Qtum

The initial supply of QTUM tokens was 100 million, with 51 million sold in the 2017 ICO, 8 million going to early private investors, and 12 million allocated to the project team with a 4-year lock-up. The remaining tokens are controlled by the Qtum Chain Foundation for business development, academic research, and promotion. The token supply is not fixed, with new tokens mined through a modified Proof-of-Stake 3.0 consensus mechanism called MPoS, which incentivizes users to stake their coins to validate blocks.

One of the key innovations of Qtum is its Account Abstraction Layer (AAL), which integrates the UTXO account layer from Bitcoin with the smart contract layer inspired by Ethereum. This enables developers to build applications and host them on various virtual machines, including the Ethereum Virtual Machine (EVM) and the x86 virtual machine. This compatibility allows for easy adoption of existing applications and programming languages, such as C, C++, Rust, and Python. Another unique feature of Qtum is its Decentralized Governance Protocol (DGP), which allows the network's core parameters, such as block size and gas fees, to be adjusted through smart contracts without the need for a hard fork. This provides a more flexible and adaptable governance model, where miners (stakers), developers, and QTUM holders can participate in the decision-making process.

Qtum uses a modified Proof-of-Stake 3.0 consensus mechanism called MPoS (mutualized Proof-of-Stake) to secure the network. In this protocol, users are incentivized to keep their coins locked to facilitate and secure the block validation process, known as staking. Block validation is a competition between coin holders, with rewards distributed proportionally based on the amount staked. This provides protection against the "nothing at stake" problem seen in early PoS protocols.