Bitcoin Forum

Hi there,

As I understood, mining bitcoin means to make SHA256(SHA256(something)). If the result has enough 0's at its beginning, you found the block. In order to be possible to get enough 0's, it is possible to change the nonce (or how it is called) and so change the result consequently.

So, if this is mining, couldn't it be possible to calculate which nonce is needed and then give this result to the pool/network?

I suppose there is something I don't know which makes this impossible and so it would be good to learn it. In the other case, well the question would be to know how long it would take to make such a miner ;)

P.S.: There might be some mistakes in the text, my English is quit bad.

The only way to calculate which nonce is needed is to try every single nonce until you get one that works. That's the point of the hashing algorithm.


If we could do what you said, that would mean the hashing algorithm had been broken.

I'm sure that we've ALL tried to find a shortcut to brute-forcing sha256(sha256(hdr-with-nonce)) as soon as we discover bitcoin mining - I know I have anyway. But inverting the process is "computationally infeasible" - google that phrase - and the guys who use phrases like that have brains the size of beachballs.

But by all means have a go at proving P=NP... hey you just might manage it! If you do, let me know how you did it and I'll pay you 100 BTC. Doesn't that sound nice?

hashing algorithms are designed to be "trap door" functions.  That is they are designed to work only one way. 

plaintext -> hash = very easy
plaintext <- hash = impossible (technically the term is infeasible)

When designing and validating a hash function researchers are looking to ensure that given a hash there is clue as to what plaintext generated it, no signature, nothing that narrows down the search space.

If you could do what you suggest then SHA-256 is broken and useless as a cryptographic hash.  Forget Bitcoin it has ramifications for everything from passwords lists to vpn to digital signatures.   The entire global cryptographic community has been looking for flaws in the algorithm for a decade.  I doubt you will find what they haven't.  The cryptographer who breaks SHA-256 will be famous (well at least in crypto-nerd circles :) ).

A well ...
After looking up, what the algorithm exactly is, I have my doubts if you can even find ANY solution to the algorithm ...

One other question:
What do I find in the hashed string?

A Trapdoor function (http://en.wikipedia.org/wiki/Trap_door_function) is not the same as a One-way function (http://en.wikipedia.org/wiki/One-way_function). The difference is that with a trapdoor function, there is some secret which, if known, allows you to compute any inverse you want of the function. If SHA-256 was a trapdoor function, it would mean that someone who knows its secret would be able to find blocks effortlessly.

I stand corrected.  Good to know.

Oh snap!  That would be bad. 

I'm always impressed how well Satoshi designed BitCoin.  There is a lot of good security in it.

There are no (publicly) known ways to cheat the system. It is possible that one exists, but not very likely. SHA256 has been around for a long time and has not been exploited (yet).