[2021]XXTEA

TEA原始加密太容易被识别了

这是XXTEA,加密强度会强很多
用法:
```cpp
int n = 2; //n的绝对值表示v的长度，取正表示加密，取负表示解密
	uint32_t const k[4] = { 2,2,3,4 };
	btea((uint32_t*)shell_code2, n, k);

btea((uint32_t*)shell_code2, -n, k);
	for (int i = 0; i < sizeof(shell_code2); i++)
		printf("0x%X,", shell_code2[i]);

```
src:
```cpp

#define DELTA 0x9e3779b9
#define MX (((z>>5^y<<2) + (y>>3^z<<4)) ^ ((sum^y) + (key[(p&3)^e] ^ z)))

void btea(uint32_t* v, int n, uint32_t const key[4])
{
	uint32_t y, z, sum;
	unsigned p, rounds, e;
	if (n > 1)            /* Coding Part */
	{
		rounds = 6 + 52 / n;
		sum = 0;
		z = v[n - 1];
		do
		{
			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;
		} while (--rounds);
	}
	else if (n < -1)      /* Decoding Part */
	{
		n = -n;
		rounds = 6 + 52 / n;
		sum = rounds * DELTA;
		y = v[0];
		do
		{
			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;
		} while (--rounds);
	}
}
```

一只鸭子

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