Blockchain Academy
We'll get together for networking with people interested in Blockchain including developers and anyone curious about Blockchain.

PoW

PoW is a type of consensus algorithm which grants the block creation authority to a miner who completed mining the earliest. Here, mining refers to the process of repeated calculation until a correct value is obtained by sequentially inputting numbers from zero to increasing one by one to nonce, which is an arbitrary number that derives a hash below the target value by computing operation. Just as gold is mined in the gold mine, mining in the blockchain is a method of giving coins as a reward to the miner, who finds the nonce first by mining with computation. It is also known as proof-of-work because it is 'proving' the nodes have been participating the 'work' of finding an arbitrary number by fully using computing operations just like gold picking. Bitcoin and Ethereum are the representative coins.

The blockchain using the PoW type consensus algorithm has strength in security that it is very difficult to hack the block data to forge, because this consumes an enormous computing power; but a slow block creation time is its weak point. As means of remittance and payment, Bitcoin only handles six to seven transactions per second, and Ethereum, which aims for a smart contract platform, approves 15~16 cases per second. Compared to a credit card, which handles 2~30,000 transactions per second, those coins don't seem to be very practical.

However the reason for the slow block creation time is to prevent many blocks to be created at the same time. In Bitcoin and Ethereum, there is a value which controls the level of difficulty to find the target hash, so eventually prevents the creation of simultaneous blocks and the monopoly of a certain miner. Another weak point is the need of tremendous computing resource for mining. The advanced device makes higher probability of successful mining, which means the PoW mechanism requires many expenses to pay for the device and electricity. This makes people, who can afford all the expenses, monopolize the mining, and the true meaning of decentralization fades away. So to resolve this problem, many other types of consensus algorithm are being introduced in the market apart from mining.