• Pioneering tech company Terra Quantum has discovered a weakness in ‘post-quantum cryptography’, the set of cryptographic systems securing communication protocols and networks against quantum computers.
• The discovered vulnerability would in future make it impossible to protect the most confidential data from hackers.
• Terra Quantum has developed an innovative approach that enables unbreakable information transmission based on the superfast quantum key distribution.    

Terra Quantum AG, one of the leading Quantum technology pioneers in Europe, announced today details of research which upends the current understanding of what constitutes unbreakable and future-proofed data encryption. The Terra Quantum’s breakthrough secures the most critical communications such as high privacy messages, online banking details, and confidential communications between international organisations.

Markus Pflitsch, Terra Quantum founder and CEO, said: “With an information society that transfers an increasingly large amount of personal data over public channels, information security is an emerging worldwide challenge. Therefore, protecting confidential data is a major dispute.

Our ground-breaking results demonstrate the vulnerability of existing post-quantum encryption schemes. Inspired by the demand to amend the unravelled weak spot, we have developed the superfast key distribution method through the optical fibre.”

What is post-quantum cryptography?

A general feeling is that the next major advance in computing power – quantum computing – is only a few years away from being realised. And when quantum computing becomes available, the past techniques of securing data by encryption will therefore become breakable.

Post-quantum cryptography is the set of methods to push protecting data to the standards required for a future technology environment in which hackers have access to quantum computing. One of the most popular is the Advanced Encryption Standard (AES), built to withstand attacks from quantum computers. Post-quantum cryptography has become the gold standard for organizations seeking long-term protection for their data.

What have Terra Quantum discovered?

Terra Quantum realised that the AES is fairly secure against already identified algorithms but may appear fenceless against upcoming threats. To build the defence, Terra Quantum set out to look for a weakness by testing the AES against new algorithms. They Terra Quantum discovered a weakness on the message-digest algorithm MD5. The Terra Quantum team found that one can crack an algorithm using a quantum annealer containing about 20,000 qubits. No such annealer exists today, and while it is impossible to predict when it may be created, it is conceivable that such an annealer could become available to hackers in the future. Thus, Terra Quantum has demonstrated the growing opportunities for an inversion of the broad class of cryptographic hash functions (the hash function is the function that irreversibly transforms a long chain of bits into a single small number) such as MD5 or AES. Hereby, Terra Quantum reveals the vulnerability of existing post-quantum encryption schemes. 

What’s the solution?

The protocol is called ‘the superfast Boltzmann-Planck-protected secure information transmission’. The critical component of the proposed protocol is the change of the security paradigm based on quantum irreversibility. Terra Quantum’s CTOs, Professors Gordey Lesovik and Valerii Vinokur, said: “A new protocol derives from the notion that Quantum Demon is a small beast. The standard approach utilises the concept that the Demon hired by an eavesdropper (Eva) is a King Kong-like hundred kilometres big monster who can successfully use all the transmission line losses to decipher the communication. But since real Quantum Demons are small, Eva has to recruit an army of a billion to successfully collect all the scattered waves leaking from the optical fibre that she needs for efficient deciphering. Terra Quantum proposes an innovative technique utilizing the fact that such an army cannot exist – in accord with the second law of thermodynamics.” 

The possibility of the local rerouting of the part of the transmitted signal remains. However, these local losses can be controlled and be kept small with great accuracy. Moreover, the quantum nature of the light additionally restricts the information available for an eavesdropper. Hence Terra Quantum’s sent signal is safe.

The protocol in detail

The history of the non-stop contest between cryptographer and decipherers traces back to the cave ages and has seen many victories for both sides. Terra Quantum bases its solution on the Vernon’s cipher, the so-called ‘one-time pad’, proven by Claude Shannon to be unbreakable. Terra Quantum introduces the superfast quantum key distribution, establishing a practical realization of this procedure in the context of the modern superfast information communications service. The innovative Terra Quantum protocol, the superfast Boltzmann-Planck-protected secure information transmission, makes the electronically transmitted communication unbreakable in principle. The critical component of the proposed protocol is the change of the security paradigm based on quantum irreversibility. The standard approach utilizes the concept that an eavesdropper (Eva) can successfully use all the transmission line losses to decipher the communication. However, the lion’s share of losses occurs due to scattering of the small imperfections (inevitably appearing during the fabrication) of a signal propagating through the optical fiber. The reversal of the scattered waves required for the efficient deciphering is similar to the famed time-reversal problem; unachievable for the extended fiber comprising billions of scatterers per kilometer. Our paradigm offers a universal approach to critically improve the efficiency of any existing quantum protocol. The innovative proposed technique enables us to develop the quantum noise protected protocol to propagate securely encrypted information most rapidly. 

The obstacle of optical fibre losses

The optical fiber losses remain the main obstacle for further progress in the information transfer efficiency, both in classical and quantum cases. Terra Quantum steps in the breach by noticing that the conventional approach to quantum communication is suffering twice. First, the losses themselves harm efficiency. Secondly, the commonly accepted belief that an eavesdropper can efficiently decipher the lost signal appears not to be completely true.

To demonstrate this, we inspect a transmission line one kilometer long. Deriving from the leakage rate, we take the initial pulse to contain a hundred million photons for the 1 sec per unit length of the transmission line and find that the real leak along the line constitutes about 4 %. Had Eva been able to use this amount of information from the local source, it would have appeared an appreciable amount. However, collecting the resulting waves containing about a million photons scattered from the billion scatterers requires an unrealistic Maxwell Demon-like device of one kilometer long. Even to collect resulting waves having 10,000 photons scattered from the 100,000 scatterers by a Maxwell Demon-like device of one meter long seems extremely challenging, if at all possible. Yet the gain of information would be just 0,04 %. This amount of leaked information can easily be compensated by postprocessing by Alice and Bob.  

Signal propagation in optical fibre

The signal propagation in the optical fiber is similar, to no small extent, to the evolution of the ensemble of particles experiencing scattering on the quenched disorder potential described by the kinetic equation, generalizing the classical Boltzmann equation. This implies that the particles’ dynamics are accompanied by the entropy growth and, therefore, irreversible as expressed by the Second Law of Thermodynamics. An irreversibility’s major implication is that Eva cannot collect any useful information from the scattering. However, the possibility of the local rerouting of the part of the transmitted signal remains. Physically this can be implemented, for example, by a local bending the fiber, which leads to mixing of the primary propagating mode with the higher-order leaking modes. This, in turn, allows for eavesdropping on the information carried by the main mode. Had the signal been classical, this “bending” would have opened unlimited access to the full content of the message for Eva. However, according to Planck’s principle, electromagnetic irradiation is quantized; hence the electromagnetic signal is a sequence of particles, the photons.   Therefore, if the initial signal contains, on average, N photons, and the local leakage is quantified by transparency, only a small fraction of the signal, TN (T stands for the transparency of the local leakage), comes to Eva. Moreover, this fraction experiences unavoidable fundamental quantum fluctuations related to alternative quantum choice proportional to TN. Accordingly, the relative fraction of the fluctuations grows as 1/TN with the decreasing number of photons and transparency. This implies that if Eva gets only a small portion of the signal, it becomes effectively decipherable, the property which we call “Planck protection” of the information transmission. The so-called quantum-noise-protected cryptography utilizes a similar property.

Planck protection

The general principle of Planck protection enables us to control the whole transmission line efficiency via the local leakage transparency. Implementing this control requires a careful study of the state of the optical fiber and the emergent scattering matrix that can be accomplished by standard telecom technology methods, particularly using the optical time-domain reflectometry. We propose a new optical fiber control method based on the direct measurement of Alice’s signal propagation to Bob. The accuracy of the effective control of the leakage transparency is as high as a few percent for the one ns measurement duration. It becomes even higher for more extended measurements. The innovative breakthrough is that the proposed scheme enables us to transfer the signal encrypted by the unbreakable one-time pads with a tremendous speed comparable to the best rates achieved by Telecommunications.