How to protect your child from strangers without fearing it

Unfortunately, in today's society, there are many patrons around us with bad intentions. With the influx of many different peoples in our country, we have become particularly suspicious, so we have to train our children how to behave towards strangers. Usually people with bad intentions never show their real face, but a completely different one. 
You should tell your children the following:
 - We never talk to strangers, no matter if they tell us they know us.
 -We are anywhere only with our parents and those who trust our parents. 
- We do not accept gifts and sweets from strangers as much as we like.
 - We never live alone outdoors. 
- We inform our parents about everything that happened during the day. If your children understand all this, be sure they are not in danger. Something very smart that you can do is to teach your children a "code" of communication. What do I mean: to teach him a secret word that you will make yourself and you will know only people of trust and whoever knows them near and does not know it means that they are bad. How to make this word: you can use syllables from your names, for example. Kostas & Maria- coma or Fani & Nik - lousi-nisi, etc. In this way the child will see it as a toy and will not be afraid. 
All of this, of course, does not happen from one moment to the next, they want time. Panic and fear do not help and risk transmitting to your children