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Re: The armour issue

1997-11-26 17:33:33
At 11:41 AM 11/26/1997 +0000, Ian Brown wrote:
Ascii armor allows PGP binary data to be held or transmitted in
any environment that may not be safe to raw binary data.
Can you give us an example of this apart from mail? Web-based keyservers
only use armour because they are based on mail servers. HTTP allows
binary data to be transferred directly.

The Web-based keyserver isn't just using armor because it's on a mailserver.
A typical Web-based PGP application requires the user to cut&paste a
PGP key or PGP-encrypted message into a web form and submit it.
Not only are window systems highly prone to munging such data
(at least white space, backspaces, CRLFs, NULs, and other control characters,
if not necessarily munging 8-bit data), but web forms aren't always
friendly about accepting it, and are likely to turn it into forms like
%FF which need to be unmunged by the receiving program.
Some of this can be avoided by adding MIME support into PGP,
so it produces MIME-armored stuff to cut&paste instead of PGP-ASCII-armored,
but you still need armor.  (If you've got a friendly way around this problem,
I'd love to see it, because I'd like to be able to have users paste 
Microsoft Word/Excel/PPT documents into forms to autoadd to web pages.)

There's also the problem of sending PGP keys in email messages,
which MIME attachments aren't always the best user interface for:
        Bob - Sorry your corporate      maildroids are using LookOutXChange!  
                (No Resemblence To Any Microsoft Product Intended.)
        If you want to buy GoodMTA, send email to alice(_at_)acme(_dot_)com 
using my
        PGP key <<KEY HERE>> and remember to also encrypt to accounting's
        key <<KEY HERE>> so the SMTP filter doesn't bounce it.
        If you want to send us your resume, purchasing's key is <<KEY>>.
It's really much cleaner if you've got a format that can stay inlined,
rather than getting transformed to ATTACH1.BIN, ATTACH2.BIN, ATTACH3.BIN.

MIME would do, if you've got a convenient interface for pasting MIME into,
but this requires making PGP aware of MIME headers - and if you do that,
you need to decide whether to build in full-scale MIME support or just
support some subset of features PGP is likely to use - do you build in both
base64 (for Real Binaries and keys) and Quoted-Printable (for clearsigned text)?

Then there's including keys inside encrypted messages - you need to
nest the armored key structure inside the encrypted message,
which means doing MIME-inside-MIME or Armor-inside-MIME or Armor-inside-Armor.
See above for difficulties with MIME-inside.

I can see very little reason why people would want to store PGP data
armoured in a system that supports 8-bit data.

1) Storing clearsigned text in files, in editor-readable form.
        Even if you use EMACS, it's nicer to have the signature
        in Armored for, and with Evil GUI Editors, it's more important,
        and in Dumb Text Editors over telnet, you'd really like
        to be able to read the signature undamaged so you can copy
        it into things.
2) Storing keys along with clear text, in editor-readable form.
        Bob - here's my Revocation Certificate - only use it 
        if my name shows up in the Dissociated Press wire stories
        or you hear periodic beeps when you call me.
                <<REVOCATION KEY>>
3) Keyservers that are going to output the data armored anyway,
whether it's by email or web.

Lastly, there are systems that use (or would like to use) PGP over systems
that are not the internet. I have given the example of pager systems
before. There are other systems that use telephones, private networks, or
other non-Internet means of data transfer.

That web form for that pager service isn't the Internet!
That web form for the text-to-speech reader isn't the Internet!
Surely you're not planning to FAX your keys in these days of Email?!
And then there's telex and TDDs ....  I'm not sure if base64 works there,
        or if you really need monocase base32 or binhex or something;
        PGP's ASCII armor may not be enough.

To forbid armor is to say that there is no conceivable use for it.
No-one has suggested this.
Heh.  Dave Crocker's sure come real close :-)

Bill Stewart, stewarts(_at_)ix(_dot_)netcom(_dot_)com
Regular Key PGP Fingerprint D454 E202 CBC8 40BF  3C85 B884 0ABE 4639

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