Funny you'd say that, Bitcoin's PoW algorithm (hashcash) was originally precisely designed for that use case: https://en.wikipedia.org/wiki/Hashcash https://en.

Funny you'd say that, Bitcoin's PoW algorithm (hashcash) was originally precisely designed for that use case: https://en.wikipedia.org/wiki/Hashcash https://en.wikipedia.org/wiki/Hashcash