From 10 to 1, a shorter block time interval can help Bitcoin scale, but is it feasible?

A small adjustment in Bitcoin could have a big impact.

This has been the focus of bitcoin’s ‘block size debate’, a long-running debate over whether to lift the mandatory limit on the amount of data that can fit in each transaction block.

One side sees increasing the block size as an easy way to increase the number of transactions the network can handle, potentially expanding Bitcoin’s user base, while opponents of increasing the block size worry about the consequences of such a change (centralization and instability), or at least question whether increasing the block size is necessary in the short term.

Other parts of Bitcoin may also be changed or moved, and any changes could have different effects on the overall health of the network - good or bad.

Earlier this month, a talk at the Scaling Bitcoin conference in Milan explored how changing parameters could affect the bitcoin network, such as adjusting the frequency of block creation, which could be a simple way to increase transaction capacity.

Using data extracted from an open-source simulator of a proof-of-work blockchain such as Bitcoin or Ethereum, researchers from ETH Zürich have argued that Bitcoin’s block time can be safely reduced from 10 minutes to 1 minute.

The idea is that this change would not negatively impact Bitcoin’s security, but would still increase the number of transactions possible on the network. So, the argument goes, this approach is better overall.

Arthur Gervais, a PhD student at the Institute for Information Security at ETH Zurich, told CoinDesk:

“Based on my research, a one-minute interval seems to make the most sense. I’m not saying this will provide full security, but I’m saying this approach will provide the same security as Bitcoin currently has.”

So how does this approach improve transaction capacity? The logic is very simple: more blocks means more transactions.

The research joins a number of other ideas focused on increasing bitcoin’s transaction capacity, including Segregated Witness, the Lightning Network and other proposals such as Schnorr signatures and an ambitious plan to restructure bitcoin with client-side validation. There are also a number of alternative bitcoin implementations, including Unlimited and Classic, that seek to increase capacity by increasing the block size limit.

The ‘block time’ debate?

Adjusting parameters to increase capacity - does this remind you of something? Bitcoin block size has long been discussed as a way to scale transaction capacity. So, does this mean we are moving from a 'block size debate' to a 'block time debate'?

Not really, according to Gervais. He sees his project more as a way to compare blockchains against objective measures, to understand how changes might affect Bitcoin, so that developers can make more informed decisions.

He said:

“If people want to scale without sacrificing security, they have a few options. I think it’s good to have options. That’s why we’ve been doing this work.”

Gervais continued:

“The impact of not only changing block size and block time is poorly understood, but also the impact on security in general. People are creating new altcoins and blockchains, and we should first step back and see what can be done with the current system.”

Others are also wary of shorter block times.

Alexandre Bergeron, a Bitcoin company consultant, said,

"From my perspective, these are high-risk propositions with uncertain outcomes. This one looks good on paper, but it could have a significant impact on the network and some unintended consequences."

He sees the combination of game theory and financial incentives as a ‘balancing act.’ It’s another lesson in weighing trade-offs; developers believe the network requires a specific combination of settings and parameters, otherwise the overall network security could be undermined.

Gervais believes that shorter block times could help scale Bitcoin, but he wouldn’t necessarily push for the change.

“We don’t get public input on what should and shouldn’t be done.”

All possible scenarios

Aside from some vague notion of fund safety, what does blockchain security actually mean in cryptocurrency?

If the conditions are not right, strange behaviors that make the network less secure will become more prevalent. This includes double spending (users spending their bitcoins more than once) or selfish mining (one miner cheating to earn more bitcoins at the expense of other miners).

This 'staleness rate' represents how often miners find blocks before they are eventually added to the blockchain. Too many stale blocks could lead to increased centralization in mining, and could also make the blockchain more vulnerable to attack.

This is what Gervais and others in the Zurich research team did to determine that a one-minute block interval is the most feasible.

Gervais said:

“We simulated every possible scenario.”

The results of this experiment show that the team observed the changing level of the stale block rate by testing block sizes ranging from 0.1MB to 16MB and block intervals from 0.5 seconds to 25 minutes.

However, like many other blockchain configuration changes, block time changes are complicated. Bitcoin Core contributor Greg Maxwell is skeptical and advocates for longer block times on Reddit. He believes that the block time issue is very thorny because if the block time interval is too short, it may cause the network security to deteriorate rapidly.