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Re: Some -15 comments

2005-11-14 19:05:21

Daniel Nagy writes:
On Mon, Nov 14, 2005 at 03:37:44PM -0800, "Hal Finney" wrote:
I'd like to use the flag as a hint to packet-dumping software: if the
human-readable flag is set, it is reasonable to dump the notation body
as text.  If it is not set, it should be dumped in hex.

Currently, the way I treat this flag is that I display the notation to the
user whenever the signature is verified. If that's not the purpuse of this
flag, then I would really like another flag with that purpose. See below
what I would like to use it for.

I don't think that will work too well on self-sigs with PGP Corp's new
preferred-email-encoding subpackets.  You don't want to print those out.

Another difference arises if the subpacket critical bit is set along with
the human-readable flag.  With the current wording it might appear that an
implementation's responsibilities are met if it somehow causes the text
of the notation packet to be displayed to the user, even if it does not
recognize the notation type.  I think that would be a serious mistake.
The critical bit should require that the notation type be recognized
and handled, in order for the signature to be considered valid.

Are you sure? I actually think that displaying some notation whenever the
signature is verified (correctly) makes a lot of sense and it may be part of
signature verification. After all, it is ultimately the user who decides
wheter he accepts a signature or not.

I'm worried that this is going to get too messy.  For a document
signature, if a user wants to put in some qualifications or conditions,
it is better to put them into the document itself rather than into a
notation packet on the signature in the hopes that it will be displayed.
There are no guarantees about display.

Then there are key signatures; and under what circumstances will they be
displayed?  When encrypting some email, do we want to see every notation
packet which every signer has decided to add to every key that we encrypt
to, and perhaps further packets from keys down the web of trust?  How to
organize it and present it in a coherent way?  It will be a mess.

If and when we come to the point where we need a kind of notation packet
that should be displayed on signature verification, we should define its
use and purpose, create a name for it, and spec it out.  I think that
is a better path than to have a flag with rather uncertain semantics
about when it might cause text to be displayed to the user.

Here is how I am planning to use human-readable notation: in an on-line
trading or auction application, where reputation tracking is important, one
can implement user comments about other users' behavior in the form of
signatures directly on their public keys with appropriate notation (think of
eBay comments). The comment text is, in my opinion, critical in the sense
that without it the signature does not make sense, but the implementation's
responsibilities are indeed met by just displaying it upon verification.

You could still do this, but do it based on the notation name rather than
a flag.  You could have a notation called 'user-reputation-comments'
or some such.  Your application could then define whatever meaning and
handling it wanted for how this type of notation packet should be used.

Hal Finney

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