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69 lines
2.0 KiB
C
69 lines
2.0 KiB
C
#include "fe25519.h"
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#include "sc25519.h"
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#include "ge25519.h"
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/* Multiples of the base point in Niels' representation */
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static const ge25519_niels ge25519_base_multiples_niels[] = {
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#ifdef SMALLTABLES
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#include "ge25519_base_niels_smalltables.data"
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#else
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#include "ge25519_base_niels.data"
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#endif
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};
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/* d */
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static const fe25519 ecd = {{0x75EB4DCA135978A3, 0x00700A4D4141D8AB, 0x8CC740797779E898, 0x52036CEE2B6FFE73}};
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void ge25519_scalarmult_base(ge25519_p3 *r, const sc25519 *s)
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{
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signed char b[64];
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int i;
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ge25519_niels t;
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fe25519 d;
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sc25519_window4(b,s);
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#ifdef SMALLTABLES
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ge25519_p1p1 tp1p1;
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choose_t((ge25519_niels *)r, 0, (signed long long) b[1], ge25519_base_multiples_niels);
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fe25519_sub(&d, &r->y, &r->x);
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fe25519_add(&r->y, &r->y, &r->x);
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r->x = d;
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r->t = r->z;
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fe25519_setint(&r->z,2);
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for(i=3;i<64;i+=2)
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{
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choose_t(&t, (unsigned long long) i/2, (signed long long) b[i], ge25519_base_multiples_niels);
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ge25519_nielsadd2(r, &t);
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}
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ge25519_dbl_p1p1(&tp1p1,(ge25519_p2 *)r);
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ge25519_p1p1_to_p2((ge25519_p2 *)r, &tp1p1);
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ge25519_dbl_p1p1(&tp1p1,(ge25519_p2 *)r);
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ge25519_p1p1_to_p2((ge25519_p2 *)r, &tp1p1);
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ge25519_dbl_p1p1(&tp1p1,(ge25519_p2 *)r);
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ge25519_p1p1_to_p2((ge25519_p2 *)r, &tp1p1);
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ge25519_dbl_p1p1(&tp1p1,(ge25519_p2 *)r);
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ge25519_p1p1_to_p3(r, &tp1p1);
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choose_t(&t, (unsigned long long) 0, (signed long long) b[0], ge25519_base_multiples_niels);
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fe25519_mul(&t.t2d, &t.t2d, &ecd);
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ge25519_nielsadd2(r, &t);
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for(i=2;i<64;i+=2)
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{
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choose_t(&t, (unsigned long long) i/2, (signed long long) b[i], ge25519_base_multiples_niels);
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ge25519_nielsadd2(r, &t);
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}
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#else
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choose_t((ge25519_niels *)r, 0, (signed long long) b[0], ge25519_base_multiples_niels);
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fe25519_sub(&d, &r->y, &r->x);
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fe25519_add(&r->y, &r->y, &r->x);
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r->x = d;
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r->t = r->z;
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fe25519_setint(&r->z,2);
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for(i=1;i<64;i++)
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{
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choose_t(&t, (unsigned long long) i, (signed long long) b[i], ge25519_base_multiples_niels);
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ge25519_nielsadd2(r, &t);
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}
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#endif
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}
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