Fwd: plausibly deniable

[Andre Amorim]

No worrys Daniel..
living and learning..

--Andre

---------- Forwarded message ----------
From: Daniel Kahn Gillmor <dkg at fifthhorseman.net>
Date: 22 July 2010 22:48
Subject: Re: plausibly deniable
To: Andre Amorim <andre at amorim.me>


Hi Andre--

Please don't reply off-list.  this discussion would be useful for others
who follow the list, or who read the archives.  By taking the discussion
off-list, this is now hidden from everyone but you and me.

I haven't replied on-list because i don't want to publish your words
without your permission.  You have my permission to re-post my text here
on the list if you want to take it back public again.

On 07/22/2010 04:43 PM, Andre Amorim wrote:
> Why I felt stupid ? LOL.. I got it, thanks But if ..someone pick me up
with
> my openpgp smartcard, put a gun in my head and say .. decrypt it or die
...

i think you might be getting data signatures confused with data encryption.

public-key signatures are a way of placing a mark on some content that
no one but the holder of your key could make.  They're often used to
mean something like "I wrote this message" or "I approve of this message".

public-key encryption is a way of making it so that only the holder of a
given key is able to access the cleartext content of your message.

Plausible Deniability as a term is usually used in reference to the idea
of signing, not encryption.  That is, a system like OTR offers
convincing proof to the other party in a conversation that you are who
you say you are, but that information is designed to be uninterpretable
to other people (because the way that per-session key material is
handled after the session is over makes it possible for anyone to craft
the same assertions).  You should read up on otr if you're interested:

 http://www.cypherpunks.ca/otr/

This "feature" is legally dubious, since courts seem prepared to convict
without cryptographic proof anyway.

The closest idea to Plausible Deniability for encryption (not
signatures) is something like hidden volumes within encrypted volumes,
which truecrypt offers:

 http://www.truecrypt.org/

This feature is also dubious, because there will be suspiciously
high-entropy on the disk, and you are known to be using tools with this
feature, you will simply be coerced until you've accounted for all the data.

And of course, when a gun is held to your head, it's hard to argue that
you are in full control of your key.

       --dkg
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