unused value sent over the wire

[themighty1]

emp-tool/emp-tool/gc/halfgate_gen.h

Line 60 in 203bc53

io->send_block(constant, 2);

constant[0] is sent to the evaluator. After that it is never used neither by the garbler nor by the evaluator.
Could you pls clarify the purpose of sending it and also the purpose of having it since it is never used.

[wangxiao1254]

They are used in "public_label()", right?

[themighty1]

Sorry for the noise, I was confused.

[themighty1]

@wangxiao1254 , I'm still confused why the garbler does

emp-tool/emp-tool/gc/halfgate_gen.h

Line 61 in 203bc53

constant[1] = constant[1] ^ delta;

after sending the public constants to the evaluator?
The parties now have different constant[1]s. One would think that the parties should have the same constants, no?

[jacob14916]

It's because halfgate_gen works by propagating the wire keys corresponding to zeros, so it expects the key for the "wire" of constant[1] if that wire were to be 0.