Hello,
I’m currently using CKKS as part of a project to perform a sequence of t operations, repeated n times. I’ve observed that after each rescaling of a ciphertext, its size becomes progressively smaller, leading to reduced computation time over successive iterations. Is this an expected behavior?
Thank you!
Yes, this is expected. One effect of Rescale is dropping the last element in the rescaled ciphertext, hence, its size decreases.
Ok thanks, and what about bootstrapping? As far as I know, CKKS bootstrapping restores the modules previously removed from the ciphertext. Can we expect an increase in size after bootstrapping?
Yes, the size will increase to the max inside bootstrapping. However, after bootstrapping is complete, the user will get a ciphertext whose number of levels is equal to levelsAvailableAfterBootstrap - the parameter used to estimate the multiplicative depth in the user application.
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