It's continually testing the strength of SHA256. If you can find a way to even partially crack it, you win money. Edit: Also, way more hashes are happening all the time now, increasing the chance that someone finds a collision if it were possible.

That's still not what the Bitcoin miners are doing. They're manipulating inputs, trillions of times a second, just to match a "magic" target for a SHA256 hash starting with a certain number of bits set to 0.

Cracking hashes would imply that they're taking pre-existing hashes and reversing them to find the input.

Hashes have multiple requirements for security. You're talking about only one facet, which is that you cannot be given a hash and produce a matching input without consulting a rainbow table (I think there's a term for this, I forget it though).

Chungy is correct though. Bitcoin has absolutely nothing to do with "cracking sha256 hashes". Bitcoin hashes until the correct output is found. There are double hashes, but that is solely to avoid collisions and has nothing to do with determining the plaintext from a known digest.

>and has nothing to do with determining the plaintext from a known digest.

So why'd you bring it up?

To add to the discussion.

User bitcoinistrash is the one that brought it up, and they're spreading incorrect information about how it works.

Cracking sha256 hashes implies trying to reverse a specific hash. There are literally thousands (millions?) of potential inputs that hash to a valid bitcoin mining block output. It's basically a race to find the first one matching the rules of the current block difficulty. The goal isn't to produce any one specific input/hash pair.

In which context would somebody try to reverse a hash? That would be like arbitrarily enhancing a bad-resolution image to see something that cannot be seen.

Hash collision should always be about finding matching content for a hash.

And if you cracked the math of sha256 you wouldnt need to search you would just calculate one of the inputs to produce whatever you want. All zeros would be as easy as one.

It's kinda sad. If we persisted all the hashes that have been tried, we'd have the mother of all rainbow tables.

Be a bitch to search. But damn would we know the topography of the function space.

Why hasn't anyone made that crypto currency yet?

Because it would actually solve a problem?

...I'll see myself out.

> hashes that begin with a certain number of bits set to 0.

This myth was always intriguing to me. Where does it come from?

It's not a number of 0s (which would imply difficulty could only be doubled or halved), it's just finding a hash that is less than the target.

It's in the original Bitcoin whitepaper

Thanks, this is likely where I read it first. I hadn't realized the actual implementation got more complicated than that. :)

Interesting. Even though I read the paper many times, I didn't catch that. I guess I always skipped that part because I assume I already knew it.

"Less than the target" in effect is "more leading zeroes" depending on how low the target is. But the lower, the more leading zeros, Right?