AryaArweave: The Permanent Data Storage
Permanent Cloud StorageIn today's digital age, cloud storage has become an essential aspect of our daily lives. With the increasing amount of data that we generate and need to store, the traditional means of data storage, such as physical hard drives or flash drives, are becoming less practical. Cloud storage offers a more convenient and accessible solution, allowing users to store their data on remote servers that they can access from anywhere, at any time, as long as they have an inter...
AryaWaves: Layer-1? Layer-0? Both?
Many layer-1 platforms exist out there. A layer-1 platform, in the blockchain world, is a blockchain able to perform smart contracts and dApps, without any dependency on any other blockchains. Actually, Waves is and is not one of these. This may sound confusing to you. How can a blockchain be both a layer-1 platform and not? Well, the answer is complex, and to get to the answer, it is best first to know what layer-0 is.Layer-0Blockchains Layer-0 blockchain is a concept that Cosmos Network int...
AryaDiscrete Logarithm in Cryptography
Discrete logarithm is one of the most important parts of cryptography. This mathematical concept is one of the most important concepts one can find in public key cryptography. Let’s first determine a very basic algorithm to make public keys in cryptography and then describe how discrete logarithm can help us in this algorithm.Diffie-Hellman Key ExchangeIn this method, there are two people, Alice and Bob, who want to make a safe channel to exchange messages, which Eve is an untrusted person wh...
Researcher, Enthusiast, Blockchain and Crypto Lover, Cryptography Lover, Ethereum is the King.
AryaArweave: The Permanent Data Storage
Permanent Cloud StorageIn today's digital age, cloud storage has become an essential aspect of our daily lives. With the increasing amount of data that we generate and need to store, the traditional means of data storage, such as physical hard drives or flash drives, are becoming less practical. Cloud storage offers a more convenient and accessible solution, allowing users to store their data on remote servers that they can access from anywhere, at any time, as long as they have an inter...
AryaWaves: Layer-1? Layer-0? Both?
Many layer-1 platforms exist out there. A layer-1 platform, in the blockchain world, is a blockchain able to perform smart contracts and dApps, without any dependency on any other blockchains. Actually, Waves is and is not one of these. This may sound confusing to you. How can a blockchain be both a layer-1 platform and not? Well, the answer is complex, and to get to the answer, it is best first to know what layer-0 is.Layer-0Blockchains Layer-0 blockchain is a concept that Cosmos Network int...
AryaDiscrete Logarithm in Cryptography
Discrete logarithm is one of the most important parts of cryptography. This mathematical concept is one of the most important concepts one can find in public key cryptography. Let’s first determine a very basic algorithm to make public keys in cryptography and then describe how discrete logarithm can help us in this algorithm.Diffie-Hellman Key ExchangeIn this method, there are two people, Alice and Bob, who want to make a safe channel to exchange messages, which Eve is an untrusted person wh...
Researcher, Enthusiast, Blockchain and Crypto Lover, Cryptography Lover, Ethereum is the King.
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In this research, we are going to study the Qtum token, QTUM. We are studying this token from the aspects of fundamentals.
Blockchain-enabled smart contracts that employ proof-of-stake validation for transactions, promise significant performance advantages compared to proof-of-work solutions. For broad industry adoption, other important requirements must be met in addition. For example, stable backwards-compatible smart-contract systems must automate cross-organizational information-logistics orchestration with lite mobile wallets that support simple payment verification (SPV) techniques. The currently leading smart-contract solution Ethereum uses computationally expensive proof-of-work validation that is expected to hard-fork multiple times in the future and requires downloading the entire blockchain. Consequently, Ethereum smart contracts have limited utility and lack formal semantics, which is a security issue. This whitepaper fills the gap in the state of the art by presenting the Qtum smart-contract framework that aims for sociotechnical application suitability, the adoption of formal-semantics language expressiveness, and the provision of smart-contract template libraries for rapid best-practice industry deployment. We discuss the Qtum utility advantages compared to the Ethereum alternative and present Qtum smart-contract future development plans for industry-cases applications. One of the primary goals of Qtum is to build the first UTXO-based smart-contract system with a proof-of-stake (PoS) consensus model. The latter means the creator of the next block is chosen based on the held wealth in cryptocurrency. Thus, blocks are usually forged or minted instead of being mined, there are block rewards in addition to transaction fees and forgers receive a percentage of ”interest” for the amount of funds they stake. Qtum is compatible with the Bitcoin- and Ethereum ecosystems and aims at producing a variation of Bitcoin with Ethereum Virtual Machine (EVM) compatibility. Note that differently from Ethereum, the Qtum EVM is constantly back-wards compatible. Pursuing a pragmatic design approach, Qtum employs industry use cases with a strategy comprising mobile devices. The latter allows Qtum to promote blockchain technology to a wide array of Internet users and thereby, decentralizing PoS transaction validation.
UTXO Vs. Account Model In the UTXO model, transactions are used as input unspent Bitcoins that are destroyed and as transaction outputs, new UTXOs are created. Unspent transaction outputs are created as change and returned to the spender. In this way, a certain volume of Bitcoins are transferred among different private key owners, and new UTXOs are spent and created in the transaction chain. The UTXO of a Bitcoin transaction is unlocked by the private key that is used to sign a modified version of a transaction. In the Bitcoin network, miners generate Bitcoins with a process called a Coinbase transaction, which does not contain any inputs. Bitcoin uses a scripting language for transactions with a limited set of operations7. In the Bitcoin network, the scripting system processes data by stacks (Main Stack and Alt Stack), which is an abstract data type following the LIFO principle of Last-In, First-Out. In the UTXO model, it is possible to transparently trace back the history of each transaction through the public ledger. The UTXO model has the parallel processing capability to initialize transactions among multiple addresses indicating the extensibility. Additionally, the UTXO model supports privacy in that users can use Change Address as the output of a UTXO. The target of Qtum is to implement smart contracts based on the innovative design of the UTXO model. Versus the UTXO model, Ethereum is an account-based system. More precisely, each account experiences direct value- and information transfers with state transitions. An Ethereum account address of 20 bytes comprises a nounce as a counter for assuring one-time processing for a transaction, the balance of the main internal crypto-fuel for paying transaction fees called Ether, an optional contract code and default-empty account storage. The two types of Ether accounts are, on the one hand, private-key controlled external and on the other hand, contract-code controlled. The former code-void account type creates and signs transactions for message transfer. The latter activates code after receiving a message for reading and writing internal storage, creating contracts, or sending other messages. In Ethereum, balance management resembles a bank account in the real world. Every newly generated block potentially influences the global status of other accounts. Every account has its own balance, storage and code-space base for calling other accounts or addresses, and stores respective execution results. In the existing Ethereum account system, users perform P2P transactions via client remote procedure calls. Although sending messages to more accounts via smart contracts is possible, these internal transactions are only visible in the balance of each account and tracking them on the public ledger of Ethereum is a challenge. Based on the discussion above, we consider the Ethereum account model to be a scalability bottleneck and see clear advantages of the Bitcoin-network UTXO model. Since the latter enhances the network effect we wish to offer, an essential design decision for the pending Qtum release is the adoption of the UTXO model. Qtum Account Abstraction Layer (AAL) In order to make a bridge between EVM and the Bitcoin core UTXO model, Qtum needs some innovation. This innovation is called Qtum Account Abstraction Layer (AAL). The EVM is designed to function on an account-based blockchain. Qtum however, being based on bitcoin, uses a UTXO-based blockchain and contains an Account Abstraction Layer (AAL) that allows the EVM to function on the Qtum blockchain without significant modifications to the virtual machine and existing Ethereum contracts. The EVM account model is simple to use for smart-contract programmers. Operations exist that check the balance of the current contract and other contracts on the blockchain, and there are operations for sending money (attached to data) to other contracts. Although these actions seem fairly basic and minimalistic, they are not trivial to apply within the UTXO-based Qtum blockchain. Thus, the AAL implementation of these operations may be more complex than expected.
The primary mechanism to perform Expected Contract Transactions is the new opcode, OP_TXHASH that is part of the image above. Internally, both OP_EXEC and OP_EXEC_ASSIGN have two different modes. Upon their execution as part of the output script processing, the EVM is executed. When the opcodes are executed as part of input script processing, however, the EVM is not executed to avoid double execution. Instead, theOP_EXEC and OP_EXEC_ASSIGNopcodes behave similarly to no-ops and return either 1 or 0, i.e., spendable or not spendable respectively, based on a given transaction hash. This is why OP_TXHASH is so important to the functioning of this concept. Briefly, OP_TXHASH is a new op-code added which pushes the current spending transaction’s SHA256 hash onto the Bitcoin Script stack. The OP_EXEC and OP_EXEC_ASSIGN opcodes check the Expected Contract Transaction List during a spend attempt. After the transaction passes (usually from OP_TXHASH) to the opcodes that exist in the Expected Contract Transaction List, the result is 1, or spend-able. Otherwise, the return is 0, or not spendable. In this way, OP_EXEC and OP_EXEC_ASSIGN using vouts are only spendable when a contract and thus, the Account Abstraction Layer, requires that the vout is spendable, i.e., while the contract attempts sending money. This results in a secure and sound way of allowing contract funds to be spent only by a respective contract in alignment with a normal UTXO transaction. A specific scenario occurs if a contract has more than one output that can be spent. Each node may pick different outputs and thus, use completely different transactions for spending OP_EXEC_ASSIGN transactions. This is resolved in Qtum by a consensus-critical coin picking algorithm. The latter is similar to the standard coin picking algorithm used within a user wallet. However, Qtum significantly simplifies the algorithm to avoid the risk of denial of service (DoS) attack vectors and to realize simple consensus rules. With this consensus-critical coin picking algorithm, there is now no possibility for other nodes to pick different coins to be spent by a contract. Any miner/node who picks different outputs must fork away from the main Qtum network, and their blocks are rendered invalid.
When an EVM contract in the image above sends money either to a pubkeyhash address or to another contract, this event constructs a new transaction. The consensus-critical coin-picking algorithm chooses the best-owned outputs of the contract pool. These outputs are spent as inputs with the input script(ScriptSig) comprising a single OP_TXHASH opcode. The outputs are thus, the destination for the funds, and a change output (if required) to send the remaining funds of the transaction back to the contract. This transaction hash is added to the Expected Contract Transaction List and then the transaction itself is added to the block immediately after the contract execution transaction. Once this constructed transaction is validated and executed, a confirmation check of the Expected Contract Transaction List follows. Next, this transaction hash is removed from the Expected Contract Transaction List. Using this model, it is impossible to spoof transactions for spending them by providing a hardcoded hash as input script, instead of using OP_TXHASH. The above-described abstraction layer renders the EVM contracts oblivious to coin picking and specific outputs. Instead, the EVM contracts know only that they and other contracts have a balance so that money can be sent to these contracts as well as outside of the contract system to pubkeyhash addresses. Consequently, contract compatibility between Qtum and Ethereum is strong and very few modifications are required to port an Ethereum contract to the Qtum blockchain.
Consensus Management There are ongoing discussions about consensus and which platform meets the needs of respective project requirements. The consensus topics most widely discussed are PoW, PoS, Dynamic PoS, and Byzantine Fault Tolerance as discussed by HyperLedger. The nature of consensus is about achieving data consistency with distributed algorithms. Available options are, e.g., the FischerLynch and Paterson theorem that states consensus cannot be reached without 100% agreement amongst nodes. In the Bitcoin network, miners participate in the verification process by hash collision through PoW. When the hash value of a miner is able to calculate and meet a certain condition, the miner may claim to the network that a new block is mined: Hash(BlockHeader) MD For the number of miners M and the mining difficulty D, the Hash() represents the SHA256 power with value range [0, M], and D. The SHA256 algorithm used by Bitcoin enables every node to verify each block quickly if the number of miners is high versus the mining difficulty. The 80-byte BlockHeader varies with each different Nonce. The overall difficulty level of mining adjusts dynamically according to the total hash power of the blockchain network. When two or more miners solve a block at the same time, a small fork happens in the network. This is the point where the blockchain needs to make a decision as to which block it should accept, or reject. In the Bitcoin network, the chain is legitimate that has the most proven work attached. Most PoS blockchains can source their heritage back to PeerCoin10that is based on an earlier version of Bitcoin Core. There are different PoW algorithms such as Scrypt, X11, Groestl, Equihash, etc. The purpose of launching a new algorithm is to prevent the accumulation of computing power by one entity and ensure that Application-Specific Integrated Circuits (ASIC) can not be introduced into the economy. Qtum Core chooses PoS based on the latest Bitcoin source code for basic consensus formation. In a traditional PoS transaction, the generation of a new block must meet the following condition: ProofHash < coins age target InProofHash, the stake modifier computes together with unspent outputs and the current time. With this method, one malicious attacker can start a double-spending attack by accumulating large amounts of coin-age. Another problem caused by coin-age is that nodes are online intermittently after reward-ing instead of being continuously online. Therefore, in the improved version ofPoS agreement, coin-age removal encourages more nodes to be online simultaneously. The original PoS implementation suffers from several security issues due to possible coin-age attacks, and other types of attacks. Qtum agrees with the security analysis of the Blackcoin team and adopts PoS 3.0 into the latest Qtum Core. PoS 3.0 theoretically rewards investors that stake their coins longer, while giving no incentive to coin holders who leave their wallets offline. Some features of the Qtum blockchain: Transaction model: UTXO (Unspent Transaction Output) from bitcoin Smart contract architecture: EVM (Ethereum Virtual Machine), and developing Neutron architecture with ARM VM. Block size: 500,000 bytes, scalable using on-chain DGP (Decentralized Governance Protocol) up to 8 million bytes Average block spacing: 32 seconds Smart contract token protocol: QRC20, based on Ethereum ERC20 plus non-fungible tokens. Consensus algorithm: Proof of Stake, version 3.5, upgraded from Blackcoin Theoretical maximum TPS (Transactions Per Second): 70 to 100. Much faster using Lightning Network and other Layer 2 technologies Block reward: 1.0 QTUM through December 2021 (halved every 4 years), plus transaction fees and gas Genesis blocks initial creation: 100 million Maximum supply: 107.8 million in 30 years, current annual inflation 0.87%
Team and Partners Team CEO & Founder: Patrick Dai Patrick graduated from Draper University and dropped out of his doctoral degree from the Chinese Academy of Sciences. Previously employed by Alibaba, CTO at Bitse group, director of Mei Link China, CTO at VeChain, and committed to blockchain technology development, with abundant blockchain industry development experience. https://www.linkedin.com/in/patrick-dai-39278a108/ https://twitter.com/PatrickXDai
Neil Mahi Neil has 20 years of experience developing software and has four years of experience in the blockchain space. Neil has a Master’s degree in Business Administration from ISCAE but later specialized in computer science. Neil was also a professional poker player and speaks four languages.
Elizaveta Larina Liza is responsible for marketing & PR in Russia and CIS. She has a bachelor's degree in political science. Liza has been working in the blockchain industry since 2017 and has prior experience working in PR. https://www.linkedin.com/in/elizaveta-larina-1a6aa811a/
Partners Qtum, an open-source public blockchain platform, has partnered with Travala.com, the leading cryptocurrency-friendly travel booking gateway. https://finance.yahoo.com/news/qtum-celebrates-partnership-travala-com-121500777.html
QTUM, announces the beginning of the partnership cooperation with the leading fiat-to-crypto exchange that allows users to purchase cryptocurrencies using bank cards, Indacoin Limited. https://www.globenewswire.com/news-release/2021/04/07/2205919/0/en/Blockchain-Platform-QTUM-Announces-Partnership-with-Indacoin-Limited.html
"We are happy to announce #Qtum was accepted as a Google Cloud partner!" https://twitter.com/qtum/status/1123936727318577157
Early backers and investors on the Qtum Project are individual investors such as Roger Ver (First Major Investor in Bitcoin Startups), Ash Han (Blockchain Evangelist and Angel Backer), Jeremy Gardner (Cofounder of Augur EIR at Blockchain Capital), Anthony Di'lorio (Founder of Ethereum CEO at JAXX Wallet), Matthew Roszak (Co-Founder of Bloq, Founding Partner Tally Capital), Jeffrey Wernick. Jeffrey is a veteran investor with over 40 years of experience. Jeffrey started his career trading options and futures on the CBOE, CBOT and the CME while studying as an undergraduate and graduate at The University of Chicago in 1971. Later he served at Salomon Brothers, and National Bank of Detroit as Senior Financial Economist and as its youngest Senior Officer of the bank. After that he opened his own venture capital company specializing in all areas of technology, created a hedge fund to manage his personal wealth, also invested in distressed and bankrupt companies, precipitating changes in the operations of the enterprises and the restructuring of their balance sheet. His background in trading, quantitative research and venture investment has given him great insight as an angel investor. As an angel investor, his extensive portfolio includes Uber and Airbnb. In addition to the sharing economy, his notable investments have been in bank transactions, lending platforms, Bitcoin and Blockchain, biomedical, human genome projects, payment systems and biotechnology. https://twitter.com/businessinsider/status/1274006234161655814
The QTUM token can be bought on Binance, Huobi, Kucoin, Bitfinex, Kraken, MEXC, Gate.io.
As we understood, the Qtum project is trying to make a better and new version of the Ethereum blockchain. Therefore, we may call it an Ethereum Killer. So there are many many projects including Ethereum itself that can be a big competitor for this project. Projects such as BSC, Solana, Cardano, Avalanche, Algorand, Polygon, etc.
As it can be seen in the roadmap, Qtum has good planning for 2021, especially knowing that the Taproot of Bitcoin happened and they said they are going to support this on their blockchain. They are also trying to make more partnerships but it is possible that it could be hard for them. This is because many big and better platforms are there for developers and industries to use.
The initial token allocation was 100 million tokens and it was distributed as 51% to the community as an ICO, 20% to the team and early backers (investors) and the foundation, and the remaining 29% used for research and development. At first, the tokens were distributed as an ERC-20 token which was later redeemed to a native token on the native blockchain. There is no way to change your ERC-20 token to a native one now and the bridge is closed completely. After that Qtum had an initial incentivised Coinbase transaction for miners who forge a block. This Coinbase transaction is going through a halving every four years exactly, which will happen in December 2021. This block reward is not the only incentive. Fees and gas fees are also going to the block submitter, like the Ethereum blockchain before EIP-1559. The maximum supply will happen in 30 years and at number 107.8 million tokens. Currently, the annual inflation is about 0.87% which is a really good inflation rate compared to other inflationary blockchains.
Community 51 Business Development 20 Academic Research, Education, and Market Expansion 9 Foundation Initiators, Backers, and the Development Team 20
References Qtum: Home, https://qtum.org/en. Accessed 22 November 2021. Qtum Web Wallet, https://qtumwallet.org/. Accessed 22 November 2021. qtum.info, https://qtum.info/. Accessed 22 November 2021. Coin Bureau. “QTUM Review: What You NEED To Know.” YouTube, 27 November 2019, https://www.youtube.com/watch?v=ef-dbIk9aaU. Accessed 22 November 2021. Dai, Ptrick, et al. “Smart-Contract Value-Transfer Protocols on a Distributed Mobile Application Platform.” Qtum. “Introduction · Qtum Documentation.” Qtum Documentation, https://docs.qtum.site/en/. Accessed 22 November 2021. Lets Learn Blockchain. “UTXO.” YouTube, 22 January 2018, https://www.youtube.com/watch?v=YjiE4SZtSlY. Accessed 22 November 2021. “Qtum (QTUM) - Price Chart and ICO Overview.” ICOmarks, https://icomarks.com/ico/qtum. Accessed 22 November 2021. “src.” GitHub, https://github.com/qtumproject/qtum/tree/master/src. Accessed 22 November 2021.
In this research, we are going to study the Qtum token, QTUM. We are studying this token from the aspects of fundamentals.
Blockchain-enabled smart contracts that employ proof-of-stake validation for transactions, promise significant performance advantages compared to proof-of-work solutions. For broad industry adoption, other important requirements must be met in addition. For example, stable backwards-compatible smart-contract systems must automate cross-organizational information-logistics orchestration with lite mobile wallets that support simple payment verification (SPV) techniques. The currently leading smart-contract solution Ethereum uses computationally expensive proof-of-work validation that is expected to hard-fork multiple times in the future and requires downloading the entire blockchain. Consequently, Ethereum smart contracts have limited utility and lack formal semantics, which is a security issue. This whitepaper fills the gap in the state of the art by presenting the Qtum smart-contract framework that aims for sociotechnical application suitability, the adoption of formal-semantics language expressiveness, and the provision of smart-contract template libraries for rapid best-practice industry deployment. We discuss the Qtum utility advantages compared to the Ethereum alternative and present Qtum smart-contract future development plans for industry-cases applications. One of the primary goals of Qtum is to build the first UTXO-based smart-contract system with a proof-of-stake (PoS) consensus model. The latter means the creator of the next block is chosen based on the held wealth in cryptocurrency. Thus, blocks are usually forged or minted instead of being mined, there are block rewards in addition to transaction fees and forgers receive a percentage of ”interest” for the amount of funds they stake. Qtum is compatible with the Bitcoin- and Ethereum ecosystems and aims at producing a variation of Bitcoin with Ethereum Virtual Machine (EVM) compatibility. Note that differently from Ethereum, the Qtum EVM is constantly back-wards compatible. Pursuing a pragmatic design approach, Qtum employs industry use cases with a strategy comprising mobile devices. The latter allows Qtum to promote blockchain technology to a wide array of Internet users and thereby, decentralizing PoS transaction validation.
UTXO Vs. Account Model In the UTXO model, transactions are used as input unspent Bitcoins that are destroyed and as transaction outputs, new UTXOs are created. Unspent transaction outputs are created as change and returned to the spender. In this way, a certain volume of Bitcoins are transferred among different private key owners, and new UTXOs are spent and created in the transaction chain. The UTXO of a Bitcoin transaction is unlocked by the private key that is used to sign a modified version of a transaction. In the Bitcoin network, miners generate Bitcoins with a process called a Coinbase transaction, which does not contain any inputs. Bitcoin uses a scripting language for transactions with a limited set of operations7. In the Bitcoin network, the scripting system processes data by stacks (Main Stack and Alt Stack), which is an abstract data type following the LIFO principle of Last-In, First-Out. In the UTXO model, it is possible to transparently trace back the history of each transaction through the public ledger. The UTXO model has the parallel processing capability to initialize transactions among multiple addresses indicating the extensibility. Additionally, the UTXO model supports privacy in that users can use Change Address as the output of a UTXO. The target of Qtum is to implement smart contracts based on the innovative design of the UTXO model. Versus the UTXO model, Ethereum is an account-based system. More precisely, each account experiences direct value- and information transfers with state transitions. An Ethereum account address of 20 bytes comprises a nounce as a counter for assuring one-time processing for a transaction, the balance of the main internal crypto-fuel for paying transaction fees called Ether, an optional contract code and default-empty account storage. The two types of Ether accounts are, on the one hand, private-key controlled external and on the other hand, contract-code controlled. The former code-void account type creates and signs transactions for message transfer. The latter activates code after receiving a message for reading and writing internal storage, creating contracts, or sending other messages. In Ethereum, balance management resembles a bank account in the real world. Every newly generated block potentially influences the global status of other accounts. Every account has its own balance, storage and code-space base for calling other accounts or addresses, and stores respective execution results. In the existing Ethereum account system, users perform P2P transactions via client remote procedure calls. Although sending messages to more accounts via smart contracts is possible, these internal transactions are only visible in the balance of each account and tracking them on the public ledger of Ethereum is a challenge. Based on the discussion above, we consider the Ethereum account model to be a scalability bottleneck and see clear advantages of the Bitcoin-network UTXO model. Since the latter enhances the network effect we wish to offer, an essential design decision for the pending Qtum release is the adoption of the UTXO model. Qtum Account Abstraction Layer (AAL) In order to make a bridge between EVM and the Bitcoin core UTXO model, Qtum needs some innovation. This innovation is called Qtum Account Abstraction Layer (AAL). The EVM is designed to function on an account-based blockchain. Qtum however, being based on bitcoin, uses a UTXO-based blockchain and contains an Account Abstraction Layer (AAL) that allows the EVM to function on the Qtum blockchain without significant modifications to the virtual machine and existing Ethereum contracts. The EVM account model is simple to use for smart-contract programmers. Operations exist that check the balance of the current contract and other contracts on the blockchain, and there are operations for sending money (attached to data) to other contracts. Although these actions seem fairly basic and minimalistic, they are not trivial to apply within the UTXO-based Qtum blockchain. Thus, the AAL implementation of these operations may be more complex than expected.
The primary mechanism to perform Expected Contract Transactions is the new opcode, OP_TXHASH that is part of the image above. Internally, both OP_EXEC and OP_EXEC_ASSIGN have two different modes. Upon their execution as part of the output script processing, the EVM is executed. When the opcodes are executed as part of input script processing, however, the EVM is not executed to avoid double execution. Instead, theOP_EXEC and OP_EXEC_ASSIGNopcodes behave similarly to no-ops and return either 1 or 0, i.e., spendable or not spendable respectively, based on a given transaction hash. This is why OP_TXHASH is so important to the functioning of this concept. Briefly, OP_TXHASH is a new op-code added which pushes the current spending transaction’s SHA256 hash onto the Bitcoin Script stack. The OP_EXEC and OP_EXEC_ASSIGN opcodes check the Expected Contract Transaction List during a spend attempt. After the transaction passes (usually from OP_TXHASH) to the opcodes that exist in the Expected Contract Transaction List, the result is 1, or spend-able. Otherwise, the return is 0, or not spendable. In this way, OP_EXEC and OP_EXEC_ASSIGN using vouts are only spendable when a contract and thus, the Account Abstraction Layer, requires that the vout is spendable, i.e., while the contract attempts sending money. This results in a secure and sound way of allowing contract funds to be spent only by a respective contract in alignment with a normal UTXO transaction. A specific scenario occurs if a contract has more than one output that can be spent. Each node may pick different outputs and thus, use completely different transactions for spending OP_EXEC_ASSIGN transactions. This is resolved in Qtum by a consensus-critical coin picking algorithm. The latter is similar to the standard coin picking algorithm used within a user wallet. However, Qtum significantly simplifies the algorithm to avoid the risk of denial of service (DoS) attack vectors and to realize simple consensus rules. With this consensus-critical coin picking algorithm, there is now no possibility for other nodes to pick different coins to be spent by a contract. Any miner/node who picks different outputs must fork away from the main Qtum network, and their blocks are rendered invalid.
When an EVM contract in the image above sends money either to a pubkeyhash address or to another contract, this event constructs a new transaction. The consensus-critical coin-picking algorithm chooses the best-owned outputs of the contract pool. These outputs are spent as inputs with the input script(ScriptSig) comprising a single OP_TXHASH opcode. The outputs are thus, the destination for the funds, and a change output (if required) to send the remaining funds of the transaction back to the contract. This transaction hash is added to the Expected Contract Transaction List and then the transaction itself is added to the block immediately after the contract execution transaction. Once this constructed transaction is validated and executed, a confirmation check of the Expected Contract Transaction List follows. Next, this transaction hash is removed from the Expected Contract Transaction List. Using this model, it is impossible to spoof transactions for spending them by providing a hardcoded hash as input script, instead of using OP_TXHASH. The above-described abstraction layer renders the EVM contracts oblivious to coin picking and specific outputs. Instead, the EVM contracts know only that they and other contracts have a balance so that money can be sent to these contracts as well as outside of the contract system to pubkeyhash addresses. Consequently, contract compatibility between Qtum and Ethereum is strong and very few modifications are required to port an Ethereum contract to the Qtum blockchain.
Consensus Management There are ongoing discussions about consensus and which platform meets the needs of respective project requirements. The consensus topics most widely discussed are PoW, PoS, Dynamic PoS, and Byzantine Fault Tolerance as discussed by HyperLedger. The nature of consensus is about achieving data consistency with distributed algorithms. Available options are, e.g., the FischerLynch and Paterson theorem that states consensus cannot be reached without 100% agreement amongst nodes. In the Bitcoin network, miners participate in the verification process by hash collision through PoW. When the hash value of a miner is able to calculate and meet a certain condition, the miner may claim to the network that a new block is mined: Hash(BlockHeader) MD For the number of miners M and the mining difficulty D, the Hash() represents the SHA256 power with value range [0, M], and D. The SHA256 algorithm used by Bitcoin enables every node to verify each block quickly if the number of miners is high versus the mining difficulty. The 80-byte BlockHeader varies with each different Nonce. The overall difficulty level of mining adjusts dynamically according to the total hash power of the blockchain network. When two or more miners solve a block at the same time, a small fork happens in the network. This is the point where the blockchain needs to make a decision as to which block it should accept, or reject. In the Bitcoin network, the chain is legitimate that has the most proven work attached. Most PoS blockchains can source their heritage back to PeerCoin10that is based on an earlier version of Bitcoin Core. There are different PoW algorithms such as Scrypt, X11, Groestl, Equihash, etc. The purpose of launching a new algorithm is to prevent the accumulation of computing power by one entity and ensure that Application-Specific Integrated Circuits (ASIC) can not be introduced into the economy. Qtum Core chooses PoS based on the latest Bitcoin source code for basic consensus formation. In a traditional PoS transaction, the generation of a new block must meet the following condition: ProofHash < coins age target InProofHash, the stake modifier computes together with unspent outputs and the current time. With this method, one malicious attacker can start a double-spending attack by accumulating large amounts of coin-age. Another problem caused by coin-age is that nodes are online intermittently after reward-ing instead of being continuously online. Therefore, in the improved version ofPoS agreement, coin-age removal encourages more nodes to be online simultaneously. The original PoS implementation suffers from several security issues due to possible coin-age attacks, and other types of attacks. Qtum agrees with the security analysis of the Blackcoin team and adopts PoS 3.0 into the latest Qtum Core. PoS 3.0 theoretically rewards investors that stake their coins longer, while giving no incentive to coin holders who leave their wallets offline. Some features of the Qtum blockchain: Transaction model: UTXO (Unspent Transaction Output) from bitcoin Smart contract architecture: EVM (Ethereum Virtual Machine), and developing Neutron architecture with ARM VM. Block size: 500,000 bytes, scalable using on-chain DGP (Decentralized Governance Protocol) up to 8 million bytes Average block spacing: 32 seconds Smart contract token protocol: QRC20, based on Ethereum ERC20 plus non-fungible tokens. Consensus algorithm: Proof of Stake, version 3.5, upgraded from Blackcoin Theoretical maximum TPS (Transactions Per Second): 70 to 100. Much faster using Lightning Network and other Layer 2 technologies Block reward: 1.0 QTUM through December 2021 (halved every 4 years), plus transaction fees and gas Genesis blocks initial creation: 100 million Maximum supply: 107.8 million in 30 years, current annual inflation 0.87%
Team and Partners Team CEO & Founder: Patrick Dai Patrick graduated from Draper University and dropped out of his doctoral degree from the Chinese Academy of Sciences. Previously employed by Alibaba, CTO at Bitse group, director of Mei Link China, CTO at VeChain, and committed to blockchain technology development, with abundant blockchain industry development experience. https://www.linkedin.com/in/patrick-dai-39278a108/ https://twitter.com/PatrickXDai
Neil Mahi Neil has 20 years of experience developing software and has four years of experience in the blockchain space. Neil has a Master’s degree in Business Administration from ISCAE but later specialized in computer science. Neil was also a professional poker player and speaks four languages.
Elizaveta Larina Liza is responsible for marketing & PR in Russia and CIS. She has a bachelor's degree in political science. Liza has been working in the blockchain industry since 2017 and has prior experience working in PR. https://www.linkedin.com/in/elizaveta-larina-1a6aa811a/
Partners Qtum, an open-source public blockchain platform, has partnered with Travala.com, the leading cryptocurrency-friendly travel booking gateway. https://finance.yahoo.com/news/qtum-celebrates-partnership-travala-com-121500777.html
QTUM, announces the beginning of the partnership cooperation with the leading fiat-to-crypto exchange that allows users to purchase cryptocurrencies using bank cards, Indacoin Limited. https://www.globenewswire.com/news-release/2021/04/07/2205919/0/en/Blockchain-Platform-QTUM-Announces-Partnership-with-Indacoin-Limited.html
"We are happy to announce #Qtum was accepted as a Google Cloud partner!" https://twitter.com/qtum/status/1123936727318577157
Early backers and investors on the Qtum Project are individual investors such as Roger Ver (First Major Investor in Bitcoin Startups), Ash Han (Blockchain Evangelist and Angel Backer), Jeremy Gardner (Cofounder of Augur EIR at Blockchain Capital), Anthony Di'lorio (Founder of Ethereum CEO at JAXX Wallet), Matthew Roszak (Co-Founder of Bloq, Founding Partner Tally Capital), Jeffrey Wernick. Jeffrey is a veteran investor with over 40 years of experience. Jeffrey started his career trading options and futures on the CBOE, CBOT and the CME while studying as an undergraduate and graduate at The University of Chicago in 1971. Later he served at Salomon Brothers, and National Bank of Detroit as Senior Financial Economist and as its youngest Senior Officer of the bank. After that he opened his own venture capital company specializing in all areas of technology, created a hedge fund to manage his personal wealth, also invested in distressed and bankrupt companies, precipitating changes in the operations of the enterprises and the restructuring of their balance sheet. His background in trading, quantitative research and venture investment has given him great insight as an angel investor. As an angel investor, his extensive portfolio includes Uber and Airbnb. In addition to the sharing economy, his notable investments have been in bank transactions, lending platforms, Bitcoin and Blockchain, biomedical, human genome projects, payment systems and biotechnology. https://twitter.com/businessinsider/status/1274006234161655814
The QTUM token can be bought on Binance, Huobi, Kucoin, Bitfinex, Kraken, MEXC, Gate.io.
As we understood, the Qtum project is trying to make a better and new version of the Ethereum blockchain. Therefore, we may call it an Ethereum Killer. So there are many many projects including Ethereum itself that can be a big competitor for this project. Projects such as BSC, Solana, Cardano, Avalanche, Algorand, Polygon, etc.
As it can be seen in the roadmap, Qtum has good planning for 2021, especially knowing that the Taproot of Bitcoin happened and they said they are going to support this on their blockchain. They are also trying to make more partnerships but it is possible that it could be hard for them. This is because many big and better platforms are there for developers and industries to use.
The initial token allocation was 100 million tokens and it was distributed as 51% to the community as an ICO, 20% to the team and early backers (investors) and the foundation, and the remaining 29% used for research and development. At first, the tokens were distributed as an ERC-20 token which was later redeemed to a native token on the native blockchain. There is no way to change your ERC-20 token to a native one now and the bridge is closed completely. After that Qtum had an initial incentivised Coinbase transaction for miners who forge a block. This Coinbase transaction is going through a halving every four years exactly, which will happen in December 2021. This block reward is not the only incentive. Fees and gas fees are also going to the block submitter, like the Ethereum blockchain before EIP-1559. The maximum supply will happen in 30 years and at number 107.8 million tokens. Currently, the annual inflation is about 0.87% which is a really good inflation rate compared to other inflationary blockchains.
Community 51 Business Development 20 Academic Research, Education, and Market Expansion 9 Foundation Initiators, Backers, and the Development Team 20
References Qtum: Home, https://qtum.org/en. Accessed 22 November 2021. Qtum Web Wallet, https://qtumwallet.org/. Accessed 22 November 2021. qtum.info, https://qtum.info/. Accessed 22 November 2021. Coin Bureau. “QTUM Review: What You NEED To Know.” YouTube, 27 November 2019, https://www.youtube.com/watch?v=ef-dbIk9aaU. Accessed 22 November 2021. Dai, Ptrick, et al. “Smart-Contract Value-Transfer Protocols on a Distributed Mobile Application Platform.” Qtum. “Introduction · Qtum Documentation.” Qtum Documentation, https://docs.qtum.site/en/. Accessed 22 November 2021. Lets Learn Blockchain. “UTXO.” YouTube, 22 January 2018, https://www.youtube.com/watch?v=YjiE4SZtSlY. Accessed 22 November 2021. “Qtum (QTUM) - Price Chart and ICO Overview.” ICOmarks, https://icomarks.com/ico/qtum. Accessed 22 November 2021. “src.” GitHub, https://github.com/qtumproject/qtum/tree/master/src. Accessed 22 November 2021.
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