timelocks

Timelocks are constraints that prevent an action from being executed until a predefined time, date, or state is reached. They are used to ensure that funds or rights cannot be accessed before a future point, or to automate delayed release or access when conditions are met. Timelocks can be absolute, locking until a specific moment, or relative, imposing a minimum delay after a triggering event.

In blockchain contexts, timelocks are implemented by scripting or contract logic. Absolute timelocks restrict actions until a fixed timestamp or block height, while relative timelocks require a delay after funding or another event. Bitcoin employs mechanisms such as CLTV (check lock time verify) and CSV (check sequence verify), and many smart contracts use time-based clauses to achieve similar outcomes. The concept also appears in other digital systems, where access or transfer is gated by time or sequence conditions.

Applications include escrow arrangements, delayed fund releases, vesting schedules for employees or investors, and the protected custody of long-term digital assets. Timelocks are used in governance processes to prevent rash changes and in digital rights management or subscription models to control access until a payment or term expires.

Limitations and considerations include the reliability of time sources, potential manipulation of time data in some environments, and the need to address clock drift and time zone independence. In blockchains, design choices about using block height versus timestamp affect security and flexibility, and improper use can lead to lockouts or unintended delays.