Levels per bitcoins
They are kept for future reference, in case one of those chains is extended to exceed the main chain in difficulty. In the next section Blockchain Forks , we will see how secondary chains occur as a result of an almost simultaneous mining of blocks at the same height. When a new block is received, a node will try to slot it into the existing blockchain.
Then, the node will attempt to find that parent in the existing blockchain. For example, the new block , has a reference to the hash of its parent block , Most nodes that receive , will already have block , as the tip of their main chain and will therefore link the new block and extend that chain. Sometimes, as we will see in Blockchain Forks , the new block extends a chain that is not the main chain.
In that case, the node will attach the new block to the secondary chain it extends and then compare the difficulty of the secondary chain to the main chain. If the secondary chain has more cumulative difficulty than the main chain, the node will reconverge on the secondary chain, meaning it will select the secondary chain as its new main chain, making the old main chain a secondary chain. If the node is a miner, it will now construct a block extending this new, longer, chain. Once the parent is received and linked into the existing chains, the orphan can be pulled out of the orphan pool and linked to the parent, making it part of a chain.
Orphan blocks usually occur when two blocks that were mined within a short time of each other are received in reverse order child before parent. By selecting the greatest-difficulty chain, all nodes eventually achieve network-wide consensus. Temporary discrepancies between chains are resolved eventually as more proof of work is added, extending one of the possible chains.
When they mine a new block and extend the chain, the new block itself represents their vote. In the next section we will look at how discrepancies between competing chains forks are resolved by the independent selection of the longest difficulty chain. Blockchain Forks Because the blockchain is a decentralized data structure, different copies of it are not always consistent.
Blocks might arrive at different nodes at different times, causing the nodes to have different perspectives of the blockchain. To resolve this, each node always selects and attempts to extend the chain of blocks that represents the most proof of work, also known as the longest chain or greatest cumulative difficulty chain. By summing the difficulty recorded in each block in a chain, a node can calculate the total amount of proof of work that has been expended to create that chain.
As long as all nodes select the longest cumulative difficulty chain, the global bitcoin network eventually converges to a consistent state. Forks occur as temporary inconsistencies between versions of the blockchain, which are resolved by eventual reconvergence as more blocks are added to one of the forks.
The diagram is a simplified representation of bitcoin as a global network. Rather, it forms a mesh network of interconnected nodes, which might be located very far from each other geographically. The representation of a geographic topology is a simplification used for the purposes of illustrating a fork.
For illustration purposes, different blocks are shown as different colors, spreading across the network and coloring the connections they traverse. In the first diagram Figure , the network has a unified perspective of the blockchain, with the blue block as the tip of the main chain.
Figure This occurs under normal conditions whenever two miners solve the proof-of-work algorithm within a short period of time from each other. Each node that receives a valid block will incorporate it into its blockchain, extending the blockchain by one block.
If that node later sees another candidate block extending the same parent, it connects the second candidate on a secondary chain. In Figure , we see two miners who mine two different blocks almost simultaneously. Both of these blocks are children of the blue block, meant to extend the chain by building on top of the blue block. To help us track it, one is visualized as a red block originating from Canada, and the other is marked as a green block originating from Australia.
Both blocks are valid, both blocks contain a valid solution to the proof of work, and both blocks extend the same parent. Both blocks likely contain most of the same transactions, with only perhaps a few differences in the order of transactions. As shown in Figure , the network splits into two different perspectives of the blockchain, one side topped with a red block, the other with a green block. Forks are almost always resolved within one block.
They immediately propagate this new block and the entire network sees it as a valid solution as shown in Figure The chain blue-green-pink is now longer more cumulative difficulty than the chain blue-red. As a result, those nodes will set the chain blue-green-pink as main chain and change the blue-red chain to being a secondary chain, as shown in Figure This is a chain reconvergence, because those nodes are forced to revise their view of the blockchain to incorporate the new evidence of a longer chain.
However, the chance of that happening is very low. Whereas a one-block fork might occur every week, a two-block fork is exceedingly rare. A faster block time would make transactions clear faster but lead to more frequent blockchain forks, whereas a slower block time would decrease the number of forks but make settlement slower. Mining and the Hashing Race Bitcoin mining is an extremely competitive industry. Some years the growth has reflected a complete change of technology, such as in and when many miners switched from using CPU mining to GPU mining and field programmable gate array FPGA mining.
In the introduction of ASIC mining lead to another giant leap in mining power, by placing the SHA function directly on silicon chips specialized for the purpose of mining. The first such chips could deliver more mining power in a single box than the entire bitcoin network in The following list shows the total hashing power of the bitcoin network, over the first five years of operation: 0. As you can see, the competition between miners and the growth of bitcoin has resulted in an exponential increase in the hashing power total hashes per second across the network.
Total hashing power, gigahashes per second, over two years As the amount of hashing power applied to mining bitcoin has exploded, the difficulty has risen to match it. The difficulty metric in the chart shown in Figure is measured as a ratio of current difficulty over minimum difficulty the difficulty of the first block. Currently, ASIC manufacturers are aiming to overtake general-purpose CPU chip manufacturers, designing chips with a feature size of 16nm, because the profitability of mining is driving this industry even faster than general computing.
Still, the mining power of the network continues to advance at an exponential pace as the race for higher density chips is matched with a race for higher density data centers where thousands of these chips can be deployed. The Extra Nonce Solution Since , bitcoin mining has evolved to resolve a fundamental limitation in the structure of the block header. In the early days of bitcoin, a miner could find a block by iterating through the nonce until the resulting hash was below the target.
As difficulty increased, miners often cycled through all 4 billion values of the nonce without finding a block. However, this was easily resolved by updating the block timestamp to account for the elapsed time.
Because the timestamp is part of the header, the change would allow miners to iterate through the values of the nonce again with different results. The timestamp could be stretched a bit, but moving it too far into the future would cause the block to become invalid. The solution was to use the coinbase transaction as a source of extra nonce values. Because the coinbase script can store between 2 and bytes of data, miners started using that space as extra nonce space, allowing them to explore a much larger range of block header values to find valid blocks.
The coinbase transaction is included in the merkle tree, which means that any change in the coinbase script causes the merkle root to change. If, in the future, miners could run through all these possibilities, they could then modify the timestamp.
There is also more space in the coinbase script for future expansion of the extra nonce space. The likelihood of them finding a block to offset their electricity and hardware costs is so low that it represents a gamble, like playing the lottery. Even the fastest consumer ASIC mining system cannot keep up with commercial systems that stack tens of thousands of these chips in giant warehouses near hydro-electric power stations.
Miners now collaborate to form mining pools, pooling their hashing power and sharing the reward among thousands of participants. By participating in a pool, miners get a smaller share of the overall reward, but typically get rewarded every day, reducing uncertainty. At current bitcoin difficulty, the miner will be able to solo mine a block approximately once every days, or every 5 months.
He might find two blocks in five months and make a very large profit. Or he might not find a block for 10 months and suffer a financial loss. Even worse, the difficulty of the bitcoin proof-of-work algorithm is likely to go up significantly over that period, at the current rate of growth of hashing power, meaning the miner has, at most, six months to break even before the hardware is effectively obsolete and must be replaced by more powerful mining hardware.
The regular payouts from a mining pool will help him amortize the cost of hardware and electricity over time without taking an enormous risk. The hardware will still be obsolete in six to nine months and the risk is still high, but the revenue is at least regular and reliable over that period. Mining pools coordinate many hundreds or thousands of miners, over specialized pool-mining protocols.
The individual miners configure their mining equipment to connect to a pool server, after creating an account with the pool. Their mining hardware remains connected to the pool server while mining, synchronizing their efforts with the other miners. Thus, the pool miners share the effort to mine a block and then share in the rewards. Successful blocks pay the reward to a pool bitcoin address, rather than individual miners.
Typically, the pool server charges a percentage fee of the rewards for providing the pool-mining service. When someone in the pool successfully mines a block, the reward is earned by the pool and then shared with all miners in proportion to the number of shares they contributed to the effort. Pools are open to any miner, big or small, professional or amateur. A pool will therefore have some participants with a single small mining machine, and others with a garage full of high-end mining hardware.
Some will be mining with a few tens of a kilowatt of electricity, others will be running a data center consuming a megawatt of power. How does a mining pool measure the individual contributions, so as to fairly distribute the rewards, without the possibility of cheating? By setting a lower difficulty for earning shares, the pool measures the amount of work done by each miner. Each time a pool miner finds a block header hash that is less than the pool difficulty, she proves she has done the hashing work to find that result.
Thousands of miners trying to find low-value hashes will eventually find one low enough to satisfy the bitcoin network target. If the dice players are throwing dice with a goal of throwing less than four the overall network difficulty , a pool would set an easier target, counting how many times the pool players managed to throw less than eight. Every now and then, one of the pool players will throw a combined dice throw of less than four and the pool wins.
Then, the earnings can be distributed to the pool players based on the shares they earned. Similarly, a mining pool will set a pool difficulty that will ensure that an individual pool miner can find block header hashes that are less than the pool difficulty quite often, earning shares.
Every now and then, one of these attempts will produce a block header hash that is less than the bitcoin network target, making it a valid block and the whole pool wins. The owner of the pool server is called the pool operator, and he charges pool miners a percentage fee of the earnings.
The pool server runs specialized software and a pool-mining protocol that coordinates the activities of the pool miners. The pool server is also connected to one or more full bitcoin nodes and has direct access to a full copy of the blockchain database. This allows the pool server to validate blocks and transactions on behalf of the pool miners, relieving them of the burden of running a full node.
For pool miners, this is an important consideration, because a full node requires a dedicated computer with at least 15 to 20 GB of persistent storage disk and at least 2 GB of memory RAM. Furthermore, the bitcoin software running on the full node needs to be monitored, maintained, and upgraded frequently. For many miners, the ability to mine without running a full node is another big benefit of joining a managed pool.
The pool server constructs a candidate block by aggregating transactions, adding a coinbase transaction with extra nonce space , calculating the merkle root, and linking to the previous block hash. The header of the candidate block is then sent to each of the pool miners as a template.
Each pool miner then mines using the block template, at a lower difficulty than the bitcoin network difficulty, and sends any successful results back to the pool server to earn shares. P2Pool Managed pools create the possibility of cheating by the pool operator, who might direct the pool effort to double-spend transactions or invalidate blocks see Consensus Attacks. Furthermore, centralized pool servers represent a single-point-of-failure. If the pool server is down or is slowed by a denial-of-service attack, the pool miners cannot mine.
In , to resolve these issues of centralization, a new pool mining method was proposed and implemented: P2Pool is a peer-to-peer mining pool, without a central operator. P2Pool works by decentralizing the functions of the pool server, implementing a parallel blockchain-like system called a share chain.
A share chain is a blockchain running at a lower difficulty than the bitcoin blockchain. The share chain allows pool miners to collaborate in a decentralized pool, by mining shares on the share chain at a rate of one share block every 30 seconds. Each of the blocks on the share chain records a proportionate share reward for the pool miners who contribute work, carrying the shares forward from the previous share block.
When one of the share blocks also achieves the difficulty target of the bitcoin network, it is propagated and included on the bitcoin blockchain, rewarding all the pool miners who contributed to all the shares that preceded the winning share block. P2Pool mining is more complex than pool mining because it requires that the pool miners run a dedicated computer with enough disk space, memory, and Internet bandwidth to support a full bitcoin node and the P2Pool node software.
P2Pool miners connect their mining hardware to their local P2Pool node, which simulates the functions of a pool server by sending block templates to the mining hardware. On P2Pool, individual pool miners construct their own candidate blocks, aggregating transactions much like solo miners, but then mine collaboratively on the share chain. P2Pool is a hybrid approach that has the advantage of much more granular payouts than solo mining, but without giving too much control to a pool operator like managed pools.
Further development of the P2Pool protocol continues with the expectation of removing the need for running a full node and therefore making decentralized mining even easier to use. Rather, P2Pool makes bitcoin more robust overall, as part of a diversified mining ecosystem. As we saw, the consensus mechanism depends on having a majority of the miners acting honestly out of self-interest.
However, if a miner or group of miners can achieve a significant share of the mining power, they can attack the consensus mechanism so as to disrupt the security and availability of the bitcoin network.
It is important to note that consensus attacks can only affect future consensus, or at best the most recent past tens of blocks. While in theory, a fork can be achieved at any depth, in practice, the computing power needed to force a very deep fork is immense, making old blocks practically immutable. A consensus attack cannot steal bitcoins, spend bitcoins without signatures, redirect bitcoins, or otherwise change past transactions or ownership records.
Consensus attacks can only affect the most recent blocks and cause denial-of-service disruptions on the creation of future blocks. With sufficient power, an attacker can invalidate six or more blocks in a row, causing transactions that were considered immutable six confirmations to be invalidated. In the first chapter, we looked at a transaction between Alice and Bob for a cup of coffee.
Bob, the cafe owner, is willing to accept payment for cups of coffee without waiting for confirmation mining in a block , because the risk of a double-spend on a cup of coffee is low in comparison to the convenience of rapid customer service. In contrast, selling a more expensive item for bitcoin runs the risk of a double-spend attack, where the buyer broadcasts a competing transaction that spends the same inputs UTXO and cancels the payment to the merchant.
A double-spend attack can happen in two ways: either before a transaction is confirmed, or if the attacker takes advantage of a blockchain fork to undo several blocks. Instead of waiting for six or more confirmations on the transaction, Carol wraps and hands the paintings to Mallory after only one confirmation.
When the blockchain fork resolves in favor of the new longer chain, the double-spent transaction replaces the original payment to Carol. Carol is now missing the three paintings and also has no bitcoin payment. That is likely to shift Bitcoin mining and electricity consumption to computers outside of China that may require different amounts of energy and rely on different sources for that energy. However, the environmental impact is an important consideration when deciding whether or not to participate in the bitcoin network or a more energy-efficient alternative.
Carbon Footprint According to Digiconomist, the carbon footprint of a single bitcoin transaction in is roughly In China, most electricity comes from coal-burning power plants, which has a huge environmental impact. So when most bitcoin mining mainly took place in China, it relied on a grid that was primarily powered by dirty, coal-burning power plants.
Electronic Waste Specialized equipment required for bitcoin mining, unlike requirements for some other cryptocurrencies , cannot be repurposed for other tasks. This generates massive amounts of electronic waste in the form of computer hardware. According to Digiconomist, in a single bitcoin transaction yields Note Some components of the mining equipment also include metals such as aluminum, copper, iron, and rare earth metals. Some researchers believe that less than ideal recycling and waste collection in countries that have large mining operations could create a risk of toxic metals polluting the soil, water, and air in those countries.
Greener Alternatives? There are other consensus mechanisms such as " proof of stake " PoS followed by cardano or the Stellar Consensus Protocol SCP used by stellar, that are designed for faster transactions and lower electricity usage. Note The ethereum network moved from a proof-of-work to a proof-of-stake consensus mechanism in Sept. By moving to PoS, the ethereum network hopes to reduce its energy consumption by For those who that stick with bitcoin mining, the best ways to cut energy use include shifting to renewable energy, like solar or wind power, or buying the most efficient mining hardware.
Miners using application-specific integrated circuits or ASIC graphics cards may use less power per Bitcoin than less efficient alternatives.
ETHEREUM MINING LINUX SETUP
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