Multi-signatures allow for compressing many signatures for the
same message that were generated under independent keys into one
small aggregated signature. This primitive is particularly useful for
proof-of-stake blockchains, like Ethereum, where the same block is
signed by many signers, who vouch for the block’s validity. Being
able to compress all signatures for the same block into a short
string significantly reduces the on-chain storage costs, which is an
important efficiency metric for blockchains.
In this work, we consider multi-signatures in the synchronized
setting, where the signing algorithm takes an additional time parameter as input and it is only required that signatures for the same time
step are aggregatable. The synchronized setting is simpler than the
general multi-signature setting, but is sufficient for most blockchain
related applications, as signers are naturally synchronized by the
length of the chain.
We present Chipmunk, a concretely efficient lattice-based multisignature scheme in the synchronized setting that allows for signing
an a-priori bounded number of messages. Chipmunk allows for noninteractive aggregation of signatures and is secure against roguekey attacks. The construction is plausibly secure against quantum
adversaries as our security relies on the assumed hardness of the
short integer solution problem.
We significantly improve upon the previously best known construction in this setting by Fleischhacker, Simkin, Zhang (CCS 2022).
Our aggregate signature size is 5× smaller and for 112 bits of security our construction allows for compressing 8192 individual
signatures into a multi-signature of size less than 200 KB. We provide a full implementation of Chipmunk and provide extensive
benchmarks studying our construction’s efficiency
