Well it could be an all '1' prefix? What do you want?
The idea here is that if you flip a coin and say head's is zero, then say you flip 20 coins what's the odd's of how ALL coins in a batch of 20, all turn up with head's? That's a well known math problem in probability, the the exact number of +51% flips required is a known-known. Thus the POW can be estimated upfront, and let the machines do the calc's. If you want the leading 30 to be zero, same deal it takes a little longer, more tosses.
KISS principal say's "Keep it Simple Stupid", I think that's what Satoshi had in mind here for his proof-of-work, a simple well known algo, and given that each sha256() call is essentially 257 random coin tosses, you can easily figure how many call's you have to make.
You could make this POW really complicated, but the question begs to be asked?? WHY?
One reason I think the POW could be made more complicated is to obsolete all the ASIC miners, say you wanted the 'lead' to be random sentence from the bible, now that would obsolete all asic boxes, but return mining to the cpus. Sort of the 1M monkey problem, if you put 1000Million monkeys on typewriters eventually one of them will write moby-dick ( well at least I'm Ishmael )
Is there a good reason any longer for the rule that the success of a Bitcoin proof of work has to be that there is an all-zero bits prefix?
The PoW is the challenge to find a hash which represents a number inferior than the target. It happens that represented in hexadecimal the target has X leading 0 but it is not all about the challenge.
For instance, suppose I want to create a blockchain just for mypersonaldomain.co.
Do you mean a network similar to Bitcoin ?
The Bitcoin block format would have to be revised to include my blockchain's 256-bit prefix
I don't think this is going to happen.
the world could benefit from 2^256 unique blockchains.
What do you mean ?
