MD5加密

• (NSString *)md5:(NSString *)str
  {
  const char *cStr = [str UTF8String];
  unsigned char result[16];
  CC_MD5(cStr, strlen(cStr), result); // This is the md5 call
  return [NSString stringWithFormat:
  @"%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x",
  result[0], result[1], result[2], result[3],
  result[4], result[5], result[6], result[7],
  result[8], result[9], result[10], result[11],
  result[12], result[13], result[14], result[15]
  ];
  }