# Adaptor Signatures Links: [[Scriptless Scripts]] ## [Bitcoin Optech page](https://bitcoinops.org/en/topics/adaptor-signatures/) Adaptor signatures (also called signature adaptors) are auxiliary signature data that commit to a hidden value. When an adaptor is combined with a corresponding signature, it reveals the hidden value. Alternatively, when combined with the hidden value, the adaptor reveals the signature. Other people may create secondary adaptors that reuse the commitment even if they don’t know the hidden value. This makes adaptors a powerful tool for implementing locking in bitcoin contracts. Contracts in Bitcoin often require a locking mechanism to ensure the atomicity of a set of payments—either all the payments succeed or all of them fail. This locking has traditionally been done by having all payments in the set commit to the same hash digest preimage; when the party who knows the preimage reveals it onchain, everyone else learns it and can unlock their own payments. Commonly used hashlocks in Bitcoin consume about 67 bytes and reveal the link between the set of payments because they all use the same preimage and digest. By comparison, signature adaptors never need to be published onchain. To anyone without a corresponding adaptor, a signature created with an adaptor looks like any other digital signature, giving adaptors significant efficiency and privacy advantages over hashlocks.