Exploring Cryptographic Key Management Schemes for Enhanced Security in WSNs

Pre-distribution schemes involve assigning cryptographic keys to SNs before deployment, ensuring that nodes can establish secure communication upon entering the network [23,24,25,26,27]. Table 3 lists the major Pre-distribution Key Management Schemes of WSNs along with their description, advantages, and disadvantages.

Dynamic schemes establish or update keys during the network’s operation, adapting to environmental changes or threats [28,29,30,31,32,33,34]. Table 4 lists the major Dynamic Key Management Schemes of WSNs along with their description, advantages, and disadvantages.

Hierarchical schemes use a multi-tier architecture where keys are distributed and managed based on the network hierarchy [35,36,37,38]. Table 5 presents the major Hierarchical Key Management Schemes of WSNs along with their description, advantages, and disadvantages. In key tree-based management schemes, a hierarchical tree structure is employed, where higher-tier nodes manage the keys for their lower-tier counterparts. This method streamlines the key distribution and revocation processes, as key updates can be propagated efficiently through the tree structure. By structuring the network in a way that allows key management at different levels, this approach helps maintain security while minimizing the computational overhead on individual nodes. One of the key advantages of this method is its ability to efficiently handle the distribution and revocation of keys, ensuring that new keys can be quickly propagated when necessary. However, the scheme has a significant drawback: it requires a central authority to manage the tree structure. If this central authority is compromised, the security of the entire network can be jeopardized, as it can impact the management of keys across the hierarchy. An example of a widely adopted hierarchical key management scheme is the Logical Key Hierarchy (LKH). LKH uses a tree structure to organize keys and ensure that key distribution and revocation are performed efficiently. The method is often employed in large-scale wireless WSNs, where it helps reduce the complexity of managing keys for each node. While LKH is effective in providing secure and efficient key management, its reliance on a central authority means that mitigating the risk of compromise at higher levels of the hierarchy is crucial for the scheme’s overall security. Node location plays a vital role in cluster-based and hierarchical key management schemes. By grouping nodes based on proximity, communication overhead can be minimized, improving energy efficiency and scalability. For instance, region-specific key pools, as used in the Multiple Key Pools scheme leverage node location to localize security breaches and enhance network resilience.

In pairwise key establishment, each pair of nodes creates a unique shared key for secure communication [39,40,41,42]. Table 6 lists the few Pairwise Key Establishment Schemes of WSNs along with their description, advantages, and disadvantages. Blom’s Scheme is a matrix-based key management approach that enables nodes within a network to calculate a shared key with any other node without the need for pre-distribution. The system works by using a matrix to generate unique keys for node pairs, with each node possessing a row of the matrix. By combining its row with the row of another node, a shared key can be computed, ensuring that communication between any two nodes is encrypted with a unique key. One of the major advantages of Blom’s Scheme is its high resilience to node capture attacks. Even if one node is compromised, only a limited amount of information is exposed, reducing the overall risk to the network’s security. This feature makes it especially effective in environments where physical security is a concern, as compromising a single node does not allow attackers to access all the keys in the network. However, the scheme has scalability limitations. As the network grows, the need for carefully selecting and managing the matrix becomes more challenging, particularly in resource-constrained environments. The complexity of the matrix also introduces overhead in both computation and storage, making the scheme less suitable for large-scale networks. Blom’s Scheme is most suitable for small to medium-sized networks that require high security, such as in military or industrial applications, where the number of nodes is manageable, but security needs are paramount.

PKC approaches leverage asymmetric cryptographic methods, which, despite being resource-intensive, are applied in certain WSN contexts [43,44,45,46,47,48,49]. Table 7 lists the few PKC approaches of WSNs along with their description, advantages, and disadvantages. ECC is a widely used cryptographic technique that offers strong security with significantly smaller key sizes compared to traditional public key cryptography methods, such as RSA. This characteristic makes ECC particularly suitable for WSNs, where SNs are often constrained by limited computational power, memory, and energy resources. The main advantage of ECC lies in its ability to provide equivalent or even superior security with much smaller key sizes, which reduces the computational and memory demands on SNs, making it an attractive solution for resource-constrained environments. However, despite its efficiency in terms of key size, ECC still involves a higher computational overhead than symmetric key schemes, which may limit its suitability for applications requiring extremely low power consumption and minimal computational load. ECC is particularly effective in high-security applications such as military or healthcare networks, where securing communication and data integrity is of paramount importance. Given its relatively low computational requirements and high security, ECC is increasingly integrated into advanced WSNs where both security and energy efficiency are critical considerations.

Asymmetric cryptography, such as RSA and ECC is highly secure due to its reliance on computationally intensive problems like prime factorization or elliptic curve discrete logarithms. While RSA remains popular, ECC has gained prominence for its strong security at smaller key sizes, making it suitable for resource-constrained WSNs. Recent advancements, such as lightweight ECC variants and hybrid approaches combining symmetric and asymmetric methods, have further enhanced their applicability in IoT and critical infrastructure [44,50].

Quantum-resistant cryptography, such as lattice-based encryption can be implemented in WSN by optimizing these algorithms for lightweight operations. For example, researchers focus on reducing the computational complexity of lattice-based schemes, allowing them to be applied in resource-constrained environments [47,50]. Techniques like reducing key sizes, simplifying encryption and decryption processes, or using hardware accelerators can ensure minimal resource overhead. By integrating these quantum-resistant methods into a hybrid cryptographic approach (e.g., combining asymmetric lattice-based encryption with symmetric encryption for data transmission), WSNs can maintain robust security against quantum threats without significantly impacting energy consumption or processing power.

Matrix-based key management schemes in WSN leverage mathematical constructs like matrices and polynomials to establish secure communication among nodes [39,40,51]. These schemes offer advantages such as scalability and resilience to node capture, but they also present challenges in terms of computational overhead and memory requirements. Table 8 presents a comparison of various matrix-based key management schemes that provide robust security through innovative approaches. Blom’s Scheme is a symmetric matrix-based approach that generates unique pairwise keys using a shared secret matrix, offering high resilience to node capture and efficiency for small to medium networks, though its memory and computation overhead increase with network size, limiting scalability [39]. The Attack Matrix Scheme employs dominance key sets in a cost-effective matrix design, making it resistant to various attacks and suitable for clustered WSNs, but its applicability is limited in highly dynamic networks and requires careful dominance set design. The Polynomial and Matrix-Based Scheme integrates polynomial-based key pre-distribution with matrix design, combining the advantages of both methods to achieve strong security against node capture. However, it incurs higher computational overhead due to polynomial calculations and has a complex setup for large networks.

Combinatorial-based key management schemes power mathematical combinatorial designs to distribute cryptographic keys efficiently among SNs in WSNs. These schemes aim to enhance security while maintaining scalability and minimizing key storage overhead. Unlike traditional random key pre-distribution schemes, combinatorial schemes provide deterministic key-sharing properties, ensuring controlled key overlap and reducing vulnerability to node capture attacks. Table 9 presents a comparison of various Combinatorial-based key management schemes that provide robust security, high scalability, and reduced memory overheads through innovative approaches. The Scalable and Storage-Efficient Dynamic Key Management scheme [54] focuses on optimizing storage while ensuring secure key distribution which makes it suitable for large-scale networks. However, it demands additional computational resources for key updates. The Key Updating for Combinatorial Design-Based Key Management scheme [55] enhances security by efficiently managing key updates, thereby improving resilience against key compromise, though it may introduce synchronization delays in large networks. The Combinatorial Design-Based Key Pre-Distribution scheme [56] ensures deterministic key assignment and scalability while reducing storage overhead but requires fine-tuned parameter selection to balance security and connectivity. Solari Esfehani & Haj Seyyed Javadi (2021) provide a comprehensive survey [57] on combinatorial design-based key management in IoT and WSNs, identifying emerging trends while acknowledging the adaptability limitations of some schemes in dynamic network environments. These combinatorial approaches collectively offer promising solutions for secure and efficient key management in resource-constrained WSNs.

Balancing key pool size and key size is critical in designing efficient key management schemes for WSN. Storage constraints play a significant role, as large key pools or long cryptographic keys require substantial memory, which may exceed the capacity of resource-constrained WSN nodes. Lightweight cryptographic schemes, such as ECC, provide a solution by offering strong security with smaller key sizes, thereby reducing storage requirements. Security requirements further influence the choice of key pool size and key length. Critical applications, such as military networks, often necessitate large key pools and longer keys to ensure robust protection against sophisticated attacks. These scenarios typically leverage advanced hardware capable of handling the increased computational demands associated with managing large keys and pools. Scalability is another vital factor, as large key pools are essential for accommodating thousands of nodes in extensive networks. This ensures that security is maintained even as the network size grows. In contrast, shorter keys and smaller key pools may suffice for small-scale networks, where conserving resources is a higher priority than accommodating large-scale deployments. Balancing these factors is crucial for meeting the diverse requirements of WSN applications while optimizing performance and resource usage. Table 10 lists Comparison of Key Pool and Key Size in Key Management Schemes for security, storage needs, energy efficiency, and scalability in WSN.

Recent advancements in key management for WSN’s have introduced adaptive and hybrid approaches to address the limitations of traditional methods. These approaches aim to optimize the balance between security, scalability, and energy efficiency, which are critical in resource-constrained environments.

Adaptive Key Management schemes dynamically adjust parameters, such as key pool size, to accommodate changing network conditions. This adaptability enhances security by responding to emerging threats while minimizing resource usage. For example, Msolli et al. proposed an adaptive key pool design that modifies the key pool size based on real-time network requirements [33]. This reduces memory overhead and improves resilience to node capture without compromising security, making it suitable for large and dynamic WSN deployments. Hybrid Approaches combine the strengths of different key management strategies to achieve enhanced performance. By integrating smaller key pools with shorter cryptographic keys, hybrid schemes reduce computational overhead and energy consumption. Baburaj [40] demonstrated that supplementing these setups with rekeying mechanisms increases security and flexibility, particularly in networks with dynamic topologies. These methods ensure that resource-constrained nodes can efficiently manage keys while maintaining robust security. Post-Quantum Integration in adaptive and hybrid frameworks is another promising research direction. Lattice-based cryptographic techniques presented by Aydeger et al. offer quantum-resistant security with efficient resource usage [50]. These methods are particularly relevant as WSNs face the growing threat of quantum computing. By integrating post-quantum cryptography into adaptive and hybrid schemes, future WSNs can achieve resilience to advanced cryptographic attacks while remaining scalable and energy efficient.

Energy consumption is a major limitation in WSNs due to the resource constraints of SNs. These nodes often rely on battery power and must minimize energy usage to extend their operational lifetime. Key management schemes, which include cryptographic operations and communication overhead, can be energy intensive. Developing lightweight key management schemes that minimize energy consumption remains a priority. Researchers are focusing on optimizing cryptographic protocols and reducing the number of communication rounds for key establishment and management, all while maintaining a high level of security. Solutions such as energy-aware key distribution and duty-cycling techniques are promising, as they aim to balance energy use with security needs [58,59,60]. For instance, more energy-efficient algorithms, such as those based on symmetric encryption techniques have been proposed to replace traditional public-key cryptography which is often too computationally expensive for low-power nodes. Lightweight cryptographic methods, such as symmetric encryption algorithms, reduce computational costs while maintaining security. Energy-harvesting technologies, which leverage ambient sources like solar energy, are increasingly integrated into key management processes to supplement battery power and enable continuous operation.

One of the major threats in WSNs is node capture. Since SNs are often deployed in open, potentially hostile environments, attackers may physically capture nodes to extract sensitive keys and compromise network security. Future key management schemes need to enhance their resilience to such attacks. This can be achieved by designing protocols that ensure that the compromise of a single or even multiple nodes does not jeopardize the entire network’s security. Techniques like dynamic key revocation, node authentication, and the use of distributed trust models can mitigate the damage caused by compromised nodes [61]. For example, schemes like those based on the hierarchical key management model provide better control over the distribution of keys and can quickly invalidate compromised keys to minimize risks. Additionally, the integration of physical-layer security methods such as secret sharing and random key pre-distribution may offer additional protection by making it more difficult for attackers to obtain the keys even after capturing a node.

As WSNs often consist of many SNs, key management schemes must be scalable to accommodate networks of varying sizes without experiencing performance degradation. Scalability challenges arise when the number of nodes increases, as the complexity of key management schemes, including the distribution, revocation, and updating of keys, grows exponentially [62,63]. The design of scalable key management solutions that can handle large-scale networks efficiently is thus an ongoing area of research. Cluster-based key management approaches, in which a subset of nodes (cluster heads) are responsible for managing key distribution within their respective clusters, have shown promise in improving scalability. By reducing the number of nodes involved in key management activities and localizing key-related operations, such schemes minimize communication overhead and maintain efficiency even in large networks. Further research is required to ensure that these methods remain effective as network sizes grow into thousands or even millions of nodes.

With the advent of quantum computing, many cryptographic algorithms used today may become vulnerable to attacks from sufficiently powerful quantum computers. Public-key cryptographic schemes such as RSA and ECC which are widely used for key management in WSNs, are particularly susceptible to quantum attacks. To address this looming threat, the development of post-quantum security solutions is becoming an urgent priority [64]. Post-quantum cryptography (PQC) aims to develop cryptographic schemes that are resistant to attacks from quantum computers [65]. Researchers are exploring the potential integration of quantum-resistant algorithms such as lattice-based cryptography and hash-based signatures into WSN key management protocols. These solutions need to be lightweight enough to fit within the constraints of SNs while offering robust protection against quantum threats [66]. Implementing post-quantum security in WSNs will not only safeguard the networks against future attacks but also ensure that the cryptographic methods used remain relevant in the quantum computing era.

Energy-efficient key management is critical in WSNs to extend their lifespan while maintaining security, given the limited energy resources of SNs. Resilience to node capture is equally important, requiring mechanisms like key revocation and distributed trust models to minimize damage from compromised nodes. As WSNs scale to thousands or millions of nodes, efficient key management strategies, such as cluster-based and hierarchical structures, address scalability challenges. Furthermore, with the advent of quantum computing, post-quantum security measures like lattice-based cryptography and hash-based signatures are essential to safeguard against future quantum attacks. These approaches collectively enhance WSN security, ensuring resilience, scalability, and protection against emerging threats.

Emerging research in WSN is focusing on innovative ways to balance security and resource efficiency. Table 12 presents such research solutions for key management in WSN One key area is hybrid cryptographic solutions, which involve combining lightweight cryptographic techniques, such as elliptic curve cryptography or lightweight block ciphers, with quantum-resistant algorithms like lattice-based encryption. This hybrid approach aims to provide a balance between robust security and minimal resource usage, with the possibility of dynamically switching between algorithms based on the network’s threat model or changing conditions [66,67]. Another promising direction is adaptive key management, where key parameters are dynamically adjusted in response to factors like communication traffic, network topology, or energy consumption. This adaptability enhances security without unnecessarily increasing the computational burden [68,69]. Lastly, machine learning for optimization is an exciting frontier, where AI can be utilized to predict energy usage, optimize key management protocols, and anticipate security threats based on the network’s behavior. This would lead to more intelligent systems that can autonomously adapt, optimizing both security and resource consumption. These combined research directions are laying the foundation for more efficient, secure, and scalable WSNs in real-world applications [70,71,72].