Re: Mr. Squirrel

||ugh Daniel raises some questions about using public keys to
verify pseudonyms:

>   Hal is somewhat right, anyone can use 'Secret Squirrel' and anyone
> can use any public key they want also.

But, once person A creates public key X, nobody else can sign messages
using X.  So if all messages from A are signed under X, we can know
that they are all from the same person, even if they are sent anonymously
or under a pseudonym.

> So, in a many-to-one scope (as
> in a maillist) where the sender can not use the one-on-one signed
> signiture method how do we have proff of who the sender really is?

You can use signatures even in a many-to-one scope.  Messages from
a particular person could be signed and the signature appended to
the message.  Then anyone who has the public key can check to see
who the message came from.  The process is a little unwieldy now
in PGP because you have to separate the signature and message into
separate files and run PGP on the signature file.  This should be
streamlined.

> [Good points about keeping track of key-pseudonym pairs]
> But all this needs to be done automaticly by the mailers and
> interfaces, else the system will be mis-used and folks will tire of
> the extra work that gets them little advantage.

Absolutely.  The most crying need now, IMO, is to better integrate the
cryptographic tools into mail readers and senders, so that it's not
such a pain to use these things.  People should be able to give a single
command or press a button to decrypt an incoming message or encrypt an
outgoing one.  Only then will these features be used by average people.

There was a message posted on alt.security.pgp describing how to
use PGP with the Emacs mail reading program.  I'd like to see more
messages telling how to use it with other systems.

Hal
74076.1041@compuserve.com

>But, once person A creates public key X, nobody else can sign messages
>using X.  So if all messages from A are signed under X, we can know
>that they are all from the same person, even if they are sent anonymously
>or under a pseudonym.

     Who's to say that person B sees a message signed under X by person A.
He copies the signature (X) onto the bottom of one of his messages and
everyone thinks they can verify that it's from A but it's really from B.
(makes sense to me anyway...)

Chael Hall

Chael Hall                                   |     Campus Phone Number
iuvax!bsu-cs!nowhere                         |       (317) 285-3648
00CCHALL@bsuvax1.bitnet                      |
iuvax!bsu-cs!bsu-ucs!00cchall                | "I hate it when that happens!"

A signature on a message is dependent on the contents of the message;
it is not a free floating bit of information.  You can't copy a
signature, therefore, without copying the message or find another
message that hashes to the same value.  This is the design criterion
behind one-way functions--that you can't (feasibly) find a message
that hashes to a given value.

Eric

A genral and powerful method of makeing sure that Headders, Bodys
and Signatures match is to use cyrpto-checksums.

  For example in NetNews I proposed changing the MessageId: headder
such that part of the gobldyguk on the left side of the atsign was a
crypto hash of the body of the message and some of the important
sending host generated headders.
  With this system of MessageId:'s anyone who corrupts a message
(intentionaly or otherwise) creates a bogus message, as the next
machine that gets the message can see that the message does not match
it MessageId: line.

  So, if we design the signature system right (with a field for a
crypto hash, or some sort of secondarys signatures to in efect counter
sign various includes such as the plain text) a plain text message can
be signed in such a way that you can be sure that the text is the
right text and none other.
  This can be sent over the airwaves as it is not hideing information
but proveing that it is the right information!

  Systems like this would be *very* usefull right now, are simple to
do (with good advice from Crypto Math types) and usefull to everybody.

		||ugh

The most pressing thing is not to integrate encryptions in mail handlers,
but at the level of ether.  Ether is an enormous security hole.  I can walk
up to anything running ether with my notebook, plug in, and listen to all
traffic.  Therefore, ether cards need public key encryption built in, so
they can communicate with eachother in a secure way.  This also applies to
all other low level protocols.

e