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A survey on Blockchain Technology and itsBog'liq Huaqun Xingjie - A Survey on blockchain Technology and its Security - 2022 MarchProof of Work (PoW). PoW selects a problem that can
only be solved by guessing. For example, when it is time to
create and validate a full block, the problem is to guess a nonce
value such that when using the transaction data and the nonce
value as inputs for a hash function, its hash output needs match
the difficulty, e.g., beginning with four leading zeros. Every
node (also called mining node) on the network is now
guessing different nonce values randomly until one node first
happens to find the nonce value that matches the difficulty. So
a mining node has to spend a lot of computational resources
on it (hence called as ‘‘work’’) and solves the problem faster
than others in order to succeed in creating a block to link to
the Blockchain, and obtain an incentive mining reward, which
is often cryptocurrency. On other hand, hash functions are
important as one cryptographic puzzle at the center of the
PoW consensus algorithm. Bitcoin network adopts the
cryptographic hash function SHA-256 [8]. We will talk more
about hash function in the following section. Bitcoin and
Ethereum public Blockchains use PoW as their consensus
algorithm. A big issue with the PoW consensus process is that
it requires a lot of time and electricity to complete.
Proof of Stake (PoS). PoS [12] [33] is the second most
prominent
consensus
method
and
requires
fewer
computations for mining than PoW. PoS solves time and
electricity consumption problems that PoW has because the
electricity requirement is associated with miners finding a
nonce and this process needs to take some time. PoS has nodes
to put up a stake to be chosen as the next block creator. When
a block is chosen, the creator will receive the transaction fees
associated with that block. If a block winner attempts to add
an invalid block, he/she will lose his/her stake. In its first
phase of Ethereum 2.0 upgrade, the Blockchain “world
computers” switch from PoW to PoS consensus algorithm.
Journal Pre-proof
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