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Our understanding of the Qtum blockchain is to a large extent a decentralized platform and the most influential public blockchain project in the world. But today I hope to bring you a different perspective which is about the advantages of Qtum in the technology development when compared with the public blockchain project on the market.

Based on the UTXO model used by Bitcoin, Qtum adopts the consensus mechanism of PoS and is the first public blockchain in the world to make this innovation. We have improved the consensus of PoS and adopted MPoS to avoid damage to the network environment by malicious nodes. At the same time, Qtum designs the AAL (account abstraction layer) so that the UTXO-based blockchain is able to support smart contracts. It is Qtum's innovation and technology upgrade to Bitcoin and Bitcoin's color coin. The DGP chain management protocol that we design and develop into the main chain also greatly reduces the harm caused by the fork and better maintains the decentralization consensus. The mobile client strategy will also make Qtum a bridge between real business and each of us, making each of us to better accept decentralized services.

• Transaction model: UTXO (Unspent Transaction Output) from bitcoin
• Smart contract architecture: EVM (Ethereum Virtual Machine), adding the x86 virtual machine in 2019
• Block size: 2 million bytes, scalable using on-chain DGP (Decentralized Governance Protocol) up to 32 million bytes
• Average block spacing: 144 seconds
• Smart contract token protocol: QRC20, based on Ethereum ERC20; QRC721 non-fungible tokens in development
• Consensus algorithm: Proof of Stake, version 3.0, upgraded from Blackcoin
• Theoretical maximum TPS (Transactions Per Second): 70 to 100. Much faster using Lightning Network and other Layer 2 technologies
• Block reward: 4.0 QTUM through February 2022 (halved every 4 years), plus a share of transaction fees and gas
• Genesis blocks initial creation: 100 million
• Maximum supply: 107.8 million in 30 years, current annual inflation 0.87%

Qtum smart contracts use the Ethereum Virtual Machine (EVM) which was designed to work with an account that holds the wallet’s balance. However, Qtum transactions are based on the bitcoin UTXO model which manages the balance of a wallet as any number of individual transactions. The Account Abstraction Layer interface abstracts all these individual transactions to present a single account balance that allows easier smart contract operation and code reuse from Ethereum smart contracts.

The resulting EVM account model is simple for smart contract programmers to use. Operations exist to check the balance of a contract and other contracts on the blockchain. There are operations for sending QTUM to other contracts. Although these operations seem simple, the AAL is fairly complex and enables the addition of new virtual machines, such as the x86 VM.

DGP uses smart contracts to control and update basic blockchain consensus parameters such as block size and gas fee (for smart contract execution). DGP will enable the upgrade of these parameters without the need for a hard fork. DGP does not eliminate hard forks for major new features and functionality.

Intel’s x86 CPU architecture is the dominant CPU platform for servers and desktop computers. The Qtum team is developing a virtual machine using the x86 machine language. A “virtual machine” is an isolated software execution environment that can run on many different hardware platforms (Macs, PCs, servers, virtual private servers in the cloud, etc.). Qtum’s current virtual machine uses EVM and Solidity.

Ethereum’s Solidity language was created for smart contract programming. As a brand-new programming language Solidity has some problems. With the x86 VM, a huge population of developers will be able to use familiar languages and tools to write Qtum smart contracts in popular and mature languages like C, C++, Rust, and Python.

Unita, previously known as Qtum Enterprise and QtumX, is a private blockchain for businesses. The Unita blockchain is based on the Qtum Mainnet code modified to use permissioned Proof of Authority consensus (block producers are designated by the blockchain owner). Unita runs very fast with 10-second block spacing.

Qtum does not have masternodes. Every Qtum Core wallet is a decentralized full node on the Qtum network. Any staking wallet can publish new blocks.

Please see the links to technical/developer documents and tools on the Developer page.
Qtum is an open source project with source code, documentation and user manuals available on GitHub.

You can buy QTUM on many cryptocurrency exchanges as shown on CoinMarketCap

You can get the news from the Latest news page, also see the Qtum blog, Twitter, Facebook and Reddit.

For general questions about Qtum, user questions, wallet questions, and developer questions, please join us on the social media channels linked at the bottom of this page. You can also reach us using the Contact us page

There is no minimum and you can stake with very small amounts of QTUM. You will need more coins for a realistic probability of winning a block reward. Block rewards are awarded in a random lottery process. The odds of winning depend on the number of coins in your wallet vs. the total number of coins being staked on the network.

The more coins a wallet is staking, the more often it will win a block reward of 4 QTUM. Staking will give block rewards of 5 to 6 percent return per year. To see the expected time to a block reward use the stake calculator. The “Expected Time” to a block reward is an estimate of the average time to a block reward. The “Expected Time” does not count down to zero. There is significant variation in the block rewards which could come earlier or much later than the Expected Time.

Wallets from the Qtum developers are shown below. These wallets support Qtum QRC20 tokens and smart contract transactions, which is not always the case for 3rd party QTUM wallets.

  • qtum-qt, desktop Core wallet with GUI (graphical user interface). A good wallet for beginners, supports staking. Wallet tutorial
  • qtumd, server Core wallet with command line interface, for more advanced users, supports staking. Can be used on a local computer or on a cloud virtual private server. Staking tutorial
  • Web wallet, a good wallet for beginners, can restore from a variety of other wallets, can use the Ledger hardware wallet. User’s manual
  • Android mobile wallet, a powerful mobile wallet with smart contract templates, wallet tutorial
  • Electrum wallet, versatile desktop wallet, supports Trezor and Ledger hardware wallets. User guide

The Qtum iOS mobile wallet is not currently available, but you can use the iOS wallet from Qtum partner Qbao Network

Only the Qtum Core wallet (desktop or server versions) can be used for staking. The Qtum Core wallet downloads and syncs the entire blockchain and smart contract state database. A staking wallet must be online 24/7 to process every transaction, new block, and smart contract call. Mobile wallets and hardware wallets have their roles but they are not full nodes and they are not capable of staking.

Make a good backup of the wallet.dat file (Core wallet), key file (Web wallet) or Save Copy (Electrum). Write down and store offline your wallet passphrase, password or seed words. Never share your private keys or seed words. Avoid handling private keys directly. Encrypt your Core wallet using these best practices.

Best practice is staking on a separate computer that is not used for general web surfing and email since those activities can be a source of malware.

QRC20 tokens are derived from the protocol of Ethereum ERC20 tokens. QRC20 tokens are created by Qtum smart contracts as a digital asset for use with DApps. Transactions with QRC20 tokens are made using contract calls and require QTUM for gas fees. Some Qtum wallets have built-in smart contracts templates to easily create QRC20 tokens by simply filling in a form and publishing that contract. See more details in the QRC20 token documentation.

Prior to Mainnet launch, QTUM tokens existed temporarily as an Ethereum ERC20 token. These tokens would have an Ethereum “0x” address. Most Qtum holders swapped these tokens for Qtum Mainnet coins, which have a “Q” address, in October 2017. If you still have Qtum ERC20 tokens you may be able to swap them for QTUM coins at gate.io using this procedure but don’t delay.

DApps use a smart contract working with external servers and user interfaces. Qtum smart contracts are written in the Solidity programming language and compiled to EVM bytecode. That code is published to the blockchain using a contract create transaction which costs approximately 1.1 QTUM in gas and transaction fees. The smart contract operation can be linked with a server and user interfaces (for example on web or mobile apps) to complete the Decentralized Application.

Publishing a smart contract on Qtum is permissionless (anyone can do it). Qtum smart contract and DApp development follows familiar patterns from Ethereum and web/mobile apps. To engage with Qtum’s experienced DApp team please submit the DApp application form.

Recommended to be set to 10 to 20.

BIP44 Coin Type is 88.

In addition to adding createcontract\sendtocontract\callcontract\searchlogs\gettransactionreceipt , all the rest of the RPC interfaces are almost identical to Bitcoin.

It is recommended to fix the gas price to 0.00000040. For QRC20 Token transactions, the gas limit is recommended to be set to 250000.

When the transaction is confirmed, the more paid gas will be in the second transaction of the block in the form of a coin stake transaction.

Please go to Testnet Faucet to apply.

Multi-signature currently does not support calling contracts and sending and receiving QRC20 Tokens. It is planned that this feature will be implemented in x86 virtual machines.