Hashcash is a proof-of-work system in which the Sender needs to find $Y$ such as the first (let's say 20) bits of $H(X+Y)$ are zeros where $H$ is a one-way hash function, $X$ is a fixed value and $+$ ...
I have such requirements to the hash function in my project: operating on 32-bit data, not mathematically breakable (built on existing hashes known to be secure), free of branching, as much as ...
In reading about the Bitcoin protocol I noticed how much its proofs-of-work apparently depend on uniformity of the SHA-256 hash function. And so presumably do many other applications. How do ...