Rolling code
A rolling code changes each use to thwart replay attacks.
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Effeietsanders · CC0
The Microchip HCS301, which uses the KeeLoq algorithm, was once the most widely used rolling-code system for garage and gate openers.[1]
Quick Facts
- Common algorithm
- KeeLoq
- Unencrypted bits
- 28-bit serial number
- 4 bits button info
- 2 status bits
- Encrypted rolling code bits
- 4 bits button info
- 2 bits OVR
- 10 bits DISC
- 16-bit counter
- Typical receiver tolerance
- next 256 codes
- Vulnerability demonstrated
- Rolljam attack
Facts from the source article.
Key facts and history
The HCS301 KeeLoq system transmits 66 data bits, of which 32 bits are the encrypted rolling code.[1] The encrypted portion includes a 16-bit counter, button information, and a discrimination value.[1] In 2015, Samy Kamkar built an inexpensive electronic device that could capture a single keyless entry code for later use.[2] The device jams the vehicle's reception while recording the owner's first two attempts.[2]
Kamkar indicated that this weakness had been recognized for many years across numerous car models but had never been publicly shown before.[2] A public demonstration took place at the DEF CON 23 conference.[2]
What the cited sources add
A 2021 source notes that a typical garage door opener has a lifespan of about 10–15 years.[3]
References
- Wikipedia, "Rolling code" (CC BY-SA 4.0), which cites: Microchip, "HC301 KeeLoq Code Hopping Encoder", Microchip Technology Inc., 2001; "Garage Door Remote Not Working Reasons", 4 November 2021 (we also read that source) en.wikipedia.org
- Wikipedia, "Rolling code" (CC BY-SA 4.0), which cites: Thompson, "A hacker made a $30 gadget that can unlock many cars that have keyless entry", Tech Insider, 2015-08-06; Kamkar, "Drive It Like You Hacked It: New Attacks and Tools to Wirelessly Steal Cars", DEF CON 23, 2015-08-07 (original not read by us) en.wikipedia.org
- "Garage Door Remote Not Working Reasons", 4 November 2021. facts only, no text reused. garagedoorpitt.com
Each numbered sentence above was checked against the source it cites before publication. Sentences citing Wikipedia adapt text from the English Wikipedia article Rolling code (contributors), used under CC BY-SA 4.0; this entry is available under the same licence. Other sources were used for facts only; no text or images are copied from them.
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Sources
Compiled from Wikipedia and the sources listed below. Text from Wikipedia is available under CC BY-SA 4.0; this entry is adapted from it.
- Wikipedia: Rolling code (CC BY-SA 4.0).
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