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10 questions to the video + answers

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DEFINITION of '51% Attack'

51% attack refers to an attack on a blockchain - usually bitcoin's, for which such an attack is still hypothetical - by a group of miners controlling more than 50% of the network's mining hashrate, or computing power. The attackers would be able to prevent new transactions from gaining confirmations, allowing them to halt payments between some or all users. They would also be able to reverse transactions that were completed while they were in control of the network, meaning they could double-spend coins.

They would almost certainly not be able to create a create new coins or alter old blocks, so a 51% attack would probably not destroy bitcoin or another blockchain-based currency outright, even if it proved highly damaging.

BREAKING DOWN '51% Attack'

Bitcoin and other cryptocurrencies are based on blockchains, otherwise referred to as distributed ledgers. These digital files record every transaction made on a cryptocurrency's network and are available to all users for review, meaning that no one can not spend a coin twice - the digital equivalent of a perfect counterfeit, this ability would quickly destroy faith in the coin's value.

As its name implies, a blockchain is a chain of blocks, bundles of data that record all completed transactions during a given period of time (for bitcoin, a new block is generated approximately every ten minutes). Once a block is finalized - or "mined," in the jargon - it cannot be altered, since a fraudulent version of the public ledger would quickly be spotted and rejected by the network's users.

However, by controlling the majority of the computing power on the network, an attacker or group of attackers can interfere with the process of recording new blocks. They can prevent other miners from completing blocks, theoretically allowing them to monopolize the mining of new blocks and earn all of the rewards (for bitcoin, the reward is currently 12.5 newly-created bitcoins, though it will eventually drop to zero). They can block other users' transactions. They can send a transaction, then reverse it, making it appear as though they still had the coin they just spent. This vulnerability, known as double-spending, is the basic cryptographic hurdle the blockchain was built to overcome, so a network that allowed for double-spending would quickly suffer a loss of confidence.

Changing historical blocks, transactions locked in prior to the start of the attack, would be extremely difficult even in the event of a 51% attack. The further back the transactions are, the more difficult it would be to change them. It would be impossible to change transactions prior to a checkpoint, past which transactions are hard-coded into bitcoin's software.

On the other hand, a form of a 51% attack is possible with less than 50% of the network's mining power, but with a lower probability of success.

Ghash.io

The mining pool ghash.io briefly exceeding 50% of the bitcoin network's computing power in July 2014, leading the pool to voluntarily commit to reducing its share of the network. It said in a statement that it would not reach 40% of the total mining power in the future.

Krypton and Shift

Krypton and Shift, two blockchains based on ethereum, suffered 51% attacks in August 2016.

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51% attack refers to an attack on a blockchain - usually bitcoin's, for which such an attack is still hypothetical - by a group of miners controlling more than 50% of the network's mining hashrate, or computing power.

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Don Tapscott: How the blockchain is changing money and business

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What is the blockchain? If you don't know, you should; if you do, chances are you still need some clarification on how it actually works. Don Tapscott is here to help, demystifying this world-changing, trust-building technology which, he says, represents nothing less than the second generation of the internet and holds the potential to transform money, business, government and society.

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December 6, 2016

by Alan Morrison and Subhankar Sinha
Tags:
There's been a lot of noise recently about bitcoin, blockchain, and cryptocurrency. Some of it is hype, but some of it points to important forces in the financial services industry. So what does it all mean?
Blockchain is the technology that enables the existence of cryptocurrency (among other things). Bitcoin is the name of the best-known cryptocurrency, the one for which blockchain technology was invented. A cryptocurrency is a medium of exchange, such as the US dollar, but is digital and uses encryption techniques to control the creation of monetary units and to verify the transfer of funds.

Blockchain also has potential applications far beyond bitcoin and cryptocurrency. Blockchain is, quite simply, a digital, decentralized ledger that keeps a record of all transactions that take place across a peer-to-peer network. The major innovation is that the technology allows market participants to transfer assets across the Internet without the need for a centralized third party.

From a business perspective, it's helpful to think of blockchain technology as a type of next-generation business process improvement software. Collaborative technology, such as blockchain, promises the ability to improve the business processes that occur between companies, radically lowering the "cost of trust." For this reason, it may offer significantly higher returns for each investment dollar spent than most traditional internal investments.

Financial institutions are exploring how they could also use blockchain technology to upend everything from clearing and settlement to insurance.

When a technology moves so quickly, it's dangerous to sit on the sidelines. We're watching blockchain move from a startup idea to an established technology in a tiny fraction of the time it took for the Internet or even the PC to be accepted as a standard tool. Blockchain technology could result in a radically different competitive future for the financial services industry.

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NEWARK - The guest list and parade of limousines with celebrities emerging from them seemed more suited to a red carpet event in Hollywood or New York than than a gritty stretch of Sussex Avenue near the former site of the James M. Baxter Terrace public housing project here.

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HOMEWORK: do internet research about blockchain technology and find the answers to the following questions:

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HOMEWORK: do internet research about blockchain technology and find the answers to the following questions:

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1. What is blockchain technology
2. What is Distributed Ledger Technology (DLT)?
3. WHat's the difference between the two?
4. What is blockchain teansaction?
5. What is blockchain banking?