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     uint8_t x;
  17
  18     // 16 rounds
  19     for (unsigned int j = 0; j < sizeof(grasshopper_lvec) / sizeof(grasshopper_lvec[0]); j++) {
  20
  21         // An LFSR with 16 elements from GF(2^8)
  22         x = w->b[15];    // since lvec[15] = 1
  23
  24         for (int i = 14; i >= 0; i--) {
  25             w->b[i + 1] = w->b[i];
  26             x ^= grasshopper_galois_mul(w->b[i], grasshopper_lvec[i]);
  27         }
  28         w->b[0] = x;
  29     }
  30 }
  31
  32 static GRASSHOPPER_INLINE void grasshopper_l_inv(grasshopper_w128_t* w) {
  33     uint8_t x;
  34
  35     // 16 rounds
  36     for (unsigned int j = 0; j < sizeof(grasshopper_lvec) / sizeof(grasshopper_lvec[0]); j++) {
  37
  38         x = w->b[0];
  39         for (int i = 0; i < 15; i++) {
  40             w->b[i] = w->b[i + 1];
  41             x ^= grasshopper_galois_mul(w->b[i], grasshopper_lvec[i]);
  42         }
  43         w->b[15] = x;
  44     }
  45 }
  46
  47 // key setup
  48
  49 void grasshopper_set_encrypt_key(grasshopper_round_keys_t* subkeys, const grasshopper_key_t* key) {
  50     grasshopper_w128_t c, x, y, z;
  51
  52     for (int i = 0; i < 16; i++) {
  53         // this will be have to changed for little-endian systems
  54         x.b[i] = key->k.b[i];
  55         y.b[i] = key->k.b[i + 16];
  56     }
  57
  58     grasshopper_copy128(&subkeys->k[0], &x);
  59     grasshopper_copy128(&subkeys->k[1], &y);
  60
  61     for (int i = 1; i <= 32; i++) {
  62
  63         // C Value
  64         grasshopper_zero128(&c);
  65         c.b[15] = (uint8_t) i;        // load round in lsb
  66         grasshopper_l(&c);
  67
  68         grasshopper_plus128(&z, &x, &c);
  69         grasshopper_convert128(&z, grasshopper_pi);
  70         grasshopper_l(&z);
  71         grasshopper_append128(&z, &y);
  72
  73         grasshopper_copy128(&y, &x);
  74         grasshopper_copy128(&x, &z);
  75
  76         if ((i & 7) == 0) {
  77             int k = i >> 2;
  78             grasshopper_copy128(&subkeys->k[k], &x);
  79             grasshopper_copy128(&subkeys->k[k + 1], &y);
  80         }
  81     }
  82
  83     // security++
  84     grasshopper_zero128(&c);
  85     grasshopper_zero128(&x);
  86     grasshopper_zero128(&y);
  87     grasshopper_zero128(&z);
  88 }
  89
  90 void grasshopper_set_decrypt_key(grasshopper_round_keys_t* subkeys, const grasshopper_key_t* key) {
  91     grasshopper_set_encrypt_key(subkeys, key);
  92
  93     for (int i = 1; i < 10; i++) {
  94         grasshopper_l_inv(&subkeys->k[i]);
  95     }
  96 }
  97
  98 void grasshopper_encrypt_block(grasshopper_round_keys_t* subkeys, grasshopper_w128_t* source,
  99                                grasshopper_w128_t* target, grasshopper_w128_t* buffer) {
 100     grasshopper_copy128(target, source);
 101
 102     for (int i = 0; i < 9; i++) {
 103         grasshopper_append128(target, &subkeys->k[i]);
 104         grasshopper_append128multi(buffer, target, grasshopper_pil_enc128);
 105     }
 106
 107     grasshopper_append128(target, &subkeys->k[9]);
 108 }
 109
 110 void grasshopper_encrypt_block2(grasshopper_round_keys_t* subkeys, grasshopper_w128_t* source,
 111                                 grasshopper_w128_t* target) {
 112     grasshopper_w128_t buffer;
 113     grasshopper_encrypt_block(subkeys, source, target, &buffer);
 114     grasshopper_zero128(&buffer);
 115 }
 116
 117 void grasshopper_decrypt_block(grasshopper_round_keys_t* subkeys, grasshopper_w128_t* source,
 118                                grasshopper_w128_t* target, grasshopper_w128_t* buffer) {
 119     grasshopper_copy128(target, source);
 120
 121     grasshopper_append128multi(buffer, target, grasshopper_l_dec128);
 122
 123     for (int i = 9; i > 1; i--) {
 124         grasshopper_append128(target, &subkeys->k[i]);
 125         grasshopper_append128multi(buffer, target, grasshopper_pil_dec128);
 126     }
 127
 128     grasshopper_append128(target, &subkeys->k[1]);
 129     grasshopper_convert128(target, grasshopper_pi_inv);
 130     grasshopper_append128(target, &subkeys->k[0]);
 131 }
 132
 133 void grasshopper_decrypt_block2(grasshopper_round_keys_t* subkeys, grasshopper_w128_t* source,
 134                                 grasshopper_w128_t* target) {
 135     grasshopper_w128_t buffer;
 136     grasshopper_decrypt_block(subkeys, source, target, &buffer);
 137     grasshopper_zero128(&buffer);
 138 }
 139
 140 #if defined(__cplusplus)
 141 }
 142 #endif