Paper 2021/1131

Multi-key Fully Homomorphic Encryption Scheme with Compact Ciphertexts

Tanping Zhou
Long Chen
Xiaoliang Che
Wenchao Liu
Zhenfeng Zhang
Xiaoyuan Yang

Multi-Key fully homomorphic encryption (MKFHE) allows computations on data encrypted by different parties. One disadvantage of previous MKFHE schemes is that the ciphertext size increases linearly or squarely with respect to the number of parties. It incurs a heavy communication and computation burden for the homomorphic evaluation, especially when the number of involved parties is large. In this paper, we propose the first method to construct MKFHE scheme while keeping the size of the ciphertext and corresponding evaluation key to be independent of the number of parties during the homomorphic evaluation. Specifically, we construct efficient compact MKFHE schemes with various advantages. On the one hand, we show how to construct compact MKFHE schemes which support the homomorphic encryption of ring elements and are friendly to floating point numbers. On the other hand, we give a compact MKFHE scheme that supports high efficient bootstrapping. In our paper, we show a novel method to reduce the cost of generating these evaluation keys from a quadratic time to a linear time with respect to the number of parties.

Available format(s)
Public-key cryptography
Publication info
Multi-key Fully homomorphic encryption Lattice cipher Bootstrapping process Homomorphic decryption
Contact author(s)
tanping2020 @ iscas ac cn
2022-05-31: revised
2021-09-06: received
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Creative Commons Attribution


      author = {Tanping Zhou and Long Chen and Xiaoliang Che and Wenchao Liu and Zhenfeng Zhang and Xiaoyuan Yang},
      title = {Multi-key Fully Homomorphic Encryption Scheme  with Compact Ciphertexts},
      howpublished = {Cryptology ePrint Archive, Paper 2021/1131},
      year = {2021},
      note = {\url{}},
      url = {}
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