Legal compulsion and self-incriminating passphrase

[David Swarbrick]

In message <000001bdab1c$b3895dc0$dc77e4d4@cpsb>, Caspar Bowden
<cb@fipr.org> writes
>> We have nothing to which a fifth amendment could be applied. The
>> statement that your passphrase contained a confession would merely be
>> seen as a source of glee by any passing officer. You have already made
>> the statement when you used it, and if it wasn't true when you made it
>> you woldn't be worried about it. They are not asking you to make a new
>> statement but executing a search on a confession already made
>
>Not literally true. The key which protects your private keyring is generated
>each time from a hash of the passphrase.

Almost, but the requirement only works (if it works) because the hash is
a direct and necesary descendent of your having made the statement. The
police could for example say that you should generate a passphrase from
the following crimes of which you are suspected:

'I killed cock-robin'
'It were me wot done in Diana'

and so forth. At the point where you generate a matching key pair to
your known key pair, they have you. What they rely upon in evidence is
not that you said it in regenerating the hash phrase, but that you must
have said it to generate the previous version.

-- 
David Swarbrick, Solicitor  
http://www.swarb.co.uk/swarbrick (office)  'a damn fine web-site'
http://www.swarb.demon.co.uk (home)