From: viking@pacifier.com (Robert East)
Date: Sat, 18 Nov 1995 06:56:57 +0800
To: cypherpunks@toad.com
Subject: Re: COE Recommendation No. R (95) 13
Message-ID: <m0tGYiZ-0008zoC@pacifier.com>
MIME-Version: 1.0
Content-Type: text/plain


>>MS> However, if I have a wall safe and
>>MS> they get a warrant to search it, can I be jailed for contempt if I
>>MS> don't give them the combination?
>>
>>	Well, IANAL, but yes, I believe that you can be.  Or, worse,
>>obstruction of justice.  Especially if they cut it open and find that
>>the knife was in the safe.
>
>So presumably the same would apply to the password that unlocks my 
>PGP private key. But there's an interesting twist. Once they open 
>up the wall safe, they can see for sure what is and isn't in it. This 
>ain't necessarily so for an encrypted file. Suppose my software has the 
>fiendish sophistication to disgorge different keys depending on what 
>password was given, and different pieces of cleartext depending 
>on what key was used. (Again, I apologize if this notion has already 
>been extensively discussed.) Is there a way to set it up such that 
>the cops couldn't be sure -- even using a logic analyzer -- that I 
>hadn't given them the complete set of keys, so as to read all the 
>cleartexts in the file? Assume that cyphertext files are guaranteed 
>to be larger, by some random factor, than the sum of all the cleartexts 
>in them, so the mere fact that a smaller quantity of cleartext was 
>disgorged than cyphertext supplied would tell them nothing. I guess this 
>is a kind of steganography, isn't it? Or at least something similar -- 
>the point would be that they couldn't tell genuine cyphertext from 
>camouflaging noise, without the key that tells them where to look. 
>
>Which brings us, in turn, to the bottom line: the only things we 
>can be certain the bad guys _won't_ do, are the things they _can't_
>do. 
> 
>
>--Michael Smith

The interesting thing about PGP is that any incriminating cypher text one
might have on his or her hard disk would, most likely, be in someone else's
public key.  So, even if they had your secret key the only thing that could
be uncovered would be cyphertext that someone else had written to you.
Granted, that this could be incriminating but, then again, not necessarily.
I'm sure that for the purposes of conducting a criminal investigation, your
own cyphertext would be far more incriminating than someone else's. (The
above is only true unless you use the single key encryption option offered
for personal files in which case your files would be readable.) 

What one should be more concerned with is sloppy handling of plain text files
used prior to encryption.  A good example of that is if you're using Windows
based applications such as MS Winword.  It has an auto-store function that
generates a "Temp" file.  Such files aren't wiped in the same fashion that PGP
uses when it wipes a text file prior to encryption.

I think that the paramount thing to consider is if you have something to
hide then it is best to store it is inside your head.  Any computer based
storage system is bound to have certain limitations that may be bridged by a
determined government agency.  The other alternative is to ensure that
potentially incriminating files be purged regularly to avoid such potential
problems.

Robert East
viking@pacifier.com