[hashcash] hashcash stamp server

Hi,
I have been quietly following the discussions on this list for a few weeks and 
have been wondering how to integrate hashcash with my favorite MUA, kmail.

What I think we need is a stamp server, that runs locally or on a remote 
machine and where the MUA can order stamps. I think the following commands 
should be in the protocol:

ORDER ressource
means "the user is writing an email message to <ressource> right now, so a 
stamp should be put into production. Returns a <stamp-id>.

GET <stamp-id>|<ressource>
means "I need a stamp for ressource or the stamp I ordered earlier right now 
because the email is ready to be sent." Blocks until the stamp is ready and 
then returns it.

Client libraries for something like this would be easy to write and would make 
it possible to integrate in any open source email client.

For having stamp management like the one discussed in this thread: 
http://news.gmane.org/find-root.php?message_id=%3c20040306205338.GB3028%
40longshot.toehold.com%3e we would also need the server to maintain a list of 
the most often needed stamps. The stamp server could prioritize in the 
following order:

1. answer GET requests
2. process stamps requested by ORDER
3. make sure we have one stamp for today for the top-n of email recepients
4. make sure we have two stamps for today for the top-n of email recepients
5. etc.
6. make sure we have one stamp for tomorrow for the top-n of email recepients
7. make sure we have two stamps for tomorrow for the top-n of email recepients
8. etc.

Maybe there should also be a way to tell the stamp server that an email has 
been received that the user might want to send an answer to soon. But with 
the amount of emails many of us receive, this would maybe be too much.

Is there a way yet to announce to someone that he has been whitelisted and 
does not need to produce stamps for me anymore.

Just my to cents.

Martin

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