[Bitcoin-development] Block Size Increase

Tier Nolan tier.nolan at gmail.com
Wed May 6 22:44:53 UTC 2015

On Wed, May 6, 2015 at 11:12 PM, Matt Corallo <bitcoin-list at bluematt.me>

> Personally, I'm rather strongly against any commitment to a block size
> increase in the near future.

Miners can already soft-fork to reduce the maximum block size.  If 51% of
miners agree to a 250kB block size, then that is the maximum block size.

The question being discussed is what is the maximum block size merchants
and users will accept.  This puts a reasonable limit on the maximum size
miners can increase the block size to.

In effect, the block size is set by the minimum of the miner's and the
merchants/user's size.min(miner, merchants/users).

> This allows the well-funded Bitcoin ecosystem to continue building
> systems which rely on transactions moving quickly into blocks while
> pretending these systems scale. Thus, instead of working on technologies
> which bring Bitcoin's trustlessness to systems which scale beyond a
> blockchain's necessarily slow and (compared to updating numbers in a
> database) expensive settlement, the ecosystem as a whole continues to
> focus on building centralized platforms and advocate for changes to
> Bitcoin which allow them to maintain the status quo[1].

Would you accept a rule that the maximum size is 20MB (doubling every 2
years), but that miners have an efficient method for choosing a lower size?

If miners could specify the maximum block size in their block headers, then
they could coordinate to adjust the block size.  If 75% vote to lower the
size, then it is lowered and vice versa for raiding.

Every 2016 blocks, the votes are counter.  If the 504th lowest of the 2016
blocks is higher than the previous size, then the size is set to that
size.  Similarly, if the 504th highest is lower than the previous size, it
becomes the new size.

There could be 2 default trajectories.  The reference client might always
vote to double the size every 4 years.

To handle large blocks (>32MB) requires a change to the p2p protocol
message size limits, or a way to split blocks over multiple messages.

It would be nice to add new features to any hard-fork.

I favour adding an auxiliary header.  The Merkle root in the header could
be replaced with hash(merkle_root | hash(aux_header)).  This is a fairly
simple change, but helps with things like commitments.  One of the fields
in the auxiliary header could be an extra nonce field.  This would mean
fast regeneration of the merkle root for ASIC miners.  This is a pretty
simple change.
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