# Is the GHS key-switching method implemented in OpenFHE?

**URL:** <https://openfhe.discourse.group/t/is-the-ghs-key-switching-method-implemented-in-openfhe/2140>\
**Category:** Library Questions\
**Created:** [August 13, 2025, 5:42am UTC](https://openfhe.discourse.group/t/is-the-ghs-key-switching-method-implemented-in-openfhe/2140 "2025-08-13T05:42:17Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![oksuman](https://avatars.discourse-cdn.com/v4/letter/o/6de8d8/32.png) [@oksuman](https://openfhe.discourse.group/u/oksuman)\
**Post date:** [August 13, 2025, 5:42am UTC](https://openfhe.discourse.group/t/is-the-ghs-key-switching-method-implemented-in-openfhe/2140/1 "2025-08-13T05:42:18Z")

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Hello.

I was wondering if the GHS (Gentry–Halevi–Smart) key-switching method described in [Revisiting Homomorphic Encryption Schemes for Finite Fields](https://eprint.iacr.org/2021/204) is implemented in OpenFHE. I could only find the BV and Hybrid methods, so I’m curious whether GHS has not been adopted in OpenFHE.

If GHS is not implemented, could you share the reason (no practical advantage over Hybrid, or other technical reasons)?

Thank you.

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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:** [August 13, 2025, 4:23pm UTC](https://openfhe.discourse.group/t/is-the-ghs-key-switching-method-implemented-in-openfhe/2140/2 "2025-08-13T16:23:05Z")

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GHS is a special case of Hybrid key switching when the number of large digits is set to 1 (it can be set via `SetNumLargeDigits`). In many cases, a configuration with 3 digits is more performant as it increases the size of ciphertext modulus size (in bits) only by one-third (rather than twice, as in the case of GHS key switching).

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**Author:** ![oksuman](https://avatars.discourse-cdn.com/v4/letter/o/6de8d8/32.png) [@oksuman](https://openfhe.discourse.group/u/oksuman)\
**Post date:** [August 14, 2025, 1:26am UTC](https://openfhe.discourse.group/t/is-the-ghs-key-switching-method-implemented-in-openfhe/2140/3 "2025-08-14T01:26:00Z")

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Thank you for your answer.