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You can’t really discuss the topic of cryptocurrency mining without getting into issues surrounding the concept of centralization. One of the greatest aspirations of cryptocurrency communities is to decentralize the monetary system and create “trustless” transactions.

While Bitcoin made a lot of headway towards a trustless currency, there are still concerns. The concentration of power among ASIC miners in a few locations make some people wonder if mining is becoming too centralized.

GPUs And Decentralization

At present there are two leading forms of mining, as Crypto Briefing has previously explained. Bitcoin, Litecoin and other leading cryptocurrencies can be mined with ASICs, highly specialized devices which can only perform a specific algorithm. Monero, Zcoin and some other cryptocurrencies can only be mined by commercially-available GPUs and CPUs

GPUs are common and relatively inexpensive. A standard gaming PC has at least one GPU in it, sometimes two. These video cards, distributed all over the world, allow for a widespread and highly decentralized network.

ASICs on the other hand, are more specialized, very expensive, and much harder to find. Because they are expensive and harder to set up, ASIC networks tend to be centralized among the wealthier people who have the means to purchase them and set them up on a large scale.

Bitmain Versus Everybody Else

It doesn’t just stop at individuals. Relatively few entities control the large mining pools which dominate the most popular Proof-of-Work coins, particularly Bitcoin. Bitmain, which manufactures the most popular ASICs (there are some competitors emerging on the scene) controls two of the largest Bitcoin mining pools, Antpool and BTC.com.

In fact, at one point in time, their pools controlled nearly 50% of Bitcoin hashrate, although their share has diminished over the past year.

But just because a pool is centralized, that does not necessarily mean that the miners within the pool are also centralized. If miners notice that their pool is acting maliciously, they can simply switch to another pool.

Even a leading pool operator, like Bitmain, would still have to work in concert with a massive number of miners, which would cost much more than it would return. In an article examining Mining Centralization Scenarios, Jimmy Song points out the extreme costs of attempting to maintain such a large-scale attack.

But when a single manufacturer produces the most popular mining equipment, “back-doors” exploits become more likely. For example, Bitmain could surreptitiously install a “kill-switch” that would reduce block productivity on non-Bitmain pools. However, these back-door tricks would also run the risk of being discovered and decimating Bitmain’s balance sheet as miners switch to different equipment in the future.

So while large entities like Bitmain may be a centralizing force in Bitcoin and a number of other cryptocurrencies, free market dynamics tend toward decentralization, competition, and innovation. Due to competition and improving profitability, the distribution of ASIC mining pools is diversifying, trending away from the possibility of monopolization.

Electricity Costs Around The World

There’s also a possibility of geographic centralization, as miners flourish in areas with the cheapest energy. This can be due to economic conditions or because of the availability of cheap sources such as hydro-electric dams.

In much of the United States, residential electricity rates range around the 13 cent per kilowatthour average, but can be as high as 20 cents in some regions and as low as nine cents in a few states. For larger mining operations, industrial rates are quite a bit cheaper, but it can still be pretty tough to compete against regions where electricity is much less expensive.

Because the cost of electricity is hugely important in figuring out the profitability of any PoW mining operation, high-capacity ASIC mining operations are drawn to locations where the electricity is cheap.

That’s why so much cryptocurrency mining is performed in China, where electricity is cheaper than almost anywhere else. Quebec is also attracting attention due to its surplus of hydro-electricity. This could be another weak point, as mining hashpower concentrates in certain regions.

Multi-million Dollar ASIC Farms Versus Multi-million Dollar GPU Farms

But even if ASICs fell by the wayside, one could also set up a hugely expensive GPU farm. GPUs themselves do not negate the centralization problem, although they may reduce it due to their widespread availability and usage.

It would be considerably more difficult to gain control of a GPU network, simply because there are already so many GPUs distributed around the world. But if someone designed a new GPU that was highly powerful, efficient, and expensive, it could result in a similar problem.

Higher Hashrates

Theoretically, the more decentralized a PoW network is, the more secure it should be, but it may sacrifice speed for safety. Miners are incentivized to increase their hashing power for more frequent block rewards, which also increases network security.

A high hashrate means that there is more competition among miners, making the network more expensive to mine. The higher the hashrate, the more expensive it is to to set up or rent the necessary hashing power to launch a 51% attack. At some point, it becomes so costly that it just isn’t worth attempting such an attack.

51% Attacks

If any single entity or group of colluding entities manage to control 51% of a network, lots of bad things can happen. Most importantly, the 51% controlling entity can essentially double-spend the currency.

In a typical double-spend, attacker creates a public transaction that spends some currency, typically by moving it to an exchange. Meanwhile, they use their superior hashing power to create a secret, longer chain, which does not include that transaction, and broadcast it to the rest of the network. Since consensus defaults to the longer chain, they have effectively spent the same tokens twice.

Some lower hashrate PoW networks like Bitcoin Private and Bytecoin are susceptible to 51% attacks because it requires relatively little hashing power to take over these networks. Even bigger names like Bitcoin Cash and Ethereum Classic have fallen victim to such attacks.

ASICs can contribute to centralization if a few wealthy and powerful parties manage to gain more than 51% of a network’s hashrate. Bitmain and some of its affiliates control somewhere around 40% of all of the Bitcoin network’s hashing power. Of course, it would not be in Bitmain’s best interests to diminish the value of the Bitcoin network since they have so much invested in it. Yet, there is a degree of trust that is necessary because of the extent of their influence in the present conditions.

Still, it looks like ASICs are here to stay, with their collectively massive computational power ensuring the security of Bitcoin and a number of other PoW-based networks. In the next and final installment in this series on mining, we will take a closer look at the numbers involved in profitable mining and will conclude with an examination of the ongoing battle for greater decentralization.

This is Part 2 of a series on cryptocurrency mining. For Part 1, click here.