安全算法-AES 加密算法源码解析

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/**
* @brief
Key Expansion
* @param
*key 密钥
* @param
*w
密钥编排结果
* @retval
*/
void aes_key_expansion(uint8_t *key, uint8_t *w)
{
uint8_t tmp[4];
uint8_t i;
uint8_t len = Nb*(Nr+1);
//分组大小*(轮数+1)
//1)将初始密钥以列为主，转化为4个32 bits的字，分别记为w[0…3]
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];
}
//2)依次求解w[i]，其中j是整数并且属于[4,43]；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];
//3)若i%4=0,则w[i]=w[i-4]⊕g(w[i-1]),否则w[i]=w[i-4]⊕w[i-1]；if (i%Nk == 0) {
rot_word(tmp);
//4)将w循环左移一个字节；sub_word(tmp);
//5)分别对每个字节按S盒进行映射；coef_add(tmp, Rcon(i/Nk), tmp);
//6)与32 bits的常量（RC[j/4],0,0,0）进行异或
} 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];
}
}

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代码如下：
/**
* @brief
Performs the AES cipher operation
* @param
*in
明文
* @param
*out
加密后的密文
* @param
*w 扩展后的密钥
* @retval
*/
void aes_cipher(uint8_t *in, uint8_t *out, uint8_t *w)
{
uint8_t state[4*Nb];
uint8_t r, i, j;
//STEP2: 把128bit字符放进状态矩阵
for (i = 0; i < 4; i++) {
for (j = 0; j < Nb; j++) {
state[Nb*i+j] = in[i+4*j];
}
}
//STEP3: 对状态矩阵进行混淆
add_round_key(state, w, 0);
//STEP4: 在执行完Nr轮加密
for (r = 1; r < Nr; r++) {
sub_bytes(state);
//字节替换
shift_rows(state);
//行移位变换
mix_columns(state);
//列混合变换
add_round_key(state, w, r);
//轮密钥加变换
}
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];
}
}
}

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/**
* @brief
Performs the AES inverse cipher operation
* @param
*in
密文
* @param
*out
密文的逆
* @param
*w 扩展后的密钥
* @retval
*/
void aes_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];
}
}
}