Possibility of Ciphertext Packing

divyesh · February 20, 2023, 10:36am

Dear Community,

Is ciphertext packing possible in tfhe-rs? If packing is possible using GLWE/GGSW ciphertexts, is it possible to apply bootstrapping on packed Ciphers?!

IceTDrinker · February 20, 2023, 10:59am

Hello @divyesh

It’s possible to pack ciphertexts using private_functional_keyswitch_lwe_ciphertext_list_and_pack_in_glwe_ciphertext see an example here (docstrings will be updated shortly):

github.com/zama-ai/tfhe-rs

How to Use the `private_functional_packing_keyswitch_key` Function in TFHE-rs

opened 10:31PM - 15 Feb 23 UTC

closed 08:44PM - 16 Feb 23 UTC

swanhong

Hi, I am currently attempting to use the packing algorithm in order to pack v…arious LWE ciphertexts into one RLWE (or GLWE) ciphertext. I believe that the `private_functional_packing_keyswitch_key` function is related to this subject and that it is based on algorithm 2 in [[CGGI20](https://eprint.iacr.org/2017/430.pdf)]. However, unlike other functions, I have not been able to find any explanation or test documentation for this function in the code, such as in `lwe_private_functional_packing_keyswitch_key_generation.rs`. Could you please provide an example code for using this function, or recommend other options for packing multiple ciphertexts? Additionally, do you have any plans to implement a public key version of this function as well?

We don’t currently have a way to bootstrap packed ciphertexts as far as I know.

Cheers

divyesh · February 21, 2023, 4:46am

And what about SIMD operations, do packed ciphers have those?!

IceTDrinker · February 21, 2023, 9:16am

Hello,

We did not write SIMD operations by hand for GLWE ciphertexts and I don’t remember GLWE ciphertexts having that many operations implemented at the moment, so I guess for some of those operations the compiler sometimes auto-vectorizes stuff for us