基于C语言实现的aes256加密算法示例

#ifndef uint8_t
#define uint8_t unsigned char
#endif
#ifdef __cplusplus
extern "C" { 
#endif
  typedef struct {
    uint8_t key[32]; 
    uint8_t enckey[32]; 
    uint8_t deckey[32];
  } aes256_context; 
  void aes256_init(aes256_context *,uint8_t * );
  void aes256_done(aes256_context *);
  void aes256_encrypt_ecb(aes256_context *,uint8_t * );
  void aes256_decrypt_ecb(aes256_context *,uint8_t * );
#ifdef __cplusplus
}
#endif

#include "aes256.h"
#define F(x)  (((x)<<1) ^ ((((x)>>7) & 1) * 0x1b))
#define FD(x) (((x) >> 1) ^ (((x) & 1) ? 0x8d : 0))
// #define BACK_TO_TABLES
#ifdef BACK_TO_TABLES
const uint8_t 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
};
const uint8_t sboxinv[256] = {
  0x52,0x16,0x63,0x7d
};
#define rj_sbox(x)   sbox[(x)]
#define rj_sbox_inv(x) sboxinv[(x)]
#else
uint8_t gf_alog(uint8_t x) // calculate anti-logarithm gen 3
{
  uint8_t atb = 1,z;
  while (x--) {z = atb; atb <<= 1; if (z & 0x80) atb^= 0x1b; atb ^= z;}
  return atb;
}
uint8_t gf_log(uint8_t x) // calculate logarithm gen 3
{
  uint8_t atb = 1,i = 0,z;
  do {
    if (atb == x) break;
    z = atb; atb <<= 1; if (z & 0x80) atb^= 0x1b; atb ^= z;
  } while (++i > 0);
  return i;
}
uint8_t gf_mulinv(uint8_t x) // calculate multiplicative inverse
{
  return (x) ? gf_alog(255 - gf_log(x)) : 0;
}
uint8_t rj_sbox(uint8_t x)
{
  uint8_t y,sb;
  sb = y = gf_mulinv(x);
  y = (y<<1)|(y>>7); sb ^= y; y = (y<<1)|(y>>7); sb ^= y; 
  y = (y<<1)|(y>>7); sb ^= y; y = (y<<1)|(y>>7); sb ^= y;
  return (sb ^ 0x63);
}
uint8_t rj_sbox_inv(uint8_t x)
{
  uint8_t y,sb;
  y = x ^ 0x63;
  sb = y = (y<<1)|(y>>7);
  y = (y<<2)|(y>>6); sb ^= y; y = (y<<3)|(y>>5); sb ^= y;
  return gf_mulinv(sb);
}
#endif
uint8_t rj_xtime(uint8_t x) 
{
  return (x & 0x80) ? ((x << 1) ^ 0x1b) : (x << 1);
}
void aes_subBytes(uint8_t *buf)
{
  register uint8_t i = 16;
  while (i--) buf[i] = rj_sbox(buf[i]);
}
void aes_subBytes_inv(uint8_t *buf)
{
  register uint8_t i = 16;
  while (i--) buf[i] = rj_sbox_inv(buf[i]);
}
void aes_addRoundKey(uint8_t *buf,uint8_t *key)
{
  register uint8_t i = 16;
  while (i--) buf[i] ^= key[i];
}
void aes_addRoundKey_cpy(uint8_t *buf,uint8_t *key,uint8_t *cpk)
{
  register uint8_t i = 16;
  while (i--) buf[i] ^= (cpk[i] = key[i]),cpk[16+i] = key[16 + i];
}
void aes_shiftRows(uint8_t *buf)
{
  register uint8_t i,j;
  i = buf[1]; buf[1] = buf[5]; buf[5] = buf[9]; buf[9] = buf[13]; buf[13] = i;
  i = buf[10]; buf[10] = buf[2]; buf[2] = i;
  j = buf[3]; buf[3] = buf[15]; buf[15] = buf[11]; buf[11] = buf[7]; buf[7] = j;
  j = buf[14]; buf[14] = buf[6]; buf[6] = j;
}
void aes_shiftRows_inv(uint8_t *buf)
{
  register uint8_t i,j;
  i = buf[1]; buf[1] = buf[13]; buf[13] = buf[9]; buf[9] = buf[5]; buf[5] = i;
  i = buf[2]; buf[2] = buf[10]; buf[10] = i;
  j = buf[3]; buf[3] = buf[7]; buf[7] = buf[11]; buf[11] = buf[15]; buf[15] = j;
  j = buf[6]; buf[6] = buf[14]; buf[14] = j;
}
void aes_mixColumns(uint8_t *buf)
{
  register uint8_t i,a,b,c,d,e;
  for (i = 0; i < 16; i += 4)
  {
    a = buf[i]; b = buf[i + 1]; c = buf[i + 2]; d = buf[i + 3];
    e = a ^ b ^ c ^ d;
    buf[i] ^= e ^ rj_xtime(a^b);  buf[i+1] ^= e ^ rj_xtime(b^c);
    buf[i+2] ^= e ^ rj_xtime(c^d); buf[i+3] ^= e ^ rj_xtime(d^a);
  }
}
void aes_mixColumns_inv(uint8_t *buf)
{
  register uint8_t i,e,x,y,z;
  for (i = 0; i < 16; i += 4)
  {
    a = buf[i]; b = buf[i + 1]; c = buf[i + 2]; d = buf[i + 3];
    e = a ^ b ^ c ^ d;
    z = rj_xtime(e);
    x = e ^ rj_xtime(rj_xtime(z^a^c)); y = e ^ rj_xtime(rj_xtime(z^b^d));
    buf[i] ^= x ^ rj_xtime(a^b);  buf[i+1] ^= y ^ rj_xtime(b^c);
    buf[i+2] ^= x ^ rj_xtime(c^d); buf[i+3] ^= y ^ rj_xtime(d^a);
  }
}
void aes_expandEncKey(uint8_t *k,uint8_t *rc) 
{
  register uint8_t i;
  k[0] ^= rj_sbox(k[29]) ^ (*rc);
  k[1] ^= rj_sbox(k[30]);
  k[2] ^= rj_sbox(k[31]);
  k[3] ^= rj_sbox(k[28]);
  *rc = F( *rc);
  for(i = 4; i < 16; i += 4) k[i] ^= k[i-4],k[i+1] ^= k[i-3],k[i+2] ^= k[i-2],k[i+3] ^= k[i-1];
  k[16] ^= rj_sbox(k[12]);
  k[17] ^= rj_sbox(k[13]);
  k[18] ^= rj_sbox(k[14]);
  k[19] ^= rj_sbox(k[15]);
  for(i = 20; i < 32; i += 4) k[i] ^= k[i-4],k[i+3] ^= k[i-1];
}
void aes_expandDecKey(uint8_t *k,uint8_t *rc) 
{
  uint8_t i;
  for(i = 28; i > 16; i -= 4) k[i+0] ^= k[i-4],k[i+3] ^= k[i-1];
  k[16] ^= rj_sbox(k[12]);
  k[17] ^= rj_sbox(k[13]);
  k[18] ^= rj_sbox(k[14]);
  k[19] ^= rj_sbox(k[15]);
  for(i = 12; i > 0; i -= 4) k[i+0] ^= k[i-4],k[i+3] ^= k[i-1];
  *rc = FD(*rc);
  k[0] ^= rj_sbox(k[29]) ^ (*rc);
  k[1] ^= rj_sbox(k[30]);
  k[2] ^= rj_sbox(k[31]);
  k[3] ^= rj_sbox(k[28]);
}
void aes256_init(aes256_context *ctx,uint8_t *k)
{
  uint8_t rcon = 1;
  register uint8_t i;
  for (i = 0; i < sizeof(ctx->key); i++) ctx->enckey[i] = ctx->deckey[i] = k[i];
  for (i = 8;--i;) aes_expandEncKey(ctx->deckey,&rcon);
}
void aes256_done(aes256_context *ctx)
{
  register uint8_t i;
  for (i = 0; i < sizeof(ctx->key); i++) 
    ctx->key[i] = ctx->enckey[i] = ctx->deckey[i] = 0;
}
void aes256_encrypt_ecb(aes256_context *ctx,uint8_t *buf)
{
  uint8_t i,rcon;
  aes_addRoundKey_cpy(buf,ctx->enckey,ctx->key);
  for(i = 1,rcon = 1; i < 14; ++i)
  {
    aes_subBytes(buf);
    aes_shiftRows(buf);
    aes_mixColumns(buf);
    if( i & 1 ) aes_addRoundKey( buf,&ctx->key[16]);
    else aes_expandEncKey(ctx->key,&rcon),aes_addRoundKey(buf,ctx->key);
  }
  aes_subBytes(buf);
  aes_shiftRows(buf);
  aes_expandEncKey(ctx->key,&rcon); 
  aes_addRoundKey(buf,ctx->key);
}
void aes256_decrypt_ecb(aes256_context *ctx,ctx->deckey,ctx->key);
  aes_shiftRows_inv(buf);
  aes_subBytes_inv(buf);
  for (i = 14,rcon = 0x80; --i;)
  {
    if( ( i & 1 ) )      
    {
      aes_expandDecKey(ctx->key,&rcon);
      aes_addRoundKey(buf,&ctx->key[16]);
    }
    else aes_addRoundKey(buf,ctx->key);
    aes_mixColumns_inv(buf);
    aes_shiftRows_inv(buf);
    aes_subBytes_inv(buf);
  }
  aes_addRoundKey( buf,ctx->key); 
}

#include
#include
#include "aes256.h"
#define DUMP(s,i,buf,sz) {printf(s);          /
               for (i = 0; i < (sz);i++)  /
                 printf("x ",buf[i]); /
               printf("/n");}
int main (int argc,char *argv[])
{
  aes256_context ctx; 
  uint8_t key[32];
  uint8_t buf[16],i;
  for (i = 0; i < sizeof(buf);i++) buf[i] = i * 16 + i;
  for (i = 0; i < sizeof(key);i++) key[i] = i;
  DUMP("txt: ",sizeof(buf));
  DUMP("key: ",key,sizeof(key));
  printf("---/n");
  aes256_init(&ctx,key);
  aes256_encrypt_ecb(&ctx,buf);
  DUMP("enc: ",sizeof(buf));
  printf("tst: 8e a2 b7 ca 51 67 45 bf ea fc 49 90 4b 49 60 89/n");
  aes256_init(&ctx,key);
  aes256_decrypt_ecb(&ctx,buf);
  DUMP("dec: ",sizeof(buf));
  aes256_done(&ctx);
  return 0;
}