> I'm a little confused as to how does that make it any different from using 
> the Pidgin OTR method.

It's a question of degree, not kind.

> I simply open up an OTR session, ask my friend a question the answer to which 
> is secret (only known to him)

How do you know the secret is known only to him?  Most "secrets" really aren't; 
a good investigator can discover an awful lot of "secret" information about 
someone.  Shared-secret authentication is one of the weakest forms out there.  
It's better than nothing, but it's not something that ought be relied upon.  
People tend to vastly overestimate how secret their secrets are.

As an example, a few years ago I saw in a spy novel (set in the modern day) two 
protagonists negotiating a phone number over an insecure line.  "Hey, that guy 
we know who did X?  Take his phone number, subtract this number from it.  The 
resulting phone number is what you need to call."  

It sounds great and reliable: it's a shared secret.  The problem is it's 
totally bogus.  Phone numbers aren't random.  In the United States, for 
instance, phone numbers follow the NPA-NXX format.  That reduces this question 
down to a glorified Sudoku: a skilled investigator could figure it out in just 
a few minutes.


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