一种简单的、可逆的加密算法
一种简单的、可逆的加密算法，两位两位置换，四位四位置换：
#include <stdio.h>#include <stdlib.h>#include <string.h>typedef unsigned long longuint64;typedef unsigned intDWORD;typedef unsigned charuchar;static uint64 ValueTmp;int f2f(uint64 *Value){uchar i;uchar tmp;uint64 tmpSave = 0;memcpy(&ValueTmp, Value, sizeof(uint64));for(i = 0; i < sizeof(uint64); i++){tmp = (ValueTmp >> (i * 8)) & 0xff;tmp = (tmp & 0x0F) << 4 | (tmp & 0xF0) >>4;tmpSave |= (((uint64)tmp&0xFF) << (i * 8));}memcpy(Value, &tmpSave, sizeof(uint64));return 0;}int t2t(uint64 *Value){uchar i;uchar tmp;uint64 tmpSave = 0;memcpy(&ValueTmp, Value, sizeof(uint64));for(i = 0; i < 2*sizeof(uint64); i++){tmp = (ValueTmp >> (i * 4)) & 0x0f;tmp = (tmp & 0x03) << 2 | (tmp & 0x0c) >>2;tmpSave |= (((uint64)tmp&0x0F) << (i * 4));}memcpy(Value, &tmpSave, sizeof(uint64));return 0;}int main(){uint64 value = 0xabcdef1234567890;uint64 value2 = 0xabcdef1234567890;printf("value: 0x%16llx\n", value);f2f(&value);printf("value: 0x%16llx\n", value);f2f(&value);printf("value: 0x%16llx\n", value);//printf("value2: 0x%16llx\n", value2);t2t(&value2);printf("value2: 0x%16llx\n", value2);t2t(&value2);printf("value2: 0x%16llx\n", value2);return 0;}
运行结果：
root@xiangpingli:/home/linux/Desktop/samba/exercise/binary# ./encrypt value: 0xabcdef1234567890value: 0xbadcfe2143658709value: 0xabcdef1234567890value2: 0xabcdef1234567890value2: 0xae37bf48c159d260value2: 0xabcdef1234567890