From: Hal <hfinney@shell.portal.com>
Date: Fri, 10 Feb 95 14:05:41 PST
To: cypherpunks@toad.com
Subject: Re: MIME based remailing commands
In-Reply-To: <9502102057.AA11903@cfdevx1.lehman.com>
Message-ID: <199502102205.OAA04014@jobe.shell.portal.com>
MIME-Version: 1.0
Content-Type: text/plain


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Rick Busdiecker <rfb@lehman.com> writes:
>Could one of the MIME supporters (I guess that would be `most
>everybody') explain why anything more than a To: header and an
>encrypted block is desireable for the in-the-clear message?

For one thing, you might want to know that you have an encrypted
message on your hands and not just somebody's misfired GIF.  For
another, you might want to know where the encrypted block begins and
where it ends.  You might also want to have information about what
kind of encoding has been done on the output of the encryption (base64,
uuencode, leave it as pure 8-bit binary, etc.)  And you might want to
have information about what kind of encryption was used, what key
was used, etc., in case you are supporting multiple encryption
formats and keys.

PGP, FYI, does include most of this information in the clear, albeit some
in binary format.

This information is generally needed for the receiver to successfully
decode and receive the message, so it does have to be in the clear.  Now,
there may be some circumstances where this is not desired, and where you
really do just want to hand the receiver a block of apparently random
data, with no indications whatsoever what it is.  Then by some
out-of-band means you have to have arranged with the receiver that he
will know exactly what transformation to do to get back the original
data.  For that I suppose you could just use text/plain (or something
like application/data?), and it looks as opaque as could be desired.

Hal

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