Taproot introduced Schnorr signatures: a fixed 64 bytes, simpler maths, batch verification and multi-party key aggregation. Learn what changed.
What changed
Schnorr signatures arrived with Taproot in November 2021 (BIP 340).
| ECDSA | Schnorr | |
|---|---|---|
| Size | 71–72 bytes | 64 bytes |
| Public key | 33 bytes | 32 bytes (x-only) |
| Malleable | Yes, needed fixes | No |
| Batch verification | No | Yes |
| Easy key aggregation | No | Yes |
Linearity: the big win
Schnorr's maths is "linear": signatures and keys can be added together. With protocols like MuSig2, several people can combine their keys into one public key and jointly produce one signature.
On-chain, a 3-of-3 multisig spend looks exactly like an ordinary single-signature spend: smaller and more private.
Batch verification
A node can check many Schnorr signatures together faster than one by one, which helps during Initial block download (IBD).
Why it took until 2021
Schnorr signatures were invented by Claus-Peter Schnorr around 1989, but a patent covered them until 2008. When Bitcoin launched, ECDSA was the standardised, patent-free option. Adding Schnorr later needed a soft fork, which arrived with Taproot.
MuSig2 and FROST
- MuSig2: n-of-n signing, where all parties combine into one key.
- FROST: threshold signing (like 2-of-3) that still produces one ordinary-looking signature.
Both make shared custody cheaper and more private on-chain.
Key takeaways
- Schnorr signatures are 64 bytes and arrived with Taproot.
- They are non-malleable and support batch verification.
- Key aggregation lets many signers look like one on-chain.
Common questions
Do Schnorr signatures use a different curve?
No, they use the same secp256k1 curve as ECDSA.
Can I use Schnorr with my old address?
No, only Taproot (bc1p) outputs use Schnorr signatures.
Are Schnorr signatures more secure than ECDSA?
They have a cleaner security proof and no malleability. Both are considered secure today.
Do Schnorr signatures save fees?
Yes, slightly per signature, and greatly when many signers aggregate into one.