[messaging] Value of deniability

Mike Hearn mike at plan99.net
Thu Dec 11 23:21:56 PST 2014

> Other examples in this spirit - you asked for a car with high maximum
speed. You said you don't care much about security ratings. This gets
> forwarded to a data broker (look up the term) who sells it to your
> insurance company

Your insurance company, faced with a claim that the well established auto
dealership and data brokers are making things up for no obvious reason,
would just conclude your denial is a lie and double your insurance costs

> higher prices for others. Having a provable transcript of a
> conversation declaring the exact margins and terms would lose that
> retailer their contract

Only if it was disclosed. Again the issue seems to be loss of privacy.

> Discussing job options. While not having told your boss about your
> plans to leave. Sometimes you have very good reasons to not let them
> know a thing until after your new job position is secured.

So if your boss finds a highly plausible chat log of you talking to a
competitor about working there, you will say "no the chat log was forged by
the competitor" and your boss will say,   "oh ok, no problem, how could I
ever doubt you"  ?

I think deniability in this case would be unlikely to have any effect.

a mean manner. This gets repeated without that context in a chat. The
> angry response gets forwarded to some authoritive person who'll
> interpret it as the recipient being the one who initiated the fight.

So show the full chat log and turn the tables on the bully. Problem solved.

> framed if the transcript gets published and the fingers are pointed at
> him (see Snowden, Manning and others), and deniability means it is
> nothing but word against word

Manning already used a deniable chat medium and was hosed anyway, despite
being somewhat technically proficient.

For deniability to have any real world effect, there'd need to be a LOT of
people forging chat logs pretty routinely. As it's only relevant when
there's some breakdown in privacy, and that should hopefully be rare in a
good cryptographic system, getting people to routinely forge or edit logs
seems .... hard.
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