Efficient decryption algorithms for extension field cancellation type encryption schemes



Publication Details

Wang, Y., Ikematsu, Y., Duong, D. Hoang. & Takagi, T. (2018). Efficient decryption algorithms for extension field cancellation type encryption schemes. Lecture Notes in Computer Science, 10946 LNCS 487-501. Information Security and Privacy 23rd Australasian Conference, ACISP 2018, Wollongong, NSW, Australia, July 11-13, 2018, Proceedings


Extension Field Cancellation (EFC) was proposed by Alan et al. at PQCrypto 2016 as a new trapdoor for constructing secure multivariate encryption cryptographic schemes. Along with this trapdoor, two schemes EFCp and EFCpt2 that apply this trapdoor and some modifiers were proposed. Though their security seems to be high enough, their decryption efficiency has room for improvement. In this paper, we introduce a new and more efficient decryption approach for EFCp and EFCpt2, which manages to avoid all redundant computation involved in the original decryption algorithms, and theoretically speed up the decryption process of EFCp and EFCpt2 by around 3.4 and 8.5 times, respectively, under 128-bit security parameters with our new designed private keys for them. Meanwhile, our approach does not interfere with the public key, so the security remains the same. The implementation results of both decryption algorithms for EFCp and EFCpt2 are also provided.

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