Plasma uses PlasmaBFT to secure its network, a consensus mechanism based on the Fast HotStuff Byzantine Fault Tolerant (BFT) protocol. HotStuff is a modern consensus method that helps blockchains stay secure even if some participants misbehave, and the Fast version reduces the amount of communication needed between validators.
PlasmaBFT builds on this idea by executing steps like proposing, voting, and confirming blocks in parallel rather than sequentially. This design enhances block production speed and enables transactions to be finalized in seconds, facilitating quicker settlement for Plasma.  
EVM Execution Layer
Plasma’s execution layer runs on Reth, an Ethereum client written in the Rust programming language. While PlasmaBFT manages sequencing and finality, Reth processes transactions, state changes, and Ethereum Virtual Machine (EVM) logic. This makes Plasma fully EVM compatible, enabling developers to use Solidity smart contracts and Ethereum tools seamlessly.
Key Features
Zero-fee USDT transfers
Plasma supports zero-fee transfers through a built-in paymaster system. The paymaster, maintained by the Plasma Foundation, covers costs for standard transfer functions, applying simple eligibility checks and rate limits to manage usage @Plasma