Paper 2022/1298

BLEACH: Cleaning Errors in Discrete Computations over CKKS

Nir Drucker, IBM Research - Israel
Guy Moshkowich, IBM Research - Israel
Tomer Pelleg, IBM Research - Israel
Hayim Shaul, IBM Research - Israel
Abstract

Approximated homomorphic encryption (HE) schemes such as CKKS are commonly used to perform computations over encrypted real numbers. It is commonly assumed that these schemes are not “exact” and thus they cannot execute circuits with unbounded depth over discrete sets, such as binary or integer numbers, without error overflows. These circuits are usually executed using BGV and B/FV for integers and TFHE for binary numbers. This artificial separation can cause users to favor one scheme over another for a given computation, without even exploring other, perhaps better, options. We show that by treating step functions as “clean-up” utilities and by leveraging the SIMD capabilities of CKKS, we can extend the homomorphic encryption toolbox with efficient tools. These tools use CKKS to run unbounded circuits that operate over binary and small-integer elements and even combine these circuits with fixed-point real numbers circuits. We demonstrate the results using the Turing-complete Conway’s Game of Life. In our evaluation, for boards of size 128x128, these tools achieved an order of magnitude faster latency than previous implementations using other HE schemes. We argue and demonstrate that for large enough real-world inputs, performing binary circuits over CKKS, while considering it as an “exact” scheme, results in comparable or even better performance than using other schemes tailored for similar inputs.

Note: Removed a left-over editing comment from the previous revision.

Metadata
Available format(s)
PDF
Category
Public-key cryptography
Publication info
Preprint.
Keywords
fully homomorphic encryption encrypted binary circuits CKKS mixed integer-floating point operations game of life
Contact author(s)
drucker nir @ gmail com
guy moshkowich @ ibm com
tomer pelleg @ ibm com
hayim shaul @ ibm com
History
2022-10-18: revised
2022-09-29: received
See all versions
Short URL
https://ia.cr/2022/1298
License
Creative Commons Attribution
CC BY

BibTeX

@misc{cryptoeprint:2022/1298,
      author = {Nir Drucker and Guy Moshkowich and Tomer Pelleg and Hayim Shaul},
      title = {BLEACH: Cleaning Errors in Discrete Computations over CKKS},
      howpublished = {Cryptology ePrint Archive, Paper 2022/1298},
      year = {2022},
      note = {\url{https://eprint.iacr.org/2022/1298}},
      url = {https://eprint.iacr.org/2022/1298}
}
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