Hacking is Made Impossible by Quantum Cryptography

Computer and Internet Safety and Security Concept

The practice of employing quantum mechanical concepts for cryptographic functions is referred to as quantum cryptography.
The quantum key distribution protocol has been improved.

The Internet is full of highly confidential information. In most cases, sophisticated encryption methods ensure that unauthorized parties cannot intercept and access the content in question. High-performance quantum computers, on the other hand, will be able to crack these keys in a matter of seconds in the not-too-distant future. As a result, quantum mechanical techniques not only provide novel algorithms that are far faster, but also incredibly effective cryptography.

Quantum key distribution, or QKD as it is known in the industry, is secure against attacks on the communication channel but not against assaults or manipulations on the devices themselves. As a result, the devices may generate a key that the manufacturer had previously stored and may have given to a hacker.

Things take a different turn when it comes to device-independent QKD (abbreviated DIQKD). The device has no effect on the cryptography protocol at all. This technology has only been conceptually understood since the 1990s; however, an international research team led by physicist Harald Weinfurter of the Ludwig Maximilian University of Munich and physicist Charles Lim of the National University of Singapore has recently experimentally implemented it (NUS).

Exchanging quantum mechanical keys can be accomplished in a variety of ways. Light signals or entangled quantum systems are used to communicate between the sender and the recipient. In this experiment, the researchers used two quantum mechanically entangled rubidium atoms housed in labs on the LMU campus that were approximately 400 meters apart. The two locations are linked by a 700-meter-long fiber optic connection that runs beneath Geschwister Scholl Square in front of the main building.

The scientists start the entanglement process by first stimulating each atom with a laser pulse. Following this, the atoms will return to their ground state on their own, each emitting a photon. The spin of the atom is inextricably linked to the polarization of the photon that it emits due to the principle of conservation of angular momentum. A combined measurement of the photons at the receiver station demonstrates the existence of atomic quantum memory. The two light particles travel to the receiver station via the fiber optic connection.

Before exchanging a key, Alice and Bob, as the two parties are commonly referred to by cryptographers, will measure the quantum states of their atoms. This is done so that the results can be compared. For each example, this is done haphazardly in two or four different directions. If the directions are the same, the measurements will produce the same results due to entanglement, allowing the generation of a secret key. When the results of the other measurements are combined, a phenomenon known as a Bell inequality can be studied. In the first place, physicist John Stewart Bell devised these inequalities to investigate whether or not nature can be modeled using variables that are hidden from view.

“This was determined to be impossible,” Weinfurter says.

The purpose of the DIQKD test, according to Weinfurter, is to “exactly confirm that there are no manipulations at the devices—that is to say, that secret measurement data have not been kept in the devices beforehand.”

The implemented protocol, developed by NUS academics, uses two measurement settings rather than one for the production of keys, as opposed to previous approaches that only used one: Charles Lim claims that “It becomes more difficult to intercept information by providing an additional option for key generation. As a result, the protocol can tolerate higher levels of noise and generate secret keys even for lower-quality entangled states.”

When using traditional QKD approaches, however, security can only be guaranteed if the quantum devices being used are well defined. Tim van Levant, one of the paper’s four lead authors, explains that users of such protocols must rely on the specifications provided by QKD providers and trust that the device will not switch to another operating mode while the key is being distributed. “As a result, users of such protocols must rely on the specifications provided by QKD providers,” he says. According to van Leent’s findings, older QKD devices have been widely known for at least a decade that they are easily hackable from the outside.

“With our technology, we can now create secret keys with uncharacterized and potentially untrustworthy devices,” Weinfurter claims. “This is made possible by the fact that we created it.”

In fact, he does.

He was initially skeptical that the experiment would be successful. His team, on the other hand, demonstrated that his concerns were unfounded and significantly improved the overall quality of the experiment, which he gladly accepts. At the same time as the LMU-NUS collaboration initiative, another research group from the University of Oxford achieved device-independent key distribution. The researchers used a device in the same laboratory that consisted of two entangled ions to accomplish this.

According to Charles Lim, these two technologies lay the groundwork for future quantum networks, which will enable safe communication even between very distant locations.

One of the following goals is to broaden the system’s scope so that it includes many entangled atom pairs. According to van Leent, this would allow for the generation of many more entanglement states, resulting in an increase in both data rate and key security.

Furthermore, the researchers wish to broaden the scope of their research. It was limited in its current configuration because approximately half of the photons were lost as they traveled through the cable that connected the two labs. The researchers were successful in modifying the wavelengths of photons into a zone with low loss that was ideal for use in telecommunications in several other tests. Using this method, they were able to increase the range of the quantum network link to 33 kilometers with only a minor increase in noise.