Authorized and Verifiable Searchable Encryption Based on Public Key Equality Test for Cloud Storage

Abstract: Cloud storage revolutionizes data management but raises conflicts between functionality and privacy. Public Key Encryption with Equality Test (PKEET), an advanced cryptographic technique, can enable multi-user searchable encryption (SE) through cross-key ciphertext comparison without shared keys. However, existing PKEET-based SE schemes lack ciphertext-file-level authorization, public verifiability, or SE-level support. This paper first proposes a novel PKEET scheme, AVPKEET (Authorized and Verifiable PKEET). It enables non-transferable and non-replayable authorization of ciphertext files, while supporting public verifiability, all without the need for trusted third parties. Then we propose an AVPKEET-based SE scheme, denoted as AVSE (Authorized and Verifiable SE), featuring one-time non-transferable tokens bound to users and nonces, batch operations, and fine-grained access control (ALL, PARTIAL, SINGLE). We prove OW-CCA2 security, token unforgeability, and verification soundness under standard assumptions. Experiment results demonstrate that AVSE achieves the most compact token size (168 bytes) while uniquely providing both ciphertext-file-level authorization and public verification, with acceptable overhead for cloud storage deployment.