aes c源码的神秘面纱，它究竟隐藏着哪些加密的秘密？

AES（Advanced Encryption Standard）是一种对称加密算法，广泛应用于数据加密和解密，以下是一个简单的C语言实现的AES加密和解密示例：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
// AES加密轮数
#define Nb 4
#define Nk 4
#define Nr 10
// S盒
unsigned char s_box[256] = {
    // ...省略具体数值
};
// 逆S盒
unsigned char inv_s_box[256] = {
    // ...省略具体数值
};
// Rcon
unsigned char rcon[11] = {
    // ...省略具体数值
};
// MixColumn矩阵
unsigned char mix_column[4][4] = {
    // ...省略具体数值
};
// InvMixColumn矩阵
unsigned char inv_mix_column[4][4] = {
    // ...省略具体数值
};
// 字节替换
void byte_substitution(unsigned char *state) {
    for (int i = 0; i < 4; i++) {
        state[i] = s_box[state[i]];
    }
}
// 逆字节替换
void inv_byte_substitution(unsigned char *state) {
    for (int i = 0; i < 4; i++) {
        state[i] = inv_s_box[state[i]];
    }
}
// 行移位
void shift_rows(unsigned char *state) {
    unsigned char temp[4];
    temp[0] = state[1];
    temp[1] = state[2];
    temp[2] = state[3];
    temp[3] = state[0];
    state[0] = temp[0];
    state[1] = temp[1];
    state[2] = temp[2];
    state[3] = temp[3];
}
// 逆行移位
void inv_shift_rows(unsigned char *state) {
    unsigned char temp[4];
    temp[0] = state[3];
    temp[1] = state[0];
    temp[2] = state[1];
    temp[3] = state[2];
    state[0] = temp[0];
    state[1] = temp[1];
    state[2] = temp[2];
    state[3] = temp[3];
}
// 列混淆
void mix_columns(unsigned char *state) {
    unsigned char temp[4];
    for (int i = 0; i < 4; i++) {
        temp[i] = 0;
        for (int j = 0; j < 4; j++) {
            temp[i] ^= mix_column[j][i] ^ (state[j] & 0x80);
        }
    }
    memcpy(state, temp, 4);
}
// 逆列混淆
void inv_mix_columns(unsigned char *state) {
    unsigned char temp[4];
    for (int i = 0; i < 4; i++) {
        temp[i] = 0;
        for (int j = 0; j < 4; j++) {
            temp[i] ^= inv_mix_column[j][i] ^ (state[j] & 0x80);
        }
    }
    memcpy(state, temp, 4);
}
// 密钥加
void add_round_key(unsigned char *state, unsigned char *key) {
    for (int i = 0; i < 4; i++) {
        state[i] ^= key[i];
    }
}
// AES加密
void aes_encrypt(unsigned char *plaintext, unsigned char *ciphertext, unsigned char *key) {
    unsigned char state[4];
    memcpy(state, plaintext, 4);
    add_round_key(state, key);
    for (int round = 1; round < Nr; round++) {
        byte_substitution(state);
        shift_rows(state);
        mix_columns(state);
        add_round_key(state, key + round * 4);
    }
    byte_substitution(state);
    shift_rows(state);
    add_round_key(state, key + Nr * 4);
    memcpy(ciphertext, state, 4);
}
// AES解密
void aes_decrypt(unsigned char *ciphertext, unsigned char *plaintext, unsigned char *key) {
    unsigned char state[4];
    memcpy(state, ciphertext, 4);
    add_round_key(state, key + Nr * 4);
    for (int round = Nr  1; round > 0; round) {
        inv_shift_rows(state);
        inv_byte_substitution(state);
        add_round_key(state, key + round * 4);
        inv_mix_columns(state);
    }
    inv_shift_rows(state);
    inv_byte_substitution(state);
    add_round_key(state, key);
    memcpy(plaintext, state, 4);
}
int main() {
    unsigned char plaintext[4] = {0x32, 0x88, 0x31, 0xe0}; // 明文
    unsigned char key[16] = {0x2b, 0x7e, 0x15, 0x16, 0x28, 0xae, 0xd2, 0xa6, 0xab, 0xf7, 0x15, 0x88, 0x09, 0xcf, 0x4f, 0x3c}; // 密钥
    unsigned char ciphertext[4]; // 密文
    unsigned char decrypted[4]; // 解密后的明文
    aes_encrypt(plaintext, ciphertext, key);
    aes_decrypt(ciphertext, decrypted, key);
    printf("明文: ");
    for (int i = 0; i < 4; i++) {
        printf("%02x ", plaintext[i]);
    }
    printf("
密文: ");
    for (int i = 0; i < 4; i++) {
        printf("%02x ", ciphertext[i]);
    }
    printf("
解密后的明文: ");
    for (int i = 0; i < 4; i++) {
        printf("%02x ", decrypted[i]);
    }
    printf("
");
    return 0;
}

注意：这个示例仅用于演示目的，实际应用中请使用更安全的加密库。

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