-rw-r--r-- 2199 lib25519-20220726/crypto_dh/x25519/ref10/fe_mul121666.c raw
#include "fe.h"
#include "crypto_int64.h"

/*
h = f * 121666
Can overlap h with f.

Preconditions:
   |f| bounded by 1.1*2^26,1.1*2^25,1.1*2^26,1.1*2^25,etc.

Postconditions:
   |h| bounded by 1.1*2^25,1.1*2^24,1.1*2^25,1.1*2^24,etc.
*/

void fe_mul121666(fe h,fe f)
{
  crypto_int32 f0 = f[0];
  crypto_int32 f1 = f[1];
  crypto_int32 f2 = f[2];
  crypto_int32 f3 = f[3];
  crypto_int32 f4 = f[4];
  crypto_int32 f5 = f[5];
  crypto_int32 f6 = f[6];
  crypto_int32 f7 = f[7];
  crypto_int32 f8 = f[8];
  crypto_int32 f9 = f[9];
  crypto_int64 h0 = f0 * (crypto_int64) 121666;
  crypto_int64 h1 = f1 * (crypto_int64) 121666;
  crypto_int64 h2 = f2 * (crypto_int64) 121666;
  crypto_int64 h3 = f3 * (crypto_int64) 121666;
  crypto_int64 h4 = f4 * (crypto_int64) 121666;
  crypto_int64 h5 = f5 * (crypto_int64) 121666;
  crypto_int64 h6 = f6 * (crypto_int64) 121666;
  crypto_int64 h7 = f7 * (crypto_int64) 121666;
  crypto_int64 h8 = f8 * (crypto_int64) 121666;
  crypto_int64 h9 = f9 * (crypto_int64) 121666;
  crypto_int64 carry0;
  crypto_int64 carry1;
  crypto_int64 carry2;
  crypto_int64 carry3;
  crypto_int64 carry4;
  crypto_int64 carry5;
  crypto_int64 carry6;
  crypto_int64 carry7;
  crypto_int64 carry8;
  crypto_int64 carry9;

  carry9 = (h9 + (crypto_int64) (1<<24)) >> 25; h0 += carry9 * 19; h9 -= carry9 << 25;
  carry1 = (h1 + (crypto_int64) (1<<24)) >> 25; h2 += carry1; h1 -= carry1 << 25;
  carry3 = (h3 + (crypto_int64) (1<<24)) >> 25; h4 += carry3; h3 -= carry3 << 25;
  carry5 = (h5 + (crypto_int64) (1<<24)) >> 25; h6 += carry5; h5 -= carry5 << 25;
  carry7 = (h7 + (crypto_int64) (1<<24)) >> 25; h8 += carry7; h7 -= carry7 << 25;

  carry0 = (h0 + (crypto_int64) (1<<25)) >> 26; h1 += carry0; h0 -= carry0 << 26;
  carry2 = (h2 + (crypto_int64) (1<<25)) >> 26; h3 += carry2; h2 -= carry2 << 26;
  carry4 = (h4 + (crypto_int64) (1<<25)) >> 26; h5 += carry4; h4 -= carry4 << 26;
  carry6 = (h6 + (crypto_int64) (1<<25)) >> 26; h7 += carry6; h6 -= carry6 << 26;
  carry8 = (h8 + (crypto_int64) (1<<25)) >> 26; h9 += carry8; h8 -= carry8 << 26;

  h[0] = h0;
  h[1] = h1;
  h[2] = h2;
  h[3] = h3;
  h[4] = h4;
  h[5] = h5;
  h[6] = h6;
  h[7] = h7;
  h[8] = h8;
  h[9] = h9;
}