No because parts of X are effectively variable, change all the time, and depend on things not controlled by any single entity (transactions, block chain, etc).

No because parts of X are effectively variable, change all the time, and depend on things not controlled by any single entity (transactions, block chain, etc). Technically X is a block header https://en.bitcoin.it/wiki/Protocol_specification#Block_Headers https://en.bitcoin.it/wiki/Protocol_specification#Block_Head... Miners change the 'nonce' part of X to attempt to satisfy the above equation.