[1659] in Software_Announce
hashcash 1.18 installed for linux in outland
daemon@ATHENA.MIT.EDU (Ken T Takusagawa)
Fri Nov 11 23:57:49 2005
Date: Fri, 11 Nov 2005 23:57:43 -0500 (EST)
From: Ken T Takusagawa <kenta@MIT.EDU>
To: bug-outland@MIT.EDU
cc: software-announce@MIT.EDU
I installed hashcash 1.18 for i386_rhel4 in the outland
locker.
I've also put hashcash.el in share/hashcash and instructions
in dot-emacs there on how to use hashcash with the Emacs
mail client.
From the manpage:
Hashcash is a denial-of-service counter measure tool. Its
main current use is to help hashcash users avoid losing
email due to content based and blacklist based anti-spam
systems.
The hashcash tool allows you to create hashcash stamps to
attach to emails you send, and to verify hashcash stamps
attached to emails you receive. Email senders attach
hashcash stamps with the X-Hashcash: header. Vendors and
authors of anti-spam tools are encouraged to exempt mail
sent with hashcash from their blacklists and content based
filtering rules.
A hashcash stamp constitutes a proof-of-work which takes a
parameterizable amount of work to compute for the sender.
The recipient can verify received stamps efficiently. This
package also includes a sha1 implementation which is
equivalent in functionality to the sha1sum program available
on some systems.
The hashcash proof-of-work function is to compute partial
hash collisions (the SHA1 hash function is used). By
choosing the number of bits of collision, the work required
to compute a collision can be made arbitrarily expensive --
from frac- tions of a second to minutes or hours. The
verification is efficient requiring the same small cost
whatever the collision size.
For more detailed discussion of other applications hashcash
has been used for see http://www.hashcash.org/
(I'm having trouble compiling for solaris: the lack of the
defined constants LOCK_{EX,SH,UH} as parameters to flock())
--ken
