path: root/rijndael.c

/*
 * Highly portable ANSI C implementation of Rijndael cipher.
 * Written by Kaz Kylheku.
 */

#include <string.h>
#include <assert.h>
#include "rijndael.h"

#define numrows_to_blocksize(N) (4 * (N))
#define max(a, b) ((a) > (b) ? (a) : (b))

static int log_table[256];
static int antilog_table[256];
static int s_box[256];
static int s_box_inverse[256];
static int rcon[30];

static int
multiply(int a, int b)
{
	if (a != 0 && b != 0)
		return antilog_table[(log_table[a] + log_table[b]) % 255];
	return 0;
}

static void
key_add(rijn_block_t *out, rijn_block_t *in, rijn_block_t *roundkey, int numrows)
{
	unsigned char *flat_out = (unsigned char *) out;
	const unsigned char *flat_in = (unsigned char *) in;
	const unsigned char *flat_rk = (unsigned char *) roundkey;
	int numbytes = numrows_to_blocksize(numrows);

	while (numbytes-- > 0)
		*flat_out++ = *flat_in++ ^ *flat_rk++;
}

static void
shift_column_routine(rijn_block_t *block, rijn_size_t numrows, int inverse)
{
	static int shifts[2][3][4] = {
		{
			{ 0, 1, 2, 3 },	/* shifts for 128 bit block */
			{ 0, 1, 2, 3 }, /* shifts for 192 bit block */
			{ 0, 1, 3, 4 }, /* shifts for 256 bit block */
		}, 
		{
			{ 0, 3, 2, 1 }, /* inverse shifts for 128 bit block */
			{ 0, 5, 4, 3 }, /* inverse shifts for 192 bit block */ 
			{ 0, 7, 5, 4 }, /* inverse shifts for 256 bit block */
		}
	};

	rijn_block_t temp;
	int shift_index = (numrows - 4) / 2;
	int i;
	int *shift_select;

	assert (numrows == rijn_128 || numrows == rijn_192 || numrows == rijn_256);
	assert (shift_index >= 0 && shift_index < 3);
	assert (inverse == 0 || inverse == 1);

	shift_select = shifts[inverse][shift_index];

	/*
	 * Create temporary block, with the columns shifted by the amount
	 * from the table. The switch is used in order to reduce the
	 * modulus to a constant.
	 */

	switch (numrows) {
	case rijn_128:
		for (i = 0; i < numrows; i++) {
			temp[i][0] = (*block)[i][0];
			temp[i][1] = (*block)[(i + shift_select[1]) % rijn_128][1];
			temp[i][2] = (*block)[(i + shift_select[2]) % rijn_128][2];
			temp[i][3] = (*block)[(i + shift_select[3]) % rijn_128][3];
		}
		break;
	case rijn_192:
		for (i = 0; i < numrows; i++) {
			temp[i][0] = (*block)[i][0];
			temp[i][1] = (*block)[(i + shift_select[1]) % rijn_192][1];
			temp[i][2] = (*block)[(i + shift_select[2]) % rijn_192][2];
			temp[i][3] = (*block)[(i + shift_select[3]) % rijn_192][3];
		}
		break;
	case rijn_256:
		for (i = 0; i < numrows; i++) {
			temp[i][0] = (*block)[i][0];
			temp[i][1] = (*block)[(i + shift_select[1]) % rijn_256][1];
			temp[i][2] = (*block)[(i + shift_select[2]) % rijn_256][2];
			temp[i][3] = (*block)[(i + shift_select[3]) % rijn_256][3];
		}
		break;
	}

	/*
	 * Block is ready, just copy it over
	 */

	memcpy(block, &temp, numrows_to_blocksize(numrows));;
}

static void
shift_column(rijn_block_t *block, rijn_size_t numrows)
{
	shift_column_routine(block, numrows, 0);
}

static void
shift_column_inverse(rijn_block_t *block, rijn_size_t numrows)
{
	shift_column_routine(block, numrows, 1);
}

static void
substitute(rijn_block_t *block, int *box, int numrows)
{
	unsigned char *flat_block = (unsigned char *) block;
	int numbytes = numrows_to_blocksize(numrows);

	while (numbytes-- > 0)
		flat_block[numbytes] = box[flat_block[numbytes]];
}

static void
mix_row(rijn_block_t *block, rijn_size_t numrows)
{
	rijn_block_t temp;
	int i, j;

	for (j = 0; j < numrows; j++) {
		for (i = 0; i < 4; i++) {
			temp[j][i] = multiply(2,(*block)[j][i])
				       ^ multiply(3,(*block)[j][(i + 1) % 4])
				       ^            (*block)[j][(i + 2) % 4]
				       ^            (*block)[j][(i + 3) % 4];
		}
	}

	memcpy(block, &temp, numrows_to_blocksize(numrows));
}

static void
mix_row_inverse(rijn_block_t *block, rijn_size_t numrows)
{
	rijn_block_t temp;
	int i, j;

	for (j = 0; j < numrows; j++) {
		for (i = 0; i < 4; i++) {
			temp[j][i] = multiply(14,(*block)[j][i])
				       ^ multiply(11,(*block)[j][(i + 1) % 4])
				       ^ multiply(13,(*block)[j][(i + 2) % 4])
				       ^ multiply( 9,(*block)[j][(i + 3) % 4]);
		}
	}

	memcpy(block, &temp, numrows_to_blocksize(numrows));
}

void 
rijn_param_init(rijn_param_t *param, rijn_size_t blocksize, rijn_size_t keysize)
{
	assert (blocksize == rijn_128 || blocksize == rijn_192 || blocksize == rijn_256);
	assert (keysize == rijn_128 || keysize == rijn_192 || keysize == rijn_256);

	param->rijn_blockrows = blocksize;
	param->rijn_keyrows = keysize;
}

void 
rijn_sched_key(rijn_keysched_t *sched, rijn_key_t *key, const rijn_param_t *param)
{
	rijn_size_t keyrows = param->rijn_keyrows;
	rijn_size_t blockrows = param->rijn_blockrows;
	rijn_key_t temp_key;
	int keybytes = numrows_to_blocksize(keyrows);
	int row, i, nrounds = 0, rcon_index = 0;

	sched->rijn_param = *param;
	switch (max(keyrows, blockrows)) {
	case rijn_128:
		nrounds = sched->rijn_nrounds = 10;
		break;
	case rijn_192:
		nrounds = sched->rijn_nrounds = 12;
		break;
	case rijn_256:
		nrounds = sched->rijn_nrounds = 14;
		break;
	}

	assert (nrounds != 0);

	memcpy(&temp_key, key, keybytes);

	for (row = 0; row < keyrows; row++) {
		sched->rijn_roundkey[row / blockrows][row % blockrows][0] = temp_key[row][0];
		sched->rijn_roundkey[row / blockrows][row % blockrows][1] = temp_key[row][1];
		sched->rijn_roundkey[row / blockrows][row % blockrows][2] = temp_key[row][2];
		sched->rijn_roundkey[row / blockrows][row % blockrows][3] = temp_key[row][3];
	}

	while (row < (nrounds + 1) * blockrows) {
		temp_key[0][0] ^= s_box[temp_key[keyrows-1][1]];
		temp_key[0][1] ^= s_box[temp_key[keyrows-1][2]];
		temp_key[0][2] ^= s_box[temp_key[keyrows-1][3]];
		temp_key[0][3] ^= s_box[temp_key[keyrows-1][0]];

		temp_key[0][0] ^= rcon[rcon_index++];

		if (keyrows == 8) {
			for (i = 1; i < keyrows / 2; i++) {
				temp_key[i][0] ^= temp_key[i-1][0];
				temp_key[i][1] ^= temp_key[i-1][1];
				temp_key[i][2] ^= temp_key[i-1][2];
				temp_key[i][3] ^= temp_key[i-1][3];
			}
			temp_key[0][i] ^= s_box[temp_key[i-1][0]];
			temp_key[1][i] ^= s_box[temp_key[i-1][1]];
			temp_key[2][i] ^= s_box[temp_key[i-1][2]];
			temp_key[3][i] ^= s_box[temp_key[i-1][3]];
			for (i++; i < keyrows; i++) {
				temp_key[i][0] ^= temp_key[i-1][0];
				temp_key[i][1] ^= temp_key[i-1][1];
				temp_key[i][2] ^= temp_key[i-1][2];
				temp_key[i][3] ^= temp_key[i-1][3];
			}
		} else {
			assert (keyrows != 8);
			for (i = 1; i < keyrows; i++) {
				temp_key[i][0] ^= temp_key[i-1][0];
				temp_key[i][1] ^= temp_key[i-1][1];
				temp_key[i][2] ^= temp_key[i-1][2];
				temp_key[i][3] ^= temp_key[i-1][3];
			}
		}

		for (i = 0; i < keyrows && row < (nrounds + 1) * blockrows; i++, row++) {
			sched->rijn_roundkey[row / blockrows][row % blockrows][0] = temp_key[i][0];
			sched->rijn_roundkey[row / blockrows][row % blockrows][1] = temp_key[i][1];
			sched->rijn_roundkey[row / blockrows][row % blockrows][2] = temp_key[i][2];
			sched->rijn_roundkey[row / blockrows][row % blockrows][3] = temp_key[i][3];
		}
	}
}

void 
rijn_encrypt(rijn_keysched_t *sched, unsigned char *out, const unsigned char *in)
{
	rijn_size_t blockrows = sched->rijn_param.rijn_blockrows;
	int round, nrounds = sched->rijn_nrounds;

	rijn_block_t *out_block = (rijn_block_t *) out;
	rijn_block_t *in_block = (rijn_block_t *) in;

	key_add(out_block, in_block, &sched->rijn_roundkey[0], blockrows);

	for (round = 1; round < nrounds; round++) {
		substitute(out_block, s_box, blockrows);
		shift_column(out_block, blockrows);
		mix_row(out_block, blockrows);
		key_add(out_block, out_block, &sched->rijn_roundkey[round], blockrows);
	}

	substitute(out_block, s_box, blockrows);
	shift_column(out_block, blockrows);
	key_add(out_block, out_block, &sched->rijn_roundkey[round], blockrows);
}

void 
rijn_decrypt(rijn_keysched_t *sched, unsigned char *out, const unsigned char *in)
{
	rijn_size_t blockrows = sched->rijn_param.rijn_blockrows;
	int round, nrounds = sched->rijn_nrounds;

	rijn_block_t *out_block = (rijn_block_t *) out;
	rijn_block_t *in_block = (rijn_block_t *) in;

	key_add(out_block, in_block, &sched->rijn_roundkey[nrounds], blockrows);
	substitute(out_block, s_box_inverse, blockrows);
	shift_column_inverse(out_block, blockrows);

	for (round = nrounds - 1; round > 0; round--) {
		key_add(out_block, out_block, &sched->rijn_roundkey[round], blockrows);
		mix_row_inverse(out_block, blockrows);
		substitute(out_block, s_box_inverse, blockrows);
		shift_column_inverse(out_block, blockrows);
	}

	assert (round == 0);
	key_add(out_block, out_block, &sched->rijn_roundkey[round], blockrows);
}

static 
void xor_mem(unsigned char *dest, const unsigned char *a, 
		const unsigned char *b, size_t n)
{
	while (n--)
		*dest++ = *a++ ^ *b++;
}

void 
rijn_cbc_encrypt(rijn_keysched_t *sched, unsigned char *iv, unsigned char *out, 
		const unsigned char *in, size_t nblocks)
{
	unsigned char *ivec = iv;
	size_t blocksize = numrows_to_blocksize(sched->rijn_param.rijn_blockrows);
	size_t i, nbytes = nblocks * blocksize;

	for (i = 0; i < nbytes; i += blocksize) {
		xor_mem(out + i, in + i, ivec, blocksize);
		rijn_encrypt(sched, out + i, out + i);
		ivec = out + i;
	}

	memcpy(iv, ivec, blocksize);
}

void 
rijn_cbc_decrypt(rijn_keysched_t *sched, unsigned char *iv, unsigned char *out,
		const unsigned char *in, size_t nblocks)
{
	rijn_block_t iv_save;
	size_t blocksize = numrows_to_blocksize(sched->rijn_param.rijn_blockrows);
	size_t i, nbytes = nblocks * blocksize;

	if (nblocks > 0) {
		memcpy(&iv_save, in + nbytes - blocksize, blocksize);

		for (i = nbytes - blocksize; i < nbytes; i -= blocksize) {
			const unsigned char *ivec = (i > 0) ? in + i - blocksize : iv;
			rijn_decrypt(sched, out + i, in + i);
			xor_mem(out + i, out + i, ivec, blocksize);
		}

		memcpy(iv, &iv_save, blocksize);
	}
}

#ifdef RIJN_TEST

#include <stdio.h>

static void hex_dump(const unsigned char *data, size_t size, FILE *stream)
{
	while (size--)
		fprintf(stream, "%02X", (unsigned int) *data++);
}

int main(void)
{
	static rijn_param_t param = RIJN_PARAM_INITIALIZER(rijn_128, rijn_192);
#if 0
	rijn_key_t key = { 0x00, 0x01, 0x02, 0x03, 0x05, 0x06, 0x07, 0x08, 0x0A,
		0x0B, 0x0C, 0x0D, 0x0F, 0x10, 0x11, 0x12 };
#else
	rijn_key_t key = { { 0x80 } };
#endif
	rijn_keysched_t sched = { 0 };
	unsigned char plaintext[32] = { 0 };
	unsigned char ciphertext[32] = { 0 };

	rijn_sched_key(&sched, &key, &param);
	rijn_encrypt(&sched, ciphertext, plaintext);
	hex_dump(ciphertext, 16, stdout);
	putchar('\n');
	rijn_decrypt(&sched, plaintext, ciphertext);
	hex_dump(plaintext, 16, stdout);
	putchar('\n');
	return 0;
}

#endif


static int log_table[256] = {
  0,   0,  25,   1,  50,   2,  26, 198,  75, 199,  27, 104,  51, 238, 223,   3,
100,   4, 224,  14,  52, 141, 129, 239,  76, 113,   8, 200, 248, 105,  28, 193,
125, 194,  29, 181, 249, 185,  39, 106,  77, 228, 166, 114, 154, 201,   9, 120,
101,  47, 138,   5,  33,  15, 225,  36,  18, 240, 130,  69,  53, 147, 218, 142,
150, 143, 219, 189,  54, 208, 206, 148,  19,  92, 210, 241,  64,  70, 131,  56,
102, 221, 253,  48, 191,   6, 139,  98, 179,  37, 226, 152,  34, 136, 145,  16,
126, 110,  72, 195, 163, 182,  30,  66,  58, 107,  40,  84, 250, 133,  61, 186,
 43, 121,  10,  21, 155, 159,  94, 202,  78, 212, 172, 229, 243, 115, 167,  87,
175,  88, 168,  80, 244, 234, 214, 116,  79, 174, 233, 213, 231, 230, 173, 232,
 44, 215, 117, 122, 235,  22,  11, 245,  89, 203,  95, 176, 156, 169,  81, 160,
127,  12, 246, 111,  23, 196,  73, 236, 216,  67,  31,  45, 164, 118, 123, 183,
204, 187,  62,  90, 251,  96, 177, 134,  59,  82, 161, 108, 170,  85,  41, 157,
151, 178, 135, 144,  97, 190, 220, 252, 188, 149, 207, 205,  55,  63,  91, 209,
 83,  57, 132,  60,  65, 162, 109,  71,  20,  42, 158,  93,  86, 242, 211, 171,
 68,  17, 146, 217,  35,  32,  46, 137, 180, 124, 184,  38, 119, 153, 227, 165,
103,  74, 237, 222, 197,  49, 254,  24,  13,  99, 140, 128, 192, 247, 112,   7
};

static int antilog_table[256] = {
  1,   3,   5,  15,  17,  51,  85, 255,  26,  46, 114, 150, 161, 248,  19,  53, 
 95, 225,  56,  72, 216, 115, 149, 164, 247,   2,   6,  10,  30,  34, 102, 170, 
229,  52,  92, 228,  55,  89, 235,  38, 106, 190, 217, 112, 144, 171, 230,  49, 
 83, 245,   4,  12,  20,  60,  68, 204,  79, 209, 104, 184, 211, 110, 178, 205, 
 76, 212, 103, 169, 224,  59,  77, 215,  98, 166, 241,   8,  24,  40, 120, 136, 
131, 158, 185, 208, 107, 189, 220, 127, 129, 152, 179, 206,  73, 219, 118, 154, 
181, 196,  87, 249,  16,  48,  80, 240,  11,  29,  39, 105, 187, 214,  97, 163, 
254,  25,  43, 125, 135, 146, 173, 236,  47, 113, 147, 174, 233,  32,  96, 160, 
251,  22,  58,  78, 210, 109, 183, 194,  93, 231,  50,  86, 250,  21,  63,  65, 
195,  94, 226,  61,  71, 201,  64, 192,  91, 237,  44, 116, 156, 191, 218, 117, 
159, 186, 213, 100, 172, 239,  42, 126, 130, 157, 188, 223, 122, 142, 137, 128, 
155, 182, 193,  88, 232,  35, 101, 175, 234,  37, 111, 177, 200,  67, 197,  84, 
252,  31,  33,  99, 165, 244,   7,   9,  27,  45, 119, 153, 176, 203,  70, 202, 
 69, 207,  74, 222, 121, 139, 134, 145, 168, 227,  62,  66, 198,  81, 243,  14, 
 18,  54,  90, 238,  41, 123, 141, 140, 143, 138, 133, 148, 167, 242,  13,  23, 
 57,  75, 221, 124, 132, 151, 162, 253,  28,  36, 108, 180, 199,  82, 246,   1, 
}; 

static int s_box[256] = {
 99, 124, 119, 123, 242, 107, 111, 197,  48,   1, 103,  43, 254, 215, 171, 118,
202, 130, 201, 125, 250,  89,  71, 240, 173, 212, 162, 175, 156, 164, 114, 192,
183, 253, 147,  38,  54,  63, 247, 204,  52, 165, 229, 241, 113, 216,  49,  21,
  4, 199,  35, 195,  24, 150,   5, 154,   7,  18, 128, 226, 235,  39, 178, 117,
  9, 131,  44,  26,  27, 110,  90, 160,  82,  59, 214, 179,  41, 227,  47, 132,
 83, 209,   0, 237,  32, 252, 177,  91, 106, 203, 190,  57,  74,  76,  88, 207,
208, 239, 170, 251,  67,  77,  51, 133,  69, 249,   2, 127,  80,  60, 159, 168,
 81, 163,  64, 143, 146, 157,  56, 245, 188, 182, 218,  33,  16, 255, 243, 210,
205,  12,  19, 236,  95, 151,  68,  23, 196, 167, 126,  61, 100,  93,  25, 115,
 96, 129,  79, 220,  34,  42, 144, 136,  70, 238, 184,  20, 222,  94,  11, 219,
224,  50,  58,  10,  73,   6,  36,  92, 194, 211, 172,  98, 145, 149, 228, 121,
231, 200,  55, 109, 141, 213,  78, 169, 108,  86, 244, 234, 101, 122, 174,   8,
186, 120,  37,  46,  28, 166, 180, 198, 232, 221, 116,  31,  75, 189, 139, 138,
112,  62, 181, 102,  72,   3, 246,  14,  97,  53,  87, 185, 134, 193,  29, 158,
225, 248, 152,  17, 105, 217, 142, 148, 155,  30, 135, 233, 206,  85,  40, 223,
140, 161, 137,  13, 191, 230,  66, 104,  65, 153,  45,  15, 176,  84, 187,  22,
};

static int s_box_inverse[256] = {
 82,   9, 106, 213,  48,  54, 165,  56, 191,  64, 163, 158, 129, 243, 215, 251,
124, 227,  57, 130, 155,  47, 255, 135,  52, 142,  67,  68, 196, 222, 233, 203,
 84, 123, 148,  50, 166, 194,  35,  61, 238,  76, 149,  11,  66, 250, 195,  78,
  8,  46, 161, 102,  40, 217,  36, 178, 118,  91, 162,  73, 109, 139, 209,  37,
114, 248, 246, 100, 134, 104, 152,  22, 212, 164,  92, 204,  93, 101, 182, 146,
108, 112,  72,  80, 253, 237, 185, 218,  94,  21,  70,  87, 167, 141, 157, 132,
144, 216, 171,   0, 140, 188, 211,  10, 247, 228,  88,   5, 184, 179,  69,   6,
208,  44,  30, 143, 202,  63,  15,   2, 193, 175, 189,   3,   1,  19, 138, 107,
 58, 145,  17,  65,  79, 103, 220, 234, 151, 242, 207, 206, 240, 180, 230, 115,
150, 172, 116,  34, 231, 173,  53, 133, 226, 249,  55, 232,  28, 117, 223, 110,
 71, 241,  26, 113,  29,  41, 197, 137, 111, 183,  98,  14, 170,  24, 190,  27,
252,  86,  62,  75, 198, 210, 121,  32, 154, 219, 192, 254, 120, 205,  90, 244,
 31, 221, 168,  51, 136,   7, 199,  49, 177,  18,  16,  89,  39, 128, 236,  95,
 96,  81, 127, 169,  25, 181,  74,  13,  45, 229, 122, 159, 147, 201, 156, 239,
160, 224,  59,  77, 174,  42, 245, 176, 200, 235, 187,  60, 131,  83, 153,  97,
 23,  43,   4, 126, 186, 119, 214,  38, 225, 105,  20,  99,  85,  33,  12, 125,
};

static int rcon[30] = {
	0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8,
	0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4,
	0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91
};