decided to test the safety features of an automatic sliding door by sticking my fingers where I shouldn't have. Luckily I did not lose any finger, but I got some ugly scars to tell the tale.

I clearly remember my reasoning: it seemed dangerous, but it was in a public place. So of course, there was a safety interlock or something, because of our litigation-happy society. I just couldn't see it. As it turned out, there wasn't any. Ouch.

I didn't sue, though...

I submit this as anecdotal evidence that the current trend towards idiot-proofing can KILL common sense.

[Citation needed]