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- #ifndef _SECP256K1_FIELD_REPR_IMPL_H_
- #define _SECP256K1_FIELD_REPR_IMPL_H_
-
- #include <assert.h>
- #include <string.h>
- #include "../num.h"
- #include "../field.h"
-
- #if defined(USE_FIELD_5X52_ASM)
- #include "field_5x52_asm.h"
- #elif defined(USE_FIELD_5X52_INT128)
- #include "field_5x52_int128.h"
- #else
- #error "Please select field_5x52 implementation"
- #endif
-
- /** Implements arithmetic modulo FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFE FFFFFC2F,
- * represented as 5 uint64_t's in base 2^52. The values are allowed to contain >52 each. In particular,
- * each FieldElem has a 'magnitude' associated with it. Internally, a magnitude M means each element
- * is at most M*(2^53-1), except the most significant one, which is limited to M*(2^49-1). All operations
- * accept any input with magnitude at most M, and have different rules for propagating magnitude to their
- * output.
- */
-
- void static secp256k1_fe_inner_start(void) {}
- void static secp256k1_fe_inner_stop(void) {}
-
- void static secp256k1_fe_normalize(secp256k1_fe_t *r) {
- uint64_t c;
- c = r->n[0];
- uint64_t t0 = c & 0xFFFFFFFFFFFFFULL;
- c = (c >> 52) + r->n[1];
- uint64_t t1 = c & 0xFFFFFFFFFFFFFULL;
- c = (c >> 52) + r->n[2];
- uint64_t t2 = c & 0xFFFFFFFFFFFFFULL;
- c = (c >> 52) + r->n[3];
- uint64_t t3 = c & 0xFFFFFFFFFFFFFULL;
- c = (c >> 52) + r->n[4];
- uint64_t t4 = c & 0x0FFFFFFFFFFFFULL;
- c >>= 48;
-
- // The following code will not modify the t's if c is initially 0.
- c = c * 0x1000003D1ULL + t0;
- t0 = c & 0xFFFFFFFFFFFFFULL;
- c = (c >> 52) + t1;
- t1 = c & 0xFFFFFFFFFFFFFULL;
- c = (c >> 52) + t2;
- t2 = c & 0xFFFFFFFFFFFFFULL;
- c = (c >> 52) + t3;
- t3 = c & 0xFFFFFFFFFFFFFULL;
- c = (c >> 52) + t4;
- t4 = c & 0x0FFFFFFFFFFFFULL;
- assert((c >> 48) == 0);
-
- // Subtract p if result >= p
- uint64_t mask = -(int64_t)((t4 < 0xFFFFFFFFFFFFULL) | (t3 < 0xFFFFFFFFFFFFFULL) | (t2 < 0xFFFFFFFFFFFFFULL) | (t1 < 0xFFFFFFFFFFFFFULL) | (t0 < 0xFFFFEFFFFFC2FULL));
- t4 &= mask;
- t3 &= mask;
- t2 &= mask;
- t1 &= mask;
- t0 -= (~mask & 0xFFFFEFFFFFC2FULL);
-
- // push internal variables back
- r->n[0] = t0; r->n[1] = t1; r->n[2] = t2; r->n[3] = t3; r->n[4] = t4;
-
- #ifdef VERIFY
- r->magnitude = 1;
- r->normalized = 1;
- #endif
- }
-
- void static inline secp256k1_fe_set_int(secp256k1_fe_t *r, int a) {
- r->n[0] = a;
- r->n[1] = r->n[2] = r->n[3] = r->n[4] = 0;
- #ifdef VERIFY
- r->magnitude = 1;
- r->normalized = 1;
- #endif
- }
-
- // TODO: not constant time!
- int static inline secp256k1_fe_is_zero(const secp256k1_fe_t *a) {
- #ifdef VERIFY
- assert(a->normalized);
- #endif
- return (a->n[0] == 0 && a->n[1] == 0 && a->n[2] == 0 && a->n[3] == 0 && a->n[4] == 0);
- }
-
- int static inline secp256k1_fe_is_odd(const secp256k1_fe_t *a) {
- #ifdef VERIFY
- assert(a->normalized);
- #endif
- return a->n[0] & 1;
- }
-
- // TODO: not constant time!
- int static inline secp256k1_fe_equal(const secp256k1_fe_t *a, const secp256k1_fe_t *b) {
- #ifdef VERIFY
- assert(a->normalized);
- assert(b->normalized);
- #endif
- return (a->n[0] == b->n[0] && a->n[1] == b->n[1] && a->n[2] == b->n[2] && a->n[3] == b->n[3] && a->n[4] == b->n[4]);
- }
-
- void static secp256k1_fe_set_b32(secp256k1_fe_t *r, const unsigned char *a) {
- r->n[0] = r->n[1] = r->n[2] = r->n[3] = r->n[4] = 0;
- for (int i=0; i<32; i++) {
- for (int j=0; j<2; j++) {
- int limb = (8*i+4*j)/52;
- int shift = (8*i+4*j)%52;
- r->n[limb] |= (uint64_t)((a[31-i] >> (4*j)) & 0xF) << shift;
- }
- }
- #ifdef VERIFY
- r->magnitude = 1;
- r->normalized = 1;
- #endif
- }
-
- /** Convert a field element to a 32-byte big endian value. Requires the input to be normalized */
- void static secp256k1_fe_get_b32(unsigned char *r, const secp256k1_fe_t *a) {
- #ifdef VERIFY
- assert(a->normalized);
- #endif
- for (int i=0; i<32; i++) {
- int c = 0;
- for (int j=0; j<2; j++) {
- int limb = (8*i+4*j)/52;
- int shift = (8*i+4*j)%52;
- c |= ((a->n[limb] >> shift) & 0xF) << (4 * j);
- }
- r[31-i] = c;
- }
- }
-
- void static inline secp256k1_fe_negate(secp256k1_fe_t *r, const secp256k1_fe_t *a, int m) {
- #ifdef VERIFY
- assert(a->magnitude <= m);
- r->magnitude = m + 1;
- r->normalized = 0;
- #endif
- r->n[0] = 0xFFFFEFFFFFC2FULL * (m + 1) - a->n[0];
- r->n[1] = 0xFFFFFFFFFFFFFULL * (m + 1) - a->n[1];
- r->n[2] = 0xFFFFFFFFFFFFFULL * (m + 1) - a->n[2];
- r->n[3] = 0xFFFFFFFFFFFFFULL * (m + 1) - a->n[3];
- r->n[4] = 0x0FFFFFFFFFFFFULL * (m + 1) - a->n[4];
- }
-
- void static inline secp256k1_fe_mul_int(secp256k1_fe_t *r, int a) {
- #ifdef VERIFY
- r->magnitude *= a;
- r->normalized = 0;
- #endif
- r->n[0] *= a;
- r->n[1] *= a;
- r->n[2] *= a;
- r->n[3] *= a;
- r->n[4] *= a;
- }
-
- void static inline secp256k1_fe_add(secp256k1_fe_t *r, const secp256k1_fe_t *a) {
- #ifdef VERIFY
- r->magnitude += a->magnitude;
- r->normalized = 0;
- #endif
- r->n[0] += a->n[0];
- r->n[1] += a->n[1];
- r->n[2] += a->n[2];
- r->n[3] += a->n[3];
- r->n[4] += a->n[4];
- }
-
- void static secp256k1_fe_mul(secp256k1_fe_t *r, const secp256k1_fe_t *a, const secp256k1_fe_t *b) {
- #ifdef VERIFY
- assert(a->magnitude <= 8);
- assert(b->magnitude <= 8);
- r->magnitude = 1;
- r->normalized = 0;
- #endif
- secp256k1_fe_mul_inner(a->n, b->n, r->n);
- }
-
- void static secp256k1_fe_sqr(secp256k1_fe_t *r, const secp256k1_fe_t *a) {
- #ifdef VERIFY
- assert(a->magnitude <= 8);
- r->magnitude = 1;
- r->normalized = 0;
- #endif
- secp256k1_fe_sqr_inner(a->n, r->n);
- }
-
- #endif
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