[hashcash] Re: Pure Python implementation of hashcash v.1

  • From: "David Mertz, Ph.D." <mertz@xxxxxxxxx>
  • To: hashcash@xxxxxxxxxxxxx
  • Date: Fri, 24 Sep 2004 15:53:09 -0400

On Sep 24, 2004, at 2:36 PM, Eric S. Johansson wrote:

I also check and write email on my Powerbook, with OSX and using Mail.app. Anyone know if anyone has figured out how to interface with Mail.app, it would certainly be nice to get hashcash integration there.

well, you could take my hacks on smtpd.py and the postfix stamping filter interface code and build yourself a stamping proxy. On the other hand, I have been intending to create a version of Camram that runs on client side machines and the mac is the most likely candidate.

Yeah, a proxy is a possibility. But it just seems so *fugly*! Adding a X-Hashcash: header doesn't have anything to do with the SMTP/IMAP/sendmail/whatever interface; it's just a text processing task on an email message.


Ideally, a mailer should just be able to post-process a message before sending it (using all the network interface code already built into the mailer. Many *nix mailer let you specify an arbitrary filter for outgoing messages... but MacOSX isn't targeted this way, unfortunately (I understand novices don't want to be confused by that, but a buried preference wouldn't hurt them). Likewise, MUAs should be able to filter using an arbitrary external utility.

FWIW, I will write a utility 'add_hashcash_stamps.py' that will simply take an rfc2822 message on STDIN, and write one with added headers on STDOUT. I reckon this utility will optionally use an external compiled minter (e.g. hashcash.exe) for speed, but use my hashcash.py if one is not available. Not sure the best way to configure the name/switches of the external tool, but I'll decide on something.

I guess while I'm at it, I might also do 'check_hashcash_stamp.py' that takes an rfc2822. This is a little tricker in a way though. How do you know whether a resource in an X-Hashcash: header is one you want to accept? For example, I use many different email addresses within my 'gnosis.cx' domain (for various contacts). In principle, I might accept a stamp with any of these resources, since I'll accept email to any of the addresses. But there are actually infinitely many resources I might accept inside a stamp (subject to it really having the right bits, date, etc). Then again, I don't want to accept just any resource... for example, what if a spammer CC:'s herself, and produces a valid stamp only for her own email address?

Yours, David...

P.S. If someone else has -already- written good 'check_hashcash_stamp' and 'add_hashcash_stamp' command-line utilities, let me know. I don't necessarily need to duplicate the work, even if those others aren't in Python.


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