495 lines
9.4 KiB
C++
495 lines
9.4 KiB
C++
/*
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Scott's AKE Client/Server testbed
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See http://eprint.iacr.org/2002/164
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Compile as
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cl /O2 /GX /DZZNS=8 ake12bna.cpp zzn12.cpp zzn6a.cpp ecn2.cpp zzn2.cpp big.cpp zzn.cpp ecn.cpp miracl.lib
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using COMBA build
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Barreto-Naehrig Curve - Ate pairing
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The curve generated is generated from a 64-bit x parameter
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This version implements the Ate pairing
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See "Pairing-Friendly Elliptic Curves of Prime Order", by Paulo S. L. M. Barreto and Michael Naehrig,
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Cryptology ePrint Archive: Report 2005/133
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NOTE: Irreducible polynomial is of the form x^6+(1+sqrt(-2))
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See bn.cpp for a program to generate suitable BN curves
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Modified to prevent sub-group confinement attack
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*/
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#include <iostream>
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#include <fstream>
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#include <string.h>
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#include "ecn.h"
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#include <ctime>
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#include "ecn2.h"
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#include "zzn12.h"
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// cofactor - number of points on curve=CF.q
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using namespace std;
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#ifdef MR_COUNT_OPS
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extern "C"
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{
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int fpc=0;
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int fpa=0;
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int fpx=0;
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}
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#endif
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Miracl precision(8,0);
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#ifdef MR_AFFINE_ONLY
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#define AFFINE
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#else
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#define PROJECTIVE
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#endif
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// Using SHA-256 as basic hash algorithm
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#define HASH_LEN 32
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//
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// Ate Pairing Code
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//
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void set_frobenius_constant(ZZn2 &X)
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{
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Big p=get_modulus();
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switch (get_mip()->pmod8)
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{
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case 5:
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X.set((Big)0,(Big)1); // = (sqrt(-2)^(p-1)/2
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break;
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case 3: // = (1+sqrt(-1))^(p-1)/2
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X.set((Big)1,(Big)1);
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break;
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case 7:
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X.set((Big)2,(Big)1); // = (2+sqrt(-1))^(p-1)/2
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default: break;
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}
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X=pow(X,(p-1)/6);
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}
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//
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// Line from A to destination C. Let A=(x,y)
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// Line Y-slope.X-c=0, through A, so intercept c=y-slope.x
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// Line Y-slope.X-y+slope.x = (Y-y)-slope.(X-x) = 0
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// Now evaluate at Q -> return (Qy-y)-slope.(Qx-x)
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//
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ZZn12 line(ECn2& A,ECn2& C,ZZn2& slope,ZZn& Qx,ZZn& Qy)
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{
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ZZn12 w;
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ZZn6 nn,dd;
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ZZn2 X,Y;
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#ifdef AFFINE
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A.get(X,Y);
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dd.set(slope*Qx,Y-slope*X);
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nn.set((ZZn2)-Qy);
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w.set(nn,dd);
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#endif
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#ifdef PROJECTIVE
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ZZn2 Z,Z2,ZZ,ZZZ;
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A.get(X,Y,Z);
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C.getZ(Z2);
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ZZ=Z*Z;
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ZZZ=ZZ*Z;
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dd.set((ZZZ*slope)*Qx,Z2*Y-Z*X*slope);
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nn.set((ZZn2)-(ZZZ*Z2)*Qy);
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w.set(nn,dd);
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#endif
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return w;
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}
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//
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// fast multiplication by p-1+t
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// We know F^2-tF+p = 0
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// So p.S=t.F(S)-F^2(S), where F is Frobenius Endomorphism
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// So (p-1+t).S = t(F(S)+S)-F^2(S)-S
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// This is just multiplication by t, which is half size of (p-1+t)
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//
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void cofactor(ECn2& S,ZZn2 &F,Big& t)
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{
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ZZn2 x,y,w,z;
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ECn2 K,T;
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K=S;
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z=F;
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w=F*F;
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S.get(x,y);
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x=w*conj(x);
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y=z*w*conj(y);
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S.set(x,y);
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x=w*conj(x);
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y=z*w*conj(y);
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T.set(x,y);
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S+=K;
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S*=t;
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S-=T;
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S-=K;
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S.norm();
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}
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//
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// Add A=A+B (or A=A+A)
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// Return line function value
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//
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ZZn12 g(ECn2& A,ECn2& B,ZZn& Qx,ZZn& Qy)
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{
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ZZn2 lam;
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ZZn12 r;
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ECn2 P=A;
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// int fpcb=fpc;
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// Evaluate line from A
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A.add(B,lam);
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//cout << "point addition/doubling= " << fpc-fpcb << endl;
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if (A.iszero()) return (ZZn12)1;
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//fpcb=fpc;
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r=line(P,A,lam,Qx,Qy);
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//cout << "line calculation= " << fpc-fpcb << endl;
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//cout << "r= " << r << endl;
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return r;
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}
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//
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// Ate Pairing - note denominator elimination has been applied
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//
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// P is a point of order q. Q(x,y) is a point of order q.
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// Note that P is a point on the sextic twist of the curve over Fp^2, Q(x,y) is a point on the
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// curve over the base field Fp
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//
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BOOL fast_pairing(ECn2& P,ZZn& Qx,ZZn& Qy,Big &x,ZZn2 &X,ZZn6& res)
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{
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ECn2 A;
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int i,nb;
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Big n;
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ZZn12 w,r,a,b,c,rp;
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n=6*x*x; // t-1
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A=P; // remember A
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nb=bits(n);
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r=1;
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#ifdef MR_COUNT_OPS
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fpc=fpa=fpx=0;
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#endif
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for (i=nb-2;i>=0;i--)
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{
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r*=r;
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r*=g(A,A,Qx,Qy);
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if (bit(n,i))
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r*=g(A,P,Qx,Qy);
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}
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#ifdef MR_COUNT_OPS
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cout << "Miller fpc= " << fpc << endl;
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cout << "Miller fpa= " << fpa << endl;
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cout << "Miller fpx= " << fpx << endl;
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fpa=fpc=fpx=0;
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#endif
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if (r.iszero()) return FALSE;
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w=r;
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r.conj();
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r/=w; // r^(p^6-1)
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r.mark_as_unitary();
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w=r;
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r.powq(X); r.powq(X);
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r*=w; // r^[(p^6-1)*(p^2+1)]
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// New idea..
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//1. Calculate a=r^(6x-5)
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//2. Calculate b=a^p using Frobenius
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//3. Calculate c=ab
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//4. Calculate r^p, r^{p^2} and r^{p^3} using Frobenius
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//5. Calculate final exponentiation as
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// r^{p^3}.[c.(r^p)^2.r^{p^2}]^(6x^2+1).c.(r^p.r)^9.a.r^4
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//
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// Does not require multi-exponentiation, but total exponent length is the same.
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// Also does not need precomputation (x is sparse).
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//
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if (x>0) a=pow(r,6*x-5);
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else a=inverse(pow(r,5-6*x)); // inverses are "free" for unitary values
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b=a; b.powq(X);
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b*=a;
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rp=r; rp.powq(X);
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a*=b;
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w=r; w*=w; w*=w;
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a*=w;
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c=rp*r; w=c; w*=w; w*=w; w*=w; w*=c;
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a*=w; w=(rp*rp);
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rp.powq(X);
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w*=(b*rp);
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c=pow(w,x);
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r=w*pow(c,6*x); // r=pow(w,6*x*x+1); // time consuming bit...
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rp.powq(X); a*=rp;
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r*=a;
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#ifdef MR_COUNT_OPS
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cout << "FE fpc= " << fpc << endl;
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cout << "FE fpa= " << fpa << endl;
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cout << "FE fpx= " << fpx << endl;
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fpa=fpc=fpx=0;
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#endif
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res= real(r); // compress to half size...
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return TRUE;
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}
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//
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// ecap(.) function
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//
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BOOL ecap(ECn2& P,ECn& Q,Big& x,ZZn2 &X,ZZn6& r)
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{
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BOOL Ok;
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Big xx,yy;
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ZZn Qx,Qy;
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P.norm();
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Q.get(xx,yy); Qx=xx; Qy=yy;
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Ok=fast_pairing(P,Qx,Qy,x,X,r);
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if (Ok) return TRUE;
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return FALSE;
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}
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//
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// Hash functions
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//
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Big H1(char *string)
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{ // Hash a zero-terminated string to a number < modulus
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Big h,p;
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char s[HASH_LEN];
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int i,j;
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sha256 sh;
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shs256_init(&sh);
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for (i=0;;i++)
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{
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if (string[i]==0) break;
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shs256_process(&sh,string[i]);
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}
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shs256_hash(&sh,s);
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p=get_modulus();
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h=1; j=0; i=1;
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forever
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{
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h*=256;
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if (j==HASH_LEN) {h+=i++; j=0;}
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else h+=s[j++];
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if (h>=p) break;
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}
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h%=p;
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return h;
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}
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Big H2(ZZn6 x)
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{ // Hash an Fp6 to a big number
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sha256 sh;
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ZZn2 u,v,w;
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ZZn h,l;
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Big a,hash,p,xx[6];
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char s[HASH_LEN];
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int i,j,m;
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shs256_init(&sh);
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x.get(u,v,w);
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u.get(l,h);
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xx[0]=l; xx[1]=h;
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v.get(l,h);
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xx[2]=l; xx[3]=h;
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w.get(l,h);
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xx[4]=l; xx[5]=h;
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for (i=0;i<6;i++)
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{
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a=xx[i];
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while (a>0)
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{
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m=a%256;
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shs256_process(&sh,m);
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a/=256;
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}
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}
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shs256_hash(&sh,s);
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hash=from_binary(HASH_LEN,s);
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return hash;
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}
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// Hash and map a Server Identity to a curve point E_(Fp2)
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ECn2 hash_and_map2(char *ID)
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{
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int i;
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ECn2 S;
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ZZn2 X;
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Big x0=H1(ID);
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forever
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{
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x0+=1;
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X.set((ZZn)0,(ZZn)x0);
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//cout << "X= " << X << endl;
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if (!S.set(X)) continue;
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break;
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}
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// cout << "S= " << S << endl;
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return S;
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}
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// Hash and map a Client Identity to a curve point E_(Fp) of order q
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ECn hash_and_map(char *ID)
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{
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ECn Q;
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Big x0=H1(ID);
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while (!Q.set(x0,x0)) x0+=1;
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return Q;
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}
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int main()
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{
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miracl* mip=&precision;
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ECn Alice,Bob,sA,sB;
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ECn2 Server,sS;
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ZZn6 sp,ap,bp,res;
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ZZn2 X;
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Big a,b,s,ss,p,q,x,y,B,cf,t;
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int i,bits,A;
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time_t seed;
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mip->IOBASE=16;
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x= (char *)"600000000000219B"; // found by BN.CPP
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p=36*pow(x,4)-36*pow(x,3)+24*x*x-6*x+1;
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t=6*x*x+1;
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q=p+1-t;
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cf=p-1+t;
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modulo(p);
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set_frobenius_constant(X);
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cout << "Initialised... " << endl;
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time(&seed);
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irand((long)seed);
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#ifdef AFFINE
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ecurve((Big)0,(Big)3,p,MR_AFFINE);
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#endif
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#ifdef PROJECTIVE
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ecurve((Big)0,(Big)3,p,MR_PROJECTIVE);
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#endif
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mip->IOBASE=16;
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mip->TWIST=MR_SEXTIC_D; // map Server to point on twisted curve E(Fp2)
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ss=rand(q); // TA's super-secret
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cout << "Mapping Server ID to point" << endl;
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Server=hash_and_map2((char *)"Server");
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cofactor(Server,X,t); // fast multiplication by cf
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cout << "Mapping Alice & Bob ID's to points" << endl;
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Alice=hash_and_map((char *)"Alice");
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Bob= hash_and_map((char *)"Robert");
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cout << "Alice, Bob and the Server visit Trusted Authority" << endl;
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sS=ss*Server;
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sA=ss*Alice;
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sB=ss*Bob;
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cout << "Alice and Server Key Exchange" << endl;
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a=rand(q); // Alice's random number
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s=rand(q); // Server's random number
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// for (i=0;i<1000;i++)
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if (!ecap(Server,sA,x,X,res)) cout << "Trouble" << endl;
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if (powl(res,q)!=(ZZn6)1)
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{
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cout << "Wrong group order - aborting" << endl;
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exit(0);
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}
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ap=powl(res,a);
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if (!ecap(sS,Alice,x,X,res)) cout << "Trouble" << endl;
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if (powl(res,q)!=(ZZn6)1)
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{
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cout << "Wrong group order - aborting" << endl;
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exit(0);
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}
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sp=powl(res,s);
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cout << "Alice Key= " << H2(powl(sp,a)) << endl;
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cout << "Server Key= " << H2(powl(ap,s)) << endl;
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cout << "Bob and Server Key Exchange" << endl;
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b=rand(q); // Bob's random number
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s=rand(q); // Server's random number
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if (!ecap(Server,sB,x,X,res)) cout << "Trouble" << endl;
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if (powl(res,q)!=(ZZn6)1)
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{
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cout << "Wrong group order - aborting" << endl;
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exit(0);
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}
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bp=powl(res,b);
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if (!ecap(sS,Bob,x,X,res)) cout << "Trouble" << endl;
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if (powl(res,q)!=(ZZn6)1)
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{
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cout << "Wrong group order - aborting" << endl;
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exit(0);
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}
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sp=powl(res,s);
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cout << "Bob's Key= " << H2(powl(sp,b)) << endl;
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cout << "Server Key= " << H2(powl(bp,s)) << endl;
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return 0;
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}
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