Twin Blockchain
Qtum is a protocol that combines both the Ethereum and Bitcoin blockchains. Qtum was created by adding an account abstraction layer on top of a Bitcoin fork code to allow sidechain interoperability with blockchain virtual machines.
Blockchain
Qtum blockchain is engineered to support a UTXO-model, while it introduces an Account Abstraction Layer (AAL) that integrates the account-based Ethereum Virtual Machines (EVM) to be run on Qtum.
EVM integration
EVM integration allows developers to migrate from Ethereum to Qtum platform. This hybrid model combines the best of both worlds, adding Bitcoin’s value-storing capabilities to Ethereum’s smart-contract platform.
Qtum employs PoS (Proof of Stake) consensus mechanism, which is different from Bitcoin's PoW (Proof of Work). The mining process in PoS system is called staking. The block producer will get 4QTUM, as well as the transaction fees and gases as a block reward. So the real reward is usually more than 4QTUM in total.
Every Qtum Core wallet is a decentralized full node on the network. The probability of winning block rewards is analogous to having a weighted lottery randomly selected, and the probability varies with the stakes committed and the total size of the stakes on the network.
To compute the proofhash, the staker calculates the hash of its PoS kernel, which consists of a set of inputs including the stake modifier, unspent output and the block timestamp. To guarantee entropy to deter an adversary from initiating a pre-computation attack, the stake modifier is reset every 16 seconds. Thus, a lottery is effectively run once every 16 seconds for the stakers to generate new hash values for their UTXOs and to see if anyone is the winner.
You can use this calculator to get a rough estimate if you plan to stake any QTUM
Qtum has developed an on-chain governance mechanism — Decentralized Governance Protocol (DGP) — that aims to automate specific network parameter settings including block size and gas price through DGP smart contracts. DGP is built using smart contract technology. It implements a decentralized and democratic governance system that can be replaced and upgraded as needed. The protocol also allows for automated smart contracts to be a voting party. A smart contract can then monitor the status of the blockchain and automatically propose and vote upon changes to fix problems that are detected.DGP supports backward compatibility by way of soft forks and it speeds up Qtum’s response time to malicious attacks. When a DGP smart contract is deployed on chain, a set of governing parties are initialized and stored in the form of addresses. The governing parties may be people or smart contracts, who submit proposals and vote on changes to update the super nodes.
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.
The EVM is stack-based with a 256-bit machine word. Smart contracts that run on Ethereum use this virtual machine for their execution. The EVM is designed for the blockchain of Ethereum and thus, assumes that all value transfer use an account-based method. Qtum is based on the blockchain design of Bitcoin and uses the UTXO-based model. Thus, Qtum has an account abstraction layer that translates the UTXO-based model to an account-based interface for the EVM. Note that an abstraction layer in computing is instrumental for hiding the implementation details of particular functionality to establish a separation of concerns for facilitating interoperability and platform independence.
Qtum’s whitepaper emphasizes on its design choice of using the unspent transaction output (UTXO) model as shared by Bitcoin. The smart contract system of Ethereum, in contrast, is account-based which is similar to how a bank account operates.
In the UTXO model, transactions use 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.
As for hardware wallets, the Ledger Nano S offers QTUM support.
Ledger
As for using the Nano Ledger S, the first step towards setting up your device is unboxing your device and checking if you have received all the accessories with the device. Once you have unboxed your device, you need to configure it and initialize it before being able to use it. The process is quite simple and will hardly take about 20-30 minutes post which you will be set to use your Ledger Nano S device.
Instructions:
The QTUM app can export your extended public key (xpub) to web apps in a U2F compatible web browser (Chrome, Opera or Firefox). The xpub is privacy-sensitive information, as all public addresses can be generated from it.
Public key exports by default require manual approval on the device to prevent inadvertent sharing of your public addresses. This setting can be configured as follows:
First, we have a favorite of ours, Jaxx.
Jaxx
Jaxx is one of the most popular and safe desktop wallets out there. What's really great about it is that it doesn’t store the private keys on its servers but on the device of your choosing. Another reason to love Jaxx is cross-platform functionality. It is available on 9 different platforms and can be interlinked with all these platforms which means that the same balances and wallets are available when a different device is being used.
Qtum Core
Qtum Core wallet is also another great choice if you’re looking for a specialized Desktop wallet. Its an official Qtum wallet that comes for both desktop and mobile devices. The Qtum Core wallet is available for Windows, Mac and Linux. The wallet has a very user-friendly design, making it convenient for all types of users, both beginners and experts The setup process is pretty simple. Just that you need to wait for the wallet to sync with the blockchain, apart from which it makes one of the most user-friendly Qtum wallets.
Qtum Web Wallet
For an online wallet, we have Qtum’s own web wallet, at https://qtumwallet.org/. The wallet is quite simple to use. Click on Generate Wallet and encrypt it with a password of your choosing. Then download the backup file and store it somewhere safe in case you lose your private key. You’re then all set and you can freely deposit any Qtum into your newly created wallet.
For credit card purchases, we have Coinmama.
Coinmama
Coinmama is a cryptocurrency broker that specializes in letting you purchase various currencies with a debit or credit card. You'll be charged a 6% fee due to the risks and processing fees that come with credit card payments. Coinmama offers high limits. It's important to note that nearly all exchanges require KYC verification, especially for credit card purchases. This is done to prevent fraudulent activity so purchasing any cryptocurrency anonymously is almost impossible nowadays.
As always, if you already have some BTC or ETH lying around, you can always go to Binance or Bitfinex and exchange them for QTUM
