Eric S. Raymond wrote:
--- draft-crocker-spam-techconsider-02.txt 2003/11/14 16:37:39 1.1
+++ draft-crocker-spam-techconsider-02.txt 2003/11/14 16:52:25
@@ -566,6 +566,19 @@
is also not clear who should receive the fees or how
they should be disbursed.
+ Another possible form of sender-pays is to impose costs
+ at mail-transaction time without trying to clear them as
+ payments in the real world -- so-called "hash-cash" schemes.
+ The purpose of such techniques is not to compensate the
+ receiver for reading spam but to impose a friction cost on
+ spammers, ideally one that would make bulk-mail prohibitively
+ expensive. Hash-cash schemes rely on the existence of
+ challenge-response methods in which the response is provably
+ expensive to compute. A difficulty with them is that their
+ effectiveness could be diluted or eliminated by techniques
+ such as zombie-flood spamming attacks in which the spammer
+ essentially does not care about the amount of time any one
+ hijacked machine has to spend shipping a spam.
I forwarded the comments to Dave Crocker. However, my question is
whether we should add a comment here about the fact that spammers can
build specialized computers to do hashcash calculations and then perhaps
rent it out to other spammers to use. That possibility has been
mentioned on the list before. Even though it increases their costs, that
increase might not be enough to make spam not profitable.
Yakov
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