Signature Aggregation

Overview

Signature aggregation compresses several independently produced signatures into one aggregate object or a more compact representation. A verifier checks the aggregate against the relevant public keys and signed messages. Schemes such as BLS are designed to support efficient aggregation, while ordinary ECDSA signatures cannot simply be concatenated and treated as one cryptographic signature. The precise verification equation depends on the Signature Scheme.

Aggregation differs from an Aggregate Signature as a stored result only in emphasis: the process is signature aggregation, while the output is an aggregate signature. It also differs from a Threshold Signature. In threshold signing, several participants jointly create one signature under a shared public key. In aggregation, participants can sign independently under separate keys and their signatures are later combined.

The benefit is reduced bandwidth and verification metadata, especially when blocks carry many validator votes or transactions require several authorizations. However, safe aggregation may require proofs of possession or other defenses against rogue public keys. Implementations must also define whether all signers sign the same message or different messages and how duplicate keys, ordering, and missing participants are handled.

Blockchain systems should preserve enough information to identify the represented signers and messages even when the signature bytes are compressed. Monitoring should distinguish an invalid aggregate from an absent signer and verify domain separation between transaction, block, and consensus contexts. Aggregation improves efficiency, but it must not make authorization or accountability ambiguous.

Implementations should keep the participating keys, messages, aggregation mode, proof-of-possession requirements, aggregate bytes, and verification result. That context supports investigation because rogue keys, duplicate inputs, or an incorrect same-message assumption can make an apparently compact proof unsafe. Controls also need to validate every participant and preserve enough metadata to reconstruct what the aggregate actually represents.