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fixes Decoder template adding missing check #81

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fixes Decoder template adding missing check #81

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9d2918e
fixes decoder adding missing check
clararod9 Oct 6, 2022
47b2c4e
improving decoder, adding decoder_strict
clararod9 Oct 8, 2022
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41 changes: 37 additions & 4 deletions circuits/multiplexer.circom
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Original file line number Diff line number Diff line change
Expand Up @@ -62,6 +62,8 @@ function log2(a) {

pragma circom 2.0.0;

include "comparators.circom";

template EscalarProduct(w) {
signal input in1[w];
signal input in2[w];
Expand All @@ -75,28 +77,59 @@ template EscalarProduct(w) {
out <== lc;
}

// in case inp >= w then witness = 0, in other case witness = 1, out[i] = 1 if i = inp and 0 otherwise
/*
Specification:
- Success := w < inp
- for i in 0..w: out[i] = 1 if i = inp, else out[i] = 0
*/

template Decoder(w) {
signal input inp;
signal output out[w];
signal output success;
var lc=0;

component checkZero[w];

for (var i=0; i<w; i++) {
checkZero[i] = IsZero();
checkZero[i].in <== inp - i;
out[i] <== checkZero[i].out;
lc = lc + out[i];
}

lc ==> success;
}

// in case inp >= w does not accept any solution -> does not generate witness
/*
Specification:
In case inp < w:
- for i in 0..w: out[i] = 1 if i = inp, else out[i] = 0
If w >= inp => the sysetm of constraints does not have any solution
*/
template Decoder_strict(w) {
signal input inp;
signal output out[w];
var lc=0;

for (var i=0; i<w; i++) {
out[i] <-- (inp == i) ? 1 : 0;
out[i] * (inp-i) === 0;
lc = lc + out[i];
}

lc ==> success;
success * (success -1) === 0;
lc === 1;
}



template Multiplexer(wIn, nIn) {
signal input inp[nIn][wIn];
signal input sel;
signal output out[wIn];
component dec = Decoder(nIn);
component dec = Decoder_strict(nIn);
component ep[wIn];

for (var k=0; k<wIn; k++) {
Expand All @@ -111,5 +144,5 @@ template Multiplexer(wIn, nIn) {
}
ep[j].out ==> out[j];
}
dec.success === 1;
}