release/src/router/libsodium/src/libsodium/crypto_sign/ed25519/ref10/fe_frombytes.c

   1 #include "fe.h"
   2 #include "crypto_int64.h"
   3 #include "crypto_uint64.h"
   4
   5 static crypto_uint64 load_3(const unsigned char *in)
   6 {
   7   crypto_uint64 result;
   8   result = (crypto_uint64) in[0];
   9   result |= ((crypto_uint64) in[1]) << 8;
  10   result |= ((crypto_uint64) in[2]) << 16;
  11   return result;
  12 }
  13
  14 static crypto_uint64 load_4(const unsigned char *in)
  15 {
  16   crypto_uint64 result;
  17   result = (crypto_uint64) in[0];
  18   result |= ((crypto_uint64) in[1]) << 8;
  19   result |= ((crypto_uint64) in[2]) << 16;
  20   result |= ((crypto_uint64) in[3]) << 24;
  21   return result;
  22 }
  23
  24 /*
  25 Ignores top bit of h.
  26 */
  27
  28 void fe_frombytes(fe h,const unsigned char *s)
  29 {
  30   crypto_int64 h0 = load_4(s);
  31   crypto_int64 h1 = load_3(s + 4) << 6;
  32   crypto_int64 h2 = load_3(s + 7) << 5;
  33   crypto_int64 h3 = load_3(s + 10) << 3;
  34   crypto_int64 h4 = load_3(s + 13) << 2;
  35   crypto_int64 h5 = load_4(s + 16);
  36   crypto_int64 h6 = load_3(s + 20) << 7;
  37   crypto_int64 h7 = load_3(s + 23) << 5;
  38   crypto_int64 h8 = load_3(s + 26) << 4;
  39   crypto_int64 h9 = (load_3(s + 29) & 8388607) << 2;
  40   crypto_int64 carry0;
  41   crypto_int64 carry1;
  42   crypto_int64 carry2;
  43   crypto_int64 carry3;
  44   crypto_int64 carry4;
  45   crypto_int64 carry5;
  46   crypto_int64 carry6;
  47   crypto_int64 carry7;
  48   crypto_int64 carry8;
  49   crypto_int64 carry9;
  50
  51   carry9 = (h9 + (crypto_int64) (1<<24)) >> 25; h0 += carry9 * 19; h9 -= carry9 << 25;
  52   carry1 = (h1 + (crypto_int64) (1<<24)) >> 25; h2 += carry1; h1 -= carry1 << 25;
  53   carry3 = (h3 + (crypto_int64) (1<<24)) >> 25; h4 += carry3; h3 -= carry3 << 25;
  54   carry5 = (h5 + (crypto_int64) (1<<24)) >> 25; h6 += carry5; h5 -= carry5 << 25;
  55   carry7 = (h7 + (crypto_int64) (1<<24)) >> 25; h8 += carry7; h7 -= carry7 << 25;
  56
  57   carry0 = (h0 + (crypto_int64) (1<<25)) >> 26; h1 += carry0; h0 -= carry0 << 26;
  58   carry2 = (h2 + (crypto_int64) (1<<25)) >> 26; h3 += carry2; h2 -= carry2 << 26;
  59   carry4 = (h4 + (crypto_int64) (1<<25)) >> 26; h5 += carry4; h4 -= carry4 << 26;
  60   carry6 = (h6 + (crypto_int64) (1<<25)) >> 26; h7 += carry6; h6 -= carry6 << 26;
  61   carry8 = (h8 + (crypto_int64) (1<<25)) >> 26; h9 += carry8; h8 -= carry8 << 26;
  62
  63   h[0] = h0;
  64   h[1] = h1;
  65   h[2] = h2;
  66   h[3] = h3;
  67   h[4] = h4;
  68   h[5] = h5;
  69   h[6] = h6;
  70   h[7] = h7;
  71   h[8] = h8;
  72   h[9] = h9;
  73 }