From: Jefferson Carpenter <jeffersoncarpenter2@gmail.com>
To: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
References: <58fa85b8-cba3-ee34-8c96-41c6c7bfbf9c@gmail.com>
Message-ID: <374ee97c-dae9-786f-5fc6-6fb6920360cb@gmail.com>
Date: Fri, 19 Jan 2018 14:54:52 -0600
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Subject: Re: [bitcoin-dev] Upgrading PoW algorithm
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Actually here's something we could possibly do:

Fork off a blockchain that accepts Bitcoin blocks with strictly less 
than max difficulty.  Because it does not accept max-difficulty blocks, 
it is a soft fork.  Additionally, if difficulty of a block is set to 
max, then the difficulty field is extended so that it represents a 
higher max difficulty under a different hashing function, maybe SHA512. 
Because this blockchain also accepts differently-formatted blocks, it is 
also a hard fork.

The idea is that this blockchain is identical to Bitcoin until the 
difficulty goes too high, at which point it diverges.

Transitioning from the current SHA256 to a higher-difficulty hashing 
function could be difficult, since they might be solvable at 
proportionally different hashrates.  In other words, max difficulty for 
SHA256 might be significantly faster than forcing the first 256 bits of 
a SHA512 hash...

On 1/17/2018 4:31 PM, Jefferson Carpenter wrote:
> Bitcoin's difficulty will be maxed out within about 400 years, by 
> Moore's law.  (After that - supposing the software does not crash when 
> difficulty overflows - block time will start decreasing, and it will not 
> take long before blocks are mined faster than photons can be sent across 
> the planet).
> 
> Bitcoin is the dominant cryptocurrency today, as the first mover: the 
> perfectly fair worldwide game of inventing the cryptocurrency has been 
> played and won.  However, unfortunately, it has a built-in end date: 
> about 400 years from now.  After that, it won't necessarily be clear 
> what the dominant cryptocurrency is.  It might be a lot like VHS vs 
> Betamax, and a lot of people could lose a lot of money.  It seems to me, 
> this could be mitigated by planning today for what we are going to do 
> when Bitcoin finally breaks 400 years from now.
> 
> Are there any distinct plans today for migrating to a PoW supporting an 
> even higher difficulty?