News Summary

• In that case you may as well use a genuine old IR remote and use the digit keys as a code with any length you want, and using the Arduino to decode IR and do the treasure box opening job..
• This actually looks like an infrared remote command without any kind of secure rolling code or something like that..
• The use case: approach door, click app button, place phone close to door, phone initiates tones then door replies (several exchanges over a couple of seconds), then door opens.A 6 pin key with 8 different possible cut depths has close to a million different combinations..
• You could also use an app to send single use or time limited URLs to your requester to limit access to the web service…This actually reminds me of the “KnockN’Lock” from like 15 years ago, which was also a pretty ingenious design..
• However, having to carry a proprietary key fob that had a keypad and mini hammer so you could use a PIN to essentially morse code the door open was a bit clunky and probably too far ahead of its time..
• As leaf points out this can be made so that the signal presented is unique per use, which would remove replay attacks from the equationi’m not quite sure from the description, but it looks like the phone just turned on its light for some fixed number of milliseconds..