Paper 2022/1772

You Can Sign but Not Decrypt: Hierarchical Integrated Encryption and Signature

Abstract

Recently, Chen et al. (ASIACRYPT 2021) introduced a notion called hierarchical integrated signature and encryption (HISE), which provides a new principle for combining public key schemes. It uses a single public key for both signature and encryption schemes, and one can derive a decryption key from the signing key but not vice versa. Whereas, they left the dual notion where the signing key can be derived from the decryption key as an open problem. In this paper, we resolve the problem by formalizing the notion called hierarchical integrated encryption and signature (HIES). Similar to HISE, it features a unique public key for both encryption and signature components and has a two-level key derivation mechanism, but reverses the hierarchy between signing key and decryption key, i.e. one can derive a signing key from the decryption key but not vice versa. This property enables secure delegation of signing capacity in the public key reuse setting. We present a generic construction of HIES from constrained identity-based encryption. Furthermore, we instantiate our generic HIES construction and implement it. The experimental result demonstrates that our HIES scheme is comparable to the best Cartesian product combined public-key scheme in terms of efficiency, and is superior in having richer functionality as well as retaining merits of key reuse.