Say that someone borrows a key, and, while it is in his possession, gets a copy made of it.

  1. Has he violated any halachos?

  2. Does it make a difference how public/private the room is?

  3. Does it matter if the key is even used for a room, as opposed to, say, an alarm, elevator, or locker?

  4. Is he able to use the copy?

  • Your last question send unrelated to the other questions. Regardless of whether one may copy a key, why on earth would I've be permitted to use the copy to do anything involving someone else's property? Regardless of how private anything is...
    – mevaqesh
    Mar 21, 2017 at 3:30

1 Answer 1


Assuming the owner did not authorize that use of the key, the act of copying itself would then be an act of stealing akin to when a shomer (watchman) of a cow uses it to plow his own field (shelichuth yad - which is treated biblically as full theft).

  • I guess I didn't make myself clear. +1 for that much, but I was also wondering about using the copy.
    – DonielF
    Mar 21, 2017 at 2:03
  • Not disagreeing with your answer, but, the question states that he is BORROWING the key, not watching it. That means that he is using the key to gain entry to the places or electronic item (e.g. alarm, etc.) that the key is for. If he makes a copy of the key to use the copy for the same access, why does that matter? I can see a problem if at the end of the borrowed time he fails to return the copy. Then, he has gained unauthorized access or use. But why would making or using a copy during his borrowing time make any difference?
    – DanF
    Mar 21, 2017 at 2:08
  • @DonielF Provided there is no dina d'malchutha otherwise, and that is recognized halachically, the second key would seem to be his, even if he formed it in a forbidden manner. If that which it accesses is also within his rights to access, it doesn't seem that there would technically be a further limitation, without further rabbinic enactments otherwise.
    – Loewian
    Mar 21, 2017 at 4:25
  • 1
    @DanF This is akin to a shomer who is authorized to manipulate an object as necessary for its protection, but not for personal use.
    – Loewian
    Mar 21, 2017 at 4:28
  • 1
    I'd like to see some link to source material as that would greatly help me understand the issue. When you borrow something, is there an inherent "authorized usage"? If I borrow your pen and I use the point to reset my modem, I'm "stealing"? I'm assuming in the case of the key, the owner has not expressly prohibited making copies.
    – DanF
    Mar 21, 2017 at 13:30

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