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NIIBE Yutaka
2014-04-17 13:41:55 +09:00
parent 62a59b56fe
commit e25f50eabc
7 changed files with 78 additions and 109 deletions
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19
src/ecc-edwards.c
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@@ -140,28 +140,27 @@ point_double (ptc *X, const ptc *A)
mod25638_sqr (d, A->y);
/* E = aC; where a = -1 */
/* Compute: E - D = -(C+D) : Y3_tmp */
/* Compute: D - E = D + C : Y3_tmp */
mod25638_add (X->y, e, d);
mod25638_neg (X->y, X->y);
/* Compute: F = E + D = D - C; where a = -1 : E */
mod25638_sub (e, d, e);
/* Compute: -F = -(E + D) = C - D; where a = -1 : E */
mod25638_sub (e, e, d);
/* Compute: H = Z1^2 : D */
mod25638_sqr (d, A->z);
/* Compute: J = F - 2*H : D */
/* Compute: -J = 2*H - F : D */
mod25638_add (d, d, d);
mod25638_sub (d, e, d);
mod25638_add (d, d, e);
/* Compute: X3 = (B-C-D)*J = (B+Y3_tmp)*J */
mod25638_add (X->x, b, X->y);
/* Compute: X3 = (B-C-D)*J = -J*(C+D-B) = -J*(Y3_tmp-B) */
mod25638_sub (X->x, X->y, b);
mod25638_mul (X->x, X->x, d);
/* Compute: Y3 = F*(E-D) = F*Y3_tmp */
/* Compute: Y3 = -F*(D-E) = -F*Y3_tmp */
mod25638_mul (X->y, X->y, e);
/* Z3 = F*J */
/* Z3 = -F*-J */
mod25638_mul (X->z, e, d);
}