trivia

[Owen Lewis]

> -----Original Message-----
> From: ukcrypto-admin@chiark.greenend.org.uk
> [mailto:ukcrypto-admin@chiark.greenend.org.uk]On Behalf Of David Howe
> Sent: 13 July 2001 11:23
> To: ukcrypto@chiark.greenend.org.uk
> Subject: Re: trivia
>
>
> "Owen Lewis" <oml@eloka.demon.co.uk> wrote:
> > The man who danced with a girl who danced with the Prince of Darkness?

> close enough - the point here is that you can be 100% in
> corresponding only
> with the innocent - and still end up with a RIPA order on your doorstep.

True. But as suggested in an earlier post, you an also be innocent and
neatly framed for murder. Life is not an entirely safe business and none of
us should expect any guarantee that it be made so.

A reminder also that such 'framing' is a serious criminal act and a perp
found guilty will be looking at a jail sentence - and quite right too.

For a complex of reasons, the chances of such a thing ever happening are
quite remote and one can reduce those chances much further by exercising
some caution in what one does and how one does it.
>
> > Return to the origins of the thread. I've not claimed that using PKC
> cannot
> > make trouble for one but only that I would try and act in a way that
> > minimise that risk. In short, I would not act as you describe.
> Hmm. I may not have explained myself well enough there.

> A and B are two other individuals - who have picked a email
> address from an
> online archive (and yes, this happens; I got spammed by that Lockdown2000
> fool who *admitted* he had harvested my email from the UKcrypto archives)
> for use as an emergency cover. You are unlucky enough to be the cover, and
> the plod have just found a big stack of correspondence,
> apparently from and
> to you, half of which (the from bit) they can read....

I'm sorry to hear that. It adds rather to my conviction that one should
never enable a personally controlled cipher to be used at the decision of
others. E.g. no key servers.

> > For the few with whom I communicate in cipher, there is a unique key for
> > every correspondent. Thus, if correspondence with one is compromised it
> has
> > no effect on the remainder. It suits me well to conduct my business this
> > way. There is no reason why others should find such a way best suited to
> > their needs. That matters not. It suits mine and those of my
> >correspondents.

> That actually makes things worse - you can't point and say "look officer,
> this is MY key and everyone knows it" if you have a policy of a
> separate key per correspondent. even less chance of a "balance of
> probabilities" defence

Perhaps I should have added that I choose not to use a PKC. My needs are
small and I manage well using several implementations of XTEA, mainly for
transmitting/receiving data dumps or documents. There are both fully
automated and  manual modes of transmission, depending on the requirement.
Works well for a business where a limited number of outstations need to
communicate with a hub but have no requirement to correspond directly
between themselves. In such a situation PKC has  probably more disadvantages
than benefits over such a 'wheel-spoke' crypto solution.

Keys are ephemeral and, after an initial seeding of the system, are unknown
to the operators. This allows for fully automated and enciphered
communications. The usual caveats apply to terminal security but that is no
more or less a worry than any other aspect of business security. Encryption
is used as a means of assuring the integrity of very large quantities of
data being communicated regularly and to provide a reasonable assurance that
neither will it be intercepted or read at the terminal by unauthorised
persons.

If security at one of the outstations fails, only its own security is
compromised. If security at the hub fails there are measures in place to
prevent the effect being catastrophic. Spoof messages should be impossible.
In the extraordinarily unlikely event that an outstation should communicate
something outside of the normal run of our business, administrative action
would follow immediately.

No, its not perfect. Nothing in life ever is. What it does is to diminish
risks to which I and others believe that our communications may be exposed
from time to time and it provided a reasonable assurance of confidentiality.
Moreover, it does not create any specific vulnerabilities, such as those we
are discussing in this thread.

Horses for courses. I see PKC as being a very useful tool, particularly in
e-commerce. I believe that one grand, overarching, PK system would bring
with it more headaches than it cures. There is room for many different
cryptosystems and I would encourage all to flourish.

For myself, I do not wish, nor need ever, to facilitate unsolicited
enciphered and personal communication from strangers. Which ever of party
initiates an exchange, I would never wish to say or hear from a complete
stinger what could not be as well said in a room full of people. If a
development from earlier exchanges indicates that enciphered communication
has become desirable, of course I will use it but it will be at my decision
and not allowed by default.


Owen