Paper 2022/696

On the Impossibility of Algebraic Vector Commitments in Pairing-Free Groups

Abstract

Vector Commitments allow one to (concisely) commit to a vector of messages so that one can later (concisely) open the commitment at selected locations. In the state of the art of vector commitments, algebraic constructions have emerged as a particularly useful class, as they enable advanced properties, such as stateless updates, subvector openings and aggregation, that are for example unknown in Merkle-tree-based schemes. In spite of their popularity, algebraic vector commitments remain poorly understood objects. In particular, no construction in standard prime order groups (without pairing) is known. In this paper, we shed light on this state of affairs by showing that a large class of concise algebraic vector commitments in pairing-free, prime order groups are impossible to realize. Our results also preclude any cryptographic primitive that implies the algebraic vector commitments we rule out, as special cases. This means that we also show the impossibility, for instance, of succinct polynomial commitments and functional commitments (for all classes of functions including linear forms) in pairing-free groups of prime order.

Note: Corrected errors regarding the attack for signature schemes in the GGM pointed out by TCC'22 reviewers. More in details, we cannot assume the existence of an almost optimal way of extracting relations among the CRS elements, and therefore replace this step of the proof with a preprocessing phase which discovers with significant probability all the relations that would be found by the underlying attacker.