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Matt BlazeonMastodon4d ago
Physical security and cryptography can learn from each other, part 11367:
Hotels wisely don't put the room number on guest keycards so if someone finds your card, they'd have to exhaustively search the hotel to find the room it opens.
Some hotels now have elevators programmed to only let you call the floor for which your keycard is coded, preventing guests from wandering to other floors.
But it also means the elevator can be used as an efficient oracle to determine the floor of a found key.
Trust Metrics
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65
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Claim Accuracy82%
Source Quality65%
Framing & Tone88%
Context80%
Analysis Summary
This is a genuine security analysis post from a credible source. Matt Blaze correctly identifies how modern key-card elevators—which do exist in hotels—could inadvertently leak floor information even though the keycard itself doesn't print it. The observation highlights how well-intentioned security controls can create unintended privacy vulnerabilities. No false claims here, just clever threat modeling.
Claims Analysis (3)
“Hotels wisely don't put the room number on guest keycards so if someone finds your card, they'd have to exhaustively search the hotel to find the room it opens.”
This is standard hotel security practice documented across hospitality industry guidance.
“Some hotels now have elevators programmed to only let you call the floor for which your keycard is coded, preventing guests from wandering to other floors.”
Key-activated elevators exist and are deployed in some hotels. Not universally adopted, but common in modern properties.
“The elevator can be used as an efficient oracle to determine the floor of a found key.”
This is the post's analytical insight—a logical inference about a security vulnerability, not a factual claim about observed behavior.
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