Qtum Research Institute | Public chain development thinking and the technological innovation road of Qtum quantum chain

​A total of 11,554 words

Estimated reading time: 30 minutes

 

Article Summary

• Briefly describe the development process, design ideas, and current problems of Bitcoin and Ethereum;

• Explains the design ideas and technological innovations of Qtum quantum chain, introduces the working mechanism and implementation methods of Qtum's account abstraction layer, consensus mechanism, distributed governance and other main components, and explains the development flexibility and performance scalability of Qtum quantum chain , Technical stability and other advantages;

• Introduced the Qtum2.0 upgrade content, and briefly explained the future development directions, such as x86 virtual machines, privacy assets, chain-cloud integration, smart contract staking, etc.;

• Combined with the current development status of the public chain field, the basic criteria for the evaluation of the public chain are proposed, and some common concepts are defined.

 

Introduction

Preface

 

In 2008, an ID named Satoshi Nakamoto published a paper titled "Bitcoin: A Peer-to-Peer Electronic Cash System" on the Internet. A set of electronic cash system that is completely peer-to-peer and does not need to trust a third party is designed in the article, named Bitcoin. At the beginning of 2009, the Bitcoin system began to run online until today. Although the proper term "blockchain" was proposed only a few years later, as the first application in this field, Bitcoin has successfully implemented a set of cryptocurrency symbol systems that cannot be "double spent" on the Internet. It has had a profound impact on all subsequent applications and innovations in the blockchain field. Among them, the most important designs, such as the application of cryptographic algorithms, consensus mechanisms, game mechanisms, peer-to-peer networks, etc., have also been used by most blockchain projects to this day. After Bitcoin, many colored coins and micro-innovative electronic cash systems based on Bitcoin have appeared one after another, which are essentially improvements to this cryptocurrency symbol system. With the iteration of technology, more and more people are participating in this technology and system experiment. In 2014, the team headed by Vitalik Buterin founded Ethereum. By introducing smart contracts and virtual machines that can program symbols, it hopes that in addition to providing standard symbologies, it can also provide services for different objects. Universal decentralized application platform. Ethereum is the beginning of the concept of public chains, and smart contracts have quickly become the standard configuration of most blockchains. Subsequently, at the end of 2015, IBM jointly developed the HyperLedger series of software with several data and software service giants, and vigorously promoted blockchain-related technologies and "licensed blockchain" services to the public, making the term "blockchain" gradually break through The original small circle is further known by the public.

 

1

The origin of Qtum quantum chain

 

Qtum Quantum Chain started in 2016, which is the time when technological innovations in the field of blockchain have emerged one after another and projects are blooming.

 

The members of the Qtum team have been in contact with and researching the technology of Bitcoin and other blockchain projects as early as 2012, and have continued to dig in this field. Until 2016, the cryptocurrency market has gone through two cycles in a small scale. Various cryptocurrency projects represented by Bitcoin are in full swing, and smart contract platform projects represented by Ethereum are also catching up. However, as the two most technologically innovative communities in the industry at that time, Bitcoin and Ethereum have always been separated, which largely hindered the further development of the industry. The original intention of Qtum is to add support for smart contracts based on the exquisite symbol system of Bitcoin, to be compatible with the existing technology accumulation and subsequent technological innovations of the two communities, to further realize richer technological evolution, and finally realize A breakthrough in the field of public chains. 

 

Qtum is the first public chain project that successfully implements smart contracts on top of the UTXO model, and its core protocol can be implemented in almost all UTXO-based blockchain projects including Bitcoin.

 

In the design of Qtum, the most important keywords are security, flexibility, decoupling, decentralization and autonomy. By reusing the underlying architecture of Bitcoin and the Ethereum Virtual Machine (EVM), Qtum can simultaneously follow up all the technical updates of Bitcoin and EVM, which not only has the security and stability of the Bitcoin UTXO model, but also has Turing completeness. EVM brings unlimited flexibility and rich supporting development tools. In order to get through the two incompatible systems, and for future expansion and iteration, Qtum designed the Account Abstraction Layer (AAL). AAL completely decouples the funding layer of UTXO from the smart contract layer. On the one hand, UTXO is abstracted into an account form that can be used by virtual machines such as EVM, and on the other hand, it is compatible with multiple virtual machines in parallel (such as WASM, Qtum x86 virtual machine, etc.) Be prepared. Qtum adopts a pure PoS consensus mechanism and further improves the security of the consensus mechanism. The nodes participating in the consensus only need to hold QTUM, and no special hardware is required. The full node can run on ordinary home computers almost insensibly, participate in network consensus, compete for block generation, and obtain rewards. This makes Qtum have thousands of full nodes online throughout the year, making it the third decentralized public chain network in the world in terms of the number of full nodes. While emphasizing decentralization, Qtum achieves a performance of 60-70TPS, which is higher than Bitcoin and Ethereum. In view of the importance of community consensus in the blockchain field, Qtum also proposed the Distributed Governance Protocol (DGP), which uses smart contracts to govern the blockchain on-chain. Ecological participants can dynamically modify the block size and contract fees through DGP. Models and other important parameters can realize the seamless upgrade of the Qtum network, while effectively avoiding divisions caused by community differences.

 

Qtum proposes its own design based on projects such as Bitcoin and Ethereum. All open source projects, it can even be said that all inventions and scientific explorations are carried forward on the shoulders of predecessors, even Bitcoin is no exception.

 

2

The history of Bitcoin

 

Bitcoin is not a product created by Satoshi Nakamoto from scratch. Some important components of the Bitcoin protocol, such as peer-to-peer communication networks, asymmetric encryption and cryptographic signatures, Merkel tree verification, and other technologies have been developed for many years before this. The design of Bitcoin also refers to the design ideas of digital currency projects such as Hashcash and Bmoney.

 

Bitcoin's goal is to become a "peer-to-peer cash system". The economic depression caused by the subprime mortgage crisis in 2008 aggravated the public’s distrust of financial institutions and the current financial system, and a cash system that cannot be over-issued, tampered with, trust-free, and transparent and traceable can solve financial institutions to some extent Ills. In the initial period of time, Bitcoin and some derivative altcoins are indeed working towards becoming a means of payment. There are many merchants and institutions accepting Bitcoin payments, and Bitcoin ATMs and other facilities have appeared, but the price fluctuates greatly, high handling fees (small payment scenarios), very limited processing capabilities, and long transaction confirmation times, etc. And so on, have restricted the application of Bitcoin in the payment field, and slowly transformed into a store of value similar to "digital gold".

 

As an electronic cash system, the design of Bitcoin takes security and stability as the primary conditions. So far, the system has not had any serious system failures and successful attacks. This is the basis of the value of Bitcoin. But paying attention to safety often means a relatively conservative upgrade strategy. In the past ten years, apart from technical improvements and maintenance, the Bitcoin protocol has not significantly expanded in terms of functionality, and its working methods and performance are still similar to those ten years ago. The Bitcoin Improvement Proposal (BIP) is the main way to upgrade the Bitcoin protocol. However, it often takes a long process from proposing a BIP to deciding whether to implement it and finally being implemented, and it may lead to a split in the community and the creation of a fork chain. s consequence. The Qtum core protocol can support smart contracts on the underlying architecture of Bitcoin. In theory, it can be used as a standard BIP to be upgraded and implemented on the Bitcoin core protocol. However, due to Bitcoin's conservative upgrade strategy, this idea is difficult to become a reality. Because of this, the Qtum team decided to re-establish a blockchain to realize this vision, and designed a decentralized governance protocol in the system to handle network upgrade decisions.

 

Bitcoin transfers are implemented by scripts. The system will generate scripts based on user requests and combine built-in operation codes to complete specific operations by executing the scripts. So in theory, Bitcoin also has a certain degree of programmability, but there are few operations that can be done, and it is difficult to operate. So in 2013, Vitalik Buterin proposed the idea of ​​Ethereum, abstracting the operation scripts and expanding them, creating a set of more feature-rich bytecodes, running on the node's virtual machine, and changing the decentralized network application scenario from The execution of the transfer script is extended to code that executes arbitrary logic, that is, smart contracts. 

 

3

The development history of Ethereum

 

The concept of smart contracts was proposed by Nick Szabo in the early 1990s, and refers to digital contracts that can be automatically executed without trust. Ethereum has designed a variety of smart contract programming languages ​​(the most popular is Solidity, the form is similar to JavaScript), and the corresponding execution environment, EVM (Ethereum Virtual Machine). After a piece of Solidity code is successfully compiled and recorded on the blockchain, it becomes a smart contract. Any action that meets the predetermined conditions, such as transferring money to the contract, will trigger the contract to execute according to the predetermined logic.

 

Ethereum's smart contracts use a gas model to achieve a certain degree of Turing completeness. However, due to the block size, cost limitation and the functionality of the Solidity language itself, it is impossible to implement overly complex logic and instructions. The fee mechanism is another creation of Ethereum. By pre-estimating the system resource consumption corresponding to each bytecode of the EVM, Ethereum gives each opcode a gas value. When the contract is running, the caller needs to pay the gas fee in advance, and the contract will stop after the gas is consumed. This design solves the problem of downtime and spam attacks on the blockchain, and ensures the normal operation of the system.

 

After Ethereum went live in 2015, it has been continuously updating and optimizing the code, including optimizing the fee model, modifying errors and vulnerabilities, adjusting the difficulty of mining, and so on. Since its development, Ethereum has undergone 7 hard forks, including scheduled upgrade hard forks and emergency forks for system security and application security reasons. The latter has caused huge controversy, resulting in the division of the community and the fork of the blockchain. Even until recently, the hidden danger of the DAO incident has not been completely eliminated. After years of development, the basic operation mode of Ethereum, namely the single-chain blockchain of the account model, the smart contract written by Solidity running on the EVM, the global verification of the full node, and the PoW consensus, have not changed. Some large-scale upgrades that were originally scheduled, such as changing the consensus mechanism to PoS algorithm, sharding structure, and switching to eWASM virtual machine, are not as good as expected, and due to the close connection between the existing blockchain contract layer and the bottom layer, these large-scale The upgrade may cause Ethereum to need to open a new blockchain.

 

After years of development, a relatively complete ecosystem has been formed around Ethereum, including core developers, Layer 2 protocol development and application development, etc. The Ethereum Foundation also supported the team's research and development of more basic modules such as decentralized storage and peer-to-peer communication protocols. At present, most of these projects are still under development, and there is no scale effect, and the user group cannot be compared with Ethereum. And Ethereum itself is also facing strong competition from emerging public chains.

 

At the same time, Ethereum's attempts at decentralized applications have been relatively successful so far. From the fundraising contract that broke out in 2017, to the CryptoKitties at the end of 2017, to today's financial applications such as MakerDAO, almost every application hotspot occurs on Ethereum. This is why Qtum prioritizes the integration of EVM. Although there have been some explorations in applications, decentralized applications are still primitive in terms of user volume, functionality, and user experience. Many application scenarios that have been mentioned many years ago are still difficult to implement. , The legendary "killer app" has not yet appeared. The important reason is that the current decentralized applications must undergo global verification, and this synchronous logic and the asynchronous logic used in real applications are often contradictory, and the application cannot be truly expanded. This is the dilemma faced by the decentralized application platform represented by Ethereum, and it is also a problem that the entire industry needs to solve.

 

4

Technological Innovation of Quantum Chain

 

Qtum Qtum successfully reused the most innovative and valuable parts of Bitcoin and Ethereum: Bitcoin's underlying UTXO accounting system and Ethereum's EVM virtual machine, combining Bitcoin's stability, security and smart contracts The infinite flexibility of the company is combined and used as a basis to realize its own innovation and iteration. Thanks to its good compatibility with Bitcoin and Ethereum, Qtum has successively released the realization of the latest technological developments in the industry, such as Lightning Network, Cross-chain Atomic Exchange, Qtum-IPFS, Qtum-Plasma, etc. At the same time, Qtum is also continuously exporting technology to the outside world, feeding back open source projects such as Bitcoin and Ethereum. The Qtum core team has discovered and fixed the loopholes in the issuance of Bitcoin, improved the security of the PoS consensus mechanism, and proposed a smart contract payment mechanism to lower the threshold of use. The privacy assets, cloud chain integration, and smart contract staking that the team is developing will also provide a technical foundation for the further development of the industry.

 

Account Abstraction Layer (AAL)

As mentioned in the first section, in order to combine Bitcoin and smart contracts, Qtum designed the Account Abstraction Layer (AAL). AAL has two main functions: one is to abstract the UTXO model of Bitcoin into an account model available for EVM, so that EVM can run on the bottom layer of Bitcoin and execute smart contracts; the other is to separate and decouple the funding layer from the contract layer. , Make the operation of each layer relatively independent, prepare for subsequent iteration and expansion. Relying on this design, Qtum's subsequent x86 virtual machines can run in parallel with the EVM on the quantum chain, without the need to make substantial changes to the underlying protocol, and retain good functional scalability. Even in the future, any virtual machine based on the account model can be adapted to run on the quantum chain. In order to achieve AAL, Qtum has made a lot of adjustments and optimizations for the correspondence and conversion between smart contract operations and UTXO operations, and designed three new opcodes:

 

• OP_CREATE: Create a smart contract

• OP_CALL: call the smart contract (send QTUM to the contract)

• OP_SPEND: Spend QTUM in the smart contract

 

When generating a new block, in addition to regular checks on the transaction script, it is also necessary to check whether the above opcodes are included. OP_CREATE is used to pass the contract bytecode to the virtual machine. OP_CALL sends the key parameters required to run smart contracts such as data, gasPrice, gasLimit, VMversion, etc. through transaction scripts, and finally to the virtual machine. OP_SPEND is used to convert the contract execution result into a standard UTXO. By introducing the above three scripts, Qtum's UTXO model has the ability to identify and process smart contract related transactions. In order to ensure the state of the contract and the consensus of UTXO, the block header of Qtum not only contains the same fields as Bitcoin, but also needs to add two fields, hashStateRoot and hashUTXORoot. More technical details can refer to this article.

 

MPoS consensus mechanism

Another innovation of Qtum is the MPoS consensus mechanism. As one of the most core parts of the public chain, the consensus mechanism is the basis for the public chain to decentrally determine the ownership of accounting rights and complete transaction verification to obtain a global consensus. The existing mainstream consensus rules all have their own problems: PoW algorithm has no barriers to entry. Anyone can use PCs and other equipment for verification and mining. However, based on the current level of computing power of professional mining farms, ordinary equipment is probable. It is almost impossible to obtain the right to produce blocks. Moreover, the PoW algorithm has been criticized for unnecessary consumption of a large amount of energy and is not friendly to the environment. Due to the pursuit of performance, algorithms such as DPoS and dBFT have a low degree of decentralization. Moreover, such networks require high-performance servers to become full nodes to participate in network verification, and the threshold for becoming a block producer is extremely high.

 

Qtum's MPoS algorithm is improved from PoS3.0, but the combination of the traditional PoS consensus mechanism and smart contracts will bring security risks such as "junk contract" attacks and cannot be directly used in Qtum. In this regard, Qtum increases the cost of attacks by allowing block producers to share revenue with other nodes and delay the revenue. Each block reward is divided equally by 10 miners, and the remaining rewards are delayed by 500 blocks. That is, the 1/10 block reward is obtained immediately, and the remaining 9/10 rewards are obtained in 9 consecutive blocks after 500 blocks. Mining reward = block income + handling fee + gas fee for running smart contracts. The improvement of this revenue mechanism does not change the core logic of PoS3.0, so that the attacker cannot predict how much block rewards will be obtained, nor can they immediately obtain block rewards, which greatly improves the launch of the aforementioned "junk contract" attacks. (There is only a theoretical possibility, and it is completely impossible to achieve in actual operation).

 

MPoS enables Qtum to achieve a balance between scalability and decentralization. The MPoS consensus has low hardware requirements and can run on almost all home computers, and the occupation of system resources will not affect the normal operation of the computer. The collateral that participates in the block generation is not computing power (hardware cost and electricity bill), but a certain amount The amount of QTUM. Compared with the current concentration of computing power of the PoW public chain and the low number of nodes of the DPoS public chain, the design of Qtum may be more in line with Satoshi Nakamoto's vision for a decentralized network. On the basis of maintaining decentralization, Qtum's scalability is far greater than Bitcoin and Ethereum, and can reach 60-70TPS, effectively alleviating network congestion problems, and with the optimization of the cost model and the application of x86 virtual machines , Scalability can be further improved.

 

Compared with other blockchains with staking function, Qtum's consensus algorithm brings Staker more flexible ways to participate and exit. Participate in Qtum's staking first. You only need to download the Qtum core wallet and use your home computer to become a full node. To participate in staking, you don’t need to trust various service providers and you don’t need to pay fees. Secondly, the UTXO model allows participants to divide the staking QTUM into multiple UTXOs. Each UTXO is independent of each other when calculating the freezing time, so the pledge voting is more flexible. Only the UTXO that has the right to block will be frozen and the time will be frozen. Only about 17 hours. Therefore, the liquidity risk of participants is also smaller than most staking projects on the market.

 

Distributed Governance Protocol (DGP)

In the future, Qtum will also develop offline staking methods such as smart contract staking to further lower the threshold for users to participate in the network and ensure the security of revenue.

 

The blockchain community has different opinions about the development direction of a project, splitting, and creating new chains through hard forks. Such different opinions can be roughly divided into three categories:

• Disagreements on the development direction of project algorithms and functions;

• Disagreements on certain parameters of the blockchain;

• Fix critical vulnerabilities and roll back.

1 and 3 must be solved with a hard fork in some cases, but the second type of problem can be reached in a more gentle way. The framework of DGP itself is realized through a number of smart contracts deployed in the founding block. Its basic governance structure is like this. In the entire ecosystem, miners (Staker), developers and QTUM holders are all blockchain governance Of participants, through voting to complete the governance process. Finally, the blockchain can realize self-management, upgrade and iteration.

 

The realization of DGP core logic is composed of a series of smart contracts (including framework contracts and feature contracts). The core code of the blockchain executes the smart contract of the agreement in the consensus process to obtain the current consensus state. At the same time, it can complete the state transition of the blockchain network by sending the corresponding transaction, and the upgrade does not need to update the blockchain network software.

 

At present, due to security considerations, only DGP is allowed to manage some parameters of the system. In the future, DGP can continue to iterate to achieve more and more complex governance. Going back to the specific implementation, the genesis block embeds a common blockchain parameter governance smart contract, and each governance theme is controlled by an independent framework contract (template), which means that each function has an independent governance and authorization mechanism And built-in restrictions Block size, Min GasPrice, Block GasLimit, Gas Schedule.

 

In addition, the DGP contract also has a self-destruct function, which can be activated when an accident occurs in the proposal governance, and the governance parameters return to the default state.

 

Qtum 2.0 and the future direction

Qtum has been focusing on the research of the underlying infrastructure of the blockchain, and iterates continuously on the basis of Bitcoin and EVM. After nearly two years of stable operation of the mainnet, Qtum exposed some flaws in the system and consensus rules. In order to adapt to the ever-changing application scenarios of blockchain technology, Qtum will gradually upgrade the underlying protocol and launch Qtum 2.0.

• Underlying protocol upgrade

Qtum completed the first hard fork upgrade of Qtum 2.0 on October 17, 2019, aiming to optimize the underlying protocol and serve as a technical preparation for subsequent upgrades. This upgrade includes the following updates:

 

• Introduced a smart contract fee payment mechanism, which fundamentally changed the logic of smart contract calls and fee payment, further lowered the threshold for use, and enriched its application scenarios;

• The addition of multiple practical precompiled contracts, especially the support for complex cryptographic logic, reduces development costs while expanding the scope of future applications of smart contracts, such as the construction of private assets, smart staking, etc.;

• Upgraded the virtual machine version to support more new features and provide developers with stronger technical support;

• Improved the difficulty adjustment algorithm to further enhance the stability of the network.

 

For the recent research and development of the project, Qtum will focus on new x86 virtual machines and privacy assets, smart contract staking, and the combination of blockchain and cloud computing. 

• x86 virtual machine

The x86 virtual machine is an important part of the Qtum project. The implementation of this virtual machine will make the development of smart contracts on Qtum closer to the mainstream programming paradigm. Although Ethereum's Solidity already has many developers, due to its design flaws and lack of many common modern programming language features, developers have high learning and development costs, and many ideas cannot be realized. Qtum's x86 virtual machine follows a completely different basic design from EVM and can support more types of general-purpose computing at a lower cost.

 

x86 is a computer instruction code architecture that has lasted for decades and is widely used by chip manufacturers such as Intel. Almost all mainstream programming languages ​​and tools are implemented on the basis of this architecture. The x86 virtual machine will automatically inherit the support for the upper-level language and tool chain, so that Qtum can get rid of the limitations of EVM computing space and functions, and unlock more features. Qtum's x86 virtual machine plans to first implement the Rust language version, and will continue to support almost all mainstream programming languages ​​including Rust/C/C++ for smart contract development.

 

Using x86 virtual machines can also provide developers with more standard libraries. These standard libraries will exist in a way similar to pre-compiled contracts, and their fees and prices can be governed by DGP, which will greatly reduce the developer’s cost of developing smart contracts. Difficulty and development and operation costs. In addition to the kernel of the virtual machine, the Qtum x86 virtual machine also designed a storage lease model and a new state storage model to slim down the blockchain. The problem of state expansion may not be obvious on Qtum, but the full nodes of Bitcoin and Ethereum have reached more than 200GB, and EOS has exceeded 1TB. If ordinary home computers cannot easily run full nodes, then the blockchain network will inevitably fall into the hands of a small number of professionals, and decentralization will be impossible. The storage space rental model designed by the x86 virtual machine will effectively solve this problem from the perspective of the cost model. The new incremental state storage model makes simple payment verification (SPV) of smart contracts possible, and in the future, even fully decentralized Qtum smart contract calls can be realized through mobile devices such as mobile phones. In addition, the x86 virtual machine will also support more complex functions such as variable length variables, larger memory space to implement smart contracts that monitor the state of the blockchain for a long time, and quick access to third-party contract states, which will greatly enrich The imagination of smart contract development.

• Private assets

For most public chains today, whether it is ordinary transfer or contract call, the address and amount of each participant, account balance and other information are transparent, which is not conducive to the commercial application of blockchain. However, existing solutions are often unable to be widely applied due to factors such as cost, efficiency, and the degree of support of the blockchain. Qtum plans to support the issuance and circulation of private assets through smart contracts, and reduce the development and use costs of private asset-related contracts on the Qtum blockchain by deploying pre-compiled contracts and optimizing the data structure of privacy certification. In the recent Qtum2.0 upgrade, the btc_ecrecover precompiled contract has been deployed, and more precompiled contracts about secp256k1 elliptic curve and Schnorr signature will be deployed in the future to further reduce the deployment and operation cost of the privacy asset solution.

• Blockchain + cloud

In addition, in response to the current difficulties faced by decentralized applications, Qtum is also actively exploring the combination of blockchain and cloud computing related technologies. The development of the blockchain to this day still has not deviated from the logic of Bitcoin's time-based block generation + global synchronization verification. This is not a big problem for the use of low interaction frequency such as transfer, but it may not be the best way for application platforms. It can be seen that some simple games can block platforms such as Ethereum and EOS, so in large-scale commercial applications, the existing public chain platforms are difficult to be trusted. Although many projects are currently exploring the direction of sharding, DAG, and off-chain computing solutions, they are still in the experimental stage. The Qtum team believes that the most important feature that blockchain brings to applications is not "decentralization", but the following three "blockchain characteristics":

• The "four in one" authority management mechanism of account, address, funds and identity;

• Bring a set of natural clearing and settlement network;

• The rapid growth brought about by incentive mechanism and liquidity.

These are the characteristics that all existing Internet applications lack. Most of the existing Internet applications are deployed on the cloud, and in the foreseeable future, applications deployed on the cloud will still be the mainstream. How to integrate the above-mentioned blockchain features with applications deployed on the cloud will be the key to whether blockchain applications can truly land, and it is also the most feasible solution to break through the dilemma of decentralized applications.

• Smart contract staking mechanism

In a standard PoS system, nodes participating in staking must remain online, and Qtum is no exception. But the disadvantage of online nodes is that, first of all, for ordinary users, although they can staking on their personal computers, it is difficult to guarantee 24 hours online without renting a server, which makes it difficult to guarantee revenue, which will affect them in the long run. The enthusiasm for participating in staking reduces the degree of network decentralization; and for "big users", that is, Staker holding more coins, they also have security concerns about keeping large amounts of coins in hot wallets. There are also mining pools in the public chain under the pure PoS mechanism. Although the mining pool has high security, users must transfer the coins to the mining pool to be staking on their behalf. This makes users lose control of the coins. The risk of losing the principal is also the risk of reducing the degree of decentralization of the network. And the proxy consensus mechanism adopted by some projects, such as dPoS, dBFT, etc., is essentially closer to a centralized network, and the revenue obtained from the coins that ordinary users delegate to super nodes is also guaranteed by on-chain logic, but according to the agreement Distributing income off the chain undoubtedly brings great uncertainty.

 

The smart contract staking mechanism that Qtum is developing can solve the above problems well. Ordinary users can delegate the rights of staking to a dedicated staking smart contract, so that they do not need to keep their nodes online, and they always have the right to control or withdraw their tokens; the big Staker can also escrow the staking rights of the coins to Contracts, and keep the coins in a safe cold wallet; the benefits of all escrow users are distributed on the chain by smart contracts, and there is no risk of centralized mining pools. Not only that, because the smart contract is programmable, this mechanism will bring more flexibility to staking. The income method and return method can be controlled by the contract logic, without the intervention of a third party, and users can choose the contract that suits them. For custody, you can also deploy your own customized staking contract.

 

5

Evaluation criteria of public chain

 

The public chain, or the permissionless blockchain, is still in the stage of barbaric growth. For public chains with different consensus mechanisms and different application scenarios, it is difficult to find a unified index to measure the pros and cons of each other. But starting from the first principle, combined with the positioning of the public chain in the infrastructure of the blockchain world, we can summarize some basic standards as a reference for evaluating the public chain:

 

The threshold to become a full node. An important feature of the public chain is that it does not require permission to join, which is also the source of its trustlessness and security. Like Bitcoin, although the current probability of obtaining block rights for home PCs is very low, there is still a certain possibility. If the project sets too high a threshold for network entry, ordinary users cannot participate, or the cost of participation is high due to technical reasons, it will inevitably result in a low level of network decentralization, which will pose a certain threat to the security of the system and users’ trust in the system .

 

The number of full nodes in the network. For blockchain, the number of full nodes in the network is an important indicator of the scale of the network. In the Internet field, there is a famous Metcalfe law, which states that the value of the network is proportional to the square of the nodes in the network. The full nodes in the blockchain network are the most important type of nodes. The number of full nodes represents the size of the community behind the network and is related to network security to a certain extent.

 

Global TPS. Qtum founder Shuai Chu once proposed a concept called Global TPS, which multiplies the total number of nodes in the network by the system's TPS to obtain an indicator that comprehensively measures the degree of decentralization and processing capabilities of the blockchain system. Compared to purely testing TPS, GTPS may be more meaningful for public chains. After all, removing the decentralized, peer-to-peer open network, it is meaningless to compete with traditional distributed systems for processing capabilities with the high redundancy of the blockchain system.

 

Governance. The governance method determines important issues such as the relationship between the token holder and the project, the way the project is going to be determined, and is of great significance to the consensus building of the community. The current common governance methods include QIP-type proposal governance, on-chain voting governance, and relatively centralized off-chain autonomous organization governance. If there is no reasonable and clear way to combine the demands of the token holders with the development of the project, and coordinate the opinions of miners, developers, users and other community members, the project will lose momentum and progress slowly, and the project will split. The loss of value of the certificate is not conducive to the long-term development of the project.

 

Token distribution and incentive methods. Decentralized distribution of certificates and clear and fair incentive mechanisms are conducive to the formation of community consensus. A clear total amount of tokens and distribution methods are one of the elements of Bitcoin's success, which also applies to all public chain projects. If the certificates are concentrated in the hands of a few people, it is easy to form manipulation of the price of the certificates and the direction of the project, and it is difficult to form a community consensus.

 

Security and stability of funds. This requires code to go through long tests, audits and iterations, which is the foundation of the public chain. It's not that a new consensus mechanism or a new virtual machine is good. For the design involving users' funds, it takes a long time to test. In a sense, part of the value of BTC is derived from the value deposited after the test of time.

 

The flexibility and scalability of the platform. An application-oriented public chain requires smart contracts to provide unlimited flexibility and unlimited scalability. Qtum is also planning a corresponding plan. At present, there is no platform in the industry to achieve unlimited scalability.

 

Decentralization, without permission, is the foundation for the blockchain to be able to trust. How to innovate on this basis, improve functions and performance, and develop meaningful application forms, is what all blockchain developers need to think together problem.

 

6

Concept definition

 

• Bitcoin

The first successful peer-to-peer electronic cash system, the global community expects to become an electronic gold system in the future.

• Cryptocurrency

In the 90s of the last century, the cypherpunk spirit continued to build a cryptocurrency that minimizes trust dependence and serves all Internet users who pay attention to privacy and personal rights. BTC (Bitcoin) is a type of cryptocurrency.

• Blockchain

IBM is the hero of this concept. In 2015, IBM vigorously promoted the concepts of Permission Blockchain and Blockchain for commercial purposes, which is a general concept.

• Public chain

Starting from Ethereum, it is hoped that a network can not only provide a standard symbology, but also provide services for different objects. An ideal public chain platform requires no threshold for joining network nodes and no threshold for service access. In addition, the services operated above must be valuable. According to this standard, the industry basically has no public chain for the mass market. But there are many different "symbol" distribution networks.

• Coinless blockchain

It should refer to a blockchain network where transaction symbols are not speculative. The transaction symbols in this network only have agreed value, and their value comes from the mapping of off-chain credit.

• Blockchain core technology

The original meaning refers to Hash Pointer, hash pointer, currently refers to the entire industry. Refers to the key technologies involved in maintaining a distributed peer-to-peer network. Such as cryptography, consensus algorithm, virtual machine technology, game mechanism, peer-to-peer network and other technologies.

• Blockchain value

Build a division of labor and collaboration infrastructure in the information age. Real assets and securities will first be circulated and traded on the currencyless blockchain. Because of its credit, it still comes from credit injection from the real world. What does not rely on real-world credit injection is the coin-owned blockchain network. It is still at a very early stage. It is very difficult to become a real public infrastructure at present, but this direction is constantly evolving and innovating. The public infrastructure here refers to: for example, putting all the commodities and financial information of a city on this network.

• currency

With the help of the Hash pointer and the Satoshi Nakamoto PoW consensus, we can create a symbol system on the Internet that cannot be double spent. Many subsequent projects have improved this symbol system and introduced a virtual machine that can program symbols. At present, it seems that many symbol systems have a large or small consensus on a global scale. However, currency is more of a legal meaning, and has nothing to do with whether the computer-based symbol system is advanced.