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TECHNOLOGY

Locus Chain is a high-performance public blockchain. Other public blockchains known to date were unable to be put in practical use due to their poor performance and lack of scalability. 


However, Locus Chain has addressed to the issues of both the performance and scalability limitations of the public blockchains based on their technology of complete decentralization.


- Transaction per Second (TPS): 4,000 ~ 10,000 

- Latency): 0.5sec ~ 7sec (Will not slow down during high amount of usage)

- Ledger Structure that separates data storage and verification (Maximum Efficiency)

 

Not only does Locus chain solve issues regarding performance and scalability, Locus Chain can operate on smartphones, internet routers, and other IOT devices due to the dramatically reduced resources required to operate the validator. As a result, the transaction fees for the Locus Chain are very insignificant, and anyone can easily operate the miner, which greatly increases the stability (security) of the blockchain network.


This marks the beginning of the true 'credit/data revolution' that the public blockchain had dreamed of.

DAG(Directed Acyclic Graph) - AWTC(Account-Wise Transaction Chain)

 

The AWTC ledger structure is a parallel, Direct Acyclic Graph (DAG)-based structure that manages transactions on an account basis, and is an important technological element in terms of fast transaction and distribution processing of the Locus Chain.

 

Ledger structure for high speed bulk processing




While many blockchains, such as Bitcoin and Ethereum, have linear chain structures, Locus Chain uses Account-Wise Transaction Chain (AWTC), a nonlinear ledger structure based on a Direct Acyclic Graph (DAG). This structure, as it is called, is a parallel structure that manages transactions on an account basis and the block lattice has a similar shape of nanocoin. The linear chain structure has only one location where the next block can be connected to the previous block, and a bottleneck phenomenon occurs when multiple nodes attempt to add the block to the same connection point at the same time.


Locus Chain’s block grid structure however, including the Locus Chain's DAG-AWTC, has as many points to connect as the number of accounts, and only proprietary account can be recorded for that particular point, so no conflicts will occur. 


In addition, the account for which the transaction was added becomes clear, so if the account owner himself is not a malicious user, the transaction is almost immediately confirmed. 


This nature of Locus Chain's ledger structure is one of the key technical features to fundamentally address the transaction delays that the existing blockchains had.


Additionally, each account has a Hierarchical Shewed Merkle Tree, rather than a flat linear chain, that separates and stores verification and data so that the blockchain can efficiently provide the function of verification rather than the means of data storage management.

POS - BFT Consensus Algorithm

 

Locus Chain executes the deterministic consensus algorithm for slightly old status of ledger, which offsets the average time required for a transaction to propagate within the shard.


Also, the new proposer committee that participates in the consensus algorithm is elected every round through Verifiable Random Function (VRF) based on Stochastic PoS (method in which the likelihood of being elected as a committee increases with higher stake). It is difficult for malicious attacks to manipulate data through this method because it is impossible to specify or predict the nodes (proposers and validators) that will participate in the consensus. Thus, Locus Chain secures fairness of the consensus result and network stability.

Deterministic Consensus:



The DAG-AWTC structure is designed to settle a transaction in a “retail processing” time scale, usually within seconds. This is possible because collisions between accounts do not occur, and the result is unlikely to change in most cases. However, a malicious account owner may cause problems like double spending on its own Transaction chain. To handle situations like this, Locus Chain executes BFT consensus periodically to check and make sure there are no issues and if problems are discovered it will be resolved.

 

Double spending in the AWTC structure is defined as a case of two or more transactions with the same index number that are simultaneously issued to an account’s transaction chain. when multiple different transactions with the same index number are issued simultaneously, the transactions propagate over the network through different nodes. During the propagation, the sum of (delegated) stake over propagated node paths of each transaction can be considered as a pseudo-vote count. The transaction with more votes is selected as the primary candidate of the nondeterministic consensus. Then, the BFT consensus committee nodes that are elected in a stochastic PoS manner, periodically (for roughly every 2 minutes) confirm and finalize the consensus in the deterministic form by signing the ledger status


Each node independently updates its view of ledger status because AWTC is a parallel data structure. Therefore, a node cannot determine the absolute state of the whole ledger in real-time. Locus Chain executes the BFT deterministic consensus algorithm based on DAG, considering the time required to fully transfer the data, for slightly old status of ledger, according to the average time required for a transaction to propagate within the shard.


Locus Chain’s consensus algorithm has improved the traditional stop-and-go method as the algorithm does not disrupt issuing transactions during the consensus algorithm and also does not interrupt DAG’s high-speed processing.


Implementation of DAG and BFT simultaneously is technologically significant since they become the basis of pruning and sharding technology to resolve the storage and network load issues later on.

Stochastic PoS Based Consensus Committee Election

 

Complete Decentralization

Locus Chain uses algorithms that are similar to Algorand implementing the BFT consensus algorithm on the DAG. A new proposer committee that participates in the consensus algorithm is elected every round through Verifiable Random Function (VRF) based on Stochastic PoS (method in which the chance of being elected as a committee increases with higher stake).


It is difficult for malicious attacks to manipulate data because it is impossible to identify the proposer in advance. Based on the number of recent votes cast and the degree of network participation (online time, etc.) a new validator committee will be elected for each round, and the round status proposed by the proposer will be determined by two votes according to the PBFT method. Since this method is unable to specify or predict which nodes (proposer, validator) will participate in the agreement, it will be difficult to manipulate them by malicious attacks, thereby ensuring authenticity of the concensus and the stability of the network.

 

Verifiable Pruning




Verifiable Pruning is a technology that deletes (pruning) previous data from a certain period of past time, in the local environment, without affecting the blockchain’s data validation function.

 

Locus Chain has successfully completed the technical development of Verifiable Pruning, a technology which deletes previous data from certain period of time (1day) from the local environment to reduce the volume of local data while not affecting the blockchain’s data validation function. 


Unlike general pruning that decreases the ledger size by simply deleting old data, Locus Chain’s Verifiable Pruning can validate data authenticity with the Skewed Merkle Tree structure, even when the majority of old data do not exist in the local environment.


Locus Chain can significantly reduce data storage on the local node because the authenticity can be validated with only the hash values of the required portion without having to possess all the relevant data. The fact that nodes can be operated with the storage size of SD cards provides an important basis for anyone to participate in the Locus Chain network without any burden, which is an important factor in achieving high decentralization. 

 

With extremely efficient data storage, Locus Chain can operate full nodes on devices such as smartphones, internet routers, and other various IoT devices that does not have much storage spaces. In addition Locus Chain implements advanced data structure of the Hierarchical Skewed Merkle Tree which exponentially reduces computations for tracing back transactions dating back to several years, reducing the storage burden on nodes and enables high-speed validation. 


However, depending on the need, you may disable the Verifiable Pruning function, in which case the ledger will not be Pruned. 

Locus Chain applies Dynamic Sharding, which divides network usage into the same amount of shards, while maintaining balance among the shards.


This will not only decrease the network usage the nodes must handle, but will also increase the transaction processing volumes of the entire network. In Locus Chain, the number and size of shards, validator ratio, etc. can be readily adjusted since it rearranges the shard based on the AWTC ledger structure. 


Dynamic Sharding




Locus Chain incorporates Dynamic Sharding to decrease the network traffic for each node and to increase the total transaction volume of the entire network.


Sharding is a data processing method that divides a large volume of data (Network or ledger) into smaller units (shards) that can be easily processed. Common sharding has the disadvantage of increasing communication ratios proportionally to the number of shards and having difficulty in referencing and verifying data between shards. Although dividing the network improves overall performance, improper dividing of shards may lead to imbalances between shards regarding number of nodes and transactions and can potentially cause instability in the entire network. Locus Chain’s Dynamic Sharding addresses this problem by dynamically determining the optimal number of shards depending on the network usage and uses algorithm to maintain the balance among the shards making sure that the performance does not shift to one side. 


Locus Chain’s ledger AWTC structure is composed of independent account chains, and each account chain can be easily relocated to different shards to adjust shard parameters like the number and size of shards, and the number of validators. With Dynamic Sharding, the amount of network traffic for each node reduces, and the transaction processing capacity of the entire network increases proportionally to the number of shards. The storage usage for the ledger also decreases in the same fashion since each shard stores the account transaction chains required for the shard.


Post Quantum Cryptography Signature

 

Locus Chain uses the dual encryption system to prepare for the Quantum Computing era. 

 

The normal signature key is used for general transactions. When the normal key is lost or exposed to others, it becomes exchanged by using the PQC applied master signature. There is less burden for PQC data and calculation volume since the master signature is only used in situations that absolutely require it. The normal signature is designed in the plug-in method that can be exchanged into the PQC algorithm in the future. 




Cryptographic Future Contrast:

One of the biggest threats to blockchains is the emerging threat of quantum computers. There is a possibility that quantum computers may neutralize many currently used signature algorithms and many researchers are conducting researches regarding Post-Quantum Cryptographies (PQC) that are secure against quantum computers. However, current Post-Quantum Cryptographies (PQC) are infeasible for personal computers and mobile devices because they require immense amount of computation and data compared to non-PQCs. Also, there are no matured standards for PQCs yet, and it is hard to tell the precise property of PQC algorithms in actual use due to the lack of scientific and technological validations and establishments


To overcome this situation, Locus Chain incorporates a layered key system composed of two cryptographic keys, a master key and a normal key, of different strengths. A user uses the normal key, which depends on a current-generation cryptography system, for signing transactions. If the user’s normal key is compromised, then PQC-applied master key is used to re-generate and change the compromised normal key. Since master keys are only used in exceptional situations the algorithm for master keys can consume significant computing resources for PQC computation. In the future, Locus Chain will be able to exchange the normal key algorithm itself with a Post-Quantum algorithm once PQC algorithms become widely available. 

Moreover, Locus Chain may use a hybrid of PQC and current-generation cryptographies for a while since the property of PQC is not yet completely understood. Even when vulnerabilities of PQC signature algorithms are found, Locus Chain can make use of current-generation algorithms to quickly, temporarily cover the vulnerabilities.

Data forgery verification API 

 

The key concept of Locus Chain's idea of blockchain technology is that the falsification and legitimacy of submitted data can be verified by anyone in an open environment rather than focusing on the storage of data. 


Many blockchain projects are trying to place the data directly into the blockchain ledger instead of the existing database management system (DBMS), but it is difficult for the blockchain platform to replace the full-scale data storage and transaction processing capabilities of the existing DBMS.


Locus Chain possess a system that can efficiently verify the legitimacy and falsification of stored data from a distant future through methods such as other DBMS, and has also completed a platform that allows users to verify falsification of data through Locus Chain's forgery verification API without having to establish their own blockchain system individually.