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/*
* Advanced Encryption Standard
* @author Dani Huertas
* @email huertas.dani@gmail.com
*
* Based on the document FIPS PUB 197
*/
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
/*
* Addition in GF(2^8)
* http://en.wikipedia.org/wiki/Finite_field_arithmetic
*/
uint8_t gadd(uint8_t a, uint8_t b) {
return a^b;
}
/*
* Subtraction in GF(2^8)
* http://en.wikipedia.org/wiki/Finite_field_arithmetic
*/
uint8_t gsub(uint8_t a, uint8_t b) {
return a^b;
}
/*
* Multiplication in GF(2^8)
* http://en.wikipedia.org/wiki/Finite_field_arithmetic
* Irreducible polynomial m(x) = x8 + x4 + x3 + x + 1
*/
uint8_t gmult(uint8_t a, uint8_t b) {
uint8_t p = 0, i = 0, hbs = 0;
for (i = 0; i < 8; i++) {
if (b & 1) {
p ^= a;
}
hbs = a & 0x80;
a <<= 1;
if (hbs) a ^= 0x1b; // 0000 0001 0001 1011
b >>= 1;
}
return (uint8_t)p;
}
/*
* Addition of 4 byte words
* m(x) = x4+1
*/
void coef_add(uint8_t a[], uint8_t b[], uint8_t d[]) {
d[0] = a[0]^b[0];
d[1] = a[1]^b[1];
d[2] = a[2]^b[2];
d[3] = a[3]^b[3];
}
/*
* Multiplication of 4 byte words
* m(x) = x4+1
*/
void coef_mult(uint8_t *a, uint8_t *b, uint8_t *d) {
d[0] = gmult(a[0],b[0])^gmult(a[3],b[1])^gmult(a[2],b[2])^gmult(a[1],b[3]);
d[1] = gmult(a[1],b[0])^gmult(a[0],b[1])^gmult(a[3],b[2])^gmult(a[2],b[3]);
d[2] = gmult(a[2],b[0])^gmult(a[1],b[1])^gmult(a[0],b[2])^gmult(a[3],b[3]);
d[3] = gmult(a[3],b[0])^gmult(a[2],b[1])^gmult(a[1],b[2])^gmult(a[0],b[3]);
}
/*
* The cipher Key.
*/
int K;
/*
* Number of columns (32-bit words) comprising the State. For this
* standard, Nb = 4.
*/
int Nb = 4;
/*
* Number of 32-bit words comprising the Cipher Key. For this
* standard, Nk = 4, 6, or 8.
*/
int Nk;
/*
* Number of rounds, which is a function of Nk and Nb (which is
* fixed). For this standard, Nr = 10, 12, or 14.
*/
int Nr;
/*
* S-box transformation table
*/
static uint8_t s_box[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 S-box transformation table
*/
static uint8_t inv_s_box[256] = {
// 0 1 2 3 4 5 6 7 8 9 a b c d e f
0x52, 0x09, 0x6a, 0xd5, 0x30, 0x36, 0xa5, 0x38, 0xbf, 0x40, 0xa3, 0x9e, 0x81, 0xf3, 0xd7, 0xfb, // 0
0x7c, 0xe3, 0x39, 0x82, 0x9b, 0x2f, 0xff, 0x87, 0x34, 0x8e, 0x43, 0x44, 0xc4, 0xde, 0xe9, 0xcb, // 1
0x54, 0x7b, 0x94, 0x32, 0xa6, 0xc2, 0x23, 0x3d, 0xee, 0x4c, 0x95, 0x0b, 0x42, 0xfa, 0xc3, 0x4e, // 2
0x08, 0x2e, 0xa1, 0x66, 0x28, 0xd9, 0x24, 0xb2, 0x76, 0x5b, 0xa2, 0x49, 0x6d, 0x8b, 0xd1, 0x25, // 3
0x72, 0xf8, 0xf6, 0x64, 0x86, 0x68, 0x98, 0x16, 0xd4, 0xa4, 0x5c, 0xcc, 0x5d, 0x65, 0xb6, 0x92, // 4
0x6c, 0x70, 0x48, 0x50, 0xfd, 0xed, 0xb9, 0xda, 0x5e, 0x15, 0x46, 0x57, 0xa7, 0x8d, 0x9d, 0x84, // 5
0x90, 0xd8, 0xab, 0x00, 0x8c, 0xbc, 0xd3, 0x0a, 0xf7, 0xe4, 0x58, 0x05, 0xb8, 0xb3, 0x45, 0x06, // 6
0xd0, 0x2c, 0x1e, 0x8f, 0xca, 0x3f, 0x0f, 0x02, 0xc1, 0xaf, 0xbd, 0x03, 0x01, 0x13, 0x8a, 0x6b, // 7
0x3a, 0x91, 0x11, 0x41, 0x4f, 0x67, 0xdc, 0xea, 0x97, 0xf2, 0xcf, 0xce, 0xf0, 0xb4, 0xe6, 0x73, // 8
0x96, 0xac, 0x74, 0x22, 0xe7, 0xad, 0x35, 0x85, 0xe2, 0xf9, 0x37, 0xe8, 0x1c, 0x75, 0xdf, 0x6e, // 9
0x47, 0xf1, 0x1a, 0x71, 0x1d, 0x29, 0xc5, 0x89, 0x6f, 0xb7, 0x62, 0x0e, 0xaa, 0x18, 0xbe, 0x1b, // a
0xfc, 0x56, 0x3e, 0x4b, 0xc6, 0xd2, 0x79, 0x20, 0x9a, 0xdb, 0xc0, 0xfe, 0x78, 0xcd, 0x5a, 0xf4, // b
0x1f, 0xdd, 0xa8, 0x33, 0x88, 0x07, 0xc7, 0x31, 0xb1, 0x12, 0x10, 0x59, 0x27, 0x80, 0xec, 0x5f, // c
0x60, 0x51, 0x7f, 0xa9, 0x19, 0xb5, 0x4a, 0x0d, 0x2d, 0xe5, 0x7a, 0x9f, 0x93, 0xc9, 0x9c, 0xef, // d
0xa0, 0xe0, 0x3b, 0x4d, 0xae, 0x2a, 0xf5, 0xb0, 0xc8, 0xeb, 0xbb, 0x3c, 0x83, 0x53, 0x99, 0x61, // e
0x17, 0x2b, 0x04, 0x7e, 0xba, 0x77, 0xd6, 0x26, 0xe1, 0x69, 0x14, 0x63, 0x55, 0x21, 0x0c, 0x7d};// f
/*
* Generates the round constant Rcon[i]
*/
uint8_t R[] = {0x02, 0x00, 0x00, 0x00};
uint8_t * Rcon(uint8_t i) {
if (i == 1) {
R[0] = 0x01; // x^(1-1) = x^0 = 1
} else if (i > 1) {
R[0] = 0x02;
i--;
while (i-1 > 0) {
R[0] = gmult(R[0], 0x02);
i--;
}
}
return R;
}
/*
* Transformation in the Cipher and Inverse Cipher in which a Round
* Key is added to the State using an XOR operation. The length of a
* Round Key equals the size of the State (i.e., for Nb = 4, the Round
* Key length equals 128 bits/16 bytes).
*/
void add_round_key(uint8_t *state, uint8_t *w, uint8_t r) {
uint8_t c;
for (c = 0; c < Nb; c++) {
state[Nb*0+c] = state[Nb*0+c]^w[4*Nb*r+4*c+0]; //debug, so it works for Nb !=4
state[Nb*1+c] = state[Nb*1+c]^w[4*Nb*r+4*c+1];
state[Nb*2+c] = state[Nb*2+c]^w[4*Nb*r+4*c+2];
state[Nb*3+c] = state[Nb*3+c]^w[4*Nb*r+4*c+3];
}
}
/*
* Transformation in the Cipher that takes all of the columns of the
* State and mixes their data (independently of one another) to
* produce new columns.
*/
void mix_columns(uint8_t *state) {
uint8_t a[] = {0x02, 0x01, 0x01, 0x03}; // a(x) = {02} + {01}x + {01}x2 + {03}x3
uint8_t i, j, col[4], res[4];
for (j = 0; j < Nb; j++) {
for (i = 0; i < 4; i++) {
col[i] = state[Nb*i+j];
}
coef_mult(a, col, res);
for (i = 0; i < 4; i++) {
state[Nb*i+j] = res[i];
}
}
}
/*
* Transformation in the Inverse Cipher that is the inverse of
* MixColumns().
*/
void inv_mix_columns(uint8_t *state) {
uint8_t a[] = {0x0e, 0x09, 0x0d, 0x0b}; // a(x) = {0e} + {09}x + {0d}x2 + {0b}x3
uint8_t i, j, col[4], res[4];
for (j = 0; j < Nb; j++) {
for (i = 0; i < 4; i++) {
col[i] = state[Nb*i+j];
}
coef_mult(a, col, res);
for (i = 0; i < 4; i++) {
state[Nb*i+j] = res[i];
}
}
}
/*
* Transformation in the Cipher that processes the State by cyclically
* shifting the last three rows of the State by different offsets.
*/
void shift_rows(uint8_t *state) {
uint8_t i, k, s, tmp;
for (i = 1; i < 4; i++) {
// shift(1,4)=1; shift(2,4)=2; shift(3,4)=3
// shift(r, 4) = r;
s = 0;
while (s < i) {
tmp = state[Nb*i+0];
for (k = 1; k < Nb; k++) {
state[Nb*i+k-1] = state[Nb*i+k];
}
state[Nb*i+Nb-1] = tmp;
s++;
}
}
}
/*
* Transformation in the Inverse Cipher that is the inverse of
* ShiftRows().
*/
void inv_shift_rows(uint8_t *state) {
uint8_t i, k, s, tmp;
for (i = 1; i < 4; i++) {
s = 0;
while (s < i) {
tmp = state[Nb*i+Nb-1];
for (k = Nb-1; k > 0; k--) {
state[Nb*i+k] = state[Nb*i+k-1];
}
state[Nb*i+0] = tmp;
s++;
}
}
}
/*
* Transformation in the Cipher that processes the State using a non­
* linear byte substitution table (S-box) that operates on each of the
* State bytes independently.
*/
void sub_bytes(uint8_t *state) {
uint8_t i, j;
uint8_t row, col;
for (i = 0; i < 4; i++) {
for (j = 0; j < Nb; j++) {
row = (state[Nb*i+j] & 0xf0) >> 4;
col = state[Nb*i+j] & 0x0f;
state[Nb*i+j] = s_box[16*row+col];
}
}
}
/*
* Transformation in the Inverse Cipher that is the inverse of
* SubBytes().
*/
void inv_sub_bytes(uint8_t *state) {
uint8_t i, j;
uint8_t row, col;
for (i = 0; i < 4; i++) {
for (j = 0; j < Nb; j++) {
row = (state[Nb*i+j] & 0xf0) >> 4;
col = state[Nb*i+j] & 0x0f;
state[Nb*i+j] = inv_s_box[16*row+col];
}
}
}
/*
* Function used in the Key Expansion routine that takes a four-byte
* input word and applies an S-box to each of the four bytes to
* produce an output word.
*/
void sub_word(uint8_t *w) {
uint8_t i;
for (i = 0; i < 4; i++) {
w[i] = s_box[16*((w[i] & 0xf0) >> 4) + (w[i] & 0x0f)];
}
}
/*
* Function used in the Key Expansion routine that takes a four-byte
* word and performs a cyclic permutation.
*/
void rot_word(uint8_t *w) {
uint8_t tmp;
uint8_t i;
tmp = w[0];
for (i = 0; i < 3; i++) {
w[i] = w[i+1];
}
w[3] = tmp;
}
/*
* Key Expansion
*/
void key_expansion(uint8_t *key, uint8_t *w) {
uint8_t tmp[4];
uint8_t i, j;
uint8_t len = Nb*(Nr+1);
for (i = 0; i < Nk; i++) {
w[4*i+0] = key[4*i+0];
w[4*i+1] = key[4*i+1];
w[4*i+2] = key[4*i+2];
w[4*i+3] = key[4*i+3];
}
for (i = Nk; i < len; i++) {
tmp[0] = w[4*(i-1)+0];
tmp[1] = w[4*(i-1)+1];
tmp[2] = w[4*(i-1)+2];
tmp[3] = w[4*(i-1)+3];
if (i%Nk == 0) {
rot_word(tmp);
sub_word(tmp);
coef_add(tmp, Rcon(i/Nk), tmp);
} else if (Nk > 6 && i%Nk == 4) {
sub_word(tmp);
}
w[4*i+0] = w[4*(i-Nk)+0]^tmp[0];
w[4*i+1] = w[4*(i-Nk)+1]^tmp[1];
w[4*i+2] = w[4*(i-Nk)+2]^tmp[2];
w[4*i+3] = w[4*(i-Nk)+3]^tmp[3];
}
}
void cipher(uint8_t *in, uint8_t *out, uint8_t *w) {
uint8_t state[4*Nb];
uint8_t r, i, j;
for (i = 0; i < 4; i++) {
for (j = 0; j < Nb; j++) {
state[Nb*i+j] = in[i+4*j];
}
}
add_round_key(state, w, 0);
for (r = 1; r < Nr; r++) {
sub_bytes(state);
shift_rows(state);
mix_columns(state);
add_round_key(state, w, r);
}
sub_bytes(state);
shift_rows(state);
add_round_key(state, w, Nr);
for (i = 0; i < 4; i++) {
for (j = 0; j < Nb; j++) {
out[i+4*j] = state[Nb*i+j];
}
}
}
void inv_cipher(uint8_t *in, uint8_t *out, uint8_t *w) {
uint8_t state[4*Nb];
uint8_t r, i, j;
for (i = 0; i < 4; i++) {
for (j = 0; j < Nb; j++) {
state[Nb*i+j] = in[i+4*j];
}
}
add_round_key(state, w, Nr);
for (r = Nr-1; r >= 1; r--) {
inv_shift_rows(state);
inv_sub_bytes(state);
add_round_key(state, w, r);
inv_mix_columns(state);
}
inv_shift_rows(state);
inv_sub_bytes(state);
add_round_key(state, w, 0);
for (i = 0; i < 4; i++) {
for (j = 0; j < Nb; j++) {
out[i+4*j] = state[Nb*i+j];
}
}
}
int main(int argc, char *argv[]) {
uint8_t i;
/*
* Appendix A - Key Expansion Examples
*/
/* 128 bits */
/* uint8_t key[] = {
0x2b, 0x7e, 0x15, 0x16,
0x28, 0xae, 0xd2, 0xa6,
0xab, 0xf7, 0x15, 0x88,
0x09, 0xcf, 0x4f, 0x3c}; */
/* 192 bits */
/* uint8_t key[] = {
0x8e, 0x73, 0xb0, 0xf7,
0xda, 0x0e, 0x64, 0x52,
0xc8, 0x10, 0xf3, 0x2b,
0x80, 0x90, 0x79, 0xe5,
0x62, 0xf8, 0xea, 0xd2,
0x52, 0x2c, 0x6b, 0x7b}; */
/* 256 bits */
/* uint8_t key[] = {
0x60, 0x3d, 0xeb, 0x10,
0x15, 0xca, 0x71, 0xbe,
0x2b, 0x73, 0xae, 0xf0,
0x85, 0x7d, 0x77, 0x81,
0x1f, 0x35, 0x2c, 0x07,
0x3b, 0x61, 0x08, 0xd7,
0x2d, 0x98, 0x10, 0xa3,
0x09, 0x14, 0xdf, 0xf4};
*/
/* uint8_t in[] = {
0x32, 0x43, 0xf6, 0xa8,
0x88, 0x5a, 0x30, 0x8d,
0x31, 0x31, 0x98, 0xa2,
0xe0, 0x37, 0x07, 0x34}; // 128
*/
/*
* Appendix C - Example Vectors
*/
/* 128 bit key */
/* uint8_t key[] = {
0x00, 0x01, 0x02, 0x03,
0x04, 0x05, 0x06, 0x07,
0x08, 0x09, 0x0a, 0x0b,
0x0c, 0x0d, 0x0e, 0x0f}; */
/* 192 bit key */
/* uint8_t key[] = {
0x00, 0x01, 0x02, 0x03,
0x04, 0x05, 0x06, 0x07,
0x08, 0x09, 0x0a, 0x0b,
0x0c, 0x0d, 0x0e, 0x0f,
0x10, 0x11, 0x12, 0x13,
0x14, 0x15, 0x16, 0x17}; */
/* 256 bit key */
uint8_t key[] = {
0x00, 0x01, 0x02, 0x03,
0x04, 0x05, 0x06, 0x07,
0x08, 0x09, 0x0a, 0x0b,
0x0c, 0x0d, 0x0e, 0x0f,
0x10, 0x11, 0x12, 0x13,
0x14, 0x15, 0x16, 0x17,
0x18, 0x19, 0x1a, 0x1b,
0x1c, 0x1d, 0x1e, 0x1f};
uint8_t in[] = {
0x00, 0x11, 0x22, 0x33,
0x44, 0x55, 0x66, 0x77,
0x88, 0x99, 0xaa, 0xbb,
0xcc, 0xdd, 0xee, 0xff};
uint8_t out[16]; // 128
uint8_t *w; // expanded key
switch (sizeof(key)) {
default:
case 16: Nk = 4; Nr = 10; break;
case 24: Nk = 6; Nr = 12; break;
case 32: Nk = 8; Nr = 14; break;
}
w = malloc(Nb*(Nr+1)*4);
key_expansion(key, w);
cipher(in /* in */, out /* out */, w /* expanded key */);
printf("out:\n");
for (i = 0; i < 4; i++) {
printf("%x %x %x %x ", out[4*i+0], out[4*i+1], out[4*i+2], out[4*i+3]);
}
printf("\n");
inv_cipher(out, in, w);
printf("msg:\n");
for (i = 0; i < 4; i++) {
printf("%x %x %x %x ", in[4*i+0], in[4*i+1], in[4*i+2], in[4*i+3]);
}
printf("\n");
exit(0);
}