Home Office response on Burden of Proof

[Nicholas Bohm]

At 12:42 PM 8/6/1999 -0500, William H. Geiger III wrote:
>In <3.0.5.32.19990805174426.00b1c9c0@mail.netkonect.co.uk>, on 08/05/99 
>   at 05:44 PM, Nicholas Bohm <nbohm@ernest.net> said:
>
>>At 12:09 PM 8/5/1999 +0100, Andrew Meredith wrote:
>>>Nicholas Bohm wrote:
>>>> 
>>>> Clearly not.  There will be cases where possession of the key
>>>> can be proved by the Crown quite easily (e.g. where the accused
>>>> has responded to encrypted messages in a way that proves he can
>>>> decrypt them) [...]
>>>
>>>Imagine for a moment that Ben's forged key was being used by its actual
>>>holder on an anonymous communications channel of some sort (Mixmaster
>>>email, smutty newsgroups etc). The email address (if present) in the key
>>>would not be used to direct responses. The holder of the key would then
>>>be in a position to reply (with a signed and/or encrypted message) to
>>>the (signed/encrypted) messages sent using the PGP key, without
>>>reference to Ben. The message that was the subject of the decryption
>>>order could have an authenticated response showing a comprehension of
>>>the content, but Ben would not have been involved.
>
>>Proving that the holder of the key responded is not the same as proving
>>that the person on whom the decryption notice was served is the holder of
>>the key.  I imagine a "sting" case where the victim is sent an encrypted
>>email inviting him to collect a prize, which turns out to be a decryption
>>notice.
>
>Still all this proves is *past* possesion of the decryption key. It shows
>nothing of the current possesion of that key. Considering that a key can
>be destroyed in a fraction of a second this is a very important
>distinction.

Certainly; but evidence of past possession of a key would at least justify
serving a notice seeking it.  If in response to the notice the key is
claimed to have been destroyed, then of course past possession does not
justify reversing the burden of proof that it is still held.  But if, after
such a claim is made, further evidence shows that the allegedly destroyed
key is still in use, bit by bit the prosecution may be accumulating enought
to make a case.  (Please bear in mind that according to John Abbott,
Director-General of the National Criminal Intelligence Service, criminals
are lazy, greedy and stupid.)

On a technical note, how can you destroy a private PGP key without
destroying all your private keys by wiping the private keyring?  Does
revoking the corresponding public key destroy the relevant private key?

Regards,

Nicholas Bohm

Salkyns, Great Canfield,
Takeley, Bishop's Stortford CM22 6SX, UK

Phone		01279 871272	(+44 1279 871272)
Fax		01279 870215	(+44 1279 870215)
Mobile   	0860 636749  	(+44 860 636749)

PGP RSA 1024 bit public key ID: 0x08340015.  Fingerprint:
9E 15 FB 2A 54 96 24 37  98 A2 E0 D1 34 13 48 07
PGP DSS/DH 1024/3072 public key ID: 0x899DD7FF.  Fingerprint:
5248 1320 B42E 84FC 1E8B  A9E6 0912 AE66 899D D7FF