Paper 2023/815

Noah's Ark: Efficient Threshold-FHE Using Noise Flooding

Morten Dahl, Zama
Daniel Demmler, Zama
Sarah El Kazdadi
Arthur Meyre, Zama
Jean-Baptiste Orfila, Zama
Dragos Rotaru, Zama
Nigel P. Smart, COSIC, KU Leuven, Zama
Samuel Tap, Zama
Michael Walter, Zama

We outline a secure and efficient methodology to do threshold distributed decryption for LWE based Fully Homomorphic Encryption schemes. Due to the smaller parameters used in some FHE schemes, such as Torus-FHE (TFHE), the standard technique of ``noise flooding'' seems not to apply. We show that noise flooding can also be used with schemes with such small parameters, by utilizing a switch to a scheme with slightly higher parameters and then utilizing the efficient bootstrapping operations which TFHE offers. Our protocol is proved secure via a simulation argument, making its integration in bigger protocols easier to manage.

Note: Correction of a minor bug

Available format(s)
Cryptographic protocols
Publication info
Published elsewhere. Major revision. WAHC 2023
FHEThreshold Decryption
Contact author(s)
morten dahl @ zama ai
daniel demmler @ zama ai
sarah elkazdadi @ zama ai
arthur meyre @ zama ai
jb orfila @ zama ai
dragos rotaru @ zama ai
nigel smart @ kuleuven be
samiel tap @ zama ai
michael walter @ zama ai
2023-10-17: last of 3 revisions
2023-06-02: received
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      author = {Morten Dahl and Daniel Demmler and Sarah El Kazdadi and Arthur Meyre and Jean-Baptiste Orfila and Dragos Rotaru and Nigel P. Smart and Samuel Tap and Michael Walter},
      title = {Noah's Ark: Efficient Threshold-{FHE} Using Noise Flooding},
      howpublished = {Cryptology ePrint Archive, Paper 2023/815},
      year = {2023},
      doi = {10.1145/3605759.3625259},
      note = {\url{}},
      url = {}
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