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Revert "Postpone from_hash()"

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Use proper reduction, and don't mask the high bit, so that
H2C-Curve25519-SHA512-Elligator-Clear can be implemented if required
This commit is contained in:
Frank Denis 2019-05-02 13:40:01 +02:00
parent 56d93ffe62
commit 4b7e497a92
5 changed files with 67 additions and 5 deletions
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20
src/libsodium/crypto_core/ed25519/core_ed25519.c
View File

@ -70,13 +70,21 @@ crypto_core_ed25519_from_uniform(unsigned char *p, const unsigned char *r)
return 0;
}
int
crypto_core_ed25519_from_hash(unsigned char *p, const unsigned char *h)
{
ge25519_from_hash(p, h);
return 0;
}
void
crypto_core_ed25519_random(unsigned char *p)
{
unsigned char r[crypto_core_ed25519_UNIFORMBYTES];
unsigned char h[crypto_core_ed25519_HASHBYTES];
randombytes_buf(r, sizeof r);
(void) crypto_core_ed25519_from_uniform(p, r);
randombytes_buf(h, sizeof h);
(void) crypto_core_ed25519_from_hash(p, h);
}
void
@ -204,6 +212,12 @@ crypto_core_ed25519_uniformbytes(void)
return crypto_core_ed25519_UNIFORMBYTES;
}
size_t
crypto_core_ed25519_hashbytes(void)
{
return crypto_core_ed25519_HASHBYTES;
}
size_t
crypto_core_ed25519_scalarbytes(void)
{

26
src/libsodium/crypto_core/ed25519/ref10/ed25519_ref10.c
View File

@ -2605,6 +2605,32 @@ ge25519_from_uniform(unsigned char s[32], const unsigned char r[32])
ge25519_elligator2(s, x_sign);
}
void
ge25519_from_hash(unsigned char s[32], const unsigned char h[64])
{
unsigned char fl[32];
unsigned char gl[32];
fe25519 fe_f;
fe25519 fe_g;
int i;
unsigned char x_sign;
x_sign = h[63] & 0x80;
memcpy(fl, &h[0], 32);
memcpy(gl, &h[32], 32);
fl[31] &= 0x7f;
gl[31] &= 0x7f;
fe25519_frombytes(fe_f, fl);
fe25519_frombytes(fe_g, gl);
fe_f[0] += (h[0 + 31] >> 7) * 19;
fe_g[0] += (h[32 + 31] >> 7) * 19;
for (i = 0; i < sizeof (fe25519) / sizeof fe_f[0]; i++) {
fe_f[i] += 38 * fe_g[i];
}
fe25519_tobytes(s, fe_f);
ge25519_elligator2(s, x_sign);
}
/* Ristretto group */
static int

8
src/libsodium/include/sodium/crypto_core_ed25519.h
View File

@ -16,6 +16,10 @@ size_t crypto_core_ed25519_bytes(void);
SODIUM_EXPORT
size_t crypto_core_ed25519_uniformbytes(void);
#define crypto_core_ed25519_HASHBYTES 64
SODIUM_EXPORT
size_t crypto_core_ed25519_hashbytes(void);
#define crypto_core_ed25519_SCALARBYTES 32
SODIUM_EXPORT
size_t crypto_core_ed25519_scalarbytes(void);
@ -42,6 +46,10 @@ SODIUM_EXPORT
int crypto_core_ed25519_from_uniform(unsigned char *p, const unsigned char *r)
__attribute__ ((nonnull));
SODIUM_EXPORT
int crypto_core_ed25519_from_hash(unsigned char *p, const unsigned char *h)
__attribute__ ((nonnull));
SODIUM_EXPORT
void crypto_core_ed25519_random(unsigned char *p)
__attribute__ ((nonnull));

2
src/libsodium/include/sodium/private/ed25519_ref10.h
View File

@ -110,6 +110,8 @@ int ge25519_has_small_order(const unsigned char s[32]);
void ge25519_from_uniform(unsigned char s[32], const unsigned char r[32]);
void ge25519_from_hash(unsigned char s[32], const unsigned char h[64]);
/*
Ristretto group
*/

16
test/default/core_ed25519.c
View File

@ -44,16 +44,17 @@ add_l64(unsigned char * const S)
int
main(void)
{
unsigned char *r;
unsigned char *h, *r;
unsigned char *p, *p2, *p3;
unsigned char *sc, *sc2, *sc3;
unsigned char *sc64;
char *hex;
unsigned int i, j;
h = (unsigned char *) sodium_malloc(crypto_core_ed25519_HASHBYTES);
r = (unsigned char *) sodium_malloc(crypto_core_ed25519_UNIFORMBYTES);
p = (unsigned char *) sodium_malloc(crypto_core_ed25519_BYTES);
for (i = 0; i < 1000; i++) {
for (i = 0; i < 500; i++) {
randombytes_buf(r, crypto_core_ed25519_UNIFORMBYTES);
if (crypto_core_ed25519_from_uniform(p, r) != 0) {
printf("crypto_core_ed25519_from_uniform() failed\n");
@ -62,6 +63,14 @@ main(void)
printf("crypto_core_ed25519_from_uniform() returned an invalid point\n");
}
randombytes_buf(h, crypto_core_ed25519_HASHBYTES);
if (crypto_core_ed25519_from_hash(p, h) != 0) {
printf("crypto_core_ed25519_from_hash() failed\n");
}
if (crypto_core_ed25519_is_valid_point(p) == 0) {
printf("crypto_core_ed25519_from_hash() returned an invalid point\n");
}
crypto_core_ed25519_random(p);
if (crypto_core_ed25519_is_valid_point(p) == 0) {
printf("crypto_core_ed25519_random() returned an invalid point\n");
@ -387,6 +396,7 @@ main(void)
sodium_free(p2);
sodium_free(p);
sodium_free(r);
sodium_free(h);
assert(crypto_core_ed25519_BYTES == crypto_core_ed25519_bytes());
assert(crypto_core_ed25519_SCALARBYTES == crypto_core_ed25519_scalarbytes());
@ -394,6 +404,8 @@ main(void)
assert(crypto_core_ed25519_NONREDUCEDSCALARBYTES >= crypto_core_ed25519_SCALARBYTES);
assert(crypto_core_ed25519_UNIFORMBYTES == crypto_core_ed25519_uniformbytes());
assert(crypto_core_ed25519_UNIFORMBYTES >= crypto_core_ed25519_BYTES);
assert(crypto_core_ed25519_HASHBYTES == crypto_core_ed25519_hashbytes());
assert(crypto_core_ed25519_HASHBYTES >= 2 * crypto_core_ed25519_BYTES);
printf("OK\n");