Oh! I remember these steps being explained on a youtube video before. So the point is that the padlock (that Adam received on the third paragraph) is like a program on my windows desktop, I can run it (here like Adam uses it to encrypt the date), I can copy it and send it to a friend, but I can't read the code which is compiled through an unknown language (i.e even if snooper received the padlock he can't figure out how to unlock it and decrypt the data)?