02-12-2021 | | By Robin Mitchell
Most security measures in communication systems focus on encryption, but researchers have recently developed a new security feature that makes signals appear as noise. Why is encryption so important, what did the researchers develop, and could it be implemented in future systems?
The act of scrambling a message to make it unintelligible is called encryption, and while computers have only been around for a century at most, the idea of encryption dates back thousands of years. One particular use of historic encryption has been sending sensitive information across hundreds of miles carried by a messenger. This message could involve troop positions, the true intention of a king, or an assassination plot, and such information must only be known by the recipient of the message. Therefore, encrypting the message with a cypher whose key is only known by the sender and receiver ensures that only they know what the message says.
Of course, a message carried by a messenger does not need encryption if one can guarantee that the messenger will not look at the message and be able to defend themself from any intrusion or attack. But what if the messenger drops the note, or an army of ten thousand soldiers blocks their path?
This is the problem basic wireless communication systems face using a single antenna as information is radially emitted in all directions. Anyone who is within range can receive the information without the sender even knowing. Therefore, encrypting data sent over wireless systems is an absolute must so that anyone receiving the signal cannot read the data.
However, encryption is not full proof, and researchers have had to develop new encryption methods over the years as hackers have continued to improve their ability to crack cyphers. To make matters worse, many devices in active use are not updated regularly (if at all), meaning they often use older encryption methods. As older methods are well understood with known vulnerabilities, attackers can exploit them to access either the devices or the network they connect to.
Recognising the challenges faced with encryption, researchers from the University of Princeton have recently developed a new wireless transmission method that helps to protect data by denying others from receiving the signal in the first place.
The new method takes advantage of phased arrays which are already in widespread use. Phased arrays consist of many antenna elements that can independently vary their signal to create constructive and destructive patterns in emitted radio signals. Long story short, this technique creates a beam of radio energy that is targeted towards a receiver while minimising the transmitted signal in all other directions.
Phased array systems allow several devices to utilise the same frequency bands without interfering with each other (5G requires this to maximise data transfer rates). However, there are still areas outside the beam path where a sufficient signal can be received to reverse-engineer the original information being transmitted. As such, attackers can still reverse engineer the signal and attempt to decipher encrypted information.
To get around this, researchers instead created a system that splits messages into slices sent randomly across the various antennas in an array. Information is still delivered correctly to the intended receiver since the path is known and accounted for by the sender. Still, eavesdroppers who are not at the receiver will only receive parts of the message which appears as noise. Furthermore, an eavesdropper who attempts to move into the beam's path will immediately alert the receiver and sender as the beam signal would be interrupted.
What makes the new research of particular importance is that instead of protecting data, the physical medium that carries the data is being protected. If an eavesdropper is denied access to the complete message in the first place, then no data can be hacked. Of course, encryption is still important as it is likely that future systems powered by AI could find a way to get around directed beams (i.e. reflections from walls and the use of multiple antennas in multiple locations to create completed packets).
But the effort needed to do this is far greater than installing a single antenna that can receive an entire packet. Furthermore, most cellular systems now incorporate phased arrays meaning that the technology could potentially be added to cellular networks with minimal effort. Of course, the researchers require using a specialised chip in both the sender and receiver, meaning that existing hardware (such as smartphones) would not be compatible with a security system utilising the described method.