circomlib/circuits/sha256/xor3.circom
2018-12-06 17:32:49 +01:00

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/*
Copyright 2018 0KIMS association.
This file is part of circom (Zero Knowledge Circuit Compiler).
circom is a free software: you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
circom is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
License for more details.
You should have received a copy of the GNU General Public License
along with circom. If not, see <https://www.gnu.org/licenses/>.
*/
/* Xor3 function for sha256
out = a ^ b ^ c =>
out = a+b+c - 2*a*b - 2*a*c - 2*b*c + 4*a*b*c =>
out = a*( 1 - 2*b - 2*c + 4*b*c ) + b + c - 2*b*c =>
mid = b*c
out = a*( 1 - 2*b -2*c + 4*mid ) + b + c - 2 * mid
*/
template Xor3(n) {
signal input a[n];
signal input b[n];
signal input c[n];
signal output out[n];
signal mid[n];
for (var k=0; k<n; k++) {
mid[k] <== b[k]*c[k];
out[k] <== a[k] * (1 -2*b[k] -2*c[k] +4*mid[k]) + b[k] + c[k] -2*mid[k];
}
}