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?
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