11. Proof of the work done by the student

11.Proof of the work done by the student.

However, this raises an important question: Without a central authority to act as a final arbiter, how does bitcoin ensure that nobody manipulates the blockchain for their own ends? The answer is proof of work.

Proof of work is a consensus mechanism used to confirm that network participants, called miners, calculate valid alphanumeric codes — called hashes — to verify bitcoin transactions and add the next block to the blockchain. It does so by having other participants in the network verify that the required amount of computing power was used by the miner that is credited with calculating the valid hash. The more miners working to verify transactions (and the faster they can generate hashes), the higher a network's hash rate.
Proof of work is all about creating a positive incentive for people to invest in the resources it takes to add valid blocks to a cryptocurrency's blockchain.
"The challenge in a blockchain like bitcoin is to maintain an agreed transaction record without having a central authority," says William J. Knottenbelt, a professor at Imperial College London's Department of Computing. "So the key question is how a group of peers of similar status can agree upon which of them should be authorized to add to the common transaction record."
The process of calculating a hash is intentionally made extremely computationally difficult. By forcing participants to invest significant amounts of money in computing resources, the proof of work mechanism creates a disincentive against trying to undermine the blockchain's integrity. It also reduces the potential for a single bitcoin being spent simultaneously more than once — known as double spending — which would destroy confidence in the cryptocurrency. "Proof of work is how miners (block publishers) prove to the world that they have put in the necessary work to create a well-formed block of transactions to add to the blockchain." says Knottenbelt. "From the miner's perspective they are turning the energy they put into the search for valid blocks (for which they typically purchase special high-performance hardware) into money (in the form of the rewards they obtain from coinbase rewards and transaction fees)."
Bitcoin mining is essentially a competition where miners are all racing to be the first to solve extremely complex cryptographic puzzles, enabling them to add the next block to the blockchain and receive payment in the form of new bitcoins. The winning miner receives the reward only after the other systems in the network, through the proof of work protocol, verify that the solution is correct and valid.
This involves a serious amount of number crunching, with the equipment used by miners having to go through much trial and error before finding the correct hash.
"Proof of work uses a lottery mechanism — miners create candidate blocks of transactions (including a reward for themselves) which must satisfy several strict conditions," Knottenbelt explains. "They then test to see if these conditions are fulfilled. Almost all of the time they are not and the miner has to go back and try again."
It's because most candidate blocks do not include the correct hash that so much work is involved in verifying bitcoin transactions. And in fact, the difficulty of this process can increase or decrease, in order to ensure that new blocks are produced at regular intervals.
"The difficulty of the lottery is adjusted periodically so that if blocks are being produced too quickly then it becomes harder to satisfy the conditions necessary for producing a valid block and if the blocks are being produced too slowly then it becomes easier," Knottenbelt adds.
With bitcoin, Nakamoto based the cryptocurrency's proof of work mechanism largely on Hashcash, a denial-of-service countermeasure outlined by Adam Back in 1997. In particular, Nakamoto envisaged proof of work as a means of ensuring that it becomes exponentially difficult to attack the bitcoin blockchain as more blocks are added to it. While proof of work is popular, another consensus mechanism known as proof of stake is also widely used. Instead of verifying the amount of computational work done, proof of stake uses the amount of cryptocurrency block publishers are willing to deposit as insurance against their misbehavior.
Read more: Proof of work vs proof of stake
"Conceptually this is quite appealing because it short-cuts the step of having to invest in high-performance mining hardware and also the energy related to the use of that hardware," Knottenbelt says.
However, proponents of proof of work argue that proof of stake and other consensus mechanisms inevitably lend themselves to some form of centralization, precisely the thing proof of work was designed to avoid.
"Proof of stake is fundamentally centralized," says Jimmy Song, a bitcoin author, educator, and developer. "There's no way to tell which to go with in case of a conflict." 
Advantages and disadvantages of proof of work
This leads to a consideration of the relative advantages and disadvantages of proof of work as compared to other mechanisms, such as proof of stake.
Most importantly, proof of work arguably provides a higher level of security than other means of consensus, with bitcoin now running for more than a decade without a significant outage or compromise.
"Security-wise, proof of work has empirically been shown to work very well for more than 10 years," Knottenbelt says. "The jury is still out on proof-of-stake."
But while proof of work does afford an optimal level of security and decentralization, it imposes one substantial cost: It consumes a considerable amount of energy.
By some estimates, proof of work leads to the bitcoin blockchain using energy each year equivalent to the consumption of a nation the size of Thailand. It Proof of work is a technique used by cryptocurrencies to verify the accuracy of new transactions that are added to a blockchain. The decentralized networks used by cryptocurrencies and other defi applications lack any central governing authority, so they employ proof of work to ensure the integrity of new data.
What Is Proof of Work?
Cryptocurrencies do not have centralized gatekeepers to verify the accuracy of new transactions and data that are added to the blockchain. Instead, they rely on a distributed network of participants to validate incoming transactions and add them as new blocks on the chain.
Proof of work is a consensus mechanism to choose which of these network participants—called miners—are allowed to handle the lucrative task of verifying new data. It’s lucrative because the miners are rewarded with new crypto when they accurately validate the new data and don’t cheat the system.
“Proof of work is a software algorithm used by Bitcoin and other blockchains to ensure blocks are only regarded as valid if they require a certain amount of computational power to produce,” says Amaury Sechet, founder of the cryptocurrency eCash. “It’s a consensus mechanism that allows anonymous entities in decentralized networks to trust one another.”
The “work” in proof of work is key: The system requires miners to compete with each other to be the first to solve arbitrary mathematical puzzles to prevent anybody from gaming the system. The winner of this race is selected to add the newest batch of data or transactions to the blockchain.
Winning miners only receive their reward of new cryptocurrency after other participants in the network verify that the data being added to the chain is correct and valid.
also produces a large amount of electronic waste in the form of mining units that are discarded for ever more powerful models.
Miners work to solve complex math problems to earn a reward,” says Dan Schwenk, chief executive officer of Digital Asset Research. These are laborious problems that require significant computer power and energy to solve. Since miners have invested significant resources in the computer equipment and energy costs required, they’re motivated to accurately validate transactions.For anyone who values bitcoin and believes it's an important contribution to the evolution of money, such energy consumption and waste is a justifiable price to pay for the only consensus mechanism that has really been proven to be robust at scale. Conversely, for anyone who remains skeptical of cryptocurrencies, it's basically a scandal.
The bottom line
Proof of work is a consensus mechanism that ensures that miners add a new block to a cryptocurrency's blockchain only after producing a substantial amount of computational work to prove that it's valid.
Because proof of work requires a significant investment in resources, it makes it increasingly less likely that miners and network participants will seek to undermine a cryptocurrency's blockchain. This is particularly the case with bitcoin, which has been running at scale for more than a decade without suffering a double-spend attack. However, proof of work also requires the expenditure of a large amount of electricity. This is something critics of bitcoin would argue produces too much of an environmental impact to justify the improved security it offers in comparison to mechanisms such as proof of stake.
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WouEvidence about what students, staff, parents and the community think about the school. In many schools, there will be few formal records of this sort of evidence. Self-appraisal – student perceptions of their own abilities, potential, achievements, attitudes. Formal and informal observations made by teachers – peer interactions, behaviour, attitudes, engagement, student-teacher relationships, learning styles, classroom dynamics.
Structured interactions – records from student interviews, parent interviews, staff conferences on students.
Externally generated reports – from ERO and NZQA (these contain data and perceptions). Student voice – student surveys, student council submissions, conferencing.
Community perception surveys.
Other informal sources – anecdotal views about the school environment, staff and student morale, board perceptions, conversations among teachers.
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There is a wide range of evidence that schools and teachers can use when inquiring into student learning. The types of evidence detailed here demonstrate this wide range and cover both primary and secondary contexts. Some evidence can be described through a quantifiable number. This is referred to as quantitative evidence or ‘data’. Other evidence is less easy to quantify.This is referred to as qualitative evidence, as it describes a quality that can be difficult to represent in The first cryptocurrency, Bitcoin, was created by Satoshi Nakamoto in 2008.
Nakamoto published a famous white paper describing a digital currency based on proof of work protocols that would allow secure, peer-to-peer transactions without the involvement of a centralized authority.
One of the issues that had prevented the development of an effective digital currency in the past was called the double-spend problem. Cryptocurrency is just data, so there needs to be a mechanism to prevent users from spending the same units in different places before the system can record the transactions.
While you’d have a hard time spending the same dollar bill on two separate purchases, anyone who’s duplicated a computer file by copying and pasting can probably imagine how you could spend digital money twice—even ten times or more. Nakamoto’s consensus mechanism solved the double-spend problem. By incentivizing miners to verify the integrity of new crypto transactions before adding them to the distributed ledger that is blockchain, proof of work helps prevent double spending.
Proof of Work and Mining
Consider a conventional bank account. If you deposit a check in your savings account, how do you know that you’ll be credited for the accurate amount? How does the writer of the check trust that they’ll only be debited for the amount they wrote on the check? The value of a bank is that all the parties to a transaction trust the bank to accurately move money around.
With cryptocurrencies, there are no bankers or financial institutions to ensure trust. Instead, miners and proof of work guarantee transparent, accurate transactions. For blockchains that use proof of work, miners are the guardians and facilitators that make the system run smoothly and accurately.
numbers. Both types of evidence are used by schools for decision making.