Paper 2026/1676

Simple and Efficient SKL-IBE with Classical Revocation from LWE

Abstract

Secure key leasing (SKL) is a quantum cryptographic primitive that enables the leasing of decryption keys to delegated users with the guarantee that, once revoked, the lessees irreversibly lose decryption capability. A key feature that makes SKL practically relevant is classical revocation: the ability to revoke keys at any time and from anywhere, without relying on a quantum channel. In this work, we revisit SKL schemes for public-key encryption (PKE) and identity-based encryption (IBE), and present a new approach for concrete efficiency under the standard Learning With Errors (LWE) assumption. First, we refine the security analysis of the Dual-Regev SKL-PKE scheme with classical revocation from [Ananth, Poremba, and Vaikuntanathan, TCC 2023; Ananth, Hu, and Huang, TCC 2024], establishing security under the polynomial hardness of LWE with polynomial modulus. Together with the resource efficiency of the Dual-Regev-based construction, our analysis shows that this approach yields the most quantum-efficient known SKL-PKE scheme. Second, we present a simple and efficient construction of selectively secure SKL-IBE with classical revocation from standard LWE. Our approach directly extends the Dual-Regev SKL-PKE within the IBE framework of [Agrawal, Boneh, and Boyen, Eurocrypt 2010], avoiding garbled circuits and obfuscation-based assumptions and achieving improved concrete efficiency over prior generic approaches.