According to MIT researchers, there are currently eight billion devices around the world that are connected to the internet. This includes cell phones, laptops, medical devices, smart home devices and more. By 2020 it is estimated that there will be 20 billion devices connected all around the world, all of which are quite vulnerable to hackers. There are new techniques and methods being tested and developed to fight against hackers.
The latest method comes from MIT researchers, based on an already trusted technique: frequency hopping.
Frequency hopping sends data packets that are filled with thousands of individual bits on a random radio frequency. This method prevents hackers from being able to pin down one packet and corrupt it. While this is a great strategy, large data packets move slow enough for hackers to still grab them.
The researchers have developed a new transmitter frequency that stops hackers from infiltrating large data packets. The frequency hops each 1 or 0 bit of a data packet every microsecond. This method makes big packets too fast for even the most seasoned hackers to catch.
The transmitter uses bulk acoustic wave (BAW) resonators. The resonators allow for rapid switching between many RF channels. There is also an incorporated channel generator that selects a new microchannel every microsecond to send out bits. The resonators have a wireless protocol that can support ultra-fast frequency hopping, the key to thwarting hackers.
There are many different types of hacking methods. One of the hardest hacks to beat is selective jamming. With selective jamming, hackers intercept and corrupt data packets that are being transmitted. This method is difficult to detect — users typically think that they just have a bad wireless connection when they are experiencing this type of hacking. The method also leaves other nearby devices untouched, so only one device is being effected at a time. Selective jamming is hard to combat with the packet-level frequency hopping transmitters that are currently used in devices.
With packet-level frequency hopping, it sends one packet at a time on a one megahertz channel across a range of 80 possible channels. It takes around 612 microseconds for a Bluetooth low energy (BLE)-type transmitter to send a packet across the channel. With the current technology, hackers can locate the channel during the first microsecond and effectively jam the packet.
"Because the packet stays in the channel for a long time, and the attacker only needs a microsecond to identify the frequency, the attacker has enough time to overwrite the data in the remainder of the packet," said Rabia Tugce Yazicigil, a postdoc researcher in the department of electrical engineering and computer science.
To expand the packet-level frequency hopping method, the researchers had to expand on the resonator. The researchers replaced the crystal oscillator that is in today’s resonators with an oscillator that is based on a BAW resonator. The BAW resonators cover four-to-five megahertz of frequency channels. This doesn’t even come close to the 80 megahertz ranges that are used in wireless communication. By combining the frequency hopping method, current resonators and the BAW oscillator, the researchers were one step closer to developing an effective method to stop hacking. The researchers also had to incorporate components that can divide input frequency into multiple frequencies. This added just another mixer component that can combine divided frequencies with the BAW radio frequencies. This allows the device to reach 80 channels instead of just four or five.
The next step was to randomize the data that is being set. The researchers created a BLE modulations method. The set is always fixed on 250 kilohertz when the bits are sent. If hackers can pinpoint the carrier frequency, they instantly have access to the sensitive information. To combat the pinpointing, the system was developed to generate a pair of separate channels across the 80 channels every microsecond. This is based on a pre-shared secret key that the transmitter had. The receiver calculates how to designate which channel will carry the one bit and which channel will carry the zero bit. The channel that carries the information bit will always have more energy than the other bit. The receiver compares the energy of the two channels and decodes the one that has higher energy.
The channel selection is quick and random. This means that there is no fixed frequency offset and the hackers can’t tell which bit is going to which channel. The hackers can’t corrupt the bits.
"For an attacker, that means they can't do any better than random guessing, making selective jamming infeasible," Yazicigil says.
The researchers incorporated the two transmitter paths into the method. This allows the inactive transmitter to receive the selected channels and the active transmitter to send data on the current channel and the workload alternates. The one-microsecond frequency hop rate is guaranteed, while the one-megabyte-per-second data rate is preserved
The paper on this research will be presented at the IEEE Radio Frequency Integrated Circuits Symposium.
