1  /*
 2      Copyright 2018 0KIMS association.
 3  
 4      This file is part of circom (Zero Knowledge Circuit Compiler).
 5  
 6      circom is a free software: you can redistribute it and/or modify it
 7      under the terms of the GNU General Public License as published by
 8      the Free Software Foundation, either version 3 of the License, or
 9      (at your option) any later version.
10  
11      circom is distributed in the hope that it will be useful, but WITHOUT
12      ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
13      or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
14      License for more details.
15  
16      You should have received a copy of the GNU General Public License
17      along with circom. If not, see <https://www.gnu.org/licenses/>.
18  */
19  pragma circom 2.0.0;
20  
21  include "bitify.circom";
22  
23  // Returns 1 if in (in binary) > ct
24  
25  template CompConstant(ct) {
26      signal input in[254];
27      signal output out;
28  
29      signal parts[127];
30      signal sout;
31  
32      var clsb;
33      var cmsb;
34      var slsb;
35      var smsb;
36  
37      var sum=0;
38  
39      var b = (1 << 128) -1;
40      var a = 1;
41      var e = 1;
42      var i;
43  
44      for (i=0;i<127; i++) {
45          clsb = (ct >> (i*2)) & 1;
46          cmsb = (ct >> (i*2+1)) & 1;
47          slsb = in[i*2];
48          smsb = in[i*2+1];
49  
50          if ((cmsb==0)&&(clsb==0)) {
51              parts[i] <== -b*smsb*slsb + b*smsb + b*slsb;
52          } else if ((cmsb==0)&&(clsb==1)) {
53              parts[i] <== a*smsb*slsb - a*slsb + b*smsb - a*smsb + a;
54          } else if ((cmsb==1)&&(clsb==0)) {
55              parts[i] <== b*smsb*slsb - a*smsb + a;
56          } else {
57              parts[i] <== -a*smsb*slsb + a;
58          }
59  
60          sum = sum + parts[i];
61  
62          b = b -e;
63          a = a +e;
64          e = e*2;
65      }
66  
67      sout <== sum;
68  
69      component num2bits = Num2Bits(135);
70  
71      num2bits.in <== sout;
72  
73      out <== num2bits.out[127];
74  }