Hashcash
= Hashcash
{wiki=Hashcash}
Hashcash is a proof-of-work system designed to limit email spam and denial-of-service attacks. It was created by Adam Back in 1997. The idea behind Hashcash is to require the sender of an email to perform a computational task, which involves calculating a hash that meets certain criteria. This process takes time and computational resources, making it more expensive for spammers to send large volumes of emails.