wangxiao1254
commented
5 years ago This is the intended behavior.
Two-output functionality can be done in two ways:
If you know the protocol and the code well, you can make it such that BOB sends back the garbled labels, where Alice can obtain the results. The fact that labels are sent will ensure authenticity.
If can also use a generic black-box transformation. See https://eprint.iacr.org/2008/049.pdf section 2.2
Xiao
On Tue, Mar 26, 2019 at 2:00 PM Daniel Lemire notifications@github.com wrote:
Thanks for making the code and the paper available for this project.
For our own research, we are trying to build upon your work.
Following your instructions and examples, we run the following code on both BOB and ALICE's server.
C2PC twopc(io, party, &cf); twopc.function_independent(); twopc.function_dependent(); twopc.online(in, out);However, looking at ALICE's code path in the online function https://github.com/emp-toolkit/emp-ag2pc/blob/master/emp-ag2pc/2pc.h#L312, we find that ALICE is not computing the circuit and getting the result of the circuit: only BOB does the computation and only BOB gets the answer. So, effectively, in ALICE's case, running the above code sequence, leads to have no result written to out.
Looking at some of the tests you published, it does appear that you check that the output matches your expectations, but only when the user is BOB. That is, we cannot find evidence that you expect ALICE to get the result of the circuit.
if(party == BOB){ // why only BOB???????????? string res = ""; for(int i = 0; i < 160; ++i) res += (out[i]?"1":"0"); cout << (res == hex_to_binary(string(out3))? "GOOD!":"BAD!")<<endl; }
Evidently, we could modify this code so that BOB sends the answer back to ALICE but this implies that ALICE trusts BOB. Another obvious fix is to run the exchange twice, flipping the role of BOB and ALICE, but that does not seem correct.
What if we wish that both parties get the output of the circuit https://en.wikipedia.org/wiki/Secure_multi-party_computation#Two-party_computation? Could we modify your code, or the way we use your code, to get this desired result?
cc @owenkaser https://github.com/owenkaser
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lemire
Thanks for making the code and the paper available for this project.
For our own research, we are trying to build upon your work.
Following your instructions and examples, we run the following code on both BOB and ALICE's server.
However, looking at ALICE's code path in the
onlinefunction, we find that ALICE is not computing the circuit and getting the result of the circuit: only BOB does the computation and only BOB gets the answer. So, effectively, in ALICE's case, running the above code sequence, leads to have no result written toout.Looking at some of the tests you published, it does appear that you check that the output matches your expectations, but only when the user is BOB. That is, we cannot find evidence that you expect ALICE to get the result of the circuit.
Evidently, we could modify this code so that BOB sends the answer back to ALICE but this implies that ALICE trusts BOB. Another obvious fix is to run the exchange twice, flipping the role of BOB and ALICE, but that does not seem correct.
What if we wish that both parties get the output of the circuit? Could we modify your code, or the way we use your code, to get this desired result?
cc @owenkaser