It isn't clear to me what you are asking. If the only thing the "thief" has is the indentation, then picture the indentation in which a disk would fit. Lets say that there are 100 pins in the door which fit into 100 holes in the sides of the disk If the range of pin lengths/hole depths is such that say there are 5 "different" lengths, then there are 5100 possible combinations. If the mechanism takes, say, 1 minute to cycle thru an attempted unlock process, then it would take about 1058 years to have a 1-in-a-million chance to "get lucky" with a random configuration of holes. (One trick I'm using here is that the mechanism can't be "attacked" sequentially, which is the way the typical tumbler & pin lock is picked. It's an "all or nothing" type lock. The mechanism for that would be complicated, justifying a long-ish opening cycle.) So, the only way to copy the key is to have either possession of it, or fairly accurate measurements of its size as well as the depths of the holes. 77
Could it be copied? Sure, but even if the copier had a portable "indentation" with pins which would record the hole depth for each of the holes, the copier would have to have physical possession of the key for long enough to use the copier (same is true of photographing or otherwise measuring the holes' depth.) But if the copier can access the key, then why not just use the original? If the key is kept somewhere that insecure, then why bother copying it? If its possible for a copier to get physical possession of the key for only a short time, then the question is one of technological reverse engineering. Say some of the holes have an electrical or magnetic or acoustic or fluidic circuit from one hole to others. And say there are 20 of those connecting two or more holes. How would the copier know that in order to copy it? Each possiblity would have to be tested. You could imagine all sorts of requirements to make it difficult to copy. Difficult as in time consuming. Difficult as requiring a lab. And as I already said, if you can take the key to a lab and spend hours and hours studying it, then you may as well just steal it. 284