AES算法重点详解和实现
可以看到，在原始数据长度为16的整数倍时，假如原始数据长度等于16*n，则使用NoPadding时加密后数据长度等于16*n，其它情况下加密数据长度等于16*(n+1)。在不足16的整数倍的情况下，假如原始数据长度等于16*n+m[其中m小于16]，除了NoPadding填充之外的任何方式，加密数据长度都等于16*(n+1)；NoPadding填充情况下，CBC、ECB和PCBC三种模式是不支持的，CFB、OFB两种模式下则加密数据长度等于原始数据长度。
下面举例演示各个填充方式：
NoPadding: 不填充
PKCS5Padding: 填充字符串由一个字节序列组成，每个字节填充该字节序列的长度，假定数据长度为9，则需要填充的长度为16 - 9 = 7，数据等于 FF FF FF FF FF FF FF FF FF， 填充后数据为FF FF FF FF FF FF FF FF FF 07 07 07 07 07 07 07
ISO10126Padding: 填充字符串由一个字节序列组成，此字节序列的最后一个字节填充字节序列的长度，其余字节填充随机数据。假定数据长度为9，则需要填充的长度为16 - 9 = 7，数据等于 FF FF FF FF FF FF FF FF FF， 填充后数据为FF FF FF FF FF FF FF FF FF 7D 2A 75 EF F8 EF 07
aes.h
/**************************************************************************
* AES declarations
**************************************************************************/
#define AES_MAXROUNDS 14
#define AES_BLOCKSIZE 16
#define AES_IV_SIZE 16
typedef struct aes_key_st
{
uint16_t rounds;
uint16_t key_size;
uint32_t ks[(AES_MAXROUNDS+1)*8];
uint8_t iv[AES_IV_SIZE];
} AES_CTX;
typedef enum
{
AES_MODE_128,
AES_MODE_256
} AES_MODE;
void AES_set_key(AES_CTX *ctx, const uint8_t *key,
const uint8_t *iv, AES_MODE mode);
void AES_cbc_encrypt(AES_CTX *ctx, const uint8_t *msg,
uint8_t *out, int length);
void AES_cbc_decrypt(AES_CTX *ks, const uint8_t *in, uint8_t *out, int length);static const uint8_t aes_sbox[256] =
{
0x63,0x7C,0x77,0x7B,0xF2,0x6B,0x6F,0xC5,
0x30,0x01,0x67,0x2B,0xFE,0xD7,0xAB,0x76,
0xCA,0x82,0xC9,0x7D,0xFA,0x59,0x47,0xF0,
0xAD,0xD4,0xA2,0xAF,0x9C,0xA4,0x72,0xC0,
0xB7,0xFD,0x93,0x26,0x36,0x3F,0xF7,0xCC,
0x34,0xA5,0xE5,0xF1,0x71,0xD8,0x31,0x15,
0x04,0xC7,0x23,0xC3,0x18,0x96,0x05,0x9A,
0x07,0x12,0x80,0xE2,0xEB,0x27,0xB2,0x75,
0x09,0x83,0x2C,0x1A,0x1B,0x6E,0x5A,0xA0,
0x52,0x3B,0xD6,0xB3,0x29,0xE3,0x2F,0x84,
0x53,0xD1,0x00,0xED,0x20,0xFC,0xB1,0x5B,
0x6A,0xCB,0xBE,0x39,0x4A,0x4C,0x58,0xCF,
0xD0,0xEF,0xAA,0xFB,0x43,0x4D,0x33,0x85,
0x45,0xF9,0x02,0x7F,0x50,0x3C,0x9F,0xA8,
0x51,0xA3,0x40,0x8F,0x92,0x9D,0x38,0xF5,
0xBC,0xB6,0xDA,0x21,0x10,0xFF,0xF3,0xD2,
0xCD,0x0C,0x13,0xEC,0x5F,0x97,0x44,0x17,
0xC4,0xA7,0x7E,0x3D,0x64,0x5D,0x19,0x73,
0x60,0x81,0x4F,0xDC,0x22,0x2A,0x90,0x88,
0x46,0xEE,0xB8,0x14,0xDE,0x5E,0x0B,0xDB,
0xE0,0x32,0x3A,0x0A,0x49,0x06,0x24,0x5C,
0xC2,0xD3,0xAC,0x62,0x91,0x95,0xE4,0x79,
0xE7,0xC8,0x37,0x6D,0x8D,0xD5,0x4E,0xA9,
0x6C,0x56,0xF4,0xEA,0x65,0x7A,0xAE,0x08,
0xBA,0x78,0x25,0x2E,0x1C,0xA6,0xB4,0xC6,
0xE8,0xDD,0x74,0x1F,0x4B,0xBD,0x8B,0x8A,
0x70,0x3E,0xB5,0x66,0x48,0x03,0xF6,0x0E,
0x61,0x35,0x57,0xB9,0x86,0xC1,0x1D,0x9E,
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,
};
/*
* AES is-box
*/
static const uint8_t aes_isbox[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
};
static const unsigned char 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,
};
#define rot1(x) (((x) << 24) | ((x) >> 8))
#define rot2(x) (((x) << 16) | ((x) >> 16))
#define rot3(x) (((x) << 8) | ((x) >> 24))
/*
* This cute trick does 4 'mul by two' at once. Stolen from
* Dr B. R. Gladman but I'm sure the u-(u>>7) is
* a standard graphics trick
* The key to this is that we need to xor with 0x1b if the top bit is set.
* a 1xxx xxxx 0xxx 0xxx First we mask the 7bit,
* b 1000 0000 0000 0000 then we shift right by 7 putting the 7bit in 0bit,
* c 0000 0001 0000 0000 we then subtract (c) from (b)
* d 0111 1111 0000 0000 and now we and with our mask
* e 0001 1011 0000 0000
*/
#define mt 0x80808080
#define ml 0x7f7f7f7f
#define mh 0xfefefefe
#define mm 0x1b1b1b1b
#define mul2(x,t) ((t)=((x)&mt), \
((((x)+(x))&mh)^(((t)-((t)>>7))&mm)))
#define inv_mix_col(x,f2,f4,f8,f9) (\
(f2)=mul2(x,f2), \
(f4)=mul2(f2,f4), \
(f8)=mul2(f4,f8), \
(f9)=(x)^(f8), \
(f8)=((f2)^(f4)^(f8)), \
(f2)^=(f9), \
(f4)^=(f9), \
(f8)^=rot3(f2), \
(f8)^=rot2(f4), \
(f8)^rot1(f9))
/*
* AES S-box
*/
static const uint8_t aes_sbox[256] =
{
0x63,0x7C,0x77,0x7B,0xF2,0x6B,0x6F,0xC5,
0x30,0x01,0x67,0x2B,0xFE,0xD7,0xAB,0x76,
0xCA,0x82,0xC9,0x7D,0xFA,0x59,0x47,0xF0,
0xAD,0xD4,0xA2,0xAF,0x9C,0xA4,0x72,0xC0,
0xB7,0xFD,0x93,0x26,0x36,0x3F,0xF7,0xCC,
0x34,0xA5,0xE5,0xF1,0x71,0xD8,0x31,0x15,
0x04,0xC7,0x23,0xC3,0x18,0x96,0x05,0x9A,
0x07,0x12,0x80,0xE2,0xEB,0x27,0xB2,0x75,
0x09,0x83,0x2C,0x1A,0x1B,0x6E,0x5A,0xA0,
0x52,0x3B,0xD6,0xB3,0x29,0xE3,0x2F,0x84,
0x53,0xD1,0x00,0xED,0x20,0xFC,0xB1,0x5B,
0x6A,0xCB,0xBE,0x39,0x4A,0x4C,0x58,0xCF,
0xD0,0xEF,0xAA,0xFB,0x43,0x4D,0x33,0x85,
0x45,0xF9,0x02,0x7F,0x50,0x3C,0x9F,0xA8,
0x51,0xA3,0x40,0x8F,0x92,0x9D,0x38,0xF5,
0xBC,0xB6,0xDA,0x21,0x10,0xFF,0xF3,0xD2,
0xCD,0x0C,0x13,0xEC,0x5F,0x97,0x44,0x17,
0xC4,0xA7,0x7E,0x3D,0x64,0x5D,0x19,0x73,
0x60,0x81,0x4F,0xDC,0x22,0x2A,0x90,0x88,
0x46,0xEE,0xB8,0x14,0xDE,0x5E,0x0B,0xDB,
0xE0,0x32,0x3A,0x0A,0x49,0x06,0x24,0x5C,
0xC2,0xD3,0xAC,0x62,0x91,0x95,0xE4,0x79,
0xE7,0xC8,0x37,0x6D,0x8D,0xD5,0x4E,0xA9,
0x6C,0x56,0xF4,0xEA,0x65,0x7A,0xAE,0x08,
0xBA,0x78,0x25,0x2E,0x1C,0xA6,0xB4,0xC6,
0xE8,0xDD,0x74,0x1F,0x4B,0xBD,0x8B,0x8A,
0x70,0x3E,0xB5,0x66,0x48,0x03,0xF6,0x0E,
0x61,0x35,0x57,0xB9,0x86,0xC1,0x1D,0x9E,
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,
};
/*
* AES is-box
*/
static const uint8_t aes_isbox[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
};
static const unsigned char 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,
};
/* ----- static functions ----- */
static void AES_encrypt(const AES_CTX *ctx, uint32_t *data);
static void AES_decrypt(const AES_CTX *ctx, uint32_t *data);
/* Perform doubling in Galois Field GF(2^8) using the irreducible polynomial
x^8+x^4+x^3+x+1 */
static unsigned char AES_xtime(uint32_t x)
{
return x = (x&0x80) ? (x<<1)^0x1b : x<<1;
}
/**
* Set up AES with the key/iv and cipher size.
*/
void AES_set_key(AES_CTX *ctx, const uint8_t *key,
const uint8_t *iv, AES_MODE mode)
{
int i, ii;
uint32_t *W, tmp, tmp2;
const unsigned char *ip;
int words;
switch (mode)
{
case AES_MODE_128:
i = 10;
words = 4;
break;
case AES_MODE_256:
i = 14;
words = 8;
break;
default: /* fail silently */
return;
}
ctx->rounds = i;
ctx->key_size = words;
W = ctx->ks;
for (i = 0; i < words; i+=2)
{
W[i+0]= ((uint32_t)key[ 0]<<24)|
((uint32_t)key[ 1]<<16)|
((uint32_t)key[ 2]<< 8)|
((uint32_t)key[ 3] );
W[i+1]= ((uint32_t)key[ 4]<<24)|
((uint32_t)key[ 5]<<16)|
((uint32_t)key[ 6]<< 8)|
((uint32_t)key[ 7] );
key += 8;
}
ip = Rcon;
ii = 4 * (ctx->rounds+1);
for (i = words; i> 8)&0xff]<<16;
tmp2|=(uint32_t)aes_sbox[(tmp>>16)&0xff]<<24;
tmp2|=(uint32_t)aes_sbox[(tmp>>24) ];
tmp=tmp2^(((unsigned int)*ip)<<24);
ip++;
}
if ((words == 8) && ((i % words) == 4))
{
tmp2 =(uint32_t)aes_sbox[(tmp )&0xff] ;
tmp2|=(uint32_t)aes_sbox[(tmp>> 8)&0xff]<< 8;
tmp2|=(uint32_t)aes_sbox[(tmp>>16)&0xff]<<16;
tmp2|=(uint32_t)aes_sbox[(tmp>>24) ]<<24;
tmp=tmp2;
}
W[i]=W[i-words]^tmp;
}
/* copy the iv across */
memcpy(ctx->iv, iv, 16);
}
/**
* Change a key for decryption.
*/
void AES_convert_key(AES_CTX *ctx)
{
int i;
uint32_t *k,w,t1,t2,t3,t4;
k = ctx->ks;
k += 4;
for (i= ctx->rounds*4; i > 4; i--)
{
w= *k;
w = inv_mix_col(w,t1,t2,t3,t4);
*k++ =w;
}
}
/**
* Encrypt a byte sequence (with a block size 16) using the AES cipher.
*/
void AES_cbc_encrypt(AES_CTX *ctx, const uint8_t *msg, uint8_t *out, int length)
{
int i;
uint32_t tin[4], tout[4], iv[4];
memcpy(iv, ctx->iv, AES_IV_SIZE);
for (i = 0; i < 4; i++)
tout[i] = ntohl(iv[i]);
for (length -= AES_BLOCKSIZE; length >= 0; length -= AES_BLOCKSIZE)
{
uint32_t msg_32[4];
uint32_t out_32[4];
memcpy(msg_32, msg, AES_BLOCKSIZE);
msg += AES_BLOCKSIZE;
for (i = 0; i < 4; i++)
tin[i] = ntohl(msg_32[i])^tout[i];
AES_encrypt(ctx, tin);
for (i = 0; i < 4; i++)
{
tout[i] = tin[i];
out_32[i] = htonl(tout[i]);
}
memcpy(out, out_32, AES_BLOCKSIZE);
out += AES_BLOCKSIZE;
}
for (i = 0; i < 4; i++)
iv[i] = htonl(tout[i]);
memcpy(ctx->iv, iv, AES_IV_SIZE);
}
/**
* Decrypt a byte sequence (with a block size 16) using the AES cipher.
*/
void AES_cbc_decrypt(AES_CTX *ctx, const uint8_t *msg, uint8_t *out, int length)
{
int i;
uint32_t tin[4], xor[4], tout[4], data[4], iv[4];
memcpy(iv, ctx->iv, AES_IV_SIZE);
for (i = 0; i < 4; i++)
xor[i] = ntohl(iv[i]);
for (length -= 16; length >= 0; length -= 16)
{
uint32_t msg_32[4];
uint32_t out_32[4];
memcpy(msg_32, msg, AES_BLOCKSIZE);
msg += AES_BLOCKSIZE;
for (i = 0; i < 4; i++)
{
tin[i] = ntohl(msg_32[i]);
data[i] = tin[i];
}
AES_decrypt(ctx, data);
for (i = 0; i < 4; i++)
{
tout[i] = data[i]^xor[i];
xor[i] = tin[i];
out_32[i] = htonl(tout[i]);
}
memcpy(out, out_32, AES_BLOCKSIZE);
out += AES_BLOCKSIZE;
}
for (i = 0; i < 4; i++)
iv[i] = htonl(xor[i]);
memcpy(ctx->iv, iv, AES_IV_SIZE);
}
/**
* Encrypt a single block (16 bytes) of data
*/
static void AES_encrypt(const AES_CTX *ctx, uint32_t *data)
{
/* To make this code smaller, generate the sbox entries on the fly.
* This will have a really heavy effect upon performance.
*/
uint32_t tmp[4];
uint32_t tmp1, old_a0, a0, a1, a2, a3, row;
int curr_rnd;
int rounds = ctx->rounds;
const uint32_t *k = ctx->ks;
/* Pre-round key addition */
for (row = 0; row < 4; row++)
data[row] ^= *(k++);
/* Encrypt one block. */
for (curr_rnd = 0; curr_rnd < rounds; curr_rnd++)
{
/* Perform ByteSub and ShiftRow operations together */
for (row = 0; row < 4; row++)
{
a0 = (uint32_t)aes_sbox[(data[row%4]>>24)&0xFF];
a1 = (uint32_t)aes_sbox[(data[(row+1)%4]>>16)&0xFF];
a2 = (uint32_t)aes_sbox[(data[(row+2)%4]>>8)&0xFF];
a3 = (uint32_t)aes_sbox[(data[(row+3)%4])&0xFF];
/* Perform MixColumn iff not last round */
if (curr_rnd < (rounds - 1))
{
tmp1 = a0 ^ a1 ^ a2 ^ a3;
old_a0 = a0;
a0 ^= tmp1 ^ AES_xtime(a0 ^ a1);
a1 ^= tmp1 ^ AES_xtime(a1 ^ a2);
a2 ^= tmp1 ^ AES_xtime(a2 ^ a3);
a3 ^= tmp1 ^ AES_xtime(a3 ^ old_a0);
}
tmp[row] = ((a0 << 24) | (a1 << 16) | (a2 << 8) | a3);
}
/* KeyAddition - note that it is vital that this loop is separate from
the MixColumn operation, which must be atomic...*/
for (row = 0; row < 4; row++)
data[row] = tmp[row] ^ *(k++);
}
}
/**
* Decrypt a single block (16 bytes) of data
*/
static void AES_decrypt(const AES_CTX *ctx, uint32_t *data)
{
uint32_t tmp[4];
uint32_t xt0,xt1,xt2,xt3,xt4,xt5,xt6;
uint32_t a0, a1, a2, a3, row;
int curr_rnd;
int rounds = ctx->rounds;
const uint32_t *k = ctx->ks + ((rounds+1)*4);
/* pre-round key addition */
for (row=4; row > 0;row--)
data[row-1] ^= *(--k);
/* Decrypt one block */
for (curr_rnd = 0; curr_rnd < rounds; curr_rnd++)
{
/* Perform ByteSub and ShiftRow operations together */
for (row = 4; row > 0; row--)
{
a0 = aes_isbox[(data[(row+3)%4]>>24)&0xFF];
a1 = aes_isbox[(data[(row+2)%4]>>16)&0xFF];
a2 = aes_isbox[(data[(row+1)%4]>>8)&0xFF];
a3 = aes_isbox[(data[row%4])&0xFF];
/* Perform MixColumn iff not last round */
if (curr_rnd<(rounds-1))
{
/* The MDS cofefficients (0x09, 0x0B, 0x0D, 0x0E)
are quite large compared to encryption; this
operation slows decryption down noticeably. */
xt0 = AES_xtime(a0^a1);
xt1 = AES_xtime(a1^a2);
xt2 = AES_xtime(a2^a3);
xt3 = AES_xtime(a3^a0);
xt4 = AES_xtime(xt0^xt1);
xt5 = AES_xtime(xt1^xt2);
xt6 = AES_xtime(xt4^xt5);
xt0 ^= a1^a2^a3^xt4^xt6;
xt1 ^= a0^a2^a3^xt5^xt6;
xt2 ^= a0^a1^a3^xt4^xt6;
xt3 ^= a0^a1^a2^xt5^xt6;
tmp[row-1] = ((xt0<<24)|(xt1<<16)|(xt2<<8)|xt3);
}
else
tmp[row-1] = ((a0<<24)|(a1<<16)|(a2<<8)|a3);
}
for (row = 4; row > 0; row--)
data[row-1] = tmp[row-1] ^ *(--k);
}
}