Paper 2026/1293

Post-quantum Secure Non-Committing Registered Functional Encryption

Abstract

Non-committing encryption (NCE) is a key primitive for proving security against adaptive corruptions, enabling simulators to generate ciphertexts before the encrypted message is known. Existing non-committing constructions for attribute-based encryption primitives [Hiroka et al., ASIACRYPT 2021; Goyal et al., PKC 2025] typically rely on centralized trust that generate users' secret keys. However, modern cryptographic systems increasingly aim to eliminate such trust assumptions through decentralized frameworks such as registered encryption, where users independently generate and register their own keys. In this work, we initiate the study of non-committing registered functional encryption (NC-RFE) as a generalization of non-committing attribute-based encryption in the decentralized framework. We formalize the notion of NC-RFE by adapting classical non-committing security to the registered setting. We then present a generic construction based on indistinguishability obfuscation and zero-knowledge arguments, and prove its security assuming a secure underlying registered functional encryption (RFE) scheme. We further provide a lattice-based instantiation, yielding a post-quantum secure NC-RFE scheme based on the hardness of the plain LWE and equivocal LWE assumptions.