QTUMUSD
Qtum / United States dollar
crypto Composite

Qtum (pronounced Quantum) is a smart contract platform that uses a Proof-of-Stake (PoS) consensus mechanism to validate transaction blocks and provide security assurances. It combines different aspects of the Ethereum and Bitcoin blockchains. Qtum uses Bitcoin core as the base of its network for security and stability reasons and, therefore, operates via a UTXO model. The project also integrated Ethereum's virtual machine (the EVM) so the chain could run Turing complete code needed to support smart contracts, and thus decentralized applications (dApps). Qtum's stack features a middleware layer, dubbed the account abstraction layer (AAL), to ensure the UTXO set was compatible with the smart contract execution layer. Qtum's native token (QTUM) allows users to pay transaction fees, participate in network security, and vote on protocol upgrade proposals. Qtum plans to implement the first iteration of a new Proof-of-Stake consensus mechanism, Incentive Proof-of-Stake (IPoS), which is compatible with UTXO-based blockchains like Bitcoin. Qtum's UTXO model was chosen to support consistent, traceable on-chain transactions and IPoS iterates on traditional PoS models by introducing reward mechanisms calculated by online node numbers estimates. Initially, Qtum will launch with a standard Proof-of-Stake (PoS) model but plans to transition to the IPoS model in later development phases. Qtum developers and consumers rely on an Ethereum Virtual Machine (EVM) just like the Ethereum blockchain does. But the Qtum EVM is distinct in that it is constantly backward compatible, unlike Ethereum's EVM. Qtum also supports an Account Abstraction Layer (AAL) that enables the EVM to run existing Ethereum smart contracts on Qtum without extensive modifications. Qtum's Contract Ledger stores smart contract language, data feeds, and oracles for contract execution. Prioritizing transaction confirmation forces Qtum to focus on two different qualities as a sort of Bitcoin-Ethereum hybrid blockchain. The size of the fee should match the size of the transaction, similar to a standard Proof-of-Work (PoW) on-chain transaction fee. The gas fee should also match expected and available funds, like gas fees, are charged for executing smart contracts on Ethereum.