C语言实现AES加密算法：代码详解及应用场景

以下是使用C语言实现AES加密算法的代码示例：

#include <stdio.h>
#include <stdint.h>

// AES S盒
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
};

// AES密钥扩展
void aes_key_expansion(const uint8_t *key, uint8_t *expanded_key) {
    uint32_t temp;
    int i = 0;
    
    while (i < 16) {
        expanded_key[i] = key[i];
        i++;
    }
    
    i = 16;
    
    while (i < 176) {
        temp = *(uint32_t*)&expanded_key[i - 4];
        
        if (i % 16 == 0) {
            temp = (temp << 8) | (temp >> 24);
            temp = sbox[temp >> 24] | (sbox[(temp >> 16) & 0xFF] << 8) | (sbox[(temp >> 8) & 0xFF] << 16) | (sbox[temp & 0xFF] << 24);
            temp ^= (0x1B << 24 >> ((i / 16) - 1));
        }
        
        *(uint32_t*)&expanded_key[i] = *(uint32_t*)&expanded_key[i - 16] ^ temp;
        i += 4;
    }
}

// AES字节替代
void aes_sub_bytes(uint8_t *state) {
    int i;
    
    for (i = 0; i < 16; i++) {
        state[i] = sbox[state[i]];
    }
}

// AES行移位
void aes_shift_rows(uint8_t *state) {
    uint8_t temp;
    
    // 第二行左移1个字节
    temp = state[1];
    state[1] = state[5];
    state[5] = state[9];
    state[9] = state[13];
    state[13] = temp;
    
    // 第三行左移2个字节
    temp = state[2];
    state[2] = state[10];
    state[10] = temp;
    temp = state[6];
    state[6] = state[14];
    state[14] = temp;
    
    // 第四行左移3个字节
    temp = state[15];
    state[15] = state[11];
    state[11] = state[7];
    state[7] = state[3];
    state[3] = temp;
}

// AES列混合
void aes_mix_columns(uint8_t *state) {
    int i;
    uint8_t a, b, c, d;
    
    for (i = 0; i < 16; i += 4) {
        a = state[i];
        b = state[i + 1];
        c = state[i + 2];
        d = state[i + 3];
        
        state[i] = (uint8_t)(mul(0x02, a) ^ mul(0x03, b) ^ mul(0x01, c) ^ mul(0x01, d));
        state[i + 1] = (uint8_t)(mul(0x01, a) ^ mul(0x02, b) ^ mul(0x03, c) ^ mul(0x01, d));
        state[i + 2] = (uint8_t)(mul(0x01, a) ^ mul(0x01, b) ^ mul(0x02, c) ^ mul(0x03, d));
        state[i + 3] = (uint8_t)(mul(0x03, a) ^ mul(0x01, b) ^ mul(0x01, c) ^ mul(0x02, d));
    }
}

// AES轮密钥加
void aes_add_round_key(uint8_t *state, const uint8_t *round_key) {
    int i;
    
    for (i = 0; i < 16; i++) {
        state[i] ^= round_key[i];
    }
}

// AES加密
void aes_encrypt(const uint8_t *plaintext, const uint8_t *key, uint8_t *ciphertext) {
    uint8_t state[16];
    uint8_t round_key[176];
    int i, j, round = 0;
    
    for (i = 0; i < 16; i++) {
        state[i] = plaintext[i];
    }
    
    aes_key_expansion(key, round_key);
    aes_add_round_key(state, key);
    
    for (round = 1; round < 10; round++) {
        aes_sub_bytes(state);
        aes_shift_rows(state);
        aes_mix_columns(state);
        aes_add_round_key(state, round_key + round * 16);
    }
    
    aes_sub_bytes(state);
    aes_shift_rows(state);
    aes_add_round_key(state, round_key + 160);
    
    for (i = 0; i < 16; i++) {
        ciphertext[i] = state[i];
    }
}

int main() {
    uint8_t plaintext[16] = {0x32, 0x88, 0x31, 0xe0, 0x43, 0x5a, 0x31, 0x37, 0xf6, 0x30, 0x98, 0x07, 0xa8, 0x8d, 0xa2, 0x34};
    uint8_t key[16] = {0x2b, 0x7e, 0x15, 0x16, 0x28, 0xae, 0xd2, 0xa6, 0xab, 0xf7, 0x15, 0x88, 0x09, 0xcf, 0x4f, 0x3c};
    uint8_t ciphertext[16];
    int i;

    aes_encrypt(plaintext, key, ciphertext);

    printf("Plaintext: ");
    for (i = 0; i < 16; i++) {
        printf("%02x ", plaintext[i]);
    }
    
    printf("
Key: ");
    for (i = 0; i < 16; i++) {
        printf("%02x ", key[i]);
    }
    
    printf("
Ciphertext: ");
    for (i = 0; i < 16; i++) {
        printf("%02x ", ciphertext[i]);
    }

    return 0;
}

该代码示例实现了AES加密算法的各个步骤，包括密钥扩展、字节替代、行移位、列混合和轮密钥加。通过调用aes_encrypt函数，可以将给定的明文和密钥进行加密，并输出加密后的密文。

注意事项

该代码示例仅供学习参考，实际应用中需要进行更完善的安全性和性能优化。
AES加密算法是一种对称加密算法，即加密和解密使用相同的密钥。
在实际应用中，密钥的生成和管理非常重要，需要采用安全可靠的机制。
AES加密算法广泛应用于网络安全、数据存储等领域。

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