95

Apart from Bitcoin and Ethereum (if we are generous) there are no major and important uses today. It is important to notice that blockchains have some severe limitations. A couple of them being: It only really works for purely digital assets The digital asset under control needs to keep its value even if it's public All transactions need to be public A ...


26

There are varying definitions of blockchain, and the answer to this question depends a lot on whether you consider the broad or the narrow interpretation. Typical cryptocurrency implementations such as Bitcoin have two parts: A chain of blocks, linked by cryptographic hashes (SHA256 in Bitcoin) so that the identity of the newest block prevents modifying any ...


11

The given answers focus on the open p2p blockchains of Bitcoin and its likes. There is however also such initiatives as Hyperledger, R3 Corda, and Enterprise Ethereum Alliance, etc. (Even cloud providers (eg aws) have offerings). These kinds of platforms tend to avoid the time-consuming proof-of-work part and do consensus between selected parties, not being ...


7

If we simplify and assume that each miner randomly guesses a hash (as opposed to being more systematic) and we discretize time, say into minutes, then each minute each miner is hoping to "roll" the right number. Let's say there are $N > 1$ possible values only one of which is correct at each minute. Then, in a world with only two miners, each minute there ...


3

Actually the differences are more intricate than that. A problem here might be that the properties of "blockchains" are not very well specified and the term is used for a wide variety of things (going as far as simple databases) for marketing. So let's see what is out there. When you are designing a fault tolerant system there are multiple properties to ...


1

Blockchain uses a cryptographic hash function that is designed to have collision resistance. Thus, while it's possible you might run into a pair of inputs that produce the same output... it's very very unlikely to happen by chance; and it is believed to be very difficult to intentionally find such a pair of inputs. Disk space has nothing to do with ...


1

What is guaranteed is that if a quorum of an intact nodes accepts a statement s, then eventually every intact node v will find itself v-blocked by a set of nodes that has accepted s, i.e. "accept s" cascades throughout all intact nodes until all have accepted and then confirmed s. This is called the cascade theorem in the paper "Fast and secure global ...


1

The blockchain would no longer be completely decentralized. You would have a dictator, or a central authority that decides which transactions get processed and which do not. At this point you could just as well skip the blockchain part of the transaction system as well.


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