50 lines
2.0 KiB
C
50 lines
2.0 KiB
C
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#ifndef ISOGENY_H_
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#define ISOGENY_H_
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// Computes [2^e](X:Z) on Montgomery curve with projective
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// constant via e repeated doublings.
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void sike_xDBLe(
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const point_proj_t P, point_proj_t Q, const f2elm_t A24plus,
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const f2elm_t C24, size_t e);
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// Simultaneous doubling and differential addition.
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void sike_xDBLADD(
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point_proj_t P, point_proj_t Q, const f2elm_t xPQ,
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const f2elm_t A24);
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// Tripling of a Montgomery point in projective coordinates (X:Z).
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void sike_xTPL(
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const point_proj_t P, point_proj_t Q, const f2elm_t A24minus,
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const f2elm_t A24plus);
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// Computes [3^e](X:Z) on Montgomery curve with projective constant
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// via e repeated triplings.
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void sike_xTPLe(
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const point_proj_t P, point_proj_t Q, const f2elm_t A24minus,
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const f2elm_t A24plus, size_t e);
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// Given the x-coordinates of P, Q, and R, returns the value A
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// corresponding to the Montgomery curve E_A: y^2=x^3+A*x^2+x such that R=Q-P on E_A.
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void sike_get_A(
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const f2elm_t xP, const f2elm_t xQ, const f2elm_t xR, f2elm_t A);
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// Computes the j-invariant of a Montgomery curve with projective constant.
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void sike_j_inv(
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const f2elm_t A, const f2elm_t C, f2elm_t jinv);
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// Computes the corresponding 4-isogeny of a projective Montgomery
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// point (X4:Z4) of order 4.
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void sike_get_4_isog(
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const point_proj_t P, f2elm_t A24plus, f2elm_t C24, f2elm_t* coeff);
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// Computes the corresponding 3-isogeny of a projective Montgomery
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// point (X3:Z3) of order 3.
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void sike_get_3_isog(
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const point_proj_t P, f2elm_t A24minus, f2elm_t A24plus,
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f2elm_t* coeff);
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// Computes the 3-isogeny R=phi(X:Z), given projective point (X3:Z3)
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// of order 3 on a Montgomery curve and a point P with coefficients given in coeff.
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void sike_eval_3_isog(
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point_proj_t Q, f2elm_t* coeff);
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// Evaluates the isogeny at the point (X:Z) in the domain of the isogeny.
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void sike_eval_4_isog(
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point_proj_t P, f2elm_t* coeff);
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// 3-way simultaneous inversion
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void sike_inv_3_way(
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f2elm_t z1, f2elm_t z2, f2elm_t z3);
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#endif // ISOGENY_H_
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