Also true of those old "lockbox" key lockers that real estate agents use to "protect" the keys to your house. This made me uncomfortable when I was selling a h

Also true of those old "lockbox" key lockers that real estate agents use to "protect" the keys to your house. This made me uncomfortable when I was selling a house, so naturally I wrote some code to generate a string of digits that would cover the full solution space most efficiently. Armed with this "master key", I had the lockbox open in negligible time. Honestly I think it was just a few minutes, and I was about halfway through the string. This let me put the key out only when a showing was happening, and I brought the lockbox to the closing, which baffled the real estate agent.