- Proof Of Work
The proof-of-work (PoW) system is a measure to prevent attacks to the blockchain network. It requires work and processing time from the requestor (computer). This protocol is in place to disallow spam on the blockchain network, deter other abuses such as double-spending, and confirm that a new block is found/formed. Ether is just one example of a coin that utilizes the PoW protocol. One important property of a block in Ethereum and many other crypto-ledgers is that the hash of the block must be smaller than some target value. The reason this is necessary is that, in a decentralized system, anyone can produce blocks, so in order to prevent the network from being flooded with blocks, and to provide a way of measuring how much consensus there is behind a particular version of the blockchain, it must in some way be hard to produce a block. Because hashes are pseudorandom, finding a block with a hash that has less than 64 bytes takes an average of 4.3 billion attempts. In all such systems, the target value self-adjusts so that on average one node in the network finds a block every N minutes (eg. N = 10 minutes for Bitcoin and 1 minute for Ethereum).