diff options
| -rw-r--r-- | aes.c | 100 |
1 files changed, 27 insertions, 73 deletions
@@ -52,15 +52,14 @@ NOTE: String length must be evenly divisible by 16byte (str_len % 16 == 0) // 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 +#ifndef MULTIPLY_AS_A_FUNCTION + #define MULTIPLY_AS_A_FUNCTION 0 +#endif /*****************************************************************************/ /* Private variables: */ /*****************************************************************************/ -// in - pointer to the CipherText to be decrypted. -// out - pointer to buffer to hold output of the decryption. // state - array holding the intermediate results during decryption. -//static uint8_t* in, *out, state[4][4]; typedef uint8_t state_t[4][4]; static state_t* state; @@ -259,12 +258,12 @@ static void ShiftRows(void) (*state)[0][2] = (*state)[2][2]; (*state)[2][2] = temp; - temp = (*state)[1][2]; + temp = (*state)[1][2]; (*state)[1][2] = (*state)[3][2]; (*state)[3][2] = temp; // Rotate third row 3 columns to left - temp = (*state)[0][3]; + temp = (*state)[0][3]; (*state)[0][3] = (*state)[3][3]; (*state)[3][3] = (*state)[2][3]; (*state)[2][3] = (*state)[1][3]; @@ -288,7 +287,7 @@ static void MixColumns(void) Tm = (*state)[i][0] ^ (*state)[i][1] ; Tm = xtime(Tm); (*state)[i][0] ^= Tm ^ Tmp ; Tm = (*state)[i][1] ^ (*state)[i][2] ; Tm = xtime(Tm); (*state)[i][1] ^= Tm ^ Tmp ; Tm = (*state)[i][2] ^ (*state)[i][3] ; Tm = xtime(Tm); (*state)[i][2] ^= Tm ^ Tmp ; - Tm = (*state)[i][3] ^ t ; Tm = xtime(Tm); (*state)[i][3] ^= Tm ^ Tmp ; + Tm = (*state)[i][3] ^ t ; Tm = xtime(Tm); (*state)[i][3] ^= Tm ^ Tmp ; } } @@ -312,8 +311,6 @@ static uint8_t Multiply(uint8_t x, uint8_t y) #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. @@ -323,13 +320,11 @@ static void InvMixColumns(void) uint8_t a,b,c,d; for(i=0;i<4;++i) { - a = (*state)[i][0]; b = (*state)[i][1]; c = (*state)[i][2]; d = (*state)[i][3]; - (*state)[i][0] = Multiply(a, 0x0e) ^ Multiply(b, 0x0b) ^ Multiply(c, 0x0d) ^ Multiply(d, 0x09); (*state)[i][1] = Multiply(a, 0x09) ^ Multiply(b, 0x0e) ^ Multiply(c, 0x0b) ^ Multiply(d, 0x0d); (*state)[i][2] = Multiply(a, 0x0d) ^ Multiply(b, 0x09) ^ Multiply(c, 0x0e) ^ Multiply(d, 0x0b); @@ -338,7 +333,7 @@ static void InvMixColumns(void) } -// The SubBytes Function Substitutes the values in the +// The SubBytes function substitutes the values in the // state matrix with values in an S-box. static void InvSubBytes(void) { @@ -384,18 +379,8 @@ static void InvShiftRows(void) // Cipher is the main function that encrypts the PlainText. static void Cipher(void) { - //uint8_t i, j, uint8_t round = 0; - // Copy the input PlainText to state array. -// for(i = 0; i < 4; ++i) -// { -// for(j = 0; j < 4 ; ++j) -// { -// (*state)[i][j] = in[(i * 4) + j]; -// } -// } - // Add the First round key to the state before starting the rounds. AddRoundKey(0); @@ -415,32 +400,12 @@ static void Cipher(void) SubBytes(); ShiftRows(); AddRoundKey(Nr); - - // The encryption process is over. - // Copy the state array to output array. -// for(i = 0; i < 4; ++i) -// { -// for(j = 0; j < 4; ++j) -// { -// out[(i * 4) + j] = (*state)[i][j]; -// } -// } } static void InvCipher(void) { - //uint8_t i,j, uint8_t round=0; - // Copy the input CipherText to state array. -// for(i=0;i<4;++i) -// { -// for(j=0;j<4;++j) -// { -// (*state)[i][j] = in[i*4 + j]; -// } -// } - // Add the First round key to the state before starting the rounds. AddRoundKey(Nr); @@ -460,58 +425,47 @@ static void InvCipher(void) InvShiftRows(); InvSubBytes(); AddRoundKey(0); +} - // The decryption process is over. - // Copy the state array to output array. -// for(i=0;i<4;++i) -// { -// for(j=0;j<4;++j) -// { -// out[i*4+j]=(*state)[i][j]; -// } -// } +// This can be replaced with a call to memcpy +static void BufferCopy(uint8_t* output, uint8_t* input) +{ + uint8_t i; + for (i=0;i<16;++i) + { + output[i] = input[i]; + } } + /*****************************************************************************/ /* Public functions: */ /*****************************************************************************/ -void AES128_ECB_encrypt_nc(uint8_t* data, const uint8_t* key) +void AES128_ECB_encrypt(uint8_t* input, const uint8_t* key, uint8_t* output) { - // Copy the Key and CipherText - Key = key; - state = (state_t*)data; + // Copy input to output, and work in-memory on output + BufferCopy(output, input); + state = (state_t*)output; // The KeyExpansion routine must be called before encryption. + Key = key; KeyExpansion(); // The next function call encrypts the PlainText with the Key using AES algorithm. Cipher(); } -void AES128_ECB_decrypt_nc(uint8_t* data, const uint8_t* key) +void AES128_ECB_decrypt(uint8_t* input, const uint8_t* key, uint8_t *output) { - Key = key; - state = (state_t*)data; + // Copy input to output, and work in-memory on output + BufferCopy(output, input); + state = (state_t*)output; + Key = key; KeyExpansion(); InvCipher(); } -void AES128_ECB_encrypt(uint8_t* input, const uint8_t* key, uint8_t *output) -{ - uint8_t i; - for (i=0;i<16;++i) - output[i] = input[i]; - AES128_ECB_encrypt_nc(output, key); -} - -void AES128_ECB_decrypt(uint8_t* input, const uint8_t* key, uint8_t *output) -{ - uint8_t i; - for (i=0;i<16;++i) - output[i] = input[i]; - AES128_ECB_decrypt_nc(output, key); -} |