Schnorr Signatures

Schnorr signatures are a digital signature scheme, devised by Claus Schnorr and patented in 1990, that bitcoin adopted through BIP 340 as part of the Taproot upgrade activated in November 2021. They joined ECDSA as a signature type on the same secp256k1 curve, becoming standard for Taproot spends.

How it works

Schnorr's advantage is linearity: signatures and keys can be added together meaningfully. Multiple signers can aggregate into one key and one signature through protocols such as MuSig2, so a multisignature spend looks identical on chain to a single-signer spend. That improves privacy, since observers cannot distinguish complex custody arrangements, and efficiency, since one 64-byte signature replaces several.

The scheme also offers cleaner security proofs than ECDSA and eliminates signature malleability by design. Its long delay in adoption owed mainly to the patent, which expired in 2008, the year bitcoin was designed with the then-standard ECDSA.

In the gold vs bitcoin debate

Schnorr adoption is evidence for the upgradeability argument in the gold vs bitcoin debate. Bitcoin improved its core cryptography network-wide without disrupting holders, something no physical asset can do. The caveat is that Schnorr remains elliptic curve cryptography, fully exposed to a future quantum computer, so the upgrade that matters most still lies ahead.