On Fri, 21 Mar 2003 19:46:08 +0000, Adam Back <adam(_at_)cypherspace(_dot_)org>
writes:
The Stamps discussion seems to be reinventing hashcash (are some not
aware of hashcash, or is there some aspect of the Stamps discussion
different from hashcash in some way I am not seeing?)
Yes, it is strongly inspired by HashCash, but it is different. The
differences is that HashCash is only used for initial communication.
In my system, almost all stamps are really one-time-use random nonces
generated by the recipient. The stamps are automatically attached to
all outgoing messages, but may be obtained by solving a CAPTCHA or
other out-of-band means. This means the HashCash stamps are relegated
to only being used for the initial message in a communication.
Thus, I can afford to make the hashcash stamps incredibly expensive,
on the order of tens of minutes, because few messages ever use them.
Since so few are used, I consider it acceptable to require the
recipient to maintain a database of all of them ever used. The lack of
datestamps allows a MUA to precompute stamps ahead-of-time based on
for addresses in the address book.
Also, since MUA's may mint arbitrary stamps and bulk mailers may send
a control message requesting the same, bulk emailers do not require
users to implement an exception mechanism.
all of the options discussed so far in this thread are documented, or
improved upon in that paper.
I ruthlessly simplified Hashcash to suit the limited situation I am
using it for.
where you can visually see the leading 33 bits of 0s.
Nice change.
Scott
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