Schnorr signature

With a digital signature, you prove that you hold the private keyGlossaryPrivate keyA secret, randomly generated number that you use to sign transactions and so control your bitcoin. Anyone who knows the private key can spend the bitcoin that belongs to it – it must never fall into anyone else’s hands.On the learning path: Stage 5 · Step 3 – Backing up your seed phrase →In the glossary →× for an address without revealing it. Bitcoin originally used only ECDSA for this. The TaprootGlossaryTaprootA soft fork from November 2021 that introduced Schnorr signatures and more flexible spending conditions. Complex arrangements such as multisig can look like a simple payment. Taproot addresses start with bc1p.In the glossary →× upgrade added Schnorr signatures on 14 November 2021, named after the mathematician Claus-Peter Schnorr.^[1],[2]

What they do better

• More compact: A signature is exactly 64 bytes, a public key 32 bytes. ECDSA signatures are up to 72 bytes long.
• Provably secure: Under recognised assumptions, it can be shown that nobody can forge signatures without the private key.
• Non-malleable: Third parties can’t turn a valid signature into a different valid one.
• Combinable: Several participants can create a joint signature for the sum of their public keys; many signatures can be verified faster together.^[1]

What this brings in practice

MuSig2 builds on this: several people form a joint key and sign with a single Schnorr signature. On the blockchain, this looks like an ordinary single-key Taproot payment. However, MuSig2 requires every participant to sign; a 2-of-3 multisigGlossaryMultisig (multi-signature)A wallet in which several keys jointly control the bitcoin – for example 2 of 3. If one key is lost or stolen, the bitcoin stays safe. In return, setting it up and backing it up is considerably more demanding.On the learning path: Stage 6 · Step 4 – Inheritance & emergency plan →In the glossary →× needs other methods.^[3]

You don’t need to do anything: if your wallet uses a Taproot address (bc1p…), it signs with Schnorr. More under Keys, addresses & seed phrases.