Do the program and inputs need to be encrypted with the same secret key?

[dhvanipa]

Do the program and inputs need to be encrypted with the same secret key?

[Janmajayamall]

We haven't added support for public key for now. But both the user and the developer will encrypt their inputs (user input and developer's input is the program) using the public key.

Both input and the program have the same access structure. In other words, the same secret can decrypt both.

[dhvanipa]

In other words, the same secret can decrypt both.

Is this the desired experience? I would assume the developer wants to keep their program private from the user, and the user their input private from the developer.

Is it possible for them to be encrypted with different keys? Or no, you'd have to use something like threshold encryption to enforce that the user doesn't see the program and the developer doesn't see the inputs?

[Janmajayamall]

Apologies for the late responses.

Or no, you'd have to use something like threshold encryption to enforce that the user doesn't see the program and the developer doesn't see the inputs?

Yes, indeed. Threshold is the way to go.

Is it possible for them to be encrypted with different keys?

It's possible. In the literature it goes by then multi-key FHE. However, multi-key FHE is way slower than normal FHE.

Threshold FHE pays little to no performance penalty over normal FHE and, in practice, is preferred over multi-key FHE. Poulpy, at the moment, does not supports threshold FHE, but we may add it in the future. Phantom is a VM implementation, it does not care about underlying secret access structure. It accepts encrypted programs and encrypted ciphertexts (input to the program) as inputs and outputs encrypted ciphertexts. Decryption of the ciphertext is handled by the secret holder(s).

[dhvanipa]

Gotcha, thanks! Very cool to see the VM run an encrypted program!!

[Janmajayamall]

I'm closing this issue for now. But please feel free to reopen.