C语言实现AES和RSA加密算法：深入代码解析

本文将介绍两种常用的加密算法：AES和RSA，并提供它们的C语言实现示例代码。示例代码深入解析了算法的加密过程，帮助读者理解加密算法的本质，并能够自主进行代码实现和应用。

AES加密算法示例代码

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

#define AES_BLOCK_SIZE 16

typedef uint8_t state_t[4][4];

static const uint8_t sbox[256] =   { /* S-box */
  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
};

static const uint8_t rcon[11] = {
  0x01, 0x00, 0x00, 0x00, 0x02, 0x00, 0x00, 0x00, 0x04, 0x00, 0x00
};

void SubBytes(state_t* state) {
  int i, j;
  for (i = 0; i < 4; ++i)
    for (j = 0; j < 4; ++j)
      (*state)[i][j] = sbox[(*state)[i][j]];
}

void ShiftRows(state_t* state) {
  uint8_t temp;

  // Rotate first row 1 columns to left
  temp           = (*state)[0][1];
  (*state)[0][1] = (*state)[1][1];
  (*state)[1][1] = (*state)[2][1];
  (*state)[2][1] = (*state)[3][1];
  (*state)[3][1] = temp;

  // Rotate second row 2 columns to left
  temp           = (*state)[0][2];
  (*state)[0][2] = (*state)[2][2];
  (*state)[2][2] = temp;

  temp           = (*state)[1][2];
  (*state)[1][2] = (*state)[3][2];
  (*state)[3][2] = temp;

  // Rotate third row 3 columns to left
  temp           = (*state)[0][3];
  (*state)[0][3] = (*state)[3][3];
  (*state)[3][3] = (*state)[2][3];
  (*state)[2][3] = (*state)[1][3];
  (*state)[1][3] = temp;
}

static void MixColumns(state_t* state) {
  int i;
  uint8_t Tmp, Tm, t;
  for (i = 0; i < 4; ++i) {
    t   = (*state)[i][0];
    Tmp = (*state)[i][0] ^ (*state)[i][1] ^ (*state)[i][2] ^ (*state)[i][3];
    Tm  = (*state)[i][0] ^ (*state)[i][1];
    Tm = xtime(Tm);
    (*state)[i][0] ^= Tm ^ Tmp;
    Tm  = (*state)[i][1] ^ (*state)[i][2];
    Tm = xtime(Tm);
    (*state)[i][1] ^= Tm ^ Tmp;
    Tm  = (*state)[i][2] ^ (*state)[i][3];
    Tm = xtime(Tm);
    (*state)[i][2] ^= Tm ^ Tmp;
    Tm  = (*state)[i][3] ^ t;
    Tm = xtime(Tm);
    (*state)[i][3] ^= Tm ^ Tmp;
  }
}

static void AddRoundKey(uint8_t round, state_t* state, const uint8_t* RoundKey) {
  uint8_t i, j;
  for (i = 0; i < 4; ++i)
    for (j = 0; j < 4; ++j)
      (*state)[i][j] ^= RoundKey[round * AES_BLOCK_SIZE + i * 4 + j];
}

void aes_encrypt(const uint8_t* input, const uint8_t* key, uint8_t* output) {
  state_t* state = (state_t*)output;

  uint8_t RoundKey[AES_BLOCK_SIZE * (10 + 1)];
  KeyExpansion(key, RoundKey);

  memcpy(state, input, AES_BLOCK_SIZE);

  AddRoundKey(0, state, RoundKey);

  for (uint8_t round = 1; round < 10; ++round) {
    SubBytes(state);
    ShiftRows(state);
    MixColumns(state);
    AddRoundKey(round, state, RoundKey);
  }

  SubBytes(state);
  ShiftRows(state);
  AddRoundKey(10, state, RoundKey);
}

RSA加密算法示例代码

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

uint64_t mod_pow(uint64_t base, uint64_t exponent, uint64_t modulus) {
  uint64_t result = 1;
  base = base % modulus;
  while (exponent > 0) {
    if (exponent & 1)
      result = (result * base) % modulus;
    exponent = exponent >> 1;
    base = (base * base) % modulus;
  }
  return result;
}

uint64_t mod_inverse(uint64_t a, uint64_t m) {
  int64_t m0 = m;
  int64_t y = 0, x = 1;

  if (m == 1)
    return 0;

  while (a > 1) {
    int64_t q = a / m;
    int64_t t = m;
    m = a % m, a = t;
    t = y;
    y = x - q * y;
    x = t;
  }

  if (x < 0)
    x += m0;

  return x;
}

uint64_t gcd(uint64_t a, uint64_t b) {
  if (b == 0)
    return a;
  return gcd(b, a % b);
}

uint64_t generate_prime(uint64_t min, uint64_t max) {
  uint64_t p;
  do {
    p = rand() % (max - min + 1) + min;
  } while (!is_prime(p));
  return p;
}

int is_prime(uint64_t n) {
  if (n <= 1)
    return 0;
  if (n <= 3)
    return 1;
  if (n % 2 == 0 || n % 3 == 0)
    return 0;
  for (uint64_t i = 5; i * i <= n; i += 6) {
    if (n % i == 0 || n % (i + 2) == 0)
      return 0;
  }
  return 1;
}

uint64_t generate_coprime(uint64_t phi_n) {
  uint64_t e;
  do {
    e = rand() % phi_n;
  } while (gcd(e, phi_n) != 1);
  return e;
}

void rsa_encrypt(uint64_t plain_text, uint64_t e, uint64_t n, uint64_t* cipher_text) {
  *cipher_text = mod_pow(plain_text, e, n);
}

注意：

以上代码仅为示例，实际使用中需要根据具体需求进行修改和完善。
代码中省略了一些重要的步骤，例如密钥生成、密钥交换等，需要根据实际情况进行补充。
在实际应用中，建议使用已经经过安全验证的加密库，避免因代码实现错误导致的安全风险。

通过深入理解和分析示例代码，读者可以更好地理解AES和RSA加密算法的原理，并将其应用到实际的项目开发中。

希望本文能够帮助您更好地了解加密算法的实现过程，并能够更好地保护您的数据安全。