gost_grasshopper_core.c

   1 /*
   2  * Maxim Tishkov 2016
   3  * This file is distributed under the same license as OpenSSL
   4  */
   5
   6 #if defined(__cplusplus)
   7 extern "C" {
   8 #endif
   9
  10 #include "gost_grasshopper_core.h"
  11 #include "gost_grasshopper_math.h"
  12 #include "gost_grasshopper_precompiled.h"
  13 #include "gost_grasshopper_defines.h"
  14
  15 static GRASSHOPPER_INLINE void grasshopper_l(grasshopper_w128_t* w) {
  16     unsigned int j;
  17     int i;
  18
  19     // 16 rounds
  20     for (j = 0; j < sizeof(grasshopper_lvec) / sizeof(grasshopper_lvec[0]); j++) {
  21         uint8_t x;
  22
  23         // An LFSR with 16 elements from GF(2^8)
  24         x = w->b[15];    // since lvec[15] = 1
  25
  26         for (i = 14; i >= 0; i--) {
  27             w->b[i + 1] = w->b[i];
  28             x ^= grasshopper_galois_mul(w->b[i], grasshopper_lvec[i]);
  29         }
  30         w->b[0] = x;
  31     }
  32 }
  33
  34 static GRASSHOPPER_INLINE void grasshopper_l_inv(grasshopper_w128_t* w) {
  35     unsigned int j;
  36     int i;
  37
  38     // 16 rounds
  39     for (j = 0; j < sizeof(grasshopper_lvec) / sizeof(grasshopper_lvec[0]); j++) {
  40         uint8_t x = w->b[0];
  41         for (i = 0; i < 15; i++) {
  42             w->b[i] = w->b[i + 1];
  43             x ^= grasshopper_galois_mul(w->b[i], grasshopper_lvec[i]);
  44         }
  45         w->b[15] = x;
  46     }
  47 }
  48
  49 // key setup
  50
  51 void grasshopper_set_encrypt_key(grasshopper_round_keys_t* subkeys, const grasshopper_key_t* key) {
  52     grasshopper_w128_t c, x, y, z;
  53     int i;
  54
  55     for (i = 0; i < 16; i++) {
  56         // this will be have to changed for little-endian systems
  57         x.b[i] = key->k.b[i];
  58         y.b[i] = key->k.b[i + 16];
  59     }
  60
  61     grasshopper_copy128(&subkeys->k[0], &x);
  62     grasshopper_copy128(&subkeys->k[1], &y);
  63
  64     for (i = 1; i <= 32; i++) {
  65
  66         // C Value
  67         grasshopper_zero128(&c);
  68         c.b[15] = (uint8_t) i;        // load round in lsb
  69         grasshopper_l(&c);
  70
  71         grasshopper_plus128(&z, &x, &c);
  72         grasshopper_convert128(&z, grasshopper_pi);
  73         grasshopper_l(&z);
  74         grasshopper_append128(&z, &y);
  75
  76         grasshopper_copy128(&y, &x);
  77         grasshopper_copy128(&x, &z);
  78
  79         if ((i & 7) == 0) {
  80             int k = i >> 2;
  81             grasshopper_copy128(&subkeys->k[k], &x);
  82             grasshopper_copy128(&subkeys->k[k + 1], &y);
  83         }
  84     }
  85
  86     // security++
  87     grasshopper_zero128(&c);
  88     grasshopper_zero128(&x);
  89     grasshopper_zero128(&y);
  90     grasshopper_zero128(&z);
  91 }
  92
  93 void grasshopper_set_decrypt_key(grasshopper_round_keys_t* subkeys, const grasshopper_key_t* key) {
  94                 int i;
  95     grasshopper_set_encrypt_key(subkeys, key);
  96
  97     for (i = 1; i < 10; i++) {
  98         grasshopper_l_inv(&subkeys->k[i]);
  99     }
 100 }
 101
 102 void grasshopper_encrypt_block(grasshopper_round_keys_t* subkeys, grasshopper_w128_t* source,
 103                                grasshopper_w128_t* target, grasshopper_w128_t* buffer) {
 104     int i;
 105     grasshopper_copy128(target, source);
 106
 107     for (i = 0; i < 9; i++) {
 108         grasshopper_append128(target, &subkeys->k[i]);
 109         grasshopper_append128multi(buffer, target, grasshopper_pil_enc128);
 110     }
 111
 112     grasshopper_append128(target, &subkeys->k[9]);
 113 }
 114
 115 void grasshopper_decrypt_block(grasshopper_round_keys_t* subkeys, grasshopper_w128_t* source,
 116                                grasshopper_w128_t* target, grasshopper_w128_t* buffer) {
 117     int i;
 118     grasshopper_copy128(target, source);
 119
 120     grasshopper_append128multi(buffer, target, grasshopper_l_dec128);
 121
 122     for (i = 9; i > 1; i--) {
 123         grasshopper_append128(target, &subkeys->k[i]);
 124         grasshopper_append128multi(buffer, target, grasshopper_pil_dec128);
 125     }
 126
 127     grasshopper_append128(target, &subkeys->k[1]);
 128     grasshopper_convert128(target, grasshopper_pi_inv);
 129     grasshopper_append128(target, &subkeys->k[0]);
 130 }
 131
 132 #if defined(__cplusplus)
 133 }
 134 #endif