From: Hal <hfinney@shell.portal.com>
Date: Thu, 30 Dec 93 15:58:16 PST
To: cypherpunks@toad.com
Subject: Re: Trapdoor vs. Escrow
Message-ID: <199312302354.PAA23404@jobe.shell.portal.com>
MIME-Version: 1.0
Content-Type: text/plain


I think the term "trapdoor" in this context merely refers to known
characteristics of the Clipper chip and does not imply any additional
abilities to decrypt messages other than what has been revealed.

A "trapdoor" is generally some secret which allows you to decrypt
messages which could not be decrypted without the secret.  It is
normally applied in the context of one-way functions but I suppose
an encryption system could be thought of as one-way.  In this case
I think the trapdoor may just refer to the Law Enforcement field
which, upon decryption, allows information to be recovered so that
the message can be read without the user's cooperation.

The comment about the trapdoor issue being independent of the escrow
issue harked back to Denning's original suggestion, which was that all
users of encryption would have to escrow their keys with the government.
This could be done in the context of any cryptosystem, such as DES or
RSA.  The trapdoor makes the system more convenient for users, hence
perhaps more acceptable.  But the escrow provision is the aspect that
the government really cares about.

BTW, there were some comments on sci.crypt about how this review document
showed that the government was not as opposed to our views as had been
thought.  On the contrary, my take was that this document reflected
something of a maverick view, one which was not politically acceptable
with those in authority.  Note the critical comments about the document
containing unsupported assertions, a common buzzword for "views I don't
agree with."  I don't think the author of this review has helped his
career.

Hal Finney
hfinney@shell.portal.com