Abstract
In this paper we present an optimized variant of Gentry, Halevi and Vaikuntanathan (GHV)’s Homomorphic Encryption (HE) scheme. Our scheme is appreciably more efficient than the original GHV scheme without losing its merits of the (multi-key) homomorphic property and matrix encryption property. In this research, we first measure the density for the trapdoor pairs that are created by using Alwen and Peikert’s trapdoor generation algorithm and Micciancio and Peikert’s trapdoor generation algorithm, respectively, and use the measurement result to precisely discuss the time and space complexity of the corresponding GHV instantiations. We then propose a generic GHV-type construction with several optimizations that improve the time and space efficiency from the original GHV scheme. In particular, our scheme can achieve asymptotically optimal time complexity and avoid generating and storing the inverse of the used trapdoor. Finally, we present an instantiation that, by using a new set of (lower) bound parameters, has the smaller sizes of the key and ciphertext than the original GHV scheme.
The full version of this work appears in [28].
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Notes
- 1.
We believe that a matrix sampled from the distribution over \(\{0,\pm 1\}^{\textit{m}_{1}\times \textit{m}_{2}}\) is generally sparser than a matrix from the discrete Gaussian distribution for some \(\beta ' \ge \eta _{\upsilon }(\mathbb {Z})\).
- 2.
Clearly, the state-of-the-art discrete Gaussian sampling algorithms over the integers (e.g., [20]) can be considered as candidates used in oGHV to replace the sampling method proposed by Gentry et al. [10]. What is important is that the corresponding parameter setting needs to ensure that oGHV still holds the desired correctness, security and homomorphism.
- 3.
The proposed optimizations are not only focus on \(\mathbf {T}^{\textit{t}}\) and \(\mathbf {\tilde{T}}\) from \(\textsf {APSTrapSamp}\). Actually, some extremely similar optimizations can be developed for any \(\textsf {APTrapSamp}\)-type trapdoor sampling algorithm (e.g., \(\textsf {MPTrapSamp}\)).
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Acknowledgments
The authors would like to thank the anonymous reviewers for providing their valuable comments. This work was supported in part by the National Natural Science Foundation of China (No. 61302161, No. 61972269, No. 62032005), in part by the Doctoral Fund, Ministry of Education, China (No. 20130181120076), and in part by the European Union’s Horizon 2020 research and innovation program under grant agreement No. 952697 (ASSURED) and grant agreement No. 101019645 (SECANT).
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Zhao, L., Chen, Z., Chen, L., Huang, X. (2022). An Optimized GHV-Type HE Scheme: Simpler, Faster, and More Versatile. In: Ateniese, G., Venturi, D. (eds) Applied Cryptography and Network Security. ACNS 2022. Lecture Notes in Computer Science, vol 13269. Springer, Cham. https://doi.org/10.1007/978-3-031-09234-3_3
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