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107 lines
2.4 KiB
C
107 lines
2.4 KiB
C
/* gen164/5/ed_add_double_scalarmult.c
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**
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*/
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#include "all.h"
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#include <ed25519.h>
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#include <ge.h>
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#include "ge_additions.h"
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/* functions
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*/
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u3_noun
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u3qc_add_double_scalarmult(u3_atom a,
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u3_atom a_point,
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u3_atom b,
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u3_atom b_point)
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{
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c3_y met_w;
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met_w = u3r_met(3, a);
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if (met_w > 32) {
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return u3m_bail(c3__exit);
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}
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c3_y a_y[32];
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memset(a_y, 0, 32);
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u3r_bytes(0, met_w, a_y, a);
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met_w = u3r_met(3, a_point);
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if (met_w > 32) {
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return u3m_bail(c3__exit);
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}
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c3_y a_point_y[32];
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memset(a_point_y, 0, 32);
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u3r_bytes(0, met_w, a_point_y, a_point);
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met_w = u3r_met(3, b);
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if (met_w > 32) {
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return u3m_bail(c3__exit);
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}
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c3_y b_y[32];
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memset(b_y, 0, 32);
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u3r_bytes(0, met_w, b_y, b);
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met_w = u3r_met(3, b_point);
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if (met_w > 32) {
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return u3m_bail(c3__exit);
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}
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c3_y b_point_y[32];
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memset(b_point_y, 0, 32);
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u3r_bytes(0, met_w, b_point_y, b_point);
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ge_p3 A;
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if (ge_frombytes_negate_vartime(&A, a_point_y) != 0) {
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return u3m_bail(c3__exit);
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}
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ge_p3 B;
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if (ge_frombytes_negate_vartime(&B, b_point_y) != 0) {
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return u3m_bail(c3__exit);
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}
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// Undo the negation from above. See add_scalar.c in the ed25519 distro.
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fe_neg(A.X, A.X);
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fe_neg(A.T, A.T);
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fe_neg(B.X, B.X);
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fe_neg(B.T, B.T);
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// Perform the multiplications of a*A and b*B
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ge_p3 a_result, b_result;
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ge_scalarmult(&a_result, a_y, &A);
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ge_scalarmult(&b_result, b_y, &B);
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// Sum those two points
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ge_cached b_result_cached;
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ge_p3_to_cached(&b_result_cached, &b_result);
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ge_p1p1 sum;
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ge_add(&sum, &a_result, &b_result_cached);
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ge_p3 final_result;
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ge_p1p1_to_p3(&final_result, &sum);
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c3_y output_y[32];
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ge_p3_tobytes(output_y, &final_result);
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return u3i_bytes(32, output_y);
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}
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u3_noun
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u3wee_add_double_scalarmult(u3_noun cor)
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{
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u3_noun a, b, c, d;
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if ( (c3n == u3r_mean(cor, u3x_sam_2, &a,
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u3x_sam_6, &b,
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u3x_sam_14, &c,
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u3x_sam_15, &d, 0)) ||
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(c3n == u3ud(a)) ||
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(c3n == u3ud(b)) ||
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(c3n == u3ud(c)) )
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{
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return u3m_bail(c3__exit);
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} else {
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return u3qc_add_double_scalarmult(a, b, c, d);
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}
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}
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