In today’s world of ever-increasing security threats and  breaches, encryption is a common technique used to protect critical information  from getting into the wrong hands. In cryptography, encryption is the process  of encoding a plaintext message in such a way that only authorized parties can  access it. The result of this process is encrypted information, also known as ciphertext.  But how is this done exactly? The plaintext message is transformed using an  algorithm (or cipher) to make it unreadable to anyone except those possessing  special knowledge, which is referred to as the key.

Diagram of encrypted information

As an example, consider encrypted information travelling  across a fiber optic cable. A hacker can tap the fiber in an attempt to access  the sensitive information it carries, as shown in this  video, but encryption prevents a hacker from deciphering the contents of the  message without the key.

Luckily, today’s state-of-art secure communications use advanced  mathematics to protect in-flight data leveraging highly secure algorithms, such  as in Ciena’s WaveLogic  Encryption solution. Even though many cryptographic algorithms used today  are publicly available, such as the popular Advanced Encryption Standard (AES),  they are very difficult to crack in a reasonable amount of time given the computational  power of today’s computers. In  fact, the  keys used in modern cryptography are so large that breaking the AES-256  standard would require “fifty supercomputers that could check a billion billion (1018) AES  keys per second [and] would, in theory, require about 3×1051 years.”

The keys used in modern cryptography are so large that breaking the AES-256 standard would require “fifty supercomputers that could check a billion billion (1018) AES keys per second [and] would, in theory, require about 3×1051 years.”

Thankfully this means that there isn't an immediate problem  now, but what does the future hold when current computers are replaced with quantum  computers? The keys that would take a trillion years to break with  conventional computers could possibly be cracked in much less time with quantum  computers. And here’s where quantum physics meets cryptography.

The field of Quantum Cryptography is an area of security  research and development focused on the introduction of new technologies that  will offer more resistance to the computing power of quantum computers. Quantum  cryptography draws its strength from the unpredictable nature of photons – the  smallest particles in the universe. The foundation of quantum physics is  defined by Heisenberg's  Uncertainty Principle, which states that  observation of these particles in any way changes their behavior. These new  quantum cryptography technologies will combine the power of quantum physics and  advanced mathematics to deliver maximum security.

Elements of Quantum  Cryptography
A key element of  quantum cryptography that is being explored to guarantee secure  communication is Quantum Key Distribution (QKD). QKD uses photons to produce  and distribute a key, not to transmit any message data. This key can then be  used with any chosen encryption algorithm (like AES) to encrypt (and decrypt) a  message, which can then be transmitted over a standard communication channel.

The  main security benefit behind QKD is the ability of the two communicating parties  to detect the presence of any third party trying to gain knowledge of the key.  This is possible as a direct result of quantum mechanics whereby the process of  measuring a quantum system in general disturbs the system changing the  particles’ behavior. This  means that a hacker trying to eavesdrop on the key must in some way measure it,  thus introducing anomalies that can be detected and used to alert the parties that a  key has been compromised and should not be used to encode information.

The main security benefit behind QKD is the ability of the two communicating parties to detect the presence of any third party trying to gain knowledge of the key. This is possible as a direct result of quantum mechanics whereby the process of measuring a quantum system in general disturbs the system changing the particles’ behavior.

It  turns out that quantum physics can play an important role in delivering maximum  security cryptographic systems. According to Born’s rule, the  measurement outcome of a quantum state can be intrinsically random, which means  that it can never be predicted better than blindly guessing. This key principle  of quantum mechanics can be exploited by leveraging the inherent randomness in  quantum measurements to generate true random numbers for highly secure cryptographic  keys. These types of random number generators are referred to as Quantum Random Number Generators (QRNG)  and are not new to the industry. Today, there are several QRNGs that are  commercially available that promise true randomness to enable generating  cryptographic keys that are impossible to predict.

Last but not least, another area of quantum  cryptography that is getting attention is Post-Quantum  Cryptography (PQC), also called quantum-resistant or quantum-safe  cryptography. Essentially, this is research towards the development of new  cryptographic algorithms that would be secure against the computational power  of both quantum and classical computers. These next-gen algorithms will serve  as replacements for our current public-key cryptosystems to prepare for the day  when large-scale quantum computers become a reality. The National Institute of  Standards and Technology (NIST) has already started to move in this direction  with the kick-off of its Post-Quantum  Crypto Project.  This project is a process to solicit,  evaluate, and standardize one or more quantum-resistant public-key  cryptographic algorithms. Nominations for post-quantum candidate algorithms  can be submitted up until November 2017. This is same type of process that was  put in place by NIST years ago when it was searching for a new algorithm to  replace the Data Encryption Standard (DES) published in 1977. This process resulted  in the AES-256 encryption algorithm extensively deployed today. These new PQC standards  will be used as quantum resistant counterparts to existing standards that are  currently available.

The Future of Encryption With Quantum Physics

Today, a  hacker can passively intercept an encrypted message sent by Alice to Bob  without either of them realizing that their message has been compromised. The  hacker can do this in different ways, including fiber tapping, and can then  spend lots of time (a trillion years!) and computing power to crack the code.

Now,  consider this same example leveraging quantum cryptography. Since we know we can't  measure a photon without affecting its behavior, a hacker cannot go undetected  when eavesdropping on a private message. After all of the photons are received  by Bob, and he and Alice have their conversation about the message transmitted,  discrepancies will emerge if a hacker has intercepted the message. If this  occurs, the 'transaction' can be aborted, and a new key sent automatically. By  sending multiple quantum keys every second, the security of a fiber line can be  constantly monitored and attempts to 'tap' the signal can be instantly  identified.

As increasingly more sensitive information gets distributed  across fiber-optic networks, today’s web-scale communications employ robust  optical in-flight encryption solutions to ensure that data is secure, whether  it is traveling across the city, across borders, or across the ocean. As the  quantum compute era approaches, research and development advances in the area  of cryptography are important to ensure that we will be able to continue to  secure critical data and the network used to transport it across the globe.

Ciena podcast: Why Cyber Security Matters to The Network Operator