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Researchers clone Tesla key in a short time with relatively cheap attack

Researchers at KU Leuven have presented an attack on keys to Tesla cars, which originated from manufacturer Pektron. They describe an attack where they can clone a key with equipment of less than a thousand euros, with which they can steal the car.

Although they have only tried the attack on a Tesla Model S, Pektron also supplies brands such as MacLaren, Karma. and Triumph, write the researchers . By using the same chip these brands are probably also vulnerable to the attack. It works by first discovering a identifier of 2 byte of a Tesla car that transmits it periodically. This allows an attacker to pretend to be the car and then send a challenge to a key in the neighborhood. On the basis of the answer of the key it is possible to retrieve the used encryption key with the aid of a predefined database of 5.4 TB. The researchers say that they have developed a proof-of-concept attack that takes a few seconds with a Raspberry Pi, a Proxmark3- sdr a Yard Stick One and a battery.

They explain that the attack is possible because the used Passive Keyless Entry and Start system is vulnerable. It first uses a challenge and response protocol that does not use authentication, so that everyone can intercept the signals between the car and the key and can act as one of the two. Secondly, the used encryption, DST40 by Texas Instruments, according to the researchers, is very outdated. For example, it uses a 40-bit secret key, of which researchers have already demonstrated in 2005 how to trace this by using an fpga.

The researchers at KU Leuven explain that a 40-bit challenge is being used. and a 24-bit response, which means that some answers are the same for certain challenges. They decided to create a database of all possible answers from a single predetermined challenge for all the secret key possibilities. Here came the aforementioned file of 5.4 TB. By sending that specific challenge to a key, it was then only necessary to search a total of 65,536 possible keys, which would be executed in two seconds on a Raspberry Pi 3 Model B +. An attacker must be within one meter of the key, but this distance would be up to eight meters with other equipment.

These findings were reported by the researchers at the end of August 2017 to Tesla and at the beginning of this year a Pektron and the other car manufacturers. According to Wired Tesla paid a $ 10,000 reward, but did not close the vulnerabilities until June with an update that allows the use of a PIN code. The company says to the site that it cooperated with its supplier on the discovery of the researchers to introduce ‘more robust cryptography’ for the Model S in June. Owners of models built before June can choose to request a new key thanks to a software update, it adds. Pektron did not respond to the researchers or to questions from Wired.

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