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

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include "bitify.circom";
include "aliascheck.circom";
include "compconstant.circom";
include "babyjub.circom";
function sqrt(n) {
if (n == 0) {
return 0;
}
// Test that have solution
var res = n ** ((-1) >> 1);
// if (res!=1) assert(false, "SQRT does not exists");
if (res!=1) return 0;
var m = 28;
var c = 19103219067921713944291392827692070036145651957329286315305642004821462161904;
var t = n ** 81540058820840996586704275553141814055101440848469862132140264610111;
var r = n ** ((81540058820840996586704275553141814055101440848469862132140264610111+1)>>1);
var sq;
var i;
var b;
var j;
while ((r != 0)&&(t != 1)) {
sq = t*t;
i = 1;
while (sq!=1) {
i++;
sq = sq*sq;
}
// b = c ^ m-i-1
b = c;
for (j=0; j< m-i-1; j ++) b = b*b;
m = i;
c = b*b;
t = t*c;
r = r*b;
}
if (r > ((-1) >> 1)) {
r = -r;
}
return r;
}
template Bits2Point() {
signal input in[256];
signal output out[2];
}
template Bits2Point_Strict() {
signal input in[256];
signal output out[2];
var i;
// Check aliasing
component aliasCheckY = AliasCheck();
for (i=0; i<254; i++) {
aliasCheckY.in[i] <== in[i];
}
in[254] === 0;
component b2nY = Bits2Num(254);
for (i=0; i<254; i++) {
b2nY.in[i] <== in[i];
}
out[1] <== b2nY.out;
var a = 168700;
var d = 168696;
var y2 = out[1] * out[1];
var x = sqrt( (1-y2)/(a - d*y2) );
if (in[255] == 1) x = -x;
out[0] <-- x;
component babyCheck = BabyCheck();
babyCheck.x <== out[0];
babyCheck.y <== out[1];
component n2bX = Num2Bits(254);
n2bX.in <== out[0];
component aliasCheckX = AliasCheck();
for (i=0; i<254; i++) {
aliasCheckX.in[i] <== n2bX.out[i];
}
component signCalc = CompConstant(10944121435919637611123202872628637544274182200208017171849102093287904247808);
for (i=0; i<254; i++) {
signCalc.in[i] <== n2bX.out[i];
}
signCalc.out === in[255];
}
template Point2Bits() {
signal input in[2];
signal output out[256];
}
template Point2Bits_Strict() {
signal input in[2];
signal output out[256];
var i;
component n2bX = Num2Bits(254);
n2bX.in <== in[0];
component n2bY = Num2Bits(254);
n2bY.in <== in[1];
component aliasCheckX = AliasCheck();
component aliasCheckY = AliasCheck();
for (i=0; i<254; i++) {
aliasCheckX.in[i] <== n2bX.out[i];
aliasCheckY.in[i] <== n2bY.out[i];
}
component signCalc = CompConstant(10944121435919637611123202872628637544274182200208017171849102093287904247808);
for (i=0; i<254; i++) {
signCalc.in[i] <== n2bX.out[i];
}
for (i=0; i<254; i++) {
out[i] <== n2bY.out[i];
}
out[254] <== 0;
out[255] <== signCalc.out;
}