Contents

#include "fe.h"

int x25519_ref10_scalarmult(uint8_t *q, const uint8_t *n, const uint8_t *p)
{
  uint8_t e[32];
  unsigned int i;
  fe x1;
  fe x2;
  fe z2;
  fe x3;
  fe z3;
  fe tmp0;
  fe tmp1;
  int pos;
  unsigned int swap;
  unsigned int b;

  for (i = 0;i < 32;++i) e[i] = n[i];
  e[0] &= 248;
  e[31] &= 127;
  e[31] |= 64;

  fe_frombytes(x1,p);
  fe_1(x2);
  fe_0(z2);
  fe_copy(x3,x1);
  fe_1(z3);

  swap = 0;
  for (pos = 254;pos >= 0;--pos) {
    b = e[pos / 8] >> (pos & 7);
    b &= 1;
    swap ^= b;
    fe_cswap(x2,x3,swap);
    fe_cswap(z2,z3,swap);
    swap = b;
#include "montgomery.h"
  }
  fe_cswap(x2,x3,swap);
  fe_cswap(z2,z3,swap);

  fe_invert(z2,z2);
  fe_mul(x2,x2,z2);
  fe_tobytes(q,x2);
  return 0;
}

Version data entries

1 entries across 1 versions & 1 rubygems

Version	Path
x25519-0.1.0	ext/x25519/ref10/scalarmult.c