CISA (Cross-Input Signature Aggregation) Explained
CISA is a way to combine multiple signature from a transaction into one
This is made possible thanks to the linearity property of Schnorr signatures, which enables aggregation of multiple signatures into a single one.
Originally, CISA was considered for inclusion in Taproot, but the idea was abandoned to keep Taproot simple and manageable.
⚠️ Don’t confuse CISA with protocols like MuSig or FROST
Signature aggregation ≠ Key aggregation
CISA vs Key Aggregation
Difference #1:
Difference #2:
- Key Aggregation: The verifier only needs the aggregated public key and a single message.
- CISA: The verifier needs all the individual public keys and their corresponding messages.
Difference #3:
- CISA is used during transaction signing
- MuSig is used during address creation
There are two types of CISA:
- Half-Agg
- Full-Agg
🧵 We’ll explain them in upcoming posts.