aes(7926).c 18 KB

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  1. /*
  2. This is an implementation of the AES128 algorithm, specifically ECB and CBC mode.
  3. The implementation is verified against the test vectors in:
  4. National Institute of Standards and Technology Special Publication 800-38A 2001 ED
  5. ECB-AES128
  6. ----------
  7. plain-text:
  8. 6bc1bee22e409f96e93d7e117393172a
  9. ae2d8a571e03ac9c9eb76fac45af8e51
  10. 30c81c46a35ce411e5fbc1191a0a52ef
  11. f69f2445df4f9b17ad2b417be66c3710
  12. key:
  13. 2b7e151628aed2a6abf7158809cf4f3c
  14. resulting cipher
  15. 3ad77bb40d7a3660a89ecaf32466ef97
  16. f5d3d58503b9699de785895a96fdbaaf
  17. 43b1cd7f598ece23881b00e3ed030688
  18. 7b0c785e27e8ad3f8223207104725dd4
  19. NOTE: String length must be evenly divisible by 16byte (str_len % 16 == 0)
  20. You should pad the end of the string with zeros if this is not the case.
  21. */
  22. /*****************************************************************************/
  23. /* Includes: */
  24. /*****************************************************************************/
  25. #include <stdint.h>
  26. #include <string.h> // CBC mode, for memset
  27. #include "aes.h"
  28. /*****************************************************************************/
  29. /* Defines: */
  30. /*****************************************************************************/
  31. // The number of columns comprising a state in AES. This is a constant in AES. Value=4
  32. #define Nb 4
  33. // The number of 32 bit words in a key.
  34. #define Nk 4
  35. // Key length in bytes [128 bit]
  36. #define KEYLEN 16
  37. // The number of rounds in AES Cipher.
  38. #define Nr 10
  39. // jcallan@github points out that declaring Multiply as a function
  40. // reduces code size considerably with the Keil ARM compiler.
  41. // See this link for more information: https://github.com/kokke/tiny-AES128-C/pull/3
  42. #ifndef MULTIPLY_AS_A_FUNCTION
  43. #define MULTIPLY_AS_A_FUNCTION 0
  44. #endif
  45. /*****************************************************************************/
  46. /* Private variables: */
  47. /*****************************************************************************/
  48. // state - array holding the intermediate results during decryption.
  49. typedef uint8_t state_t[4][4];
  50. static state_t* state;
  51. // The array that stores the round keys.
  52. static uint8_t RoundKey[176];
  53. // The Key input to the AES Program
  54. static const uint8_t* Key;
  55. #if defined(CBC) && CBC
  56. // Initial Vector used only for CBC mode
  57. static uint8_t* Iv;
  58. #endif
  59. // The lookup-tables are marked const so they can be placed in read-only storage instead of RAM
  60. // The numbers below can be computed dynamically trading ROM for RAM -
  61. // This can be useful in (embedded) bootloader applications, where ROM is often limited.
  62. static const uint8_t sbox[256] = {
  63. //0 1 2 3 4 5 6 7 8 9 A B C D E F
  64. 0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
  65. 0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
  66. 0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
  67. 0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
  68. 0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
  69. 0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
  70. 0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
  71. 0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
  72. 0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
  73. 0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
  74. 0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
  75. 0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
  76. 0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
  77. 0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
  78. 0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
  79. 0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16 };
  80. static const uint8_t rsbox[256] =
  81. { 0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb,
  82. 0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb,
  83. 0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e,
  84. 0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25,
  85. 0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92,
  86. 0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84,
  87. 0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06,
  88. 0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b,
  89. 0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73,
  90. 0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e,
  91. 0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b,
  92. 0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4,
  93. 0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f,
  94. 0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef,
  95. 0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61,
  96. 0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d };
  97. // The round constant word array, Rcon[i], contains the values given by
  98. // x to th e power (i-1) being powers of x (x is denoted as {02}) in the field GF(2^8)
  99. // Note that i starts at 1, not 0).
  100. static const uint8_t Rcon[255] = {
  101. 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a,
  102. 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39,
  103. 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a,
  104. 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8,
  105. 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef,
  106. 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc,
  107. 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b,
  108. 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3,
  109. 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94,
  110. 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20,
  111. 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35,
  112. 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd, 0x61, 0xc2, 0x9f,
  113. 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb, 0x8d, 0x01, 0x02, 0x04,
  114. 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63,
  115. 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91, 0x39, 0x72, 0xe4, 0xd3, 0xbd,
  116. 0x61, 0xc2, 0x9f, 0x25, 0x4a, 0x94, 0x33, 0x66, 0xcc, 0x83, 0x1d, 0x3a, 0x74, 0xe8, 0xcb };
  117. /*****************************************************************************/
  118. /* Private functions: */
  119. /*****************************************************************************/
  120. static uint8_t getSBoxValue(uint8_t num)
  121. {
  122. return sbox[num];
  123. }
  124. static uint8_t getSBoxInvert(uint8_t num)
  125. {
  126. return rsbox[num];
  127. }
  128. // This function produces Nb(Nr+1) round keys. The round keys are used in each round to decrypt the states.
  129. static void KeyExpansion(void)
  130. {
  131. uint32_t i, j, k;
  132. uint8_t tempa[4]; // Used for the column/row operations
  133. // The first round key is the key itself.
  134. for(i = 0; i < Nk; ++i)
  135. {
  136. RoundKey[(i * 4) + 0] = Key[(i * 4) + 0];
  137. RoundKey[(i * 4) + 1] = Key[(i * 4) + 1];
  138. RoundKey[(i * 4) + 2] = Key[(i * 4) + 2];
  139. RoundKey[(i * 4) + 3] = Key[(i * 4) + 3];
  140. }
  141. // All other round keys are found from the previous round keys.
  142. for(; (i < (Nb * (Nr + 1))); ++i)
  143. {
  144. for(j = 0; j < 4; ++j)
  145. {
  146. tempa[j]=RoundKey[(i-1) * 4 + j];
  147. }
  148. if (i % Nk == 0)
  149. {
  150. // This function rotates the 4 bytes in a word to the left once.
  151. // [a0,a1,a2,a3] becomes [a1,a2,a3,a0]
  152. // Function RotWord()
  153. {
  154. k = tempa[0];
  155. tempa[0] = tempa[1];
  156. tempa[1] = tempa[2];
  157. tempa[2] = tempa[3];
  158. tempa[3] = k;
  159. }
  160. // SubWord() is a function that takes a four-byte input word and
  161. // applies the S-box to each of the four bytes to produce an output word.
  162. // Function Subword()
  163. {
  164. tempa[0] = getSBoxValue(tempa[0]);
  165. tempa[1] = getSBoxValue(tempa[1]);
  166. tempa[2] = getSBoxValue(tempa[2]);
  167. tempa[3] = getSBoxValue(tempa[3]);
  168. }
  169. tempa[0] = tempa[0] ^ Rcon[i/Nk];
  170. }
  171. else if (Nk > 6 && i % Nk == 4)
  172. {
  173. // Function Subword()
  174. {
  175. tempa[0] = getSBoxValue(tempa[0]);
  176. tempa[1] = getSBoxValue(tempa[1]);
  177. tempa[2] = getSBoxValue(tempa[2]);
  178. tempa[3] = getSBoxValue(tempa[3]);
  179. }
  180. }
  181. RoundKey[i * 4 + 0] = RoundKey[(i - Nk) * 4 + 0] ^ tempa[0];
  182. RoundKey[i * 4 + 1] = RoundKey[(i - Nk) * 4 + 1] ^ tempa[1];
  183. RoundKey[i * 4 + 2] = RoundKey[(i - Nk) * 4 + 2] ^ tempa[2];
  184. RoundKey[i * 4 + 3] = RoundKey[(i - Nk) * 4 + 3] ^ tempa[3];
  185. }
  186. }
  187. // This function adds the round key to state.
  188. // The round key is added to the state by an XOR function.
  189. static void AddRoundKey(uint8_t round)
  190. {
  191. uint8_t i,j;
  192. for(i=0;i<4;++i)
  193. {
  194. for(j = 0; j < 4; ++j)
  195. {
  196. (*state)[i][j] ^= RoundKey[round * Nb * 4 + i * Nb + j];
  197. }
  198. }
  199. }
  200. // The SubBytes Function Substitutes the values in the
  201. // state matrix with values in an S-box.
  202. static void SubBytes(void)
  203. {
  204. uint8_t i, j;
  205. for(i = 0; i < 4; ++i)
  206. {
  207. for(j = 0; j < 4; ++j)
  208. {
  209. (*state)[j][i] = getSBoxValue((*state)[j][i]);
  210. }
  211. }
  212. }
  213. // The ShiftRows() function shifts the rows in the state to the left.
  214. // Each row is shifted with different offset.
  215. // Offset = Row number. So the first row is not shifted.
  216. static void ShiftRows(void)
  217. {
  218. uint8_t temp;
  219. // Rotate first row 1 columns to left
  220. temp = (*state)[0][1];
  221. (*state)[0][1] = (*state)[1][1];
  222. (*state)[1][1] = (*state)[2][1];
  223. (*state)[2][1] = (*state)[3][1];
  224. (*state)[3][1] = temp;
  225. // Rotate second row 2 columns to left
  226. temp = (*state)[0][2];
  227. (*state)[0][2] = (*state)[2][2];
  228. (*state)[2][2] = temp;
  229. temp = (*state)[1][2];
  230. (*state)[1][2] = (*state)[3][2];
  231. (*state)[3][2] = temp;
  232. // Rotate third row 3 columns to left
  233. temp = (*state)[0][3];
  234. (*state)[0][3] = (*state)[3][3];
  235. (*state)[3][3] = (*state)[2][3];
  236. (*state)[2][3] = (*state)[1][3];
  237. (*state)[1][3] = temp;
  238. }
  239. static uint8_t xtime(uint8_t x)
  240. {
  241. return ((x<<1) ^ (((x>>7) & 1) * 0x1b));
  242. }
  243. // MixColumns function mixes the columns of the state matrix
  244. static void MixColumns(void)
  245. {
  246. uint8_t i;
  247. uint8_t Tmp,Tm,t;
  248. for(i = 0; i < 4; ++i)
  249. {
  250. t = (*state)[i][0];
  251. Tmp = (*state)[i][0] ^ (*state)[i][1] ^ (*state)[i][2] ^ (*state)[i][3] ;
  252. Tm = (*state)[i][0] ^ (*state)[i][1] ; Tm = xtime(Tm); (*state)[i][0] ^= Tm ^ Tmp ;
  253. Tm = (*state)[i][1] ^ (*state)[i][2] ; Tm = xtime(Tm); (*state)[i][1] ^= Tm ^ Tmp ;
  254. Tm = (*state)[i][2] ^ (*state)[i][3] ; Tm = xtime(Tm); (*state)[i][2] ^= Tm ^ Tmp ;
  255. Tm = (*state)[i][3] ^ t ; Tm = xtime(Tm); (*state)[i][3] ^= Tm ^ Tmp ;
  256. }
  257. }
  258. // Multiply is used to multiply numbers in the field GF(2^8)
  259. #if MULTIPLY_AS_A_FUNCTION
  260. static uint8_t Multiply(uint8_t x, uint8_t y)
  261. {
  262. return (((y & 1) * x) ^
  263. ((y>>1 & 1) * xtime(x)) ^
  264. ((y>>2 & 1) * xtime(xtime(x))) ^
  265. ((y>>3 & 1) * xtime(xtime(xtime(x)))) ^
  266. ((y>>4 & 1) * xtime(xtime(xtime(xtime(x))))));
  267. }
  268. #else
  269. #define Multiply(x, y) \
  270. ( ((y & 1) * x) ^ \
  271. ((y>>1 & 1) * xtime(x)) ^ \
  272. ((y>>2 & 1) * xtime(xtime(x))) ^ \
  273. ((y>>3 & 1) * xtime(xtime(xtime(x)))) ^ \
  274. ((y>>4 & 1) * xtime(xtime(xtime(xtime(x)))))) \
  275. #endif
  276. // MixColumns function mixes the columns of the state matrix.
  277. // The method used to multiply may be difficult to understand for the inexperienced.
  278. // Please use the references to gain more information.
  279. static void InvMixColumns(void)
  280. {
  281. int i;
  282. uint8_t a,b,c,d;
  283. for(i=0;i<4;++i)
  284. {
  285. a = (*state)[i][0];
  286. b = (*state)[i][1];
  287. c = (*state)[i][2];
  288. d = (*state)[i][3];
  289. (*state)[i][0] = Multiply(a, 0x0e) ^ Multiply(b, 0x0b) ^ Multiply(c, 0x0d) ^ Multiply(d, 0x09);
  290. (*state)[i][1] = Multiply(a, 0x09) ^ Multiply(b, 0x0e) ^ Multiply(c, 0x0b) ^ Multiply(d, 0x0d);
  291. (*state)[i][2] = Multiply(a, 0x0d) ^ Multiply(b, 0x09) ^ Multiply(c, 0x0e) ^ Multiply(d, 0x0b);
  292. (*state)[i][3] = Multiply(a, 0x0b) ^ Multiply(b, 0x0d) ^ Multiply(c, 0x09) ^ Multiply(d, 0x0e);
  293. }
  294. }
  295. // The SubBytes Function Substitutes the values in the
  296. // state matrix with values in an S-box.
  297. static void InvSubBytes(void)
  298. {
  299. uint8_t i,j;
  300. for(i=0;i<4;++i)
  301. {
  302. for(j=0;j<4;++j)
  303. {
  304. (*state)[j][i] = getSBoxInvert((*state)[j][i]);
  305. }
  306. }
  307. }
  308. static void InvShiftRows(void)
  309. {
  310. uint8_t temp;
  311. // Rotate first row 1 columns to right
  312. temp=(*state)[3][1];
  313. (*state)[3][1]=(*state)[2][1];
  314. (*state)[2][1]=(*state)[1][1];
  315. (*state)[1][1]=(*state)[0][1];
  316. (*state)[0][1]=temp;
  317. // Rotate second row 2 columns to right
  318. temp=(*state)[0][2];
  319. (*state)[0][2]=(*state)[2][2];
  320. (*state)[2][2]=temp;
  321. temp=(*state)[1][2];
  322. (*state)[1][2]=(*state)[3][2];
  323. (*state)[3][2]=temp;
  324. // Rotate third row 3 columns to right
  325. temp=(*state)[0][3];
  326. (*state)[0][3]=(*state)[1][3];
  327. (*state)[1][3]=(*state)[2][3];
  328. (*state)[2][3]=(*state)[3][3];
  329. (*state)[3][3]=temp;
  330. }
  331. // Cipher is the main function that encrypts the PlainText.
  332. static void Cipher(void)
  333. {
  334. uint8_t round = 0;
  335. // Add the First round key to the state before starting the rounds.
  336. AddRoundKey(0);
  337. // There will be Nr rounds.
  338. // The first Nr-1 rounds are identical.
  339. // These Nr-1 rounds are executed in the loop below.
  340. for(round = 1; round < Nr; ++round)
  341. {
  342. SubBytes();
  343. ShiftRows();
  344. MixColumns();
  345. AddRoundKey(round);
  346. }
  347. // The last round is given below.
  348. // The MixColumns function is not here in the last round.
  349. SubBytes();
  350. ShiftRows();
  351. AddRoundKey(Nr);
  352. }
  353. static void InvCipher(void)
  354. {
  355. uint8_t round=0;
  356. // Add the First round key to the state before starting the rounds.
  357. AddRoundKey(Nr);
  358. // There will be Nr rounds.
  359. // The first Nr-1 rounds are identical.
  360. // These Nr-1 rounds are executed in the loop below.
  361. for(round=Nr-1;round>0;round--)
  362. {
  363. InvShiftRows();
  364. InvSubBytes();
  365. AddRoundKey(round);
  366. InvMixColumns();
  367. }
  368. // The last round is given below.
  369. // The MixColumns function is not here in the last round.
  370. InvShiftRows();
  371. InvSubBytes();
  372. AddRoundKey(0);
  373. }
  374. static void BlockCopy(uint8_t* output, uint8_t* input)
  375. {
  376. uint8_t i;
  377. for (i=0;i<KEYLEN;++i)
  378. {
  379. output[i] = input[i];
  380. }
  381. }
  382. /*****************************************************************************/
  383. /* Public functions: */
  384. /*****************************************************************************/
  385. #if defined(ECB) && ECB
  386. void AES128_ECB_encrypt(uint8_t* input, const uint8_t* key, uint8_t* output)
  387. {
  388. // Copy input to output, and work in-memory on output
  389. BlockCopy(output, input);
  390. state = (state_t*)output;
  391. Key = key;
  392. KeyExpansion();
  393. // The next function call encrypts the PlainText with the Key using AES algorithm.
  394. Cipher();
  395. }
  396. void AES128_ECB_decrypt(uint8_t* input, const uint8_t* key, uint8_t *output)
  397. {
  398. // Copy input to output, and work in-memory on output
  399. BlockCopy(output, input);
  400. state = (state_t*)output;
  401. // The KeyExpansion routine must be called before encryption.
  402. Key = key;
  403. KeyExpansion();
  404. InvCipher();
  405. }
  406. #endif // #if defined(ECB) && ECB
  407. #if defined(CBC) && CBC
  408. static void XorWithIv(uint8_t* buf)
  409. {
  410. uint8_t i;
  411. for(i = 0; i < KEYLEN; ++i)
  412. {
  413. buf[i] ^= Iv[i];
  414. }
  415. }
  416. void AES128_CBC_encrypt_buffer(uint8_t* output, uint8_t* input, uint32_t length, const uint8_t* key, const uint8_t* iv)
  417. {
  418. uintptr_t i;
  419. uint8_t remainders = length % KEYLEN; /* Remaining bytes in the last non-full block */
  420. BlockCopy(output, input);
  421. state = (state_t*)output;
  422. // Skip the key expansion if key is passed as 0
  423. if(0 != key)
  424. {
  425. Key = key;
  426. KeyExpansion();
  427. }
  428. if(iv != 0)
  429. {
  430. Iv = (uint8_t*)iv;
  431. }
  432. for(i = 0; i < length; i += KEYLEN)
  433. {
  434. XorWithIv(input);
  435. BlockCopy(output, input);
  436. state = (state_t*)output;
  437. Cipher();
  438. Iv = output;
  439. input += KEYLEN;
  440. output += KEYLEN;
  441. }
  442. if(remainders)
  443. {
  444. BlockCopy(output, input);
  445. memset(output + remainders, 0, KEYLEN - remainders); /* add 0-padding */
  446. state = (state_t*)output;
  447. Cipher();
  448. }
  449. }
  450. void AES128_CBC_decrypt_buffer(uint8_t* output, uint8_t* input, uint32_t length, const uint8_t* key, const uint8_t* iv)
  451. {
  452. uintptr_t i;
  453. uint8_t remainders = length % KEYLEN; /* Remaining bytes in the last non-full block */
  454. BlockCopy(output, input);
  455. state = (state_t*)output;
  456. // Skip the key expansion if key is passed as 0
  457. if(0 != key)
  458. {
  459. Key = key;
  460. KeyExpansion();
  461. }
  462. // If iv is passed as 0, we continue to encrypt without re-setting the Iv
  463. if(iv != 0)
  464. {
  465. Iv = (uint8_t*)iv;
  466. }
  467. for(i = 0; i < length; i += KEYLEN)
  468. {
  469. BlockCopy(output, input);
  470. state = (state_t*)output;
  471. InvCipher();
  472. XorWithIv(output);
  473. Iv = input;
  474. input += KEYLEN;
  475. output += KEYLEN;
  476. }
  477. if(remainders)
  478. {
  479. BlockCopy(output, input);
  480. memset(output+remainders, 0, KEYLEN - remainders); /* add 0-padding */
  481. state = (state_t*)output;
  482. InvCipher();
  483. }
  484. }
  485. #endif // #if defined(CBC) && CBC