TEA算法
1.简介
TEA算法全称微型加密算法（Tiny Encryption Algorithm）是一种简单容易实现的加密算法，通常只需要很少的代码就可以实现
2.加密过程
在加密过程中，需要使用2个32位的无符号整数，密钥为128位，四个32位无符号整数
流程图：
加密中一共有五个量参与运算，l(第一个明文)，r(第二个明文)，sum=0，delta给定一个定值，密钥key每一轮：
sum+=delta;
l += ((r << 4) + key[0]) ^ (r + sum) ^ ((r >> 5) + key[1]);
r += ((l << 4) + key[2]) ^ (l + sum) ^ ((l >> 5) + key[3]);
一共执行32次，最后将l，r放入v[0],v[1]中存储，得到密文
void encrypt(unsigned int* v, unsigned int* key) {
unsigned int l = v[0], r = v[1], sum = 0, delta = 0x9e3779b9;
for (size_t i = 0; i < 32; i++) {
sum += delta;
l += ((r << 4) + key[0]) ^ (r + sum) ^ ((r >> 5) + key[1]);
r += ((l << 4) + key[2]) ^ (l + sum) ^ ((l >> 5) + key[3]);
}
v[0] = l;
v[1] = r;
}
解密流程跟加密相反
void decrypt(unsigned int* v, unsigned int* key) {
unsigned int l = v[0], r = v[1], sum = 0, delta = 0x9e3779b9;
sum = delta * 32;
for (size_t i = 0; i < 32; i++) {
r -= ((l << 4) + key[2]) ^ (l + sum) ^ ((l >> 5) + key[3]);
l -= ((r << 4) + key[0]) ^ (r + sum) ^ ((r >> 5) + key[1]);
sum -= delta;
}
v[0] = l;
v[1] = r;
}
XTEA算法
跟TEA算法很类似，差别就是将r的变化结果和l变化结果进行了交替赋值，同时位移次数进行了一些变化，也掺杂了一些与操作
void encrypt(unsigned int* v, unsigned int* key) {
unsigned int l = v[0], r = v[1], sum = 0, delta = 0x9e3779b9;
for (size_t i = 0; i < 32; i++) {
l += (((r << 4) ^ (r >> 5)) + r) ^ (sum + key[sum & 3]);
sum += delta;
r += (((l << 4) ^ (l >> 5)) + l) ^ (sum + key[(sum >> 11) & 3]);
}
v[0] = l;
v[1] = r;
}
解密：
void decrypt(unsigned int* v, unsigned int* key) {
unsigned int l = v[0], r = v[1], sum = 0, delta = 0x9e3779b9;
sum = delta * 32;
for (size_t i = 0; i < 32; i++) {
r -= (((l << 4) ^ (l >> 5)) + l) ^ (sum + key[(sum >> 11) & 3]);
sum -= delta;
l -= (((r << 4) ^ (r >> 5)) + r) ^ (sum + key[sum & 3]);
}
v[0] = l;
v[1] = r;
}
XXTEA算法
#include <stdbool.h>
#include <stdio.h>
#define MX \
((z >> 5 ^ y << 2) + (y >> 3 ^ z << 4) ^ (sum ^ y) + (k[p & 3 ^ e] ^ z))
bool btea(unsigned int* v, int n, unsigned int* k) {
unsigned int z = v[n - 1], y = v[0], sum = 0, e, DELTA = 0x9e3779b9;
unsigned int p, q;
if (n > 1) {
/* Coding Part */
q = 6 + 52 / n;
while (q-- > 0) {
sum += DELTA;
e = (sum >> 2) & 3;
for (p = 0; p < n - 1; p++)
y = v[p + 1], z = v[p] += MX;
y = v[0];
z = v[n - 1] += MX;
}
return 0;
} else if (n < -1) {
/* Decoding Part */
n = -n;
q = 6 + 52 / n;
sum = q * DELTA;
while (sum != 0) {
e = (sum >> 2) & 3;
for (p = n - 1; p > 0; p--)
z = v[p - 1], y = v[p] -= MX;
z = v[n - 1];
y = v[0] -= MX;
sum -= DELTA;
}
return 0;
}
return 1;
}
int main(int argc, char const* argv[]) {
// test
unsigned int v[2] = {
1, 2}, key[4] = {
1, 2, 3, 4};
printf("%u,%u\n", v[0], v[1]);
btea(v, 2, key);
printf("%u,%u\n", v[0], v[1]);
btea(v, -2, key);
printf("%u,%u\n", v[0], v[1]);
return 0;
}
TXTEA
和TEA算法的唯一区别就是仅使用了16轮加密，还有就是使用了魔改的CBC模式
TXCBC模式：
#include <stdint.h>
void encrypt (uint32_t* v, uint32_t* k) {
uint32_t v0=v[0], v1=v[1], sum=0, i; /* set up */
uint32_t delta=0x9e3779b9; /* a key schedule constant */
uint32_t k0=k[0], k1=k[1], k2=k[2], k3=k[3]; /* cache key */
for (i=0; i < 16; i++) {
/* basic cycle start */
sum += delta;
v0 += ((v1<<4) + k0) ^ (v1 + sum) ^ ((v1>>5) + k1);
v1 += ((v0<<4) + k2) ^ (v0 + sum) ^ ((v0>>5) + k3);
} /* end cycle */
v[0]=v0; v[1]=v1;
}
void decrypt (uint32_t* v, uint32_t* k) {
uint32_t v0=v[0], v1=v[1], i; /* set up */
uint32_t delta=0x9e3779b9; /* a key schedule constant */
uint32_t sum = delta << 4;
uint32_t k0=k[0], k1=k[1], k2=k[2], k3=k[3]; /* cache key */
for (i=0; i<16; i++) {
/* basic cycle start */
v1 -= ((v0<<4) + k2) ^ (v0 + sum) ^ ((v0>>5) + k3);
v0 -= ((v1<<4) + k0) ^ (v1 + sum) ^ ((v1>>5) + k1);
sum -= delta;
} /* end cycle */
v[0]=v0; v[1]=v1;
}
参考链接：
https://bbs.pediy.com/thread-253844.htm