Beat spam using hashcash

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If they want to send spam, make them pay a price
Level: Intermediate

David Mertz, Ph.D. (
Developer, Gnosis Software, Inc.
09 Nov 2004

Built on the widely available SHA-1 algorithm, hashcash is a clever system that requires a parameterizable amount of work on the part of a requester while staying “cheap” for an evaluator to check. In other words, the sender has to do real work to put something into your inbox. You can certainly use hashcash in preventing spam, but it has other applications as well, including keeping spam off of Wikis and speeding the work of distributed parallel applications. In this article, you’ll meet David’s own Python-based hashcash implementation.

HashCash article continued


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