Notes
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It is a form of cryptography zero-knowledge proof that one part, the prover, proves to others, the verifies, that they used some amount of computational resources to complete some task.
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Cynthia Dwork and Moni Namor invented it in 1993 to deter denial-of-service attacks and other service abuses such as spam.
- It costs some effort for the attacker to make a request. Thus, it becomes inviable to send a large number of requests in a short period.
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It's asymmetric:
- It must be hard enough to provers finish the work.
- It must be easy to validate the prover's result.
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Bitcoin popularized it.
- Miners spend some computational resources to append blocks on the blockchain.
Questions
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It is a cryptography zero-knowledge. May we compare this to the gold miners, who need primarily physical force to find gold?
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What is the difference between CAPTCHA and proof of work?