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Bit What? Bitcoin!

Posted: August 9th, 2011 | Author: | Filed under: Favorite New Thought, Michael Courtenay | Tags: , , , , | Comments Off

Bit What? Bitcoin!

In early June 2011 the interweb spruked the Bitcoin “Recent weeks have been exciting for a relatively new kind of currency speculator. In just three weeks, the total value of a unique new digital currency called Bitcoin has jumped four times, to over $40 million” and though the currency was created in 2009, the hype didn’t hit until 2011

Bitcoin is not underwritten by a government, but by a clever cryptographic scheme. For now, little can be bought with bitcoins, and the new currency is still a long way from competing with the dollar. But this explainer lays out what Bitcoin is, why it matters, and what needs to happen for it to succeed ::::

In 2008, a programmer known as Satoshi Nakamoto  posted a paper outlining Bitcoin’s design to a cryptography e-mail list. Then, in early 2009, he (or she) released software that can be used to exchange bitcoins using the scheme. That software is now maintained by a volunteer open-source community coordinated by four core developers.

“Satoshi’s a bit of a mysterious figure,” says Jeff Garzik, a member of that core team and founder of Bitcoin Watch, which tracks the Bitcoin economy. “I and the other core developers have occasionally corresponded with him by e-mail, but it’s always a crapshoot as to whether he responds,” says Garzik. “That and the forum are the entirety of anyone’s experience with him.”

Nakamoto wanted people to be able to exchange money electronically securely without the need for a third party, such as a bank or a company like PayPal. He based Bitcoin on cryptographic techniques that allow you to be sure the money you receive is genuine, even if you don’t trust the sender.

Today: Bitcoin, the world’s first peer-to-peer digital currency, has lost more than half of its initialvalue against the dollar, since the end of June 2011 it’s tumble has been catastrophic, falling from $13.50 to around $7 – from an initial float of almost $40.

It’s been a rough trot for Bitcoin. First, Bitcoin malware hit the Web just weeks after it’s hyped launch. The Melware attempts to steal a Bitcoin user’s wallet and email it to an email address. Guess you kind of had to expect cyber crime on a cyber currency!?. Now, Mt.Gox, Bitcoins largest exchange was seriously compromised. The exchange’s system was hacked, obtaining a Mt.Gox database consisting of user names, email addresses, and password hashes. Additionally, they used the credentials of one account which contained a large number of bitcoins to log in, sell $1000 worth of bitcoins, then buy them back and withdraw them. This series of events caused the market to flash-crash, thus taking the value of bitcoins down to one cent per bitcoin for a moment before jumping back up to ~$13 per bitcoin, ouch. So we now know Bitcoin suffers the same frailty as offline markets, but whats it all based on?

Timothy B. Lee puts it succinctly, “Most assets have a “fundamental” value: the value that reflects the practical use to which that asset can be put. You can always live in a house regardless of what happens to the real estate market, so we can be confident that house prices won’t fall to zero. Similarly, if the price of gold fell too much, people could always use it to make jewelry, so gold is a relatively safe investment”

The puzzling thing about Bitcoin is that the currency doesn’t seem to have any fundamental value at all. You can currently purchase a very limited selection of goods and services with Bitcoins.  While we’re not as pesimistic as Mr Lee, we do wonder where this is all going to end up. Let’s not get ahead of ourselves though.  Why should anyone give a side-ways about  Bitcoins? Well, today on Mt. Gox alone, approximately $2M USD in Bitcoins were bought and sold in 5,871 trades, a total of $19M USD in trading volume occurred over the past six months.

The bottom line is that several things are clear from recent Bitcoin trading.

  • The Bitcoin market endured its first digital equivalent of a “bank rush” with people rushing to exchange their BTC for U.S. Dollars.
  • People have a large amount of money — millions of USD sunk into Bitcoins lost big in the flash crash.
  • Unlike modern markets, which automatically close to prevent massive inflation, the digital Bitcoin markets stayed open.
  • Something major is moving the Bitcoin market in a sharp inflationary direction, in contrast to the predict deflationary trend

So what are Bitcoins and why is this intriguing?  Checkout https://en.bitcoin.it/wiki/FAQ for a comprehensive – all you need to know – rundown on the coins.

So how do you get you hands on Bitcoins? There are a variety of ways to acquire Bitcoins:

  • Accept Bitcoins as payment for goods or services.
  • There are several services where you can trade them for traditional currency.
  • Find a local trader on tradebitcoin (or somewhere else) and trade with him in cash.
  • Create a new block (currently yields 50 Bitcoins).
  • Participate in a mining pool.

Get out of the house: Bitcoins are literaly an online currency. To understand the way they work, you need to NOT THINK in terms of paper currency! It is all cyber, once you download and run the Bitcoin client software, it connects over the Internet to the decentralized network of all Bitcoin users and also generates a pair of unique, mathematically linked keys, which you’ll need to exchange bitcoins with any other client. One key is private and kept hidden on your computer. The other is public and a version of it dubbed a Bitcoin address is given to other people so they can send you bitcoins. Crucially, it is practically impossible—even with the most powerful supercomputer—to work out someone’s private key from their public key. This prevents anyone from impersonating you. Your public and private keys are stored in a file that can be transferred to another computer, for example if you upgrade.

A Bitcoin address looks something like this: 15VjRaDX9zpbA8LVnbrCAFzrVzN7ixHNsC. Stores that accept bitcoins—for example, this one, selling alpaca socks—provide you with their address so you can pay for goods.

When you perform a transaction, your Bitcoin software performs a mathematical operation to combine the other party’s public key and your own private key with the amount of bitcoins that you want to transfer. The result of that operation is then sent out across the distributed Bitcoin network so the transaction can be verified by Bitcoin software clients not involved in the transfer.

Those clients make two checks on a transaction. One uses the public key to confirm that the true owner of the pair sent the money, by exploiting the mathematical relationship between a person’s public and private keys; the second refers to a public transaction log stored on the computer of every Bitcoin user to confirm that the person has the bitcoins to spend.

When a client verifies a transaction, it forwards the details to others in the network to check for themselves. In this way a transaction quickly reaches and is verified by every Bitcoin client that is online. Some of those clients – “miners” – also try to add the new transfer to the public transaction log, by racing to solve a cryptographic puzzle. Once one of them wins the updated log is passed throughout the Bitcoin network. When your software receives the updated log it knows your payment was successful.

The nature of the mathematics ensures that it is computationally easy to verify a transaction but practically impossible to generate fake transactions and spend bitcoins you don’t own. The existence of a public log of all transactions also provides a deterrent to money laundering, says Garzik. “You’re looking at a global public transaction register,” he says. “You can trace the history of every single Bitcoin through that log, from its creation through every transaction.”

Exchanges like Mt. Gox provide a place for people to trade bitcoins for other types of currency. Some enthusiasts have also started doing work, such as designing websites, in exchange for bitcoins. This jobs board advertises contract work paying in bitcoins.

But bitcoins also need to be generated in the first place. Bitcoins are “mined” when you set your Bitcoin client to a mode that has it compete to update the public log of transactions. All the clients set to this mode race to solve a cryptographic puzzle by completing the next “block” of the shared transaction log. Winning the race to complete the next block wins you a 50-Bitcoin prize. This feature exists as a way to distribute bitcoins in the currency’s early years. Eventually, new coins will not be issued this way; instead, mining will be rewarded with a small fee taken from some of the value of a verified transaction.

Mining is very computationally intensive, to the point that any computer without a powerful graphics card is unlikely to mine any bitcoins in less than a few years.

There aren’t a lot of places to spend up right now. Some Bitcoin enthusiasts with their own businesses have made it possible to swap bitcoins for teabooks, or Web design (check the comprehensive list here). But no major retailers accept the new currency yet.

Nakamoto’s rules specify that the amount of bitcoins in circulation will grow at an ever-decreasing rate toward a maximum of 21 million. Currently there are just over 6 million; in 2030, there will be over 20 million bitcoins.

Nakamoto’s scheme includes one loophole, however: if more than half of the Bitcoin network’s computing power comes under the control of one entity, then the rules can change. This would prevent, for example, a criminal cartel faking a transaction log in its own favor to dupe the rest of the community.

It is unlikely that anyone will ever obtain this kind of control. “The combined power of the network is currently equal to one of the most powerful supercomputers in the world,” says Garzik. “Satoshi’s rules are probably set in stone.”

Bitcoins are certainly different. “Elaborate controls to make sure that currency is not produced in greater numbers is not something any other currency, like the dollar or the euro, has,” says Russ Roberts, professor of economics at George Mason University. The consequence will likely be slow and steady deflation, as the growth in circulating bitcoins declines and their value rises.

“That is considered very destructive in today’s economies, mostly because when it occurs, it is unexpected,” says Roberts. But he thinks that won’t apply in an economy where deflation is expected. “In a Bitcoin world, everyone would anticipate that, and they know what they got paid would buy more then than it would now.”

That’s unlikely. “It might have a niche as a way to pay for certain technical services,” says Roberts, adding that even limited success could allow Bitcoin to change the fate of more established currencies. “Competition is good, even between currencies—perhaps the example of Bitcoin could influence the behavior of the Federal Reserve.”

Central banks the world over have freely increased the money supply of their currencies in response to the global downturn. Roberts suggests that Bitcoin could set a successful, if smaller scale, example of how economies that forbid such intervention can also succeed.

What are bitcoins?

Bitcoins are the unit of currency of the Bitcoin system. A commonly used shorthand for this is “BTC” to refer to a price or amount (eg: “100 BTC”). A Bitcoin isn’t tangible. It is just a number associated with a Bitcoin Address. See also an easy intro to bitcoin.

How can I get Bitcoins?

There are a variety of ways to acquire Bitcoins:

  • Accept Bitcoins as payment for goods or services.
  • There are several services where you can trade them for traditional currency.
  • Find a local trader on tradebitcoin (or somewhere else) and trade with him in cash.
  • Create a new block (currently yields 50 Bitcoins).
  • Participate in a mining pool.

Can I buy Bitcoins with Paypal?

While it’s possible to find an individual who wishes to sell Bitcoin to you via Paypal, (perhaps via #bitcoin-otc ) most major exchanges do not allow funding through Paypal. This is due to repeated cases where someone pays for Bitcoins with Paypal, receives their Bitcoins, and then fraudulently complains to Paypal that they never received their goods. Paypal too often sides with the fraudulent buyer in this case, and so exchangers no longer allow this method of funding.

Buying Bitcoins from individuals with this method is still possible, but requires mutual trust. In this case, Bitcoin seller beware.

Where can I find a forum of Bitcoin users?

There is no longer an “official” forum for Bitcoin. The Community Portal includes links to some forums.

How are new Bitcoins created?

New coins are generated by a network node each time it finds the solution to a certain mathematical problem (i.e. creates a new block), which is difficult to perform and can demonstrate a proof of work. The reward for solving a block is automatically adjusted so that in the first 4 years of the Bitcoin network, 10,500,000 BTC will be created. The amount is halved each 4 years, so it will be 5,250,000 over years 4-8, 2,625,000 over years 8-12 and so on. Thus the total number of coins will approach 21,000,000 BTC over time.

Blocks should be generated every 10 minutes, on average. As the number of people who attempt to generate these new coins changes, the difficulty of creating new coins changes. This happens in a manner that is agreed upon in advance by the network as a whole, based upon the time taken to generate the previous 2016 blocks. The difficulty is therefore related to the average computing resources devoted to generate these new coins over the time it took to create these previous blocks. The likelihood of somebody creating a block is based on the calculation speed of the system that they are using compared to the aggregate calculation speed of all the other systems generating blocks on the network.

What’s the current total number of Bitcoins in existence?

Current count

The number of blocks times the coin value of a block is the number of coins in existence. The coin value of a block is 50 BTC for each of the first 210,000 blocks, 25 BTC for the next 210,000 blocks, then 12.5 BTC, 6.25 BTC and so on.

How divisible are Bitcoins?

Technically, a Bitcoin can be divided down to 8 decimals using existing data structures, so 0.00000001 BTC is the smallest amount currently possible. Discussions about and ideas for ways to provide for even smaller quantities of Bitcoins may be created in the future if the need for them ever arises.

What do I call the various denominations of Bitcoins?

There is a lot of discussion about the naming of these fractions of Bitcoins. The leading candidates are:

  • 1 BTC = 1 Bitcoin
  • 0.01 BTC = 1 cBTC = 1 Centi-Bitcoin (also referred to as Bitcent)
  • 0.001 BTC = 1 mBTC = 1 Milli-Bitcoin (also referred to as mbit (pronounced em-bit) or millibit)
  • 0.000 001 BTC = 1 μBTC = 1 Micro-Bitcoin (also referred to as ubit (pronounced yu-bit) or microbit)

The above follows the accepted international SI units for thousandths, millionths and billionths. There are many arguments against the special case of 0.01 BTC since it is unlikely to represent anything meaningful as the Bitcoin economy grows (it certainly won’t be the equivalent of 0.01 USD, GBP or EUR). Equally, the inclusion of existing national currency denominations such as “cent”, “nickel”, “dime”, “pence”, “pound”, “kopek” and so on are to be discouraged. This is a worldwide currency.

One exception is the “satoshi” which is smallest denomination currently possible

  • 0.000 000 01 BTC = 1 Satoshi (pronounced sa-toh-shee)

which is so named in honour of Satoshi Nakamoto the pseudonym of the inventor of Bitcoin.

For an overview of all defined units of Bitcoin (including less common and niche units), see Units.

Further discussion on this topic can be found on the forums here:

How does the halving work when the number gets really small?

The reward will go from 0.00000001 BTC to 0. Then no more coins will likely be created.

The calculation is done as a right bitwise shift of a 64-bit signed integer, which means it is divided by 2 and rounded down. The integer is equal to the value in BTC * 100,000,000. This is how all Bitcoin balances/values are stored internally.

Keep in mind that using current rules this will take nearly 100 years before it becomes an issue and Bitcoins may change considerably before that happens.

How long will it take to generate all the coins?

The last block that will generate coins will be block #6,929,999. This should be generated around year 2140. Then the total number of coins in circulation will remain static at 20,999,999.9769 BTC.

Even if the allowed precision is expanded from the current 8 decimals, the total BTC in circulation will always be slightly below 21 million (assuming everything else stays the same). For example, with 16 decimals of precision, the end total would be 20999999.999999999496 BTC.

If no more coins are going to be generated, will more blocks be created?

Absolutely! Even before the creation of coins ends, the use of transaction fees will likely make creating new blocks more valuable from the fees than the new coins being created. When coin generation ends, what will sustain the ability to use bitcoins will be these fees entirely. There will be blocks generated after block #6,929,999.

But if no more coins are generated, what happens when Bitcoins are lost? Won’t that be a problem?

Because of the law of supply and demand, when fewer bitcoins are available the ones that are left will be in higher demand, and therefore will have a higher value. So, as Bitcoins are lost, the remaining bitcoins will increase in value to compensate. As the value of a bitcoin increases, the number of bitcoins required to purchase an item decreases. This is a deflationary economic model. As the average transaction size reduces, transactions will probably be denominated in sub-units of a bitcoin such as millibitcoins (“Millies”) or microbitcoins (“Mikes”).

The Bitcoin protocol uses a base unit of one hundred-millionth of a Bitcoin (“a Satoshi”), but unused bits are available in the protocol fields that could be used to denote even smaller subdivisions.

If every transaction is broadcast via the network, does BitCoin scale?

The Bitcoin protocol allows lightweight clients that can use Bitcoin without downloading the entire transaction history. As traffic grows and this becomes more critical, implementations of the concept will be developed. Full network nodes will at some point become a more specialized service.

With some modifications to the software, full BitCoin nodes could easily keep up with both VISA and MasterCard combined, using only fairly modest hardware (a couple of racks of machines using todays hardware). It’s worth noting that the MasterCard network is structured somewhat like BitCoin itself – as a peer to peer broadcast network.

Learn more about Scalability.

Economy

Where does the value of Bitcoin stem from? What backs up Bitcoin?

Bitcoins have value because they are accepted as payment by many. See the list of Bitcoin-accepting sites.

When we say that a currency is backed up by gold, we mean that there’s a promise in place that you can exchange the currency for gold. In a sense, you could say that Bitcoin is “backed up” by the price tags of merchants – a price tag is a promise to exchange goods for a specified amount of currency.

It’s a common misconception that Bitcoins gain their value from the cost of electricity required to generate them. Cost doesn’t equal value – hiring 1,000 men to shovel a big hole in the ground may be costly, but not valuable. Also, even though scarcity is a critical requirement for a useful currency, it alone doesn’t make anything valuable. For example, your fingerprints are scarce, but that doesn’t mean they have any exchange value.

What if someone bought up all the existing Bitcoins?

What if somebody bought up all the gold in the world? Well, by attempting to buy it all, the buyer would just drive the prices up until he runs out of money.

Not all Bitcoins are for sale. Just as with gold, no one can buy a Bitcoin that isn’t available for sale.

Won’t Bitcoin’s deflationary tendencies cause a deflationary spiral?

See the article Deflationary spiral.

Doesn’t Bitcoin unfairly benefit early adopters?

Early adopters have a large number of bitcoins now because they took a risk and invested resources in an unproven technology. By so doing, they have helped Bitcoin become what it is now and what it will be in the future (hopefully, a ubiquitous decentralized digital currency). It is only fair they will reap the benefits of their successful investment.

In any case, any bitcoin generated will probably change hands dozens of time as a medium of exchange, so the profit made from the initial distribution will be insignificant compared to the total commerce enabled by Bitcoin.

Is Bitcoin a Ponzi scheme?

In a Ponzi Scheme, the founders persuade investors that they’ll profit. Bitcoin does not make such a guarantee. There is no central entity, just individuals building an economy.

A ponzi scheme is a zero sum game. Early adopters can only profit at the expense of late adopters. Bitcoin has possible win-win outcomes. Early adopters profit from the rise in value. Late adopters profit from the usefulness of a stable and widely accepted p2p currency.

The fact that early adopters benefit more doesn’t alone make anything a ponzi scheme. Apple stocks aren’t ponzi even though the early investors got rich.

Is Bitcoin a bubble?

Yes, in the same way as the euro and dollar are. They only have value in exchange and no value in use. If everyone suddenly stopped accepting your dollars, euros or bitcoins, the “bubble” would burst and their value would drop to zero. But that is unlikely to happen: even in Somalia, where the government collapsed 20 years ago, Somali shillings are still accepted as payment.

Sending and Receiving Payments

Why do I have to wait 10 minutes before I can spend money I received?

10 minutes is the average time taken to find a block. It can be significantly more or less time than that depending on luck; 10 minutes is simply the average case.

Blocks (shown as “confirmations” in the GUI) are how the BitCoin achieves consensus on who owns what. Once a block is found everyone agrees that you now own those coins, so you can spend them again. Until then it’s possible that some network nodes believe otherwise, if somebody is attempting to defraud the system by reversing a transaction. The more confirmations a transaction has, the less risk there is of a reversal. Only 6 blocks or 1 hour is enough to make reversal computationally impractical. This is dramatically better than credit cards which can see chargebacks occur up to three months after the original transaction!

Why ten minutes specifically? It is a tradeoff chosen by Satoshi between propagation time of new blocks in large networks and the amount of work wasted due to chain splits. If that made no sense to you, don’t worry. Reading the technical paper should make things clearer.

Do you have to wait 10 minutes in order to buy or sell things with BitCoin?

No, it’s reasonable to sell things without waiting for a confirmation as long as the transaction is not of high value.

When people ask this question they are usually thinking about applications like supermarkets or snack machines, as discussed in this thread from July 2010. Zero confirmation transactions still show up in the GUI, but you cannot spend them. You can however reason about the risk involved in assuming you will be able to spend them in future. In general, selling things that are fairly cheap (like snacks, digital downloads etc) for zero confirmations will not pose a problem if you are running a well connected node.

I sent some bitcoins and they haven’t arrived yet! Where are they?

Don’t panic! There are a number of reasons why your bitcoins might not show up yet, and a number of ways to diagnose them. First of all, check the current max block count by going here and comparing that to the number in the bottom right hand corner of your client. If these numbers are different by more than 1 or 2 then you need to wait for your block chain to download. If not, then it’s possible that your transaction hasn’t been included in a block yet. You can check pending transactions in the network by going here and then searching for your address. If the transaction is listed here then it’s a matter of waiting until it gets included in a block before it will show in your client. Bear in mind that if the transaction is based on a coin that was in a recent transaction then it will take longer to transfer e.g. someone just sent you a coin, if you send that again, it will take a while to transfer unless you put a large (0.01) fee on it. Transactions with 0 fees might take hours or days to be included in a block.

Why does my Bitcoin address keep changing?

Whenever the address listed in “Your address” receives a transaction, Bitcoin replaces it with a new address. This is meant to encourage you to use a new address for every transaction, which enhances anonymity. All of your old addresses are still usable: you can see them in Settings -> Your Receiving Addresses.

How much will the transaction fee be?

Some transactions might require a transaction fee for them to get confirmed in a timely manner. The transaction fee is processed by and received by the bitcoin miner. The most recent version of the Bitcoin client will estimate an appropriate fee when a fee might be required.

The fee is added to the payment amount. For example, if you are sending a 1.234 BTC payment and the client requires a 0.0005 BTC fee, then 1.2345 BTC will be subtracted from the wallet balance for the entire transaction and the address for where the payment was sent will receive a payment of 1.234 BTC.

Because the fee is related to the amount of data that makes up the transaction and not to the amount of bitcoins being sent, the fee may seem extremely low (0.0005 BTC for a 1,000 BTC transfer) or unfairly high (0.004 BTC for a 0.02 BTC payment, or about 20%). If you are receiving tiny amounts (e.g., as small payments from a mining pool) then fees when sending will be higher than if your activity follows a more normal consumer or business transaction pattern.

Networking

Do I need to configure my firewall to run bitcoin?

Bitcoin will connect to other nodes, usually on tcp port 8333. You will need to allow outgoing TCP connections to port 8333 if you want to allow your bitcoin client to connect to many nodes. Bitcoin will also try to connect to IRC (tcp port 6667) to meet other nodes to connect to.

If you want to restrict your firewall rules to a few ips and/or don’t want to allow IRC connection, you can find stable nodes in the fallback nodes list. If your provider blocks the common IRC ports, note that lfnet also listens on port 7777. Connecting to this alternate port currently requires either recompiling Bitcoin, or changing routing rules.

How does the peer finding mechanism work?

Bitcoin finds peers primarily by connecting to an IRC server (channel #bitcoin on irc.lfnet.org). If a connection to the IRC server cannot be established (like when connecting through TOR), an in-built node list will be used and the nodes will be queried for more node addresses.

Mining

What is mining?

Mining is the process of spending computation power to find valid blocks and thus create new Bitcoins.

Technically speaking, mining is the calculation of a hash of the a block header, which includes among other things a reference to the previous block, a hash of a set of transactions and a nonce. If the hash value is found to be less than the current target (which is inversely proportional to the difficulty), a new block is formed and the miner gets 50 newly generated Bitcoins. If the hash is not less than the current target, a new nonce is tried, and a new hash is calculated. This is done millions of times per second by each miner.

Why was the “Generate coin” option of the client software removed?

In the early days of Bitcoin, it was easy for anyone to find new blocks using standard CPUs. As more and more people started mining, the difficulty of finding new blocks has greatly increased to the point where the average time for a CPU to find a single block can be many years. The only cost-effective method of mining is using a high-end graphics card with special software (see also Why a GPU mines faster than a CPU) and/or joining a mining pool. Since solo CPU mining is essentially useless, it was removed from the GUI of the Bitcoin software.

Is mining used for some useful computation?

The computations done when mining are internal to Bitcoin and not related to any other distributed computing projects. They serve the purpose of securing the Bitcoin network, which is useful.

Is it not a waste of energy?

Spending energy on creating a free monetary system is hardly a waste. Also, services necessary for the operation of currently widespread monetary systems, such as banks and credit card companies, also spend energy, arguably more than Bitcoin would.

Why don’t we use calculations that are also useful for some other purpose?

To provide security for the Bitcoin network, the calculations involved need to have some very specific features. These features are incompatible with leveraging the computation for other purposes.

How does the proof-of-work system help secure Bitcoin?

To give a general idea of the mining process, imagine this setup:

 payload = <some data related to things happening on the Bitcoin network>
 nonce = 1
 hash = SHA2( SHA2( payload + nonce ) )

The work performed by a miner consists of repeatedly increasing “nonce” until the hash function yields a value, that has the rare property of being below a certain target threshold. (In other words: The hash “starts with a certain number of zeroes”, if you display it in the fixed-length representation, that is typically used.)

As can be seen, the mining process doesn’t compute anything special. It merely tries to find a number (also referred to as nonce) which – in combination with the payload – results in a hash with special properties.

The advantage of using such a mechanism consists of the fact, that it is very easy to check a result: Given the payload and a specific nonce, only a single call of the hashing function is needed to verify that the hash has the required properties. Since there is no known way to find these hashes other than brute force, this can be used as a “proof of work” that someone invested a lot of computing power to find the correct nonce for this payload.

This feature is then used in the Bitcoin network to secure various aspects. An attacker that wants to introduce malicious payload data into the network, will need to do the required proof of work before it will be accepted. And as long as honest miners have more computing power, they can always outpace an attacker.

Also see SHA2 and Proof-of-work system on Wikipedia.

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