The growing importance of Underwater Networks (UNs) in mission-critical activities at sea enforces the need for secure Underwater Communications (UCs). Classical encryption techniques can be used to achieve secure data exchange in UNs. However, the advent of Quantum Computing will pose threats to classical cryptography, thus challenging also UCs. Currently, underwater crypto-systems mostly adopt symmetric ciphers, which are considered computationally quantum-robust, but pose the challenge of distributing the secret key upfront. Post-Quantum Public-Key (PQPK) protocols promise to overcome the key distribution problem. The security of PQPK protocols, however, only relies on the assumed computational complexity of some underlying mathematical problems. Moreover, the use of resource hungry PQPK algorithms in resource-constrained environments such as UNs can require non-trivial hardware/software optimization efforts. An alternative approach is underwater Quantum Key Distribution (QKD), which promises unconditional security built upon the physical principles of Quantum Mechanics. This tutorial provides a basic introduction to free-space Underwater QKD (UQKD). At first, the basic concepts of QKD are presented, based on a fully worked out QKD example. A thorough state-of-the-art analysis of UQKD is carried out. The paper subsequently provides a theoretical analysis of the QKD performance through free-space underwater channels, and its dependence on the key optical parameters of the system and seawater. Finally, open challenges, points of strength and perspectives of UQKD are identified and discussed.
The growing importance of Underwater Networks (UNs) in mission-critical activities at sea enforces the need for secure Underwater Communications (UCs). Classical encryption techniques can be used to achieve secure data exchange in UNs. However, the advent of Quantum Computing will pose threats to classical cryptography, thus challenging also UCs. Currently, underwater crypto-systems mostly adopt symmetric ciphers, which are considered computationally quantum-robust, but pose the challenge of distributing the secret key upfront. Post-Quantum Public-Key (PQPK) protocols promise to overcome the key distribution problem. The security of PQPK protocols, however, only relies on the assumed computational complexity of some underlying mathematical problems. Moreover, the use of resource hungry PQPK algorithms in resource-constrained environments such as UNs can require non-trivial hardware/software optimization efforts. An alternative approach is underwater Quantum Key Distribution (QKD), which promises unconditional security built upon the physical principles of Quantum Mechanics. This tutorial provides a basic introduction to free-space Underwater QKD (UQKD). At first, the basic concepts of QKD are presented, based on a fully worked out QKD example. A thorough state-of-the-art analysis of UQKD is carried out. The paper subsequently provides a theoretical analysis of the QKD performance through free-space underwater channels, and its dependence on the key optical parameters of the system and seawater. Finally, open challenges, points of strength and perspectives of UQKD are identified and discussed.
The growing importance of Underwater Networks (UNs) in mission-critical activities at sea enforces the need for secure Underwater Communications (UCs). Classical encryption techniques can be used to achieve secure data exchange in UNs. However, the advent of Quantum Computing will pose threats to classical cryptography, thus challenging also UCs. Currently, underwater crypto-systems mostly adopt symmetric ciphers, which are considered computationally quantum-robust, but pose the challenge of distributing the secret key upfront. Post-Quantum Public-Key (PQPK) protocols promise to overcome the key distribution problem. The security of PQPK protocols, however, only relies on the assumed computational complexity of some underlying mathematical problems. Moreover, the use of resource hungry PQPK algorithms in resource-constrained environments such as UNs can require non-trivial hardware/software optimization efforts. An alternative approach is underwater Quantum Key Distribution (QKD), which promises unconditional security built upon the physical principles of Quantum Mechanics. This tutorial provides a basic introduction to free-space Underwater QKD (UQKD). At first, the basic concepts of QKD are presented, based on a fully worked out QKD example. A thorough state-of-the-art analysis of UQKD is carried out. The paper subsequently provides a theoretical analysis of the QKD performance through free-space underwater channels, and its dependence on the key optical parameters of the system and seawater. Finally, open challenges, points of strength and perspectives of UQKD are identified and discussed.
The growing importance of Underwater Networks (UNs) in mission-critical activities at sea enforces the need for secure Underwater Communications (UCs). Classical encryption techniques can be used to achieve secure data exchange in UNs. However, the advent of Quantum Computing will pose threats to classical cryptography, thus challenging also UCs. Currently, underwater crypto-systems mostly adopt symmetric ciphers, which are considered computationally quantum-robust, but pose the challenge of distributing the secret key upfront. Post-Quantum Public-Key (PQPK) protocols promise to overcome the key distribution problem. The security of PQPK protocols, however, only relies on the assumed computational complexity of some underlying mathematical problems. Moreover, the use of resource hungry PQPK algorithms in resource-constrained environments such as UNs can require non-trivial hardware/software optimization efforts. An alternative approach is underwater Quantum Key Distribution (QKD), which promises unconditional security built upon the physical principles of Quantum Mechanics. This tutorial provides a basic introduction to free-space Underwater QKD (UQKD). At first, the basic concepts of QKD are presented, based on a fully worked out QKD example. A thorough state-of-the-art analysis of UQKD is carried out. The paper subsequently provides a theoretical analysis of the QKD performance through free-space underwater channels, and its dependence on the key optical parameters of the system and seawater. Finally, open challenges, points of strength and perspectives of UQKD are identified and discussed.
The growing importance of Underwater Networks (UNs) in mission-critical activities at sea enforces the need for secure Underwater Communications (UCs). Classical encryption techniques can be used to achieve secure data exchange in UNs. However, the advent of Quantum Computing will pose threats to classical cryptography, thus challenging also UCs. Currently, underwater crypto-systems mostly adopt symmetric ciphers, which are considered computationally quantum-robust, but pose the challenge of distributing the secret key upfront. A promising approach to overcome the key distribution problem is based on Post-Quantum Public-Key (PQPK) protocols. The security of PQPK protocols, however, only relies on the assumed computational complexity of some underlying mathematical problems. Moreover, the use of resource hungry PQPK algorithms in resource-constrained environments such as UNs can require non-trivial hardware/software optimization efforts. An alternative approach is underwater Quantum Key Distribution (QKD), which promises unconditional security built upon the physical principles of Quantum Mechanics. This tutorial provides a basic introduction to free-space Underwater QKD (UQKD). At first, the basic concepts of QKD are presented, based on a fully worked out QKD example. A thorough state-of-the-art analysis of UQKD is carried out. The paper subsequently provides a theoretical analysis of the QKD performance through free-space underwater channels, and its dependence on the key optical parameters of the system and seawater. Finally, open challenges, points of strength and perspectives of UQKD are identified and discussed.
The growing importance of underwater networks (UNs) in mission-critical activities at sea enforces the need for secure underwater communications (UCs). Classical encryption techniques can be used to achieve secure data exchange in UNs. However, the advent of quantum computing will pose threats to classical cryptography, thus challenging UCs. Currently, underwater cryptosystems mostly adopt symmetric ciphers, which are considered computationally quantum robust but pose the challenge of distributing the secret key upfront. Post-quantum public-key (PQPK) protocols promise to overcome the key distribution problem. The security of PQPK protocols, however, only relies on the assumed computational complexity of some underlying mathematical problems. Moreover, the use of resource-hungry PQPK algorithms in resource-constrained environments such as UNs can require nontrivial hardware/software optimization efforts. An alternative approach is underwater quantum key distribution (QKD), which promises unconditional security built upon the physical principles of quantum mechanics (QM). This tutorial provides a basic introduction to free-space underwater QKD (UQKD). At first, the basic concepts of QKD are presented, based on a fully worked out QKD example. A thorough state-of-the-art analysis of UQKD is carried out. The paper subsequently provides a theoretical analysis of the QKD performance through free-space underwater channels and its dependence on the key optical parameters of the system and seawater. Finally, open challenges, points of strength, and perspectives of UQKD are identified and discussed.
Quantum key distribution (QKD) allows for the establishment of a secret key between two parties, secure against computationally unbounded adversaries. Most experimental and theoretical research in this area, investigates the performance of QKD over fiber or free space channels. A growing body of work, however, has begun to investigate its performance in underwater scenarios. Here, we consider the realistic finite key scenario, and evaluate the simulated performance of two different decoy state protocols. We show that there are certain underwater channels where "simpler" QKD protocols outperform more complex ones. Finally, we also investigate methods to improve QKD performance underwater, specifically looking at classical advantage distillation, which we show can greatly improve the maximal distance supported by QKD underwater.
Quantum technology, and especially quantum computing, is advancing rapidly. Our every-day secure communication infrastructure relies heavily on public key cryptography; unfortunately, many public key schemes are in fact insecure against quantum algorithms. Furthermore, adversaries who, today, capture information encrypted using classical key distribution systems, can wait and, as soon as quantum computers of sufficient power become available, they may decipher all previously captured information. While some new “post-quantum” public key systems are assumed to be secure against quantum computers, this is only an assumption and, even if the assumption remains valid, still results in systems that are less efficient for end-users than the more commonly used public key systems employed today. While the advent of quantum technology may seem detrimental to security, in fact, one may harness the power of quantum through quantum key distribution (QKD) for stronger security guarantees. Such QKD protocols allow two (or more) parties to establish a shared secret key, secure against an all-powerful adversary. Perhaps surprising is that QKD technology is already here both experimentally and commercially. This tutorial serves as an introduction to basic QKD along with QKD technology from a practical perspective. Quantum communication is a highly interdisciplinary field of research and one of the goals of this article is to introduce a larger set of researchers and practitioners to its study in the hopes of furthering its progress and eventual wide-scale adoption.