mirror of
https://github.com/data61/MP-SPDZ.git
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98 lines
2.3 KiB
C++
98 lines
2.3 KiB
C++
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#include "Subroutines.h"
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#include "Math/modp.h"
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#include "Math/modp.hpp"
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void Subs(modp& ans,const vector<int>& poly,const modp& x,const Zp_Data& ZpD)
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{
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modp one,co;
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assignOne(one,ZpD);
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assignZero(ans,ZpD);
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for (int i=poly.size()-1; i>=0; i--)
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{ Mul(ans,ans,x,ZpD);
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if (poly[i] > 0)
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{
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for (int j = 0; j < poly[i]; j++)
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Add(ans, ans, one, ZpD);
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}
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if (poly[i] < 0)
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{
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for (int j = 0; j < -poly[i]; j++)
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Sub(ans, ans, one, ZpD);
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}
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}
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}
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/* Find a m'th primitive root moduli the current prime
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* This is deterministic so all players have the same root of unity
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* poly is Phi_m(X)
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*/
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modp Find_Primitive_Root_m(int m,const vector<int>& poly,const Zp_Data& ZpD)
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{
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modp ans,e,one,base;
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assignOne(one,ZpD);
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assignOne(base,ZpD);
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bigint exp;
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exp=(ZpD.pr-1)/m;
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bool flag=true;
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while (flag)
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{ Add(base,base,one,ZpD); // Keep incrementing base until we hit the answer
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Power(ans,base,exp,ZpD);
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// e=Phi(ans)
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Subs(e,poly,ans,ZpD);
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if (isZero(e,ZpD)) { flag=false; }
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}
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return ans;
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}
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/* Find a (2m)'th primitive root moduli the current prime
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* This is deterministic so all players have the same root of unity
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* poly is Phi_m(X)
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*/
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modp Find_Primitive_Root_2m(int m,const vector<int>& poly,const Zp_Data& ZpD)
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{
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// Thin out poly, where poly is Phi_m(X) by 2
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vector<int> poly2;
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poly2.resize(2*poly.size());
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for (unsigned int i=0; i<poly.size(); i++)
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{ poly2[2*i]=poly[i];
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poly2[2*i+1]=0;
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}
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modp ans=Find_Primitive_Root_m(2*m,poly2,ZpD);
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return ans;
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}
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/* Find an mth primitive root moduli the current prime
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* This is deterministic so all players have the same root of unity
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* This assumes m is a power of two and so the cyclotomic polynomial
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* is F=X^{m/2}+1
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*/
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modp Find_Primitive_Root_2power(int m,const Zp_Data& ZpD)
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{
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assert((m & (m - 1)) == 0);
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assert(m > 1);
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modp ans,e,one,base;
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assignOne(one,ZpD);
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assignOne(base,ZpD);
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bigint exp;
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exp=(ZpD.pr-1)/m;
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assert(exp * m == ZpD.pr - 1);
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bool flag=true;
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while (flag)
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{ Add(base,base,one,ZpD); // Keep incrementing base until we hit the answer
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Power(ans,base,exp,ZpD);
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// e=ans^{m/2}+1
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Power(e,ans,m/2,ZpD);
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Add(e,e,one,ZpD);
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if (isZero(e,ZpD)) { flag=false; }
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}
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return ans;
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}
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