# Polynomial Multiplication in CKKS

**URL:** <https://openfhe.discourse.group/t/polynomial-multiplication-in-ckks/845>\
**Category:** FHE Questions\
**Created:** [October 13, 2023, 3:31pm UTC](https://openfhe.discourse.group/t/polynomial-multiplication-in-ckks/845 "2023-10-13T15:31:00Z")\
**Posts on this page:** 1\
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**Author:** ![narger](https://yyz1.discourse-cdn.com/flex031/user_avatar/openfhe.discourse.group/narger/32/420_2.png) [@narger](https://openfhe.discourse.group/u/narger)\
**Post date:** [October 23, 2023, 8:29am UTC](https://openfhe.discourse.group/t/polynomial-multiplication-in-ckks/845/8 "2023-10-23T08:29:08Z")

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@marc-alonso I think the drawback about their approach is about ReLU evaluation, since slot-wise multiplications are more difficult (check [this recent thread](https://openfhe.discourse.group/t/format-switching-in-ckks/851/3))

Edit: ReLU was ok (is indeed computed after the CtoS step, on the re-encoded ciphertext), I think the way they consider convolutions as polynomial negacyclic convolutions is cool, it indeed avoids to run multiple multiplications and rotations. I guess the main issue is about packing LWE ciphertexts (which needs many rotation keys), but as soon as you have enough RAM, it is ok.

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