# Research and Applied Perspective to Blockchain Technology: A Comprehensive Survey
## 5 Consensus Algorithms
### Consensus Algorithms Used by Various Cryptocurrencies  
Digital currencies have gained faster payment methods by using blockchain. Bitcoin was the first cryptocurrency used by blockchain. After gaining popularity in bitcoin other applications were/are implemented. Table 3 defines some of the important characteristics of consensus algorithms used in cryptocurrencies. Figure 5: Categorization of the consensus algorithms. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**S.No** & **Consensus Algorithms** & **Permissioned/Permissionlessless** & **Platform** & **Pogramming Language** & **Advantages** & **Disadvantages** \\ \hline
1 & Proof of Work (PoW) [67] & Permissionlessless & Bitcoin & C++ & Better security, Suitable for variety of applications &
\begin{tabular}{c} Wastes considerable energy, \\ 51\% Attack possible Advance \\ hardware required \\ \end{tabular} \\ \hline
2 & \begin{tabular}{c} Delayed Proof of \\ Work (DPoW) [68] \\ \end{tabular} & Permissionlessless (But it can be customized as permissioned) & Komodo & Python & \
\begin{tabular}{c} Energy efficient, \\ Increased security \\ \end{tabular} &
\begin{tabular}{c} Blockchain using Pow and PoS \\ can be part of this consensus \\ \end{tabular} \\ \hline
3 & Proof of Stack (PoS) [21] & Permissionless & \
\begin{tabular}{c} Permissionless \\ blockchain, Shadow \\ coin, Ethereum \\ \end{tabular} & Java &
\begin{tabular}{c} High speed Less energy \\ consumption, No advance \\ hardware required \\ \end{tabular} & Rich get richer \\ \hline
4 & \begin{tabular}{c} Seller Consensus \\ Protocol (SCP) [20] \\ \end{tabular} & Permissionlessless & \begin{tabular}{c} Stem, it, EOS, \\ Bitshares, Lik \\ \end{tabular} & Javascript, C++, Ark & \
\begin{tabular}{c} Secure Real-time Voting, Better \\ distribution of rewards \\ \end{tabular} &
\begin{tabular}{c} Cartel formation, Easier for \\ 51\% attack, Partially decentralized \\ \end{tabular} \\ \hline
6 & \begin{tabular}{c} Leased Proof of \\ Stack (LPoS) [70] \\ \end{tabular} & Permissionless & \
\begin{tabular}{c} Waves \\ \end{tabular} & Scala & Fair usage, base coins &
\begin{tabular}{c} Decentralization issue \\ \end{tabular} \\ \hline
7 & \begin{tabular}{c} Byzantine Fault \\ Tolerance (BPT) [1/2] \\ \end{tabular} & Permissionless & \begin{tabular}{c} Ripple, Steller, \\ Hyperledger Fabric \\ \end{tabular} & Not known & \
\begin{tabular}{c} Less Energy consumption, \\ No advance hardware, \\ Fast, Scalable \\ \end{tabular} &
\begin{tabular}{c} Less suitable for \\ public blockchain \\ \end{tabular} \\ \hline
8 & \begin{tabular}{c} Directed Acyclic \\ Graph (DAG) [73] \\ \end{tabular} & Permissionless & \
\begin{tabular}{c} Iota, Hashgraph, \\ Byteball, \\ Raiblocks/Nano \\ \end{tabular} & Javascript, Rust, Java, Go, C++ & Low-cost Network, Scalable &
\begin{tabular}{c} Difficult implementation, \\ Not good for smart contracts \\ \end{tabular} \\ \hline
9 & Proof of Weight [74] & Not Known & \
\begin{tabular}{c} Filecoin, \\ Algorand, Chia \\ \end{tabular} &
\begin{tabular}{c} Succinct Non-interactive \\ Argument of Knowledge \\ (SNARK)/Succinct \\ Transparent Argument of \\ Knowledge (STARK) \\ \end{tabular} & Scalable, Customizable & Incentvitization issue \\ \hline
10 & \
\begin{tabular}{c} Delegated \\ Byzantine Fault \\ Tolerance (DBTT) [75] \\ \end{tabular} & Permissioned/Permissionless & Neo &
\begin{tabular}{c} Cr, Python, NET, Java, C++, \\ C, Go, Kotlin, Javascript \\ \end{tabular} & Fast, scalable & Conflictions on the chain \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Characteristics of cryptocurrency consensus algorithms.