07-22-2013, 04:24 PM | #23 |
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Pretty short range as well. Not sure if this is due to the fob or not. The car does not detect the fob sometimes when it is in the car. I have to push the start button twice a few times in order to get the car started
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07-23-2013, 11:51 AM | #24 |
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That sounds like you have a bigger problem. For my other cars, I often left the car keys on the sunroof of the car in my garage. With the F30, it apparently thinks I am in the car and the radio et al continue, as opposed to walking away with the FOB.
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07-23-2013, 12:14 PM | #25 | |
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As security technologies advance, so too do criminal technologies. You would be amazed how simple it is to monitor transmissions these days. Hell, in my world, the "Smart Card" (a credential with imbedded integrated circuitry) was supposed to be one of the most secure means of providing identification authentication. Until it was discovered that folks were setting up with scanners housed in briefcases in building lobbies and skimming all of the data off of the cards. Now most of the agencies that are aware of this require folks to keep them in metal sleeves now. I don't think it's wise to implement a high power transmitter in a fob. Especially for the comfort access authentication. |
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07-23-2013, 06:16 PM | #26 |
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Tint the windows and it gets much worse.. also i have been using the chin antenna gain and it works.
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07-26-2013, 10:15 AM | #27 | |
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To prevent exactly the sort of attack you are talking about (any sort of replay), fobs should transmit the next pseudo-random number in a pseudo-random sequence generated from a common seed known only by the car and the fob. The car should accept only the next N pseudo-random numbers in the sequence since the last one it saw from the fob, meaning that if you press "open" too far away from car too many times the fob will stop working until it and the car are back in sync. Hmm, that's a bit jargon-filled, but it's a bit like this: The car and the fob have a random list of page numbers from a common dictionary. Nobody else knows the page numbers. When you press open, the fob skips to the next random page number and transmits the first word on that page. The car keeps track of the last page it saw and will only accept the next few "first" words from the page list. Once the car has accepted the "word" it memorizes that page number as the last page used and will from then on only accept words "after" that in the page list. If some nefarious third party sees the word (or even a number of words) that doesn't really tell them anything useful because reusing that specific word will no longer open the car and they don't have the page list to figure out what the next words would be. All of that pseudo-random jargon is just a clever way of having this "page list" without actually needing to store a list of "page numbers". (This only applies to non-CA. Automated forms of access have a totally different problem and power-limiting is undoubtably a necessity for CA.) Last edited by JesseS; 07-26-2013 at 10:49 AM.. |
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07-26-2013, 10:38 AM | #28 |
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07-26-2013, 10:49 PM | #29 | |
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http://www.guardian.co.uk/technology...ker+News+50%29 |
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07-27-2013, 01:44 PM | #31 | |
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Stupid. IMO, any car company that knowingly implements poor security and then tries to cover it up with "gag orders" is criminally negligent. |
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07-27-2013, 01:47 PM | #32 |
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Replay attacks are relatively easy to protect against. What's harder to protect against is a proxying attack, where one attacker follows you while another one stands close to your car, and they both carry transmitters that repeat the transactions between the car and the remote, essentially acting as an extension cable for your car remote.
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07-27-2013, 02:24 PM | #33 | |
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Some manufacturers try to protect against this by having a very strict latency bounds check (time between when the car asks the fob to respond and when the fob's response comes back). Because the proxy attacker's retransmission algorithm and electronics will always induce some sort of latency this theoretically can prevent the attack. Of course, it also creates an arms race in terms of retransmission speeds (as well as potential well-timed replay attacks if there are any flaws in the request/response algorithm). Personally, I would love to have a fob with a complete power-down switch, so I could ensure the fob would never respond to any transmissions when I was at home/office. Perhaps with a safety check to ensure you could only power-down after the car acknowledged it was completely off and locked. (Note: One thing you can do is construct or buy a small faraday cage and put your fob in it at work/home. Something like http://www.select-fabricators.com/pr...lding-pouches/, which should attenuate RF signals sufficiently to prevent the fob from "seeing" proxy attacks and/or responding. You need to make sure the cage attenuates the correct frequencies though; I think most fobs are in the 300-500 mhz spectrum, but I'm not 100% on that.) Last edited by JesseS; 07-27-2013 at 02:36 PM.. |
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09-01-2019, 10:11 AM | #34 |
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lost range when comfort access closing was active
This happened to my 2014 328I after i enabled comfort access for closing. the range was random and sometimes it would not start unless i held the key close to the steering wheel. When i took of comfort access the range came back
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09-01-2019, 06:13 PM | #35 | |
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I have nothing to back this up, other than it worked when I was in my teens. |
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