diff options
| -rw-r--r-- | aes.c | 78 |
1 files changed, 46 insertions, 32 deletions
@@ -18,10 +18,10 @@ ECB-AES128 2b7e151628aed2a6abf7158809cf4f3c resulting cipher - 50fe67cc996d32b6da0937e99bafec60 - d9a4dada0892239f6b8b3d7680e15674 - a78819583f0308e7a6bf36b1386abf23 - c6d3416d29165c6fcb8e51a227ba994e + 3ad77bb40d7a3660a89ecaf32466ef97 + f5d3d58503b9699de785895a96fdbaaf + 43b1cd7f598ece23881b00e3ed030688 + 7b0c785e27e8ad3f8223207104725dd4 NOTE: String length must be evenly divisible by 16byte (str_len % 16 == 0) @@ -29,9 +29,6 @@ NOTE: String length must be evenly divisible by 16byte (str_len % 16 == 0) */ -#ifndef _AES_C_ -#define _AES_C_ - /*****************************************************************************/ /* Includes: */ @@ -52,6 +49,10 @@ NOTE: String length must be evenly divisible by 16byte (str_len % 16 == 0) // The number of rounds in AES Cipher. #define Nr 10 +// jcallan@github points out that declaring Multiply as a function +// reduces code size considerably with the Keil ARM compiler. +// See this link for more information: https://github.com/kokke/tiny-AES128-C/pull/3 +#define MULTIPLY_AS_A_FUNCTION 0 /*****************************************************************************/ /* Private variables: */ @@ -143,9 +144,8 @@ static uint8_t getSBoxInvert(uint8_t num) return rsbox[num]; } - // This function produces Nb(Nr+1) round keys. The round keys are used in each round to decrypt the states. -static void KeyExpansion() +static void KeyExpansion(void) { uint32_t i, j, k; uint8_t tempa[4]; // Used for the column/row operations @@ -212,10 +212,10 @@ static void KeyExpansion() // This function adds the round key to state. // The round key is added to the state by an XOR function. -static void AddRoundKey(uint8_t round) +static void AddRoundKey(uint8_t round) { uint8_t i,j; - for(i=0;i<4;i++) + for(i=0;i<4;++i) { for(j = 0; j < 4; ++j) { @@ -226,7 +226,7 @@ static void AddRoundKey(uint8_t round) // The SubBytes Function Substitutes the values in the // state matrix with values in an S-box. -static void SubBytes() +static void SubBytes(void) { uint8_t i, j; for(i = 0; i < 4; ++i) @@ -241,7 +241,7 @@ static void SubBytes() // The ShiftRows() function shifts the rows in the state to the left. // Each row is shifted with different offset. // Offset = Row number. So the first row is not shifted. -static void ShiftRows() +static void ShiftRows(void) { uint8_t temp; @@ -275,7 +275,7 @@ static uint8_t xtime(uint8_t x) } // MixColumns function mixes the columns of the state matrix -static void MixColumns() +static void MixColumns(void) { uint8_t i; uint8_t Tmp,Tm,t; @@ -290,18 +290,36 @@ static void MixColumns() } } -// Multiplty is a macro used to multiply numbers in the field GF(2^8) -#define Multiply(x,y) (((y & 1) * x) ^ ((y>>1 & 1) * xtime(x)) ^ ((y>>2 & 1) * xtime(xtime(x))) ^ ((y>>3 & 1) * xtime(xtime(xtime(x)))) ^ ((y>>4 & 1) * xtime(xtime(xtime(xtime(x)))))) +// Multiply is used to multiply numbers in the field GF(2^8) +#if MULTIPLY_AS_A_FUNCTION +static uint8_t Multiply(uint8_t x, uint8_t y) +{ + return (((y & 1) * x) ^ + ((y>>1 & 1) * xtime(x)) ^ + ((y>>2 & 1) * xtime(xtime(x))) ^ + ((y>>3 & 1) * xtime(xtime(xtime(x)))) ^ + ((y>>4 & 1) * xtime(xtime(xtime(xtime(x)))))); + } +#else +#define Multiply(x, y) \ + ( ((y & 1) * x) ^ \ + ((y>>1 & 1) * xtime(x)) ^ \ + ((y>>2 & 1) * xtime(xtime(x))) ^ \ + ((y>>3 & 1) * xtime(xtime(xtime(x)))) ^ \ + ((y>>4 & 1) * xtime(xtime(xtime(xtime(x)))))) \ + +#endif + // MixColumns function mixes the columns of the state matrix. // The method used to multiply may be difficult to understand for the inexperienced. // Please use the references to gain more information. -static void InvMixColumns() +static void InvMixColumns(void) { int i; uint8_t a,b,c,d; - for(i=0;i<4;i++) + for(i=0;i<4;++i) { a = state[0][i]; @@ -320,20 +338,19 @@ static void InvMixColumns() // The SubBytes Function Substitutes the values in the // state matrix with values in an S-box. -static void InvSubBytes() +static void InvSubBytes(void) { uint8_t i,j; - for(i=0;i<4;i++) + for(i=0;i<4;++i) { - for(j=0;j<4;j++) + for(j=0;j<4;++j) { state[i][j] = getSBoxInvert(state[i][j]); } } } - -static void InvShiftRows() +static void InvShiftRows(void) { uint8_t temp; @@ -363,7 +380,7 @@ static void InvShiftRows() // Cipher is the main function that encrypts the PlainText. -static void Cipher() +static void Cipher(void) { uint8_t i, j, round = 0; @@ -407,14 +424,14 @@ static void Cipher() } } -static void InvCipher() +static void InvCipher(void) { uint8_t i,j,round=0; // Copy the input CipherText to state array. - for(i=0;i<4;i++) + for(i=0;i<4;++i) { - for(j=0;j<4;j++) + for(j=0;j<4;++j) { state[j][i] = in[i*4 + j]; } @@ -442,9 +459,9 @@ static void InvCipher() // The decryption process is over. // Copy the state array to output array. - for(i=0;i<4;i++) + for(i=0;i<4;++i) { - for(j=0;j<4;j++) + for(j=0;j<4;++j) { out[i*4+j]=state[j][i]; } @@ -481,6 +498,3 @@ void AES128_ECB_decrypt(uint8_t* input, uint8_t* key, uint8_t *output) InvCipher(); } -#endif //_AES_C_ - - |