OP_VAULT, put forward by James O’Beirne in BIP 345 (with Greg Sanders added later as a co-author), is a covenant designed to implement vaults. It depends additionally on CTV (or TXHASH or other similar opcodes) to complete the construction of a vault.

The purpose of a vault is to improve the security of your bitcoin storage. This is accomplished by the introduction of a delay period during any attempt to spend from the vault. Rather than being able to directly send your bitcoin from the vault, the vault restricts them so that they can only be sent to a “middle ground” address. While coins being withdrawn from the vault are in this middle ground state, they can be spent at any time into a deep cold storage wallet under your control (ideally a geographically distributed vault multisig), and only to that deep cold storage. After a pre-defined timelock the coins can then be spent onwards to the ultimate intended destination.

This is the fourth article in a series deep diving into individual covenant proposals that have reached a point of maturity meriting an in-depth breakdown.