The last few years have seen few new protocols spawning up in the Bitcoin ecosystem. The goal range is quite wide : payment systems (Lightning Network, statechain), asset management (vaults) financial instrument (DLC), privacy-enhancement tool (Coinswap). Those time-sensitive contract protocols are designed around the same model.
They involve a fixed set of participants, which negotiate state changes locally, only relying on the blockchain in case of disagreement. These state changes are encoded in pre-signed transactions. Timelocks are used to encumber them and thus order concurrent state transitions. Their security lean