diff options
| -rw-r--r-- | aes.c | 161 |
1 files changed, 157 insertions, 4 deletions
@@ -18,10 +18,10 @@ ECB-AES128 2b7e151628aed2a6abf7158809cf4f3c resulting cipher - 3ad77bb40d7a3660a89ecaf32466ef97 - f5d3d58503b9699de785895a96fdbaaf - 43b1cd7f598ece23881b00e3ed030688 - 7b0c785e27e8ad3f8223207104725dd4 + 50fe67cc996d32b6da0937e99bafec60 + d9a4dada0892239f6b8b3d7680e15674 + a78819583f0308e7a6bf36b1386abf23 + c6d3416d29165c6fcb8e51a227ba994e NOTE: String length must be evenly divisible by 16byte (str_len % 16 == 0) @@ -89,6 +89,25 @@ static const uint8_t sbox[256] = { 0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf, 0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16 }; +static const uint8_t rsbox[256] = +{ 0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb +, 0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb +, 0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e +, 0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25 +, 0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92 +, 0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84 +, 0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06 +, 0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b +, 0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73 +, 0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e +, 0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b +, 0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4 +, 0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f +, 0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef +, 0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61 +, 0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d }; + + // The round constant word array, Rcon[i], contains the values given by // x to th e power (i-1) being powers of x (x is denoted as {02}) in the field GF(2^8) // Note that i starts at 1, not 0). @@ -119,6 +138,12 @@ static uint8_t getSBoxValue(uint8_t num) return sbox[num]; } +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() { @@ -265,6 +290,78 @@ 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)))))) + + +// 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() +{ + int i; + uint8_t a,b,c,d; + for(i=0;i<4;i++) + { + + a = state[0][i]; + b = state[1][i]; + c = state[2][i]; + d = state[3][i]; + + + state[0][i] = Multiply(a, 0x0e) ^ Multiply(b, 0x0b) ^ Multiply(c, 0x0d) ^ Multiply(d, 0x09); + state[1][i] = Multiply(a, 0x09) ^ Multiply(b, 0x0e) ^ Multiply(c, 0x0b) ^ Multiply(d, 0x0d); + state[2][i] = Multiply(a, 0x0d) ^ Multiply(b, 0x09) ^ Multiply(c, 0x0e) ^ Multiply(d, 0x0b); + state[3][i] = Multiply(a, 0x0b) ^ Multiply(b, 0x0d) ^ Multiply(c, 0x09) ^ Multiply(d, 0x0e); + } +} + + +// The SubBytes Function Substitutes the values in the +// state matrix with values in an S-box. +static void InvSubBytes() +{ + uint8_t i,j; + for(i=0;i<4;i++) + { + for(j=0;j<4;j++) + { + state[i][j] = getSBoxInvert(state[i][j]); + } + } +} + + +static void InvShiftRows() +{ + uint8_t temp; + + // Rotate first row 1 columns to right + temp=state[1][3]; + state[1][3]=state[1][2]; + state[1][2]=state[1][1]; + state[1][1]=state[1][0]; + state[1][0]=temp; + + // Rotate second row 2 columns to right + temp=state[2][0]; + state[2][0]=state[2][2]; + state[2][2]=temp; + + temp=state[2][1]; + state[2][1]=state[2][3]; + state[2][3]=temp; + + // Rotate third row 3 columns to right + temp=state[3][0]; + state[3][0]=state[3][1]; + state[3][1]=state[3][2]; + state[3][2]=state[3][3]; + state[3][3]=temp; +} + + // Cipher is the main function that encrypts the PlainText. static void Cipher() { @@ -310,6 +407,50 @@ static void Cipher() } } +static void InvCipher() +{ + uint8_t i,j,round=0; + + //Copy the input CipherText to state array. + for(i=0;i<4;i++) + { + for(j=0;j<4;j++) + { + state[j][i] = in[i*4 + j]; + } + } + + // Add the First round key to the state before starting the rounds. + AddRoundKey(Nr); + + // There will be Nr rounds. + // The first Nr-1 rounds are identical. + // These Nr-1 rounds are executed in the loop below. + for(round=Nr-1;round>0;round--) + { + InvShiftRows(); + InvSubBytes(); + AddRoundKey(round); + InvMixColumns(); + } + + // The last round is given below. + // The MixColumns function is not here in the last round. + 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[j][i]; + } + } +} + /*****************************************************************************/ /* Public functions: */ @@ -329,5 +470,17 @@ void AES128_ECB_encrypt(uint8_t* input, uint8_t* key, uint8_t *output) Cipher(); } +void AES128_ECB_decrypt(uint8_t* input, uint8_t* key, uint8_t *output) +{ + Key = key; + in = input; + out = output; + + KeyExpansion(); + + InvCipher(); +} #endif //_AES_C_ + + |