Other Parts Discussed in Thread: AES-128, , EK-TM4C129EXL
Tool/software: TI-RTOS
Hi,
I need to do 1KB of data to encrypt using AES. I found API function For AES-128 Encryption. But That API doesnt work Propperly.
Here is That Function.
// foreward sbox
const unsigned char sbox[256] = {
//0 1 2 3 4 5 6 7 8 9 A B C D E F
0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76, //0
0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0, //1
0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15, //2
0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75, //3
0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84, //4
0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf, //5
0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8, //6
0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2, //7
0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73, //8
0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb, //9
0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79, //A
0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08, //B
0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a, //C
0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e, //D
0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf, //E
0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16 }; //F
// inverse sbox
const unsigned char 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 };
// round constant
const unsigned char Rcon[10] = {
0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36};
// multiply by 2 in the galois field
unsigned char galois_mul2(unsigned char value)
{
signed char temp;
// cast to signed value
temp = (signed char) value;
// if MSB is 1, then this will signed extend and fill the temp variable with 1's
temp = temp >> 7;
// AND with the reduction variable
temp = temp & 0x1b;
// finally shift and reduce the value
return ((value << 1)^temp);
}
// AES encryption and decryption function
// The code was optimized for memory (flash and ram)
// Combining both encryption and decryption resulted in a slower implementation
// but much smaller than the 2 functions separated
// This function only implements AES-128 encryption and decryption (AES-192 and
// AES-256 are not supported by this code)
void aes_enc_dec(unsigned char *state, unsigned char *key, unsigned char dir)
{
unsigned char buf1, buf2, buf3, buf4, round, i;
// In case of decryption
if (dir) {
// compute the last key of encryption before starting the decryption
for (round = 0 ; round < 10; round++) {
//key schedule
key[0] = sbox[key[13]]^key[0]^Rcon[round];
key[1] = sbox[key[14]]^key[1];
key[2] = sbox[key[15]]^key[2];
key[3] = sbox[key[12]]^key[3];
for (i=4; i<16; i++) {
key[i] = key[i] ^ key[i-4];
}
}
//first Addroundkey
for (i = 0; i <16; i++){
state[i]=state[i] ^ key[i];
}
}
// main loop
for (round = 0; round < 10; round++){
if (dir){
//Inverse key schedule
for (i=15; i>3; --i) {
key[i] = key[i] ^ key[i-4];
}
key[0] = sbox[key[13]]^key[0]^Rcon[9-round];
key[1] = sbox[key[14]]^key[1];
key[2] = sbox[key[15]]^key[2];
key[3] = sbox[key[12]]^key[3];
} else {
for (i = 0; i <16; i++){
// with shiftrow i+5 mod 16
state[i]=sbox[state[i] ^ key[i]];
}
//shift rows
buf1 = state[1];
state[1] = state[5];
state[5] = state[9];
state[9] = state[13];
state[13] = buf1;
buf1 = state[2];
buf2 = state[6];
state[2] = state[10];
state[6] = state[14];
state[10] = buf1;
state[14] = buf2;
buf1 = state[15];
state[15] = state[11];
state[11] = state[7];
state[7] = state[3];
state[3] = buf1;
}
//mixcol - inv mix
if ((round > 0 && dir) || (round < 9 && !dir)) {
for (i=0; i <4; i++){
buf4 = (i << 2);
if (dir){
// precompute for decryption
buf1 = galois_mul2(galois_mul2(state[buf4]^state[buf4+2]));
buf2 = galois_mul2(galois_mul2(state[buf4+1]^state[buf4+3]));
state[buf4] ^= buf1; state[buf4+1] ^= buf2; state[buf4+2] ^= buf1; state[buf4+3] ^= buf2;
}
// in all cases
buf1 = state[buf4] ^ state[buf4+1] ^ state[buf4+2] ^ state[buf4+3];
buf2 = state[buf4];
buf3 = state[buf4]^state[buf4+1]; buf3=galois_mul2(buf3); state[buf4] = state[buf4] ^ buf3 ^ buf1;
buf3 = state[buf4+1]^state[buf4+2]; buf3=galois_mul2(buf3); state[buf4+1] = state[buf4+1] ^ buf3 ^ buf1;
buf3 = state[buf4+2]^state[buf4+3]; buf3=galois_mul2(buf3); state[buf4+2] = state[buf4+2] ^ buf3 ^ buf1;
buf3 = state[buf4+3]^buf2; buf3=galois_mul2(buf3); state[buf4+3] = state[buf4+3] ^ buf3 ^ buf1;
}
}
if (dir) {
//Inv shift rows
// Row 1
buf1 = state[13];
state[13] = state[9];
state[9] = state[5];
state[5] = state[1];
state[1] = buf1;
//Row 2
buf1 = state[10];
buf2 = state[14];
state[10] = state[2];
state[14] = state[6];
state[2] = buf1;
state[6] = buf2;
//Row 3
buf1 = state[3];
state[3] = state[7];
state[7] = state[11];
state[11] = state[15];
state[15] = buf1;
for (i = 0; i <16; i++){
// with shiftrow i+5 mod 16
state[i]=rsbox[state[i]] ^ key[i];
}
} else {
//key schedule
key[0] = sbox[key[13]]^key[0]^Rcon[round];
key[1] = sbox[key[14]]^key[1];
key[2] = sbox[key[15]]^key[2];
key[3] = sbox[key[12]]^key[3];
for (i=4; i<16; i++) {
key[i] = key[i] ^ key[i-4];
}
}
}
if (!dir) {
//last Addroundkey
for (i = 0; i <16; i++){
// with shiftrow i+5 mod 16
state[i]=state[i] ^ key[i];
} // enf for
} // end if (!dir)
} // end function
since i have to encrypt larger data, and AES-128 only Encrypt 16 Bytes. so i am using for loop to encrypt All the Data and Decrypt As Well.
for( i=0; i<strlen(str1); i=i+16 )
{
aes_enc_dec( &str1[i], key, 1);
}
for( i=0; i<strlen(str1); i=i+16 )
{
aes_enc_dec( &str1[i], key, 0);
}
I given 16 byte key. and 36 Byte string value
The problem i am facing is :
(1) This Function only support AES 128, I need to do also AES 192/256 Encryption.
(2) After Encrypting, If i Decrypt that Encrypted Data From Another Tool It With same key, It will not giving currect data.
(3) After Decrypting It change the key value as well, which should not be done.
