# Using BV in CKKS
**URL:** https://openfhe.discourse.group/t/using-bv-in-ckks/1041
**Category:** FHE Questions
**Created:** [January 26, 2024, 1:26pm UTC](https://openfhe.discourse.group/t/using-bv-in-ckks/1041 "2024-01-26T13:26:32Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@LHenke](https://openfhe.discourse.group/u/LHenke)
#### Post date: [January 26, 2024, 1:26pm UTC](https://openfhe.discourse.group/t/using-bv-in-ckks/1041/1 "2024-01-26T13:26:32Z")
I have question in terms of using different keyswitching techniques in CKKS:
I want to keep my ring dimension low, since it highly impacts the performance. No for that I want to set the KeySwitching technique to BV, since this lets me keep a ring dimension at 128 bit security. Now when I run my circuit using BV as a KeySwitch technique, the decryption fails, due to the approximation error being to high. Now it seems that I do not know enough about Keyswitching in order to make this work. Is there any resource you can point me to?
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### Author:  [@ypolyakov](https://openfhe.discourse.group/u/ypolyakov)
#### Post date: [February 1, 2024, 4:23am UTC](https://openfhe.discourse.group/t/using-bv-in-ckks/1041/2 "2024-02-01T04:23:07Z")
BV key switching has a higher approximation error (especially when doing rotations). Instead you can use the Hybrid key switching operation with the number of digits set to multiplicative depth + 1 (or 2), depending on the scaling technique (basically this will add only extra 60 bits to \log Q).
A good resource on key switching is Appendix B of [Revisiting Homomorphic Encryption Schemes for Finite Fields](https://eprint.iacr.org/2021/204)