Proof of work

Proof of work is a simple method of rate limiting and spam reduction. The most famous use case for it is Bitcoin. But it has also been used for website rate limiting, and email spam filtering.

Basic idea of proof-of-work.

1. I want to prove that I did some amount of computation for ID XYZ.
2. I hash XYZ + a counter. I count the number of leading 0 bits in the hash.
3. If the number of 0 bits is greater than the difficulty, I am done.
4. Otherwise, I increment the counter and try again.

One of the earlier examples of proof-of-work is Hashcash.

Backlinks

• Bitcoin
• Bitmessage
• Nostr

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