Transciphering with fhEVM

Hi, how does fhEVM solves the ciphertext expansion ratio problem? I know that some part of the fhe community is trying to fix this problem by combining symmetric ciphers with homomorphic ciphers and then evaluating the symmetric-decryption circuit (transicphering). How can I achieve that with tfhe?

Hi Fede,

We have plans of managing ciphertext expansion in the future using techniques that you mention (see Trivial Transciphering With Trivium and TFHE).
Currently, we use compact ciphertexts to reduce the blowup in size.


Thanks for the answer, Louis!
I was wondering that because I’m building a hybrid scheme combining BFV and PASTA integrated into another blockchain (rootstock). Now, I got stuck with the setup of the scheme because I couldn’t figure out how to set up the evaluation keys that support transciphering without compromising the secret key and without dealing with a huge evaluation key.
I’ll check out your compact technique as well and see If I can come up with any ideas.
Also, I’ll consider experimenting with tfhe since I really like this community.

Cool, that seems like a fun project :slight_smile:
Out of curiosity, is there a specific reason why you’re trying to integrate an FHE scheme into another smart contract blockchain instead of using the fhEVM?