From: monty.harder@famend.com (MONTY HARDER)
Date: Thu, 10 Aug 95 20:38:33 PDT
To: CYPHERPUNKS@toad.com
Subject: If only Vxxxx Fxxxxx had used encryption....
Message-ID: <8AEE4DC.0003000301.uuout@famend.com>
MIME-Version: 1.0
Content-Type: text/plain


 C'punks:

                [Wait!  This =is= crypto-related!  I promise!]

  Heard on the news today that Bernard Nussbaum said he had done
"nothing irregular" in going through Vince Foster's effects immediately
after his demise, in order to secure "sensitive information".
Presumably, Nussbaum's contention is that some of the information in
Foster's possession was covered by attorney-client privelege, and
therefore the Authorities had no right to take it into possession.

                 (IANAL-Comments from those who are?)

  Anyway, this case got me to thinking: If Vince had kept all his
"sensitive" things encrypted, and never written down the passphrase,
then the data would effectively have died with him. In this case, lack
of key escrow is not a bug, but a feature!

  Then I thought some more - that the whole Key Escrow thing needs to be
rethought: Instead of escrowing the private key, we need to develop
better key management techniques for multiple recipients.

  For example, if Alice is an attorney representing Carol Client, Bob
and Ray are partners in Alice's firm, which uses escrow agent E; and A,
B, C, R and E are the public keys (and A'... are the private keys) of
our dramatis personae:

  Carol sends her message to Alice as usual, generating the session key
S, and encrypting it S'=A(S).

  Whenever Alice recieves a message, after decrypting the session key
[S= A'(S')] she adds to it an additional S"= E( B(S) ) and S"'= E( R(S)
) or some other construct which involving Shamir Sharing or whatever.
The details of the protocol(s) can be worked out after the basic premise:

       There is no reason for anyone to give up the "master key" to all
     of their business, when the minimal overhead in storage space for
     adding an escrowed =session= key will suffice.

  PGP needs a mechanism to handle "detatched session keys", so that our
escrow agent can, upon notification by Bob and Ray that Alice has [died
| left the firm], process the whole package of S" and S"' back into B(S)
and R(S), so that Bob and Ray can carry on their work. Just as with a
detatched signature certificate going to a notary, the detatched session
key does not give the escrow agent any knowledge of the content of the
message itself.

  Another option is to put the whole creation of S" and S"' on to Carol,
which requires a public key that specifies E and {B, R}, as well as the
particular escrow protocol involved. This could be tricky to implement.

  Also, Carol needs to be able to specify to Alice that she is retaining
a copy of the communication, encrypted to self, and therefore Alice need
not escrow the session key for this particular message.


  Comments?



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