Bitcoin trusted peer incentive


However, this will never be a limitation because transactions can be denominated in smaller sub-units of a bitcoin, such as bits - there are 1,, bits in 1 bitcoin.

Bitcoins can be divided up to 8 decimal places 0. The deflationary spiral theory says that if prices are expected to fall, people will move purchases into the future in order to benefit from the lower prices.

That fall in demand will in turn cause merchants to lower their prices to try and stimulate demand, making the problem worse and leading to an economic depression. Although this theory is a popular way to justify inflation amongst central bankers, it does not appear to always hold true and is considered controversial amongst economists. Consumer electronics is one example of a market where prices constantly fall but which is not in depression.

Similarly, the value of bitcoins has risen over time and yet the size of the Bitcoin economy has also grown dramatically along with it.

Because both the value of the currency and the size of its economy started at zero in , Bitcoin is a counterexample to the theory showing that it must sometimes be wrong. Notwithstanding this, Bitcoin is not designed to be a deflationary currency.

It is more accurate to say Bitcoin is intended to inflate in its early years, and become stable in its later years. The only time the quantity of bitcoins in circulation will drop is if people carelessly lose their wallets by failing to make backups. With a stable monetary base and a stable economy, the value of the currency should remain the same. This is a chicken and egg situation. For bitcoin's price to stabilize, a large scale economy needs to develop with more businesses and users.

For a large scale economy to develop, businesses and users will seek for price stability. Fortunately, volatility does not affect the main benefits of Bitcoin as a payment system to transfer money from point A to point B. It is possible for businesses to convert bitcoin payments to their local currency instantly, allowing them to profit from the advantages of Bitcoin without being subjected to price fluctuations. Since Bitcoin offers many useful and unique features and properties, many users choose to use Bitcoin.

With such solutions and incentives, it is possible that Bitcoin will mature and develop to a degree where price volatility will become limited. Only a fraction of bitcoins issued to date are found on the exchange markets for sale.

Bitcoin markets are competitive, meaning the price of a bitcoin will rise or fall depending on supply and demand. Additionally, new bitcoins will continue to be issued for decades to come. Therefore even the most determined buyer could not buy all the bitcoins in existence. This situation isn't to suggest, however, that the markets aren't vulnerable to price manipulation; it still doesn't take significant amounts of money to move the market price up or down, and thus Bitcoin remains a volatile asset thus far.

For now, Bitcoin remains by far the most popular decentralized virtual currency, but there can be no guarantee that it will retain that position. There is already a set of alternative currencies inspired by Bitcoin. It is however probably correct to assume that significant improvements would be required for a new currency to overtake Bitcoin in terms of established market, even though this remains unpredictable.

Bitcoin could also conceivably adopt improvements of a competing currency so long as it doesn't change fundamental parts of the protocol. Receiving notification of a payment is almost instant with Bitcoin. However, there is a delay before the network begins to confirm your transaction by including it in a block. A confirmation means that there is a consensus on the network that the bitcoins you received haven't been sent to anyone else and are considered your property. Once your transaction has been included in one block, it will continue to be buried under every block after it, which will exponentially consolidate this consensus and decrease the risk of a reversed transaction.

Each confirmation takes between a few seconds and 90 minutes, with 10 minutes being the average. If the transaction pays too low a fee or is otherwise atypical, getting the first confirmation can take much longer.

Every user is free to determine at what point they consider a transaction sufficiently confirmed, but 6 confirmations is often considered to be as safe as waiting 6 months on a credit card transaction. Transactions can be processed without fees, but trying to send free transactions can require waiting days or weeks. Although fees may increase over time, normal fees currently only cost a tiny amount. By default, all Bitcoin wallets listed on Bitcoin. Transaction fees are used as a protection against users sending transactions to overload the network and as a way to pay miners for their work helping to secure the network.

The precise manner in which fees work is still being developed and will change over time. Because the fee is not related to the amount of bitcoins being sent, it may seem extremely low or unfairly high. Instead, the fee is relative to the number of bytes in the transaction, so using multisig or spending multiple previously-received amounts may cost more than simpler transactions.

If your activity follows the pattern of conventional transactions, you won't have to pay unusually high fees. The bitcoins will appear next time you start your wallet application. Bitcoins are not actually received by the software on your computer, they are appended to a public ledger that is shared between all the devices on the network.

If you are sent bitcoins when your wallet client program is not running and you later launch it, it will download blocks and catch up with any transactions it did not already know about, and the bitcoins will eventually appear as if they were just received in real time. Your wallet is only needed when you wish to spend bitcoins. Long synchronization time is only required with full node clients like Bitcoin Core.

Technically speaking, synchronizing is the process of downloading and verifying all previous Bitcoin transactions on the network. For some Bitcoin clients to calculate the spendable balance of your Bitcoin wallet and make new transactions, it needs to be aware of all previous transactions. This step can be resource intensive and requires sufficient bandwidth and storage to accommodate the full size of the block chain. For Bitcoin to remain secure, enough people should keep using full node clients because they perform the task of validating and relaying transactions.

Mining is the process of spending computing power to process transactions, secure the network, and keep everyone in the system synchronized together. It can be perceived like the Bitcoin data center except that it has been designed to be fully decentralized with miners operating in all countries and no individual having control over the network. This process is referred to as "mining" as an analogy to gold mining because it is also a temporary mechanism used to issue new bitcoins.

Unlike gold mining, however, Bitcoin mining provides a reward in exchange for useful services required to operate a secure payment network. Mining will still be required after the last bitcoin is issued.

Anybody can become a Bitcoin miner by running software with specialized hardware. Mining software listens for transactions broadcast through the peer-to-peer network and performs appropriate tasks to process and confirm these transactions. Bitcoin miners perform this work because they can earn transaction fees paid by users for faster transaction processing, and newly created bitcoins issued into existence according to a fixed formula.

For new transactions to be confirmed, they need to be included in a block along with a mathematical proof of work. Such proofs are very hard to generate because there is no way to create them other than by trying billions of calculations per second. This requires miners to perform these calculations before their blocks are accepted by the network and before they are rewarded.

As more people start to mine, the difficulty of finding valid blocks is automatically increased by the network to ensure that the average time to find a block remains equal to 10 minutes. As a result, mining is a very competitive business where no individual miner can control what is included in the block chain. The proof of work is also designed to depend on the previous block to force a chronological order in the block chain.

This makes it exponentially difficult to reverse previous transactions because this requires the recalculation of the proofs of work of all the subsequent blocks. When two blocks are found at the same time, miners work on the first block they receive and switch to the longest chain of blocks as soon as the next block is found. This allows mining to secure and maintain a global consensus based on processing power.

Bitcoin miners are neither able to cheat by increasing their own reward nor process fraudulent transactions that could corrupt the Bitcoin network because all Bitcoin nodes would reject any block that contains invalid data as per the rules of the Bitcoin protocol. Consequently, the network remains secure even if not all Bitcoin miners can be trusted.

Spending energy to secure and operate a payment system is hardly a waste. Like any other payment service, the use of Bitcoin entails processing costs. Services necessary for the operation of currently widespread monetary systems, such as banks, credit cards, and armored vehicles, also use a lot of energy. Although unlike Bitcoin, their total energy consumption is not transparent and cannot be as easily measured.

Bitcoin mining has been designed to become more optimized over time with specialized hardware consuming less energy, and the operating costs of mining should continue to be proportional to demand. When Bitcoin mining becomes too competitive and less profitable, some miners choose to stop their activities. Furthermore, all energy expended mining is eventually transformed into heat, and the most profitable miners will be those who have put this heat to good use.

An optimally efficient mining network is one that isn't actually consuming any extra energy. While this is an ideal, the economics of mining are such that miners individually strive toward it.

Mining creates the equivalent of a competitive lottery that makes it very difficult for anyone to consecutively add new blocks of transactions into the block chain. This protects the neutrality of the network by preventing any individual from gaining the power to block certain transactions. This also prevents any individual from replacing parts of the block chain to roll back their own spends, which could be used to defraud other users. Mining makes it exponentially more difficult to reverse a past transaction by requiring the rewriting of all blocks following this transaction.

In the early days of Bitcoin, anyone could find a new block using their computer's CPU. As more and more people started mining, the difficulty of finding new blocks increased greatly to the point where the only cost-effective method of mining today is using specialized hardware.

You can visit BitcoinMining. The Bitcoin technology - the protocol and the cryptography - has a strong security track record, and the Bitcoin network is probably the biggest distributed computing project in the world. Bitcoin's most common vulnerability is in user error. Bitcoin wallet files that store the necessary private keys can be accidentally deleted, lost or stolen. This is pretty similar to physical cash stored in a digital form. Fortunately, users can employ sound security practices to protect their money or use service providers that offer good levels of security and insurance against theft or loss.

The rules of the protocol and the cryptography used for Bitcoin are still working years after its inception, which is a good indication that the concept is well designed. However, security flaws have been found and fixed over time in various software implementations. Like any other form of software, the security of Bitcoin software depends on the speed with which problems are found and fixed.

The more such issues are discovered, the more Bitcoin is gaining maturity. There are often misconceptions about thefts and security breaches that happened on diverse exchanges and businesses.

Although these events are unfortunate, none of them involve Bitcoin itself being hacked, nor imply inherent flaws in Bitcoin; just like a bank robbery doesn't mean that the dollar is compromised. However, it is accurate to say that a complete set of good practices and intuitive security solutions is needed to give users better protection of their money, and to reduce the general risk of theft and loss. Over the course of the last few years, such security features have quickly developed, such as wallet encryption, offline wallets, hardware wallets, and multi-signature transactions.

It is not possible to change the Bitcoin protocol that easily. Any Bitcoin client that doesn't comply with the same rules cannot enforce their own rules on other users. As per the current specification, double spending is not possible on the same block chain, and neither is spending bitcoins without a valid signature. Therefore, it is not possible to generate uncontrolled amounts of bitcoins out of thin air, spend other users' funds, corrupt the network, or anything similar.

However, powerful miners could arbitrarily choose to block or reverse recent transactions. A majority of users can also put pressure for some changes to be adopted. Because Bitcoin only works correctly with a complete consensus between all users, changing the protocol can be very difficult and requires an overwhelming majority of users to adopt the changes in such a way that remaining users have nearly no choice but to follow. As a general rule, it is hard to imagine why any Bitcoin user would choose to adopt any change that could compromise their own money.

Yes, most systems relying on cryptography in general are, including traditional banking systems. However, quantum computers don't yet exist and probably won't for a while. In the event that quantum computing could be an imminent threat to Bitcoin, the protocol could be upgraded to use post-quantum algorithms. Given the importance that this update would have, it can be safely expected that it would be highly reviewed by developers and adopted by all Bitcoin users.

You can find more information and help on the resources and community pages or on the Wiki FAQ. Frequently Asked Questions Find answers to recurring questions and myths about Bitcoin. Table of contents General What is Bitcoin? Who controls the Bitcoin network? How does Bitcoin work? Is Bitcoin really used by people? How does one acquire bitcoins?

How difficult is it to make a Bitcoin payment? What are the advantages of Bitcoin? What are the disadvantages of Bitcoin? Why do people trust Bitcoin?

Can I make money with Bitcoin? Is Bitcoin fully virtual and immaterial? What happens when bitcoins are lost? Can Bitcoin scale to become a major payment network? Legal Is Bitcoin legal? Is Bitcoin useful for illegal activities? Can Bitcoin be regulated? What about Bitcoin and taxes? What about Bitcoin and consumer protection? Economy How are bitcoins created? Why do bitcoins have value? Can bitcoins become worthless? Is Bitcoin a bubble? Is Bitcoin a Ponzi scheme?

Doesn't Bitcoin unfairly benefit early adopters? Won't the finite amount of bitcoins be a limitation? Won't Bitcoin fall in a deflationary spiral? Isn't speculation and volatility a problem for Bitcoin? What if someone bought up all the existing bitcoins? What if someone creates a better digital currency? Transactions Why do I have to wait for confirmation? How much will the transaction fee be? What if I receive a bitcoin when my computer is powered off?

What does "synchronizing" mean and why does it take so long? Mining What is Bitcoin mining? How does Bitcoin mining work?

Isn't Bitcoin mining a waste of energy? How does mining help secure Bitcoin? What do I need to start mining? Security Is Bitcoin secure? Hasn't Bitcoin been hacked in the past? Could users collude against Bitcoin? Is Bitcoin vulnerable to quantum computing? After each transaction, the coin must be returned to the mint to issue a new coin, and only coins issued directly from the mint are trusted not to be double-spent. The problem with this solution is that the fate of the entire money system depends on the company running the mint, with every transaction having to go through them, just like a bank.

We need a way for the payee to know that the previous owners did not sign any earlier transactions. For our purposes, the earliest transaction is the one that counts, so we don't care about later attempts to double-spend. The only way to confirm the absence of a transaction is to be aware of all transactions.

In the mint based model, the mint was aware of all transactions and decided which arrived first. To accomplish this without a trusted party, transactions must be publicly announced [1] , and we need a system for participants to agree on a single history of the order in which they were received.

The payee needs proof that at the time of each transaction, the majority of nodes agreed it was the first received. The solution we propose begins with a timestamp server. A timestamp server works by taking a hash of a block of items to be timestamped and widely publishing the hash, such as in a newspaper or Usenet post [].

The timestamp proves that the data must have existed at the time, obviously, in order to get into the hash. Each timestamp includes the previous timestamp in its hash, forming a chain, with each additional timestamp reinforcing the ones before it. To implement a distributed timestamp server on a peer-to-peer basis, we will need to use a proof-of-work system similar to Adam Back's Hashcash [6] , rather than newspaper or Usenet posts.

The proof-of-work involves scanning for a value that when hashed, such as with SHA, the hash begins with a number of zero bits. The average work required is exponential in the number of zero bits required and can be verified by executing a single hash. For our timestamp network, we implement the proof-of-work by incrementing a nonce in the block until a value is found that gives the block's hash the required zero bits. Once the CPU effort has been expended to make it satisfy the proof-of-work, the block cannot be changed without redoing the work.

As later blocks are chained after it, the work to change the block would include redoing all the blocks after it. The proof-of-work also solves the problem of determining representation in majority decision making. If the majority were based on one-IP-address-one-vote, it could be subverted by anyone able to allocate many IPs.

Proof-of-work is essentially one-CPU-one-vote. The majority decision is represented by the longest chain, which has the greatest proof-of-work effort invested in it. If a majority of CPU power is controlled by honest nodes, the honest chain will grow the fastest and outpace any competing chains. To modify a past block, an attacker would have to redo the proof-of-work of the block and all blocks after it and then catch up with and surpass the work of the honest nodes.

We will show later that the probability of a slower attacker catching up diminishes exponentially as subsequent blocks are added. To compensate for increasing hardware speed and varying interest in running nodes over time, the proof-of-work difficulty is determined by a moving average targeting an average number of blocks per hour.

If they're generated too fast, the difficulty increases. Nodes always consider the longest chain to be the correct one and will keep working on extending it.

If two nodes broadcast different versions of the next block simultaneously, some nodes may receive one or the other first. In that case, they work on the first one they received, but save the other branch in case it becomes longer. The tie will be broken when the next proof-of-work is found and one branch becomes longer; the nodes that were working on the other branch will then switch to the longer one.

New transaction broadcasts do not necessarily need to reach all nodes. As long as they reach many nodes, they will get into a block before long. Block broadcasts are also tolerant of dropped messages. If a node does not receive a block, it will request it when it receives the next block and realizes it missed one. By convention, the first transaction in a block is a special transaction that starts a new coin owned by the creator of the block.

This adds an incentive for nodes to support the network, and provides a way to initially distribute coins into circulation, since there is no central authority to issue them. The steady addition of a constant of amount of new coins is analogous to gold miners expending resources to add gold to circulation. In our case, it is CPU time and electricity that is expended.

The incentive can also be funded with transaction fees. If the output value of a transaction is less than its input value, the difference is a transaction fee that is added to the incentive value of the block containing the transaction. Once a predetermined number of coins have entered circulation, the incentive can transition entirely to transaction fees and be completely inflation free.

The incentive may help encourage nodes to stay honest. If a greedy attacker is able to assemble more CPU power than all the honest nodes, he would have to choose between using it to defraud people by stealing back his payments, or using it to generate new coins.

He ought to find it more profitable to play by the rules, such rules that favour him with more new coins than everyone else combined, than to undermine the system and the validity of his own wealth. Once the latest transaction in a coin is buried under enough blocks, the spent transactions before it can be discarded to save disk space.

To facilitate this without breaking the block's hash, transactions are hashed in a Merkle Tree [7] [2] [5] , with only the root included in the block's hash. Old blocks can then be compacted by stubbing off branches of the tree. The interior hashes do not need to be stored.

A block header with no transactions would be about 80 bytes. It is possible to verify payments without running a full network node. A user only needs to keep a copy of the block headers of the longest proof-of-work chain, which he can get by querying network nodes until he's convinced he has the longest chain, and obtain the Merkle branch linking the transaction to the block it's timestamped in.

He can't check the transaction for himself, but by linking it to a place in the chain, he can see that a network node has accepted it, and blocks added after it further confirm the network has accepted it. As such, the verification is reliable as long as honest nodes control the network, but is more vulnerable if the network is overpowered by an attacker.

While network nodes can verify transactions for themselves, the simplified method can be fooled by an attacker's fabricated transactions for as long as the attacker can continue to overpower the network. One strategy to protect against this would be to accept alerts from network nodes when they detect an invalid block, prompting the user's software to download the full block and alerted transactions to confirm the inconsistency.

Businesses that receive frequent payments will probably still want to run their own nodes for more independent security and quicker verification.

Although it would be possible to handle coins individually, it would be unwieldy to make a separate transaction for every cent in a transfer. To allow value to be split and combined, transactions contain multiple inputs and outputs. Normally there will be either a single input from a larger previous transaction or multiple inputs combining smaller amounts, and at most two outputs: It should be noted that fan-out, where a transaction depends on several transactions, and those transactions depend on many more, is not a problem here.

There is never the need to extract a complete standalone copy of a transaction's history. The traditional banking model achieves a level of privacy by limiting access to information to the parties involved and the trusted third party. The necessity to announce all transactions publicly precludes this method, but privacy can still be maintained by breaking the flow of information in another place: