Efficiently-Thresholdizable Batched Identity Based Encryption, with Applications

Amit Agarwal, Rex Fernando, Benny Pinkas

Abstract: We propose a new cryptographic primitive called “batched identity-based encryption” (Batched IBE) and its thresholdized version. The new primitive allows encrypting messages with specific identities and batch labels, where the latter can represent, for example, a block number on a blockchain. Given an arbitrary subset of identities for a particular batch, our primitive enables efficient issuance of a single decryption key that can be used to decrypt all ciphertexts having identities that are included in the subset while preserving the privacy of all other ciphertexts. At the heart of our construction is a new technique that enables public aggregation (i.e. without knowledge of any secrets) of any subset of identities, into a succinct digest. This digest is used to derive, via a master secret key, a single succinct decryption key for all identities that were digested in this batch. In a threshold system, where the master key is distributed as secret shares among multiple authorities, our method significantly reduces the communication (and in some cases, computation) of the authorities. It achieves this by making their costs for key issuance independent of the batch size.

External IDs:dblp:conf/crypto/AgarwalFP25