historytechnicalfundamentals

Hashcash

Definition

Hashcash is a proof-of-work algorithm invented by Adam Back in 1997. It was originally designed to limit email spam by requiring senders to spend computational effort before sending a message. Satoshi Nakamoto cited Hashcash in the Bitcoin whitepaper as the basis for Bitcoin’s mining mechanism.

Example

Adam Back invented Hashcash to fight email spam; Bitcoin's mining system is based on the same idea.

Related Terms

Mining

The process of using computational power to verify transactions and add new blocks to the blockchain.

Block reward

The amount of new Bitcoin a miner receives for successfully adding a block to the blockchain.

Related Articles

Hal Finney and the Cypherpunks: The People Before Bitcoin

Bitcoin didn't appear from nowhere. Decades of cryptographic work by the cypherpunk movement laid the foundation for Satoshi's breakthrough.

8 min read Read More →

What is Proof of Work?

Proof of work is the engine that keeps Bitcoin secure. Learn how miners compete to protect the network.

7 min read Read More →

The Bitcoin Whitepaper Explained

In 2008, Satoshi Nakamoto published nine pages that changed money forever. Here is what the Bitcoin whitepaper says in plain English.

4 min read Read More →