External Client IO using garbled circuit protocols

[anyejunwang1]

Hello, mkskeller!

ExternalIO/ describes the communication between .mpc and the external client, but it emphasizes that binary protocols cannot be used. Therefore, I can only use secret sharing protocols such as Scripts/ring.sh, Scripts/semi2k.sh.

I would like to know how to achieve similar client communication using garbled circuit protocols such as Scripts/yao.sh or Scripts/semi-bmr.sh. Otherwise, I'll have to use

sbitint.get_type(32).get_input_from(0)

But in that case, I would have to transfer the original data file to the .mpc file. Wouldn't that expose the data? Or are there any other methods?

[mkskeller]

The protocol used for external client input (https://eprint.iacr.org/2015/1006) only works for secret sharing schemes. External client input in this case means that the client is independent of all computing parties. In contrast, the input facility above means that the data goes through the computing party named in the function call. The data doesn't go through the .mpc file. Instead, you have to put it in Player-Data/Input-P<party>-<thread> as ASCII with whitespace separation. You can use -I/--interactive and -IF/--input-file to modify the details, see https://mp-spdz.readthedocs.io/en/latest/io.html#private-inputs-from-computing-parties