Abstract
Functional encryption (FE for short) can be used to calculate a function output of a message when given the corresponding function key, without revealing other information about the message. However, the original FE does not guarantee the unforgeability of either ciphertexts or function keys. In 2016, Badrinarayanan et al. provide a new primitive called verifiable functional encryption (VFE for short), and give a generic transformation from FE to VFE using non-interactive witness-indistinguishable proof (NIWI proof). In their construction, each VFE ciphertext (resp. function key) consists of 4 FE ciphertexts (resp. function keys) generated from independent FE public keys (resp. secret keys) and a NIWI proof on the correctness.
In this paper, we show that there is redundancy in their construction. Concretely, we give a new construction for VFE which uses only 3 FE ciphertexts and function keys, and prove the verifiability and security of the construction. Since the NIWI proof is also simpler in our scheme, our construction may lead to an about 25% decrease in both ciphertext/key size and encryption/decryption cost.
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Acknowledgement
This work is partially supported by the National Key R &D Program of China (No. 2020YFA0712300) and the National Natural Science Foundation of China (No. 62202294).
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Wang, G., Wan, M., Gu, D. (2022). More Efficient Verifiable Functional Encryption. In: Ge, C., Guo, F. (eds) Provable and Practical Security. ProvSec 2022. Lecture Notes in Computer Science, vol 13600. Springer, Cham. https://doi.org/10.1007/978-3-031-20917-8_3
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