Hashcashs
Hashcash is a proof-of-work system developed by Adam Back in 1997. Its primary purpose is to deter denial-of-service attacks and email spam. The system works by requiring the sender to compute a hash value with a certain number of leading zero bits. This computational effort acts as a form of "cost" or "proof" that the sender has expended resources. The more computationally difficult the required hash, the higher the cost.
When a user sends an email, for example, their computer might perform a hash calculation on the
Hashcash has been influential in the development of cryptocurrencies, notably Bitcoin, which uses a similar proof-of-work
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