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What Is Proof of Work (PoW)?

What Is Proof of Work (PoW)?
Contents
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Introduction
Proof of Work (commonly abbreviated to PoW) is a mechanism for preventing double-spends. Most major cryptocurrencies use this as their consensus algorithm. That’s just what we call a method for securing the cryptocurrency’s ledger.
Proof of Work was the first consensus algorithm to surface, and, to date, remains the dominant one. It was introduced by Satoshi Nakamoto in the 2008 Bitcoin white paper, but the technology itself was conceived long before then.
Adam Back’s HashCash is an early example of a Proof of Work algorithm in the pre-cryptocurrency days. By requiring senders to perform a small amount of computing before sending an email, receivers could mitigate spam. This computation would cost virtually nothing to a legitimate sender, but quickly add up for someone sending emails en masse.

What is a double-spend?

A double-spend occurs when the same funds are spent more than once. The term is used almost exclusively in the context of digital money — after all, you’d have a hard time spending the same physical cash twice. When you pay for a coffee today, you hand cash over to a cashier who probably locks it in a register. You can’t go to the coffee shop across the road and pay for another coffee with the same bill.
In digital cash schemes, there’s the possibility that you could. You’ve surely duplicated a computer file before — you just copy and paste it. You can email the same file to ten, twenty, fifty people.
Since digital money is just data, you need to prevent people from copying and spending the same units in different places. Otherwise, your currency will collapse in no time.
For a more in-depth look at double-spending, check out Double Spending Explained.

Why is Proof of Work necessary?

If you’ve read our guide to blockchain technology, you’ll know that users broadcast transactions to the network. Those transactions aren’t immediately considered valid, though. That only happens when they get added to the blockchain.
The blockchain is a big database that every user can see, so they can check if funds have been spent before. Picture it like this: you and three friends have a notepad. Anytime one of you wants to make a transfer of whatever units you’re using, you write it down — Alice pays Bob five units, Bob pays Carol two units, etc.
There’s another intricacy here — each time you make a transaction, you refer to the transaction where the funds came from. So, if Bob was paying Carol with two units, the entry would actually look like the following: Bob pays Carol two units from this earlier transaction with Alice.
Now, we have a way to track the units. If Bob tries to make another transaction using the same units he just sent to Carol, everyone will know immediately. The group won’t allow the transaction to be added to the notepad.
Now, this might work well in a small group. Everyone knows each other, so they’ll probably agree on which of the friends should add transactions to the notepad. What if we want a group of 10,000 participants? The notepad idea doesn’t scale well, because nobody wants to trust a stranger to manage it.
This is where Proof of Work comes in. It ensures that users aren’t spending money that they don’t have the right to spend. By using a combination of game theory and cryptography, a PoW algorithm enables anyone to update the blockchain according to the rules of the system.

How does PoW work?

Our notepad above is the blockchain. But we don’t add transactions one by one — instead, we lump them into blocks. We announce the transactions to the network, then users creating a block will include them in a candidate block. The transactions will only be considered valid once their candidate block becomes a confirmed block, meaning that it has been added to the blockchain.
Appending a block isn’t cheap, however. Proof of Work requires that a miner (the user creating the block) uses up some of their own resources for the privilege. That resource is computing power, which is used to hash the block’s data until a solution to a puzzle is found.
Hashing the block’s data means that you pass it through a hashing function to generate a block hash. The block hash works like a “fingerprint” — it’s an identity for your input data and is unique to each block.
It’s virtually impossible to reverse a block hash to get the input data. Knowing an input, however, it’s trivial for you to confirm that the hash is correct. You just have to submit the input through the function and check if the output is the same.
In Proof of Work, you must provide data whose hash matches certain conditions. But you don’t know how to get there. Your only option is to pass your data through a hash function and to check if it matches the conditions. If it doesn’t, you’ll have to change your data slightly to get a different hash. Changing even one character in your data will result in a totally different result, so there’s no way of predicting what an output might be.
As a result, if you want to create a block, you’re playing a guessing game. You typically take information on all of the transactions that you want to add and some other important data, then hash it all together. But since your dataset won’t change, you need to add a piece of information that is variable. Otherwise, you would always get the same hash as output. This variable data is what we call a nonce. It’s a number that you’ll change with every attempt, so you’re getting a different hash every time. And this is what we call mining.
Summing up, mining is the process of gathering blockchain data and hashing it along with a nonce until you find a particular hash. If you find a hash that satisfies the conditions set out by the protocol, you get the right to broadcast the new block to the network. At this point, the other participants of the network update their blockchains to include the new block.
For major cryptocurrencies today, the conditions are incredibly challenging to satisfy. The higher the hash rate on the network, the more difficult it is to find a valid hash. This is done to ensure that blocks aren’t found too quickly.
As you can imagine, trying to guess massive amounts of hashes can be costly on your computer. You’re wasting computational cycles and electricity. But the protocol will reward you with cryptocurrency if you find a valid hash.
Let’s recap what we know so far:
  • It’s expensive for you to mine.
  • You’re rewarded if you produce a valid block.
  • Knowing an input, a user can easily check its hash — non-mining users can verify that a block is valid without expending much computational power.
So far, so good. But what if you try to cheat? What’s to stop you from putting a bunch of fraudulent transactions into the block and producing a valid hash?
That’s where public-key cryptography comes in. We won’t go into depth in this article, but check out What is Public-Key Cryptography? for a comprehensive look at it. In short, we use some neat cryptographic tricks that allow any user to verify whether someone has a right to move the funds they’re attempting to spend.
When you create a transaction, you sign it. Anyone on the network can compare your signature with your public key, and check whether they match. They’ll also check if you can actually spend your funds and that the sum of your inputs is higher than the sum of your outputs (i.e., that you’re not spending more than you have).
Any block that includes an invalid transaction will be automatically rejected by the network. It’s expensive for you to even attempt to cheat. You’ll waste your own resources without any reward.
Therein lies the beauty of Proof of Work: it makes it expensive to cheat, but profitable to act honestly. Any rational miner will be seeking ROI, so they can be expected to behave in a way that guarantees revenue.

Proof of Work vs. Proof of Stake

There are many consensus algorithms, but one of the most highly-anticipated ones is Proof of Stake (PoS). The concept dates back to 2011, and has been implemented in some smaller protocols. But it has yet to see adoption in any of the big blockchains.
In Proof of Stake systems, miners are replaced with validators. There’s no mining involved and no race to guess hashes. Instead, users are randomly selected — if they’re picked, they must propose (or “forge”) a block. If the block is valid, they’ll receive a reward made up of the fees from the block’s transactions.
Not just any user can be selected, though — the protocol chooses them based on a number of factors. To be eligible, participants must lock up a stake, which is a predetermined amount of the blockchain’s native currency. The stake works like bail: just as defendants put up a large sum of money to disincentivize them from skipping trial, validators lock up a stake to disincentivize cheating. If they act dishonestly, their stake (or a portion of it) will be taken.
Proof of Stake does have some benefits over Proof of Work. The most notable one is the smaller carbon footprint — since there’s no need for high-powered mining farms in PoS, the electricity consumed is only a fraction of that consumed in PoW.
That said, it has nowhere near the track record of PoW. Although it could be perceived as wasteful, mining is the only consensus algorithm that’s proven itself at scale. In just over a decade, it has secured trillions of dollars worth of transactions. To say with certainty whether PoS can rival its security, staking needs to be properly tested in the wild.

Closing thoughts

Proof of Work was the original solution to the double-spend problem and has proven to be reliable and secure. Bitcoin proved that we don’t need centralized entities to prevent the same funds from being spent twice. With clever use of cryptography, hash functions, and game theory, participants in a decentralized environment can agree on the state of a financial database.
submitted by D-platform to u/D-platform [link] [comments]

Information and FAQ

Hi, for everyone looking for help and support for IOTA you have come to the right place. Please read this information, the FAQ and the side bar before asking for help.

Information

IOTA

IOTA is an open-source distributed ledger protocol launched in 2015 that goes 'beyond blockchain' through its core invention of the blockless ‘Tangle’. The IOTA Tangle is a quantum-resistant Directed Acyclic Graph (DAG), whose digital currency 'iota' has a fixed money supply with zero inflationary cost.
IOTA uniquely offers zero-fee transactions & no fixed limit on how many transactions can be confirmed per second. Scaling limitations have been removed, since throughput grows in conjunction with activity; the more activity, the more transactions can be processed & the faster the network. Further, unlike blockchain architecture, IOTA has no separation between users and validators (miners / stakers); rather, validation is an intrinsic property of using the ledger, thus avoiding centralization.
IOTA is focused on being useful for the emerging machine-to-machine (m2m) economy of the Internet-of-Things (IoT), data integrity, micro-/nano- payments, and other applications where a scalable decentralized system is warranted.
More information can be found here.

Non reusable addresses

Contrary to traditional blockchain based systems such as Bitcoin, where your wallet addresses can be reused, IOTA's addresses should only be used once (for outgoing transfers). That means there is no limit to the number of transactions an address can receive, but as soon as you've used funds from that address to make a transaction, this address should not be used anymore.
The reason for this is, by making an outgoing transaction a part of the private key of that specific address is revealed, and it opens the possibility that someone may brute force the full private key to gain access to all funds on that address. The more outgoing transactions you make from the same address, the easier it will be to brute force the private key.
It should be noted that having access to the private key of an address will not reveal your seed or the private key of the other addresses within your seed / "account".
This piggy bank diagram can help visualize non reusable addresses. imgur link

Address Index

When a new address is generated it is calculated from the combination of a seed + Address Index, where the Address Index can be any positive Integer (including "0"). The wallet usually starts from Address Index 0, but it will skip any Address Index where it sees that the corresponding address has already been attached to the tangle.

Private Keys

Private keys are derived from a seeds key index. From that private key you then generate an address. The key index starting at 0, can be incremented to get a new private key, and thus address.
It is important to keep in mind that all security-sensitive functions are implemented client side. What this means is that you can generate private keys and addresses securely in the browser, or on an offline computer. All libraries provide this functionality.
IOTA uses winternitz one-time signatures, as such you should ensure that you know which private key (and which address) has already been used in order to not reuse it. Subsequently reusing private keys can lead to the loss of funds (an attacker is able to forge the signature after continuous reuse).
Exchanges are advised to store seeds, not private keys.

Double spending

Sending a transaction will move your entire balance to a completely new address, if you have more than one pending transaction only one can eventually be confirmed and the resulting balance is sent to your next wallet address. This means that the other pending transactions are now sent from an address that has a balance of 0 IOTA, and thus none of these pending transactions can ever be confirmed.

Transaction Process

As previously mentioned, in IOTA there are no miners. As such the process of making a transaction is different from any Blockchain out there today. The process in IOTA looks as follows:
  • Signing: You sign the transaction inputs with your private keys. This can be done offline.
  • Tip Selection: MCMC is used to randomly select two tips, which will be referenced by your transaction (branchTransaction and trunkTransaction)
  • Proof of Work: In order to have your transaction accepted by the network, you need to do some Proof of Work - similar to Hashcash, not Bitcoin (spam and sybil-resistance). This usually takes a few minutes on a modern pc.
After this is completed, the trunkTransaction, branchTransaction and nonce of the transaction object should be updated. This means that you can broadcast the transaction to the network now and wait for it to be approved by someone else.

FAQ

How do I to buy IOTA?

Currently not all exchanges support IOTA and those that do may not support the option to buy with fiat currencies.
One way to buy IOTA is to buy with bitcoin (BTC) or Ether (ETH), first you will need to deposit BTC/ETH onto an exchange wallet and you can the exchange them for IOTA.
You can buy BTC or ETH through coinbase. And exchange those for IOTA on Binance or Bitfinex (other exchanges do exist, some linked in the side bar).
A detailed guide to buying can be found here.

What is MIOTA?

MIOTA is a unit of IOTA, 1 Mega IOTA or 1 Mi. It is equivalent to 1,000,000 IOTA and is the unit which is currently exchanged.
We can use the metric prefixes when describing IOTA e.g 2,500,000,000 i is equivalent to 2.5 Gi.
Note: some exchanges will display IOTA when they mean MIOTA.

Can I mine IOTA?

No you can not mine IOTA, all the supply of IOTA exist now and no more can be made.
If you want to send IOTA, your 'fee' is you have to verify 2 other transactions, thereby acting like a minenode.

Where should I store IOTA?

It is not recommended to store large amounts of IOTA on the exchange as you will not have access to the private keys of the addresses generated.
However many people have faced problems with the current GUI Wallet and therefore group consensus at the moment is to store your IOTA on the exchange, until the release of the UCL Wallet, or the Paper Wallet.

What is the GUI wallet?

What is the UCL Wallet?

What is a seed?

A seed is a unique identifier that can be described as a combined username and password that grants you access to your wallet.
Your seed is used to generate the addresses linked to your account and so this should be kept private and not shared with anyone. If anyone obtains your seed, they can login and access your IOTA.

How do I generate a seed?

You must generate a random 81 character seed using only A-Z and the number 9.
It is recommended to use offline methods to generate a seed, and not recommended to use any non community verified techniques. To generate a seed you could:

On a Linux Terminal use the following command:

 cat /dev/urandom |tr -dc A-Z9|head -c${1:-81} 

On a Mac Terminal use the following command:

 cat /dev/urandom |LC_ALL=C tr -dc 'A-Z9' | fold -w 81 | head -n 1 

With KeePass on PC

A helpful guide for generating a secure seed on KeePass can be found here.

With a dice

Dice roll template

Is my seed secure?

  1. All seeds should be 81 characters in random order composed of A-Z and 9.
  2. Do not give your seed to anyone, and don’t keep it saved in a plain text document.
  3. Don’t input your seed into any websites that you don’t trust.
Is this safe? Can’t anyone guess my seed?
What are the odds of someone guessing your seed?
  • IOTA seed = 81 characters long, and you can use A-Z, 9
  • Giving 2781 = 8.7x10115 possible combinations for IOTA seeds
  • Now let's say you have a "super computer" letting you generate and read every address associated with 1 trillion different seeds per second.
  • 8.7x10115 seeds / 1x1012 generated per second = 8.7x10103 seconds = 2.8x1096 years to process all IOTA seeds.

Why does balance appear to be 0 after a snapshot?

When a snapshot happens, all transactions are being deleted from the Tangle, leaving only the record of how many IOTA are owned by each address. However, the next time the wallet scans the Tangle to look for used addresses, the transactions will be gone because of the snapshot and the wallet will not know anymore that an address belongs to it. This is the reason for the need to regenerate addresses, so that the wallet can check the balance of each address. The more transactions were made before a snapshot, the further away the balance moves from address index 0 and the more addresses have to be (re-) generated after the snapshot.

Why is my transaction pending?

IOTA's current Tangle implementation (IOTA is in constant development, so this may change in the future) has a confirmation rate that is ~66% at first attempt.
So, if a transaction does not confirm within 1 hour, it is necessary to "reattach" (also known as "replay") the transaction one time. Doing so one time increases probability of confirmation from ~66% to ~89%.
Repeating the process a second time increases the probability from ~89% to ~99.9%.

What does attach to the tangle mean?

The process of making an transaction can be divided into two main steps:
  1. The local signing of a transaction, for which your seed is required.
  2. Taking the prepared transaction data, choosing two transactions from the tangle and doing the POW. This step is also called “attaching”.
The following analogy makes it easier to understand:
Step one is like writing a letter. You take a piece of paper, write some information on it, sign it at the bottom with your signature to authenticate that it was indeed you who wrote it, put it in an envelope and then write the recipient's address on it.
Step two: In order to attach our “letter” (transaction), we go to the tangle, pick randomly two of the newest “letters” and tie a connection between our “letter” and each of the “letters” we choose to reference.
The “Attach address” function in the wallet is actually doing nothing else than making an 0 value transaction to the address that is being attached.

How do I reattach a transaction.

Reattaching a transaction is different depending on where you send your transaction from. To reattach using the GUI Desktop wallet follow these steps:
  1. Click 'History'.
  2. Click 'Show Bundle' on the 'pending' transaction.
  3. Click 'Reattach'.
  4. Click 'Rebroadcast'. (optional, usually not required)
  5. Wait 1 Hour.
  6. If still 'pending', repeat steps 1-5 once more.

What happens to pending transactions after a snapshot?

How do I recover from a long term pending transaction?

How can I support IOTA?

You can support the IOTA network by setting up a Full Node, this will help secure the network by validating transactions broadcast by other nodes.
Running a full node also means you don't have to trust a 3rd party in showing you the correct balance and transaction history of your wallet.
By running a full node you get to take advantage of new features that might not be installed on 3rd party nodes.

How to set up a full node?

To set up a full node you will need to follow these steps:
  1. Download the full node software: either GUI, or headless CLI for lower system requirements and better performance.
  2. Get a static IP for your node.
  3. Join the network by adding 7-9 neighbours.
  4. Keep your full node up and running as much as possible.
A detailed user guide on how to set up a VTS IOTA Full Node from scratch can be found here.

How do I get a static IP?

To learn how to setup a hostname (~static IP) so you can use the newest IOTA versions that have no automated peer discovery please follow this guide.

How do I find a neighbour?

Are you a single IOTA full node looking for a partner? You can look for partners in these place:

Extras

Transaction Example:

Multiple Address in 1 Wallet Explained:

submitted by Boltzmanns_Constant to IOTASupport [link] [comments]

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