lib/block/rc5.c

   1 /*
   2  * Written in 2013 by Gregor Pintar <grpintar@gmail.com>
   3  *
   4  * To the extent possible under law, the author(s) have dedicated
   5  * all copyright and related and neighboring rights to this software
   6  * to the public domain worldwide.
   7  *
   8  * This software is distributed without any warranty.
   9  *
  10  * You should have received a copy of the CC0 Public Domain Dedication.
  11  * If not, see <http://creativecommons.org/publicdomain/zero/1.0/>.
  12  */
  13
  14 #include <stdint.h>
  15 #include <stdlib.h>
  16 #include <limits.h>
  17
  18 #include <kripto/cast.h>
  19 #include <kripto/loadstore.h>
  20 #include <kripto/rotate.h>
  21 #include <kripto/memwipe.h>
  22 #include <kripto/block.h>
  23 #include <kripto/desc/block.h>
  24 #include <kripto/object/block.h>
  25
  26 #include <kripto/block/rc5.h>
  27
  28 struct kripto_block
  29 {
  30         struct kripto_block_object obj;
  31         unsigned int r;
  32         size_t size;
  33         uint32_t *k;
  34 };
  35
  36 static void rc5_setup
  37 (
  38         kripto_block *s,
  39         const uint8_t *key,
  40         unsigned int key_len
  41 )
  42 {
  43         unsigned int i;
  44         unsigned int j;
  45         unsigned int k;
  46         uint32_t a;
  47         uint32_t b;
  48         uint32_t x[64];
  49         const unsigned int ls = (key_len + 3) >> 2;
  50
  51         for(i = 0; i < ls; i++) x[i] = 0;
  52
  53         for(j = key_len - 1; j != UINT_MAX; j--)
  54                 x[j >> 2] = (x[j >> 2] << 8) | key[j];
  55
  56         *s->k = 0xB7E15163;
  57         for(i = 1; i < ((s->r + 1) << 1); i++)
  58                 s->k[i] = s->k[i - 1] + 0x9E3779B9;
  59
  60         a = b = i = j = k = 0;
  61         while(k < (s->r + 1) * 6)
  62         {
  63                 a = s->k[i] = ROL32_03(s->k[i] + a + b);
  64                 b = x[j] = ROL32(x[j] + a + b, a + b);
  65                 if(++i == ((s->r + 1) << 1)) i = 0;
  66                 if(++j == ls) j = 0;
  67                 k++;
  68         }
  69
  70         kripto_memwipe(x, ls << 2);
  71         kripto_memwipe(&a, sizeof(uint32_t));
  72         kripto_memwipe(&b, sizeof(uint32_t));
  73 }
  74
  75 static void rc5_encrypt(const kripto_block *s, const void *pt, void *ct)
  76 {
  77         uint32_t a;
  78         uint32_t b;
  79         unsigned int i = 2;
  80
  81         a = LOAD32L(CU8(pt));
  82         b = LOAD32L(CU8(pt) + 4);
  83
  84         a += s->k[0];
  85         b += s->k[1];
  86
  87         while(i <= s->r << 1)
  88         {
  89                 a ^= b; a = ROL32(a, b) + s->k[i++];
  90                 b ^= a; b = ROL32(b, a) + s->k[i++];
  91         }
  92
  93         STORE32L(a, U8(ct));
  94         STORE32L(b, U8(ct) + 4);
  95 }
  96
  97 static void rc5_decrypt(const kripto_block *s, const void *ct, void *pt)
  98 {
  99         uint32_t a;
 100         uint32_t b;
 101         unsigned int i = (s->r + 1) << 1;
 102
 103         a = LOAD32L(CU8(ct));
 104         b = LOAD32L(CU8(ct) + 4);
 105
 106         while(i > 2)
 107         {
 108                 b -= s->k[--i]; b = ROR32(b, a) ^ a;
 109                 a -= s->k[--i]; a = ROR32(a, b) ^ b;
 110         }
 111
 112         b -= s->k[1];
 113         a -= s->k[0];
 114
 115         STORE32L(a, U8(pt));
 116         STORE32L(b, U8(pt) + 4);
 117 }
 118
 119 static kripto_block *rc5_create
 120 (
 121         unsigned int r,
 122         const void *key,
 123         unsigned int key_len
 124 )
 125 {
 126         kripto_block *s;
 127
 128         if(!r) r = 12;
 129
 130         s = malloc(sizeof(kripto_block) + ((r + 1) << 3));
 131         if(!s) return 0;
 132
 133         s->obj.desc = kripto_block_rc5;
 134         s->size = sizeof(kripto_block) + ((r + 1) << 3);
 135         s->r = r;
 136         s->k = (uint32_t *)((uint8_t *)s + sizeof(kripto_block));
 137
 138         rc5_setup(s, key, key_len);
 139
 140         return s;
 141 }
 142
 143 static void rc5_destroy(kripto_block *s)
 144 {
 145         kripto_memwipe(s, s->size);
 146         free(s);
 147 }
 148
 149 static kripto_block *rc5_recreate
 150 (
 151         kripto_block *s,
 152         unsigned int r,
 153         const void *key,
 154         unsigned int key_len
 155 )
 156 {
 157         if(!r) r = 12;
 158
 159         if(sizeof(kripto_block) + ((r + 1) << 3) > s->size)
 160         {
 161                 rc5_destroy(s);
 162                 s = rc5_create(r, key, key_len);
 163         }
 164         else
 165         {
 166                 s->r = r;
 167                 rc5_setup(s, key, key_len);
 168         }
 169
 170         return s;
 171 }
 172
 173 static const kripto_block_desc rc5 =
 174 {
 175         &rc5_create,
 176         &rc5_recreate,
 177         0, /* tweak */
 178         &rc5_encrypt,
 179         &rc5_decrypt,
 180         &rc5_destroy,
 181         8, /* block size */
 182         255, /* max key */
 183         0 /* max tweak */
 184 };
 185
 186 const kripto_block_desc *const kripto_block_rc5 = &rc5;