diff --git a/src/field.h b/src/field.h index b338047b5d..6e348693cd 100644 --- a/src/field.h +++ b/src/field.h @@ -110,7 +110,14 @@ static void secp256k1_fe_get_hex(char *r64, const secp256k1_fe_t *a); /** Convert a 64-character hexadecimal string to a field element. */ static int secp256k1_fe_set_hex(secp256k1_fe_t *r, const char *a64); +/** Convert a field element to the storage type. */ +static void secp256k1_fe_to_storage(secp256k1_fe_storage_t *r, const secp256k1_fe_t*); + +/** Convert a field element back from the storage type. */ +static void secp256k1_fe_from_storage(secp256k1_fe_t *r, const secp256k1_fe_storage_t*); + /** If flag is true, set *r equal to *a; otherwise leave it. Constant-time. */ static void secp256k1_fe_cmov(secp256k1_fe_t *r, const secp256k1_fe_t *a, int flag); +static void secp256k1_fe_storage_cmov(secp256k1_fe_storage_t *r, const secp256k1_fe_storage_t *a, int flag); #endif diff --git a/src/field_10x26.h b/src/field_10x26.h index e3c243649f..1f855285e1 100644 --- a/src/field_10x26.h +++ b/src/field_10x26.h @@ -37,4 +37,10 @@ typedef struct { #define SECP256K1_FE_CONST(d7, d6, d5, d4, d3, d2, d1, d0) {SECP256K1_FE_CONST_INNER((d7), (d6), (d5), (d4), (d3), (d2), (d1), (d0))} #endif +typedef struct { + uint32_t n[8]; +} secp256k1_fe_storage_t; + +#define SECP256K1_FE_STORAGE_CONST(d7, d6, d5, d4, d3, d2, d1, d0) {{ (d0), (d1), (d2), (d3), (d4), (d5), (d6), (d7) }} + #endif diff --git a/src/field_10x26_impl.h b/src/field_10x26_impl.h index 3f942b0d47..d35bb3ca79 100644 --- a/src/field_10x26_impl.h +++ b/src/field_10x26_impl.h @@ -1083,4 +1083,47 @@ static void secp256k1_fe_cmov(secp256k1_fe_t *r, const secp256k1_fe_t *a, int fl #endif } +static inline void secp256k1_fe_storage_cmov(secp256k1_fe_storage_t *r, const secp256k1_fe_storage_t *a, int flag) { + uint32_t mask0 = flag + ~((uint32_t)0), mask1 = ~mask0; + r->n[0] = (r->n[0] & mask0) | (a->n[0] & mask1); + r->n[1] = (r->n[1] & mask0) | (a->n[1] & mask1); + r->n[2] = (r->n[2] & mask0) | (a->n[2] & mask1); + r->n[3] = (r->n[3] & mask0) | (a->n[3] & mask1); + r->n[4] = (r->n[4] & mask0) | (a->n[4] & mask1); + r->n[5] = (r->n[5] & mask0) | (a->n[5] & mask1); + r->n[6] = (r->n[6] & mask0) | (a->n[6] & mask1); + r->n[7] = (r->n[7] & mask0) | (a->n[7] & mask1); +} + +static void secp256k1_fe_to_storage(secp256k1_fe_storage_t *r, const secp256k1_fe_t *a) { +#ifdef VERIFY + VERIFY_CHECK(a->normalized); +#endif + r->n[0] = a->n[0] | a->n[1] << 26; + r->n[1] = a->n[1] >> 6 | a->n[2] << 20; + r->n[2] = a->n[2] >> 12 | a->n[3] << 14; + r->n[3] = a->n[3] >> 18 | a->n[4] << 8; + r->n[4] = a->n[4] >> 24 | a->n[5] << 2 | a->n[6] << 28; + r->n[5] = a->n[6] >> 4 | a->n[7] << 22; + r->n[6] = a->n[7] >> 10 | a->n[8] << 16; + r->n[7] = a->n[8] >> 16 | a->n[9] << 10; +} + +static inline void secp256k1_fe_from_storage(secp256k1_fe_t *r, const secp256k1_fe_storage_t *a) { + r->n[0] = a->n[0] & 0x3FFFFFFUL; + r->n[1] = a->n[0] >> 26 | ((a->n[1] << 6) & 0x3FFFFFFUL); + r->n[2] = a->n[1] >> 20 | ((a->n[2] << 12) & 0x3FFFFFFUL); + r->n[3] = a->n[2] >> 14 | ((a->n[3] << 18) & 0x3FFFFFFUL); + r->n[4] = a->n[3] >> 8 | ((a->n[4] << 24) & 0x3FFFFFFUL); + r->n[5] = (a->n[4] >> 2) & 0x3FFFFFFUL; + r->n[6] = a->n[4] >> 28 | ((a->n[5] << 4) & 0x3FFFFFFUL); + r->n[7] = a->n[5] >> 22 | ((a->n[6] << 10) & 0x3FFFFFFUL); + r->n[8] = a->n[6] >> 16 | ((a->n[7] << 16) & 0x3FFFFFFUL); + r->n[9] = a->n[7] >> 10; +#ifdef VERIFY + r->magnitude = 1; + r->normalized = 1; +#endif +} + #endif diff --git a/src/field_5x52.h b/src/field_5x52.h index 13934d0b2d..7b38324143 100644 --- a/src/field_5x52.h +++ b/src/field_5x52.h @@ -32,4 +32,15 @@ typedef struct { #define SECP256K1_FE_CONST(d7, d6, d5, d4, d3, d2, d1, d0) {SECP256K1_FE_CONST_INNER((d7), (d6), (d5), (d4), (d3), (d2), (d1), (d0))} #endif +typedef struct { + uint64_t n[4]; +} secp256k1_fe_storage_t; + +#define SECP256K1_FE_STORAGE_CONST(d7, d6, d5, d4, d3, d2, d1, d0) {{ \ + (d0) | ((uint64_t)(d1)) << 32, \ + (d2) | ((uint64_t)(d3)) << 32, \ + (d4) | ((uint64_t)(d5)) << 32, \ + (d6) | ((uint64_t)(d7)) << 32 \ +}} + #endif diff --git a/src/field_5x52_impl.h b/src/field_5x52_impl.h index 34b4d49c34..1b4af2cb2b 100644 --- a/src/field_5x52_impl.h +++ b/src/field_5x52_impl.h @@ -413,4 +413,34 @@ static void secp256k1_fe_cmov(secp256k1_fe_t *r, const secp256k1_fe_t *a, int fl #endif } +static inline void secp256k1_fe_storage_cmov(secp256k1_fe_storage_t *r, const secp256k1_fe_storage_t *a, int flag) { + uint64_t mask0 = flag + ~((uint64_t)0), mask1 = ~mask0; + r->n[0] = (r->n[0] & mask0) | (a->n[0] & mask1); + r->n[1] = (r->n[1] & mask0) | (a->n[1] & mask1); + r->n[2] = (r->n[2] & mask0) | (a->n[2] & mask1); + r->n[3] = (r->n[3] & mask0) | (a->n[3] & mask1); +} + +static void secp256k1_fe_to_storage(secp256k1_fe_storage_t *r, const secp256k1_fe_t *a) { +#ifdef VERIFY + VERIFY_CHECK(a->normalized); +#endif + r->n[0] = a->n[0] | a->n[1] << 52; + r->n[1] = a->n[1] >> 12 | a->n[2] << 40; + r->n[2] = a->n[2] >> 24 | a->n[3] << 28; + r->n[3] = a->n[3] >> 36 | a->n[4] << 16; +} + +static inline void secp256k1_fe_from_storage(secp256k1_fe_t *r, const secp256k1_fe_storage_t *a) { + r->n[0] = a->n[0] & 0xFFFFFFFFFFFFFULL; + r->n[1] = a->n[0] >> 52 | ((a->n[1] << 12) & 0xFFFFFFFFFFFFFULL); + r->n[2] = a->n[1] >> 40 | ((a->n[2] << 24) & 0xFFFFFFFFFFFFFULL); + r->n[3] = a->n[2] >> 28 | ((a->n[3] << 36) & 0xFFFFFFFFFFFFFULL); + r->n[4] = a->n[3] >> 16; +#ifdef VERIFY + r->magnitude = 1; + r->normalized = 1; +#endif +} + #endif diff --git a/src/tests.c b/src/tests.c index 21eb696892..13e9d4cefc 100644 --- a/src/tests.c +++ b/src/tests.c @@ -627,6 +627,42 @@ int check_fe_inverse(const secp256k1_fe_t *a, const secp256k1_fe_t *ai) { return check_fe_equal(&x, &one); } +void run_field_convert(void) { + static const unsigned char b32[32] = { + 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, + 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, + 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, + 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x40 + }; + static const char *c64 = "0001020304050607111213141516171822232425262728293334353637383940"; + static const secp256k1_fe_storage_t fes = SECP256K1_FE_STORAGE_CONST( + 0x00010203UL, 0x04050607UL, 0x11121314UL, 0x15161718UL, + 0x22232425UL, 0x26272829UL, 0x33343536UL, 0x37383940UL + ); + static const secp256k1_fe_t fe = SECP256K1_FE_CONST( + 0x00010203UL, 0x04050607UL, 0x11121314UL, 0x15161718UL, + 0x22232425UL, 0x26272829UL, 0x33343536UL, 0x37383940UL + ); + secp256k1_fe_t fe2; + unsigned char b322[32]; + char c642[64]; + secp256k1_fe_storage_t fes2; + /* Check conversions to fe. */ + CHECK(secp256k1_fe_set_b32(&fe2, b32)); + CHECK(secp256k1_fe_equal_var(&fe, &fe2)); + CHECK(secp256k1_fe_set_hex(&fe2, c64)); + CHECK(secp256k1_fe_equal_var(&fe, &fe2)); + secp256k1_fe_from_storage(&fe2, &fes); + CHECK(secp256k1_fe_equal_var(&fe, &fe2)); + /* Check conversion from fe. */ + secp256k1_fe_get_b32(b322, &fe); + CHECK(memcmp(b322, b32, 32) == 0); + secp256k1_fe_get_hex(c642, &fe); + CHECK(memcmp(c642, c64, 64) == 0); + secp256k1_fe_to_storage(&fes2, &fe); + CHECK(memcmp(&fes2, &fes, sizeof(fes)) == 0); +} + void run_field_misc(void) { const unsigned char f32_5[32] = { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, @@ -1668,6 +1704,7 @@ int main(int argc, char **argv) { run_field_inv_var(); run_field_inv_all_var(); run_field_misc(); + run_field_convert(); run_sqr(); run_sqrt();