From: Matt Blaze <mab@crypto.com>
Date: Fri, 10 Feb 95 11:48:38 PST
To: Eric Hollander <hh@xcf.berkeley.edu>
Subject: Re: why pgp sucks
In-Reply-To: <9502101849.AA21833@xcf.Berkeley.EDU>
Message-ID: <199502101951.OAA28877@crypto.com>
MIME-Version: 1.0
Content-Type: text/plain



>if i use a command like
>
>	pgp filename
>
>it will automatically figure out the right thing to do with the file.  if
>it's encrypted, and i have the key, it will attempt to decrypt it.  if it
>contains keys, it will ask if i want to add them to my keyring.  if it's
>signed, it checks the signature.
>
>this sucks!
>
>if i'm trying to write a program to automatically process incoming mail (for
>instance, to see if it's encrypted with a specific key), i certainly don't
>want to have the possibility of people being able to add garbage to my
>keyring just by mailing it to me.
>
...

PGP suffers from its failure to separate cleanly its primary
mechanism (encrypting and signing messages) from policy (what to
do with those signed and encrypted mechansims).  Without a clean
separation, the mechanism is limited to use in those applications
narrowly envisioned by the system's authors.  Of course, PGP is
hardly unique here; designing clean interfaces and separation-of-
functions isn't easy, and its even harder in the face of meeting
the needs of an existing installed base of first-generation users.

Personally, I'd much rather see a suite of tools: an encryption/signature
tool (or maybe tools - let me apply them in whatever order is
approprate), a decryption verification tool, a certificate management
system that operates on messages signed with the signature tool and a
top level that glues all this together and implements local policy
(like what consitutes a valid signature, key revocation, etc).  If
we had a system that worked like this,, we could more easily create
richer key certificates that specify restrictions on what is being
signed, revocation conditions, etc.  (As it is, there isn't even
any way for a key signer to revoke a signature, let alone describe
what purpose the signature exists for.)

Of course, you could probably build all this ON TOP of the existing
pgp and pem, but you'd still be left with bloated underlying tools
that implement more policy than they need to.

Oh well.

-matt