# Parameters selection with logN=16 or bigger

**URL:** https://openfhe.discourse.group/t/parameters-selection-with-logn-16-or-bigger/1210
**Category:** FHE Questions
**Created:** [April 19, 2024, 4:13pm UTC](https://openfhe.discourse.group/t/parameters-selection-with-logn-16-or-bigger/1210 "2024-04-19T16:13:25Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![yhh](https://avatars.discourse-cdn.com/v4/letter/y/c57346/32.png) [@yhh](https://openfhe.discourse.group/u/yhh)
#### Post date: [April 19, 2024, 4:13pm UTC](https://openfhe.discourse.group/t/parameters-selection-with-logn-16-or-bigger/1210/1 "2024-04-19T16:13:25Z")

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Hi

In my case, I would need to do a lot of multiplications, therefore leading to the need of larger logN like 16,17 or maybe even 18. Hence, I would like to know what’s the range of logPQ for certain security level (128,196 etc.). I cant find a guide for selecting such large N.

Thanks for your time!

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### Author: ![Caesar](https://yyz1.discourse-cdn.com/flex031/user_avatar/openfhe.discourse.group/caesar/32/63_2.png) [@Caesar](https://openfhe.discourse.group/u/Caesar)
#### Post date: [April 19, 2024, 7:18pm UTC](https://openfhe.discourse.group/t/parameters-selection-with-logn-16-or-bigger/1210/2 "2024-04-19T19:18:58Z")

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What scheme are you using?  
If you are using CKKS, it might be more efficient to bootstrap after consuming the multiplicative depth.  
This [paper](https://eprint.iacr.org/2024/463.pdf) has some parameters for up to N = 2^{17}.

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### Author: ![ypolyakov](https://yyz1.discourse-cdn.com/flex031/user_avatar/openfhe.discourse.group/ypolyakov/32/47_2.png) [@ypolyakov](https://openfhe.discourse.group/u/ypolyakov)
#### Post date: [April 21, 2024, 10:38pm UTC](https://openfhe.discourse.group/t/parameters-selection-with-logn-16-or-bigger/1210/4 "2024-04-21T22:38:21Z")

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For N \> 2^{16}, you can use the table 4.2 from [https://eprint.iacr.org/2024/463.pdf](https://eprint.iacr.org/2024/463.pdf) (it includes the threshold for N=2^{17}). Although this document is still work in progress (after review by the community, it will eventually replace [https://homomorphicencryption.org/wp-content/uploads/2018/11/HomomorphicEncryptionStandardv1.1.pdf](https://homomorphicencryption.org/wp-content/uploads/2018/11/HomomorphicEncryptionStandardv1.1.pdf)), the table can be used for practical applications. As @Caesar pointed out, CKKS bootstrapping could also be used to keep N \leq 2^{17}