Schnorr Signature

A Schnorr signature is the digital-signature scheme Bitcoin adopted in the November 2021 Taproot soft fork, specified in BIP340. It produces a compact 64-byte signature paired with a 32-byte x-only public key over the same secp256k1 curve Bitcoin already used for ECDSA, but with cleaner mathematical properties that unlock features ECDSA cannot offer.

Why Schnorr matters

The defining property of Schnorr signatures is linearity. Because the math is additive, multiple keys and multiple signatures can be combined into a single key and a single signature. This is the foundation for key aggregation (MuSig) and for advanced constructions like threshold signatures and adaptor signatures used in Lightning and discreet log contracts.

Privacy and efficiency gains

With aggregation, a complex 3-of-5 multisig spend can be made to look identical on-chain to an ordinary single-signer payment. That improves privacy and shrinks the data footprint, which lowers fees and frees block space. BIP340 also introduced tagged hashes and supports batch verification, letting a node validate many signatures together faster than checking each one individually.

For the sovereign Bitcoiner running a node or constructing multisig vaults, Schnorr is the cryptographic groundwork that makes modern collaborative custody both cheaper and more private. See how the signing workflow is coordinated in a Partially Signed Bitcoin Transaction (PSBT), and how Schnorr pairs with the Merkelized Alternative Script Tree (MAST) inside Taproot.