Can Bitcoin Scale?
The ability for bitcoin to compete with other payment systems has long been up for debate in the cryptocurrency community. When Satoshi Nakamoto programmed the blocks to have a size limit of approximately 1MB each to prevent network spam, he also created the problem of bitcoin illiquidity.
Since each block takes an average of 10 minutes to process, only a small number of transactions can go through at a time. For a system that many claimed could replace fiat payments, this was a big barrier. While Visa handles around 1,700 transactions a second, bitcoin could process up to 7. An increase in demand would inevitably lead to an increase in fees, and bitcoin’s utility would be limited even further.
The scaling debate has unleashed a wave of technological innovation in the search of workarounds. While significant progress has been made, a sustainable solution is still far from clear.
A simple solution initially appeared to be an increase in the block size. Yet that idea turned out to be not simple at all.
First, there was no clear agreement as to how much it should be increased by. Some proposals advocated for 2MB, another for 8MB, and one wanted to go as high as 32MB.
The core development team argued that increasing the block size at all would weaken the protocol’s decentralization by giving more power to miners with bigger blocks. Plus, the race for faster machines could eventually make bitcoin mining unprofitable. Also, the number of nodes able to run a much heavier blockchain could decrease, further centralizing a network that depends on decentralization.
Second, not everyone agrees on this method of change. How do you execute a system-wide upgrade when participation is decentralized? Should everyone have to update their bitcoin software? What if some miners, nodes and merchants don’t?
And finally, bitcoin is bitcoin, why mess with it? If someone didn’t like it, they were welcome to modify the open-source code and launch their own coin.
One of the earliest solutions to this issue was proposed by developer Pieter Wiulle in 2015. It’s called Segregated Witness, or SegWit.
This process would increase the capacity of the bitcoin blocks without changing their size limit, by altering how the transaction data was stored. (For a more detailed account, see our explainer.)
SegWit was deployed on the bitcoin network in August 2017 via a soft fork to make it compatible with nodes that did not upgrade. While many wallets and other bitcoin services are gradually adjusting their software, others are reluctant to do so because of the perceived risk and cost.
Several industry players argued that SegWit didn’t go far enough – it might help in the short term, but sooner or later bitcoin would again be up against a limit to its growth.
In 2017, coinciding with CoinDesk’s Consensus conference in New York, a new approach was revealed: Segwit2X. This idea – backed by several of the sector’s largest exchanges – combined SegWit with an increase in the block size to 2MB, effectively multiplying the pre-SegWit transaction capacity by a factor of 8.
Far from solving the problem, the proposal created a further wave of discord. The manner of its unveiling (through a public announcement rather than an upgrade proposal) and its lack of replay protection (transactions could happen on both versions, potentially leading to double spending) rankled many. And the perceived redistribution of power away from developers towards miners and businesses threatened to cause a fundamental split in the community.
Other technological approaches are being developed as a potential way to increase capacity.
Schnorr signatures offer a way to consolidate signature data, reducing the space it takes up within a bitcoin block (and enhancing privacy). Combined with SegWit, this could allow a much greater number of transactions, without changing the block size limit
And work is proceeding on the lightning network, a second layer protocol that runs on top of bitcoin, opening up channels of fast microtransactions that only settle on the bitcoin network when the channel participants are ready.
Adoption of the SegWit upgrade is slowly spreading throughout the network, increasing transaction capacity and lowering fees.
Progress is accelerating on more advanced solutions such as lightning, with transactions being sent on testnets (as well as some using real bitcoin). And the potential of Schnorr signatures is attracting increasing attention, with several proposals working on detailing functionality and integration.
While bitcoin’s use as a payment mechanism seems to have taken a back seat to its value as an investment asset, the need for a greater number of transactions is still pressing as the fees charged by the miners for processing are now more expensive than fiat equivalents. More importantly, the development of new features that enhance functionality is crucial to unlocking the potential of the underlying blockchain technology.
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