TEA

[TOC]

TEA算法简介

TEA算法是一种分组密码算法，其明文密文块为64比特，密钥长度为128比特。TEA算法利用不断增加的Delta(黄金分割率)值作为变化，使得每轮的加密是不同，该加密算法的迭代次数可以改变，建议的迭代次数为32轮。

TEA采用移位和异或操作，所以加密解密算法形式非常相似

TEA

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

//加密函数
void encrypt(uint32_t* data, uint32_t* key){
        uint32_t data0 = data[0], data1 = data[1];
        uint32_t sum = 0, i = 0;
        uint32_t delta = 0x9e3779b9;
        for(i = 0; i < 32; i++){
                sum += delta;
                data0 += ((data1<<4) + key[0]) ^ (data1 + sum) ^ ((data1>>5) + key[1]);
                data1 += ((data0<<4) + key[2]) ^ (data0 + sum) ^ ((data0>>5) + key[3]);
        }
        data[0] = data0;
        data[1] = data1;
}

//解密函数
void decrypt(uint32_t* data, uint32_t* key){
        uint32_t data0 = data[0], data1 = data[1];
        uint32_t sum = 0, i = 0;
        uint32_t delta = 0x9e3779b9;
        sum = delta * 32;
        for(i = 0; i < 32; i++){
                data1 -= ((data0<<4) + key[2]) ^ (data0 + sum) ^ ((data0>>5) + key[3]);
                data0 -= ((data1<<4) + key[0]) ^ (data1 + sum) ^ ((data1>>5) + key[1]);
                sum -= delta;
        }
        data[0] = data0;
        data[1] = data1;
}

int main(){
        uint32_t data[2] = {200, 100};
        uint32_t key[4] = {2, 3, 4, 5};
        printf("加密前原始数据：%u, %u\n", data[0], data[1]);
        encrypt(data, key);
        printf("加密后数据：%u, %u\n", data[0], data[1]);
        decrypt(data, key);
        printf("解密后原始数据：%u, %u\n", data[0], data[1]);
        return 0;
}

XTEA

XTEA是TEA的扩展，也称做TEAN，它使用与TEA相同的简单运算，同样是一个64位块的Feistel密码，使用128位密钥，建议64轮, 但四个子密钥采取不正规的方式进行混合以阻止密钥表攻击；

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

//加密函数
void encrypt(unsigned int num_rounds, uint32_t* data, uint32_t* key){
        uint32_t data0 = data[0], data1 = data[1];
        uint32_t delta = 0x9e3779b9, i = 0;
        uint32_t sum = 0;
        for(i = 0; i < 32; i++){
                data0 += (((data1<<4) ^ (data1>>5)) + data1) ^ (sum + key[sum&3]);
                sum += delta;
                data1 += (((data0<<4) ^ (data0>>5)) + data0) ^ (sum + key[(sum>>11)&3]);
        }
        data[0] = data0;
        data[1] = data1;
}

//解密函数
void decrypt(unsigned int num_rounds, uint32_t* data, uint32_t* key){
        uint32_t data0 = data[0], data1 = data[1];
        uint32_t delta = 0x9e3779b9, i = 0;
        uint32_t sum = 0;
        sum = delta * num_rounds;
        for(i = 0; i < 32; i++){
                data1 -= (((data0<<4) ^ (data0>>5)) + data0) ^ (sum + key[(sum>>11)&3]);
                sum -= delta;
                data0 -= (((data1<<4) ^ (data1>>5)) + data1) ^ (sum + key[sum&3]);
        }
        data[0] = data0;
        data[1] = data1;
}

int main(){

        uint32_t data[2] = {200, 100};
        uint32_t key[4] = {2, 3, 4, 5};
        printf("加密前原始数据：%u, %u\n", data[0], data[1]);
        encrypt(32, data, key);
        printf("加密后数据：%u, %u\n", data[0], data[1]);
        decrypt(32, data, key);
        printf("解密后原始数据：%u, %u\n", data[0], data[1]);
        return 0;
}

XXTEA

XXTEA是一个非平衡Feistel网络分组密码，在可变长度块上运行，这些块是32位大小的任意倍数（最小64位），使用128位密钥, 是目前TEA系列中最安全的算法，但性能较上两种有所降低。

#include <stdio.h>
#include <stdint.h>
#define delta 0x9e3779b9
#define MX (((z>>5^y<<2) + (y>>3^z<<4)) ^ ((sum^y) + (key[(p&3)^e] ^ z)))
//加密算法
void encrypt(int n, uint32_t* data, uint32_t* key){
        uint32_t y, z, sum;
        unsigned int p, rounds, e;
        rounds = 6 + 52/n;
        sum = 0;
        z = data[n-1];
        do{
                sum += delta;
                e = (sum>>2) & 3;
                for(p = 0; p < n-1; p++){
                        y = data[p+1];
                        z = data[p] += MX;
                }
                y = data[0];
                z = data[n-1] += MX;

        }while(--rounds);
}

//解密算法
void decrypt(int n, uint32_t* data, uint32_t* key){
        uint32_t y, z, sum;
        unsigned int p, rounds, e;
        rounds = 6 + 52/n;
        sum = delta * rounds;
        y = data[0];
        do{
                e = (sum>>2) & 3;
                for(p = n-1; p > 0; p--){
                        z = data[p-1];
                        y = data[p] -= MX;
                }
                z = data[n-1];
                y = data[0] -= MX;
                sum -= delta;

        }while(--rounds);
}

int main(){

        uint32_t data[3] = {200, 100, 600};
        uint32_t key[4] = {2, 3, 4, 5};
        printf("加密前原始数据：%u, %u, %u\n", data[0], data[1], data[2]);
        encrypt(3, data, key);
        printf("加密后数据：%u, %u, %u\n", data[0], data[1], data[2]);
        decrypt(3, data, key);
        printf("解密后原始数据：%u, %u, %u\n", data[0], data[1], data[2]);
        return 0;
}