RC5加密算法C++实现过程

#include <iostream>
#include <cstring>

typedef unsigned int uint32_t; //定义32位无符号整数

const uint32_t P = 0xb7e15163; //定义P值
const uint32_t Q = 0x9e3779b9; //定义Q值

// 左移函数
uint32_t rotate_left(uint32_t x, uint32_t y) {
    return (x << y) | (x >> (32 - y));
}

// 右移函数
uint32_t rotate_right(uint32_t x, uint32_t y) {
    return (x >> y) | (x << (32 - y));
}

// 加密函数
void rc5_encrypt(uint32_t *pt, uint32_t *ct, uint32_t *key, int rounds) {
    uint32_t i, j, a, b, *s, t, u;
    s = new uint32_t[2*rounds + 2];
    s[0] = P;
    for (i = 1; i < 2*rounds + 2; i++)
        s[i] = s[i-1] + Q;

    i = j = 0;
    a = b = 0;

    for (int k = 0; k < 4; k++) {
        a |= key[k] << (k*8);
        b |= key[k+4] << (k*8);
    }

    a = a + s[0];
    b = b + s[1];

    for (i = 2; i <= 2*rounds; i++) {
        t = rotate_left(a + b, 3);
        a = t;
        u = t + b;
        t = rotate_left(b, u);
        b = t;
        u = t + a;

        a = rotate_left(a + s[i], u);
        t = rotate_left(b + s[i+1], u);
        b = t;

        i += 1;
    }

    ct[0] = a;
    ct[1] = b;
}

// 解密函数
void rc5_decrypt(uint32_t *ct, uint32_t *pt, uint32_t *key, int rounds) {
    uint32_t i, j, a, b, *s, t, u;
    s = new uint32_t[2*rounds + 2];
    s[0] = P;
    for (i = 1; i < 2*rounds + 2; i++)
        s[i] = s[i-1] + Q;

    i = j = 0;
    a = b = 0;

    for (int k = 0; k < 4; k++) {
        a |= key[k] << (k*8);
        b |= key[k+4] << (k*8);
    }

    ct[0] = ct[0] - s[2*rounds + 1];
    ct[1] = ct[1] - s[2*rounds];

    for (i = 2*rounds; i >= 2; i--) {
        t = rotate_left(b, u);
        b = ct[1] - s[i-1];
        u = t + b;
        t = rotate_left(a, u);
        a = ct[0] - s[i-2];
        b = t + a;
        a = t - rotate_left(a + s[i-1], u);
        i -= 1;
    }

    pt[0] = a;
    pt[1] = b;
}

// 测试函数
int main() {
    uint32_t pt[2] = {0x01234567, 0x89abcdef};
    uint32_t key[8] = {0x00010203, 0x04050607, 0x08090a0b, 0x0c0d0e0f,
                       0x10111213, 0x14151617, 0x18191a1b, 0x1c1d1e1f};
    uint32_t ct[2];
    int rounds = 12;

    rc5_encrypt(pt, ct, key, rounds);
    std::cout << "Encrypted message: " << std::hex << ct[0] << " " << ct[1] << std::endl;

    rc5_decrypt(ct, pt, key, rounds);
    std::cout << "Decrypted message: " << std::hex << pt[0] << " " << pt[1] << std::endl;

    return 0;
}