tea&xtea加解密函数模板(c语言)

tea和xtea的核心在v0的状态是根据v1和sum来更新的，v1的状态是根据v0和sum来更新的，ctf中经常遇到各种变种的tea xtea，可能是修改了delta，或者是更改了v0 v1更新的方式，或者是修改了更新的轮数，编写decrypt方式都大同小异，可以根据下面的模板来修改

xtea在tea的基础上，取k的时候使用k[] 这种方式动态的取key，感觉是为了使每次更新v0 v1更随机

tea的实现

void teacrypt(uint32_t* v,uint32_t* k) {
    uint32_t v0 = v[0], v1 = v[1], sum = 0, i;
    uint32_t delta = 0x9e3779b9;
    uint32_t k0 = k[0], k1 = k[1], k2 = k[2], k3 = k[3];
    for (i = 0; i < 32; i++)
    {
        sum += delta;
        v0 += ((v1 << 4) + k0) ^ (v1 + sum) ^ ((v1 >> 5) + k1);
        v1 += ((v0 << 4) + k2) ^ (v0 + sum) ^ ((v0 >> 5) + k3);

    }
    v[0] = v0; v[1] = v1;
}

void teadecrypto(uint32_t* v, uint32_t* k) {
    uint32_t v0 = v[0], v1 = v[1], sum = 0xc6ef3720, i;
    uint32_t delta = 0x9e3779b9;
    uint32_t k0 = k[0], k1 = k[1], k2 = k[2], k3 = k[3];
    for (i = 0; i < 32; i++)
    {
        v1 -= ((v0 << 4) + k2) ^ (v0 + sum) ^ ((v0 >> 5) + k3);
        v0 -= ((v1 << 4) + k0) ^ (v1 + sum) ^ ((v1 >> 5) + k1);
        sum -= delta;
    }
    v[0] = v0; v[1] = v1;
}

xtea的实现

void xteacrypt(uint32_t *v, uint32_t *k) {
    uint32_t v0 = v[0], v1 = v[1];
    uint32_t k0 = k[0], k1 = k[1], k2 = k[2], k3 = k[3];

    int sum = 0, delta = 0x9e3779b9;

    for (size_t i = 0; i < 32; i++)
    {
        v0 += (((v1 << 4) ^ (v1 >> 5)) + v1) ^ (sum + k[sum & 3]);
        sum += delta;
        v1 += (((v0 << 4) ^ (v0 >> 5)) + v0) ^ (sum + k[(sum >> 11) & 3]);
    }
    v[0] = v0; v[1] = v1;
}

void xteadecrypt(uint32_t* v, uint32_t* k) {

    uint32_t v0 = v[0], v1 = v[1];
    uint32_t k0 = k[0], k1 = k[1], k2 = k[2], k3 = k[3];

    int sum = 0x9e3779b9 * 32, delta = 0x9e3779b9;

    for (size_t i = 0; i < 32; i++)
    {

        v1 -= (((v0 << 4) ^ (v0 >> 5)) + v0) ^ (sum + k[(sum >> 11) & 3]);
        sum -= delta;
        v0 -= (((v1 << 4) ^ (v1 >> 5)) + v1) ^ (sum + k[sum & 3]);
    }
    v[0] = v0; v[1] = v1;
}