41 lines
938 B
Plaintext
41 lines
938 B
Plaintext
# Edwards curve arithmetic
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edwards_add(p,a,d, X1,Y1,Z1,T1, X2,Y2,Z2,T2, X3,Y3,Z3,T3) mod(p) {
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A = X1*X2;
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B = Y1*Y2;
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C = d*T1*T2;
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D = Z1*Z2;
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E = (X1+Y1)*(X2+Y2);
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E = E - A - B;
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F = D - C;
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G = D + C;
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H = B - a*A;
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X3 = E*F;
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Y3 = G*H;
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Z3 = F*G;
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T3 = E*H;
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}
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edwards_sel(s, X1,Y1,Z1,T1, X2,Y2,Z2,T2, X3,Y3,Z3,T3){
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X3 = s != 0 ? X1 : X2;
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Y3 = s != 0 ? Y1 : Y2;
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Z3 = s != 0 ? Z1 : Z2;
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T3 = s != 0 ? T1 : T2;
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}
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edwards_new(x,y,z,t, X,Y,Z,T) {
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X = x;
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Y = y;
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Z = z;
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T = t;
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}
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edwards_scale(p,a,d, s, X1,Y1,Z1,T1, X3,Y3,Z3,T3) {
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X2,Y2,Z2,T2 = edwards_new(X1,Y1,Z1,T1);
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X4,Y4,Z4,T4 = edwards_new( 0, 1, 1, 0);
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X3,Y3,Z3,T3 = edwards_sel(s % 2, X2,Y2,Z2,T2, X4,Y4,Z4,T4);
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k = s >> 1; j = p >> 1;
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while(j != 0){
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X2,Y2,Z2,T2 = edwards_add(p,a,d, X2,Y2,Z2,T2, X2,Y2,Z2,T2);
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X4,Y4,Z4,T4 = edwards_add(p,a,d, X2,Y2,Z2,T2, X3,Y3,Z3,T3);
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X3,Y3,Z3,T3 = edwards_sel(k % 2, X4,Y4,Z4,T4, X3,Y3,Z3,T3);
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k = k >> 1; j = j >> 1;
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}
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}
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