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+ ge_is_less_than_p()

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This commit is contained in:
Frank Denis 2017-10-23 00:00:25 +02:00
parent 9acbc82a6d
commit 15649c5849
2 changed files with 21 additions and 2 deletions
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21
src/libsodium/crypto_core/curve25519/ref10/curve25519_ref10.c
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@ -2126,6 +2126,23 @@ ge_is_on_main_subgroup(const ge_p3 *p)
return fe_iszero(pl.X);
}
int
ge_is_less_than_p(const unsigned char *s)
{
unsigned char c;
unsigned char d;
unsigned int i;
c = (s[31] & 0x7f) ^ 0x7f;
for (i = 30; i > 0; i--) {
c |= s[i] ^ 0xff;
}
c = (((unsigned int) c) - 1U) >> 8;
d = (0xed - 1U - (unsigned int) s[0]) >> 8;
return 1 - (c & d & 1);
}
int
ge_has_small_order(const unsigned char s[32])
{
@ -2153,11 +2170,11 @@ ge_has_small_order(const unsigned char s[32])
{ 0xec, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x7f },
/* p (order 4) */
/* p (=0, order 4) */
{ 0xed, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x7f },
/* p+1 (order 2) */
/* p+1 (=1, order 1) */
{ 0xee, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x7f }

2
src/libsodium/include/sodium/private/curve25519_ref10.h
View File

@ -104,6 +104,7 @@ typedef struct {
#define ge_scalarmult_base crypto_core_curve25519_ref10_ge_scalarmult_base
#define ge_double_scalarmult_vartime crypto_core_curve25519_ref10_ge_double_scalarmult_vartime
#define ge_scalarmult_vartime crypto_core_curve25519_ref10_ge_scalarmult_vartime
#define ge_is_less_than_p crypto_core_curve25519_ref10_ge_is_less_than_p
#define ge_is_on_curve crypto_core_curve25519_ref10_ge_is_on_curve
#define ge_is_on_main_subgroup crypto_core_curve25519_ref10_ge_is_on_main_subgroup
#define ge_has_small_order crypto_core_curve25519_ref10_ge_has_small_order
@ -120,6 +121,7 @@ extern void ge_scalarmult_base(ge_p3 *,const unsigned char *);
extern void ge_double_scalarmult_vartime(ge_p2 *,const unsigned char *,const ge_p3 *,const unsigned char *);
extern void ge_scalarmult(ge_p3 *,const unsigned char *,const ge_p3 *);
extern void ge_scalarmult_vartime(ge_p3 *,const unsigned char *,const ge_p3 *);
extern int ge_is_less_than_p(const unsigned char *s);
extern int ge_is_on_curve(const ge_p3 *p);
extern int ge_is_on_main_subgroup(const ge_p3 *p);
extern int ge_has_small_order(const unsigned char s[32]);