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participate their Blockchain networks, which are also called asBog'liq Huaqun Xingjie - A Survey on blockchain Technology and its Security - 2022 March
participate their Blockchain networks, which are also called as
permissionless Blockchains. The various Hyperledger
Blockchain networks are private Blockchains since the
participants are needed to be verified first before joining the
network, which are also called as permissioned Blockchains.
Fig. 1. History of Blockchain
III.
B
LOCKCHAIN
T
ECHNOLOGY
A. Consensus Algorithms
As one of desired Blockchain features, anonymity also
poses a problem when it comes to trust. How can be 100
percent ensured that anonymous users are honest when they
add transactions to a ledger? The answer is to validate every
transaction to be legal (not malicious, double spends etc.) and
then put the transactions into a block. The agreement of adding
a block to the Blockchain is through consensus algorithms.
These consensus algorithms take advantage of the fact that the
majority of users on a Blockchain have a common interest to
keep the Blockchain honest. A Blockchain system uses a
consensus algorithm to build its trust and properly stores the
transactions on the blocks. Thus, consensus algorithms can be
considered the heart of all transactions of Blockchains.
A consensus protocol is essentially a set of rules to be
followed by every participant. As distributed technology
without a universal trust, Blockchain needs a distributed
consensus mechanism for all participants to agree on the
Blcokchain’s current state. The Blockchain’s consensus is
based on scarcity that controlling more of a scarce resource
gives more control over the Blockchain’s operation. A number
of unique consensus mechanisms have been designed for
Blockchains, which include Proof of Work (PoW) [8], Prof of
State (PoS) [12], Delegated Proof of State (DPoS) [13], Proof
of Elapsed Time (PoET) [14], Practical Byzantine Fault
Tolerance (PBFT) [15], Directed Acyclic Graph (DAG) [16]
[17], Proof of Authority (PoA) [18], Tendermint [19], Ripple
[20], Scalable Byzantine Consensus Protocol (SCP) [21],
Proof of Bandwidth (PoB) [22], Proof-of-Importance (PoI)
[23], Proof of Burn [24], Proof of Capacity [25], depending on
their unique requirements.
Based on algorithms appeared in other survey work [26]
[27] [2] [28] [3] [29] [30] [31] [32], PoW, PoS, DPoS and
PBFT are the most common consensus algorithms. DAG is
the most different from other consensus algorithm. PoET is
developed by Intel Corporation and used in Hyperledger
Sawtooth. Thus, these six consensus algorithms are further
described in the below.
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