# Core Primitives

These pages cover the low-level mechanisms that make Atomiq's trustless swap protocol possible. They define how Bitcoin state is verified on-chain, how funds are escrowed across chains, and how settlement can be enforced without relying on a trusted intermediary.

This section introduces these foundational primitives before moving into higher-level swap flows and contract architecture

## [📄️Hash-time locked contract (HTLC)](https://docs.atomiq.exchange/overview/core-primitives/htlc.md)

[Established HTLC primitive used for Lightning Network swaps.](https://docs.atomiq.exchange/overview/core-primitives/htlc.md)

## [📄️Bitcoin Light Client](https://docs.atomiq.exchange/overview/core-primitives/bitcoin-light-client.md)

[Verifies Bitcoin block headers on the smart chain.](https://docs.atomiq.exchange/overview/core-primitives/bitcoin-light-client.md)

## [📄️Proof-time locked contract (PrTLC)](https://docs.atomiq.exchange/overview/core-primitives/prtlc.md)

[Light client-based HTLC-like escrow used for Bitcoin on-chain swaps.](https://docs.atomiq.exchange/overview/core-primitives/prtlc.md)

## [📄️UTXO-controlled Vault](https://docs.atomiq.exchange/overview/core-primitives/utxo-controlled-vault.md)

[Enables PSBT-based swaps between Bitcoin and Smart chains.](https://docs.atomiq.exchange/overview/core-primitives/utxo-controlled-vault.md)