自定义的高效加密解密算法

相同的key每一次加密的密文都不一样.难于破解.整个密文相关.修改其中一段后,以后的数据解密不正确

typedef unsigned int Unit;

std::string encrypt(const std::string &src,Unit key)
{
  Unit seed = 0;
  const size_t unitlen = sizeof(Unit);
 
  size_t len = (src.length() + unitlen-1) & ~(unitlen-1);
 
  Unit *srcdata = (Unit*)malloc(len);
  bzero(srcdata,len);
 
  memcpy(srcdata,src.data(),src.size());
 
  std::string dest;
 
 
  int i = 0;
 
  srand(time(NULL));
  seed = rand()%0xFFFF;
  dest.append((char*)&seed,sizeof(Unit));
  do
  {
    seed = *(srcdata+i) ^ seed ^ key;
    dest.append((char*)&seed,unitlen);
    i++;
  }while(i<len/unitlen);
  free(srcdata);
 
  return dest;
}


std::string dencrypt(const std::string &src, Unit key)
{
  Unit seed = 0;
  Unit *srcData = NULL;
  std::string dest;
 
  const size_t unitlen = sizeof(Unit);
 
  srcData = (Unit*)src.data();
  seed = *((Unit*)srcData);
 
  int i = 1;
  while(i<src.size()/unitlen)
  {
    seed = *(srcData + i) ^ key ^ seed;
    dest.append((char*)&seed,unitlen);
    seed =  *(srcData + i);
    i++;
  }
 
  return dest;
}