Quantum-Resistant Blockchain and Distributed Ledger Security Models
As quantum computing continues to grow rapidly, researchers and implementing organizations have made it a top priority to develop new forms of cryptography that are resistant to quantum attacks. Public key cryptography, including RSA and Elliptic Curve Cryptography, is built around assumptions about the difficulty of solving two mathematical problems: the integer factorization problem, which uses an integer’s factors to produce another integer; and the discrete logarithm problem, which are both problems capable of being solved much faster through Shor’s algorithm on a sufficiently powerful quantum computer. Grover’s Algorithm also has an impact on the security of symmetric-key algorithms, such as AES, in that it can reduce the effective key length of symmetric-key algorithms by a factor of 2 because it allows for a quadratic speedup in setting up brute-force searches.
As a result, as industries and governments around the world’s prepare for the day when cryptographically relevant quantum computers can be utilized, the primary focus of their development efforts has shifted away from classical forms of modern day cryptography (PKC) to more modern forms of traditional public-key cryptography that have been specifically developed for use with quantum computers (i.e., post-quantum cryptography). Currently, post-quantum cryptography includes many mathematical families believed to be secure against existing quantum algorithms, with lattice-based cryptography appearing to be one of the most practical and efficient forms of cryptography being researched today and utilized for providing strong security guarantees for both key encapsulation and digital signature schemes. Lattice-based problems like Learning With Errors (LWE) and Ring-LWE provide the basis for the development of key encapsulation methods and digital signature methods.
Besides hash-based and lattice-based constructions, there is an array of post-quantum cryptography such as code-based, multivariate and isogeny based systems. Code based systems are based on the difficulty of decoding random linear codes, and have been studied extensively for decades. They do typically have larger public keys than most systems. Multivariate systems work on the basis of solving systems of multivariate polynomial equations. Isogeny based systems make use of properties of elliptic curve isogenies; several isogeny proposals have experienced significant cryptanalytic breakthroughs, which serve to highlight the importance of rigorous examination of their security. As a result, the future-proofing of cryptographic designs will require more conservative security assumptions to be made, and there will need to be broader peer reviews and greater transparency during the development of standards.
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The process of future-proofing cryptography does not stop with the selection of quantum resistant algorithms. The need for future-proofing is also about designing cryptographic systems that will be modular, adaptable, and crypto-agile. Using a crypto-agile approach, organizations can replace/up-date their cryptographic algorithms with minimal disruption to their existing infrastructure by only having small incremental changes made. During the transition from classical to post-quantum security, many organizations are implementing hybrid schemes which make use of both types of algorithm concurrently. For example, a secure communication session could use both a classical elliptic curve digital signature scheme and a lattice-based digital signature scheme concurrently, and a shared secret would be established using either method.
Protecting long-term data confidentiality also means that the use of post-quantum cryptography (PQC) will enable industries to future-proof their encryption methods against quantum decryption methods that develop in the future. Recently, there has been a significant amount of concern about the possibility for an adversary to decrypt sensitive data that has been encrypted now, by acquiring it now and storing it with the intention of using their quantum computer to decrypt it later (sometimes called “harvesting now, decrypting later”). Consequently, many industries (e.g., financial services, healthcare, military and critical infrastructure sectors) are actively pursuing early adoption of PQC to provide security for their long-lived data assets, which are data assets that need to be retained and protected for an extended period of time. Concurrently, there is ongoing research to develop lightweight PQC systems that can be deployed in resource limited environments such as the Internet of Things (IoT) and 6G networks where computational efficiency and energy consumption remain two significant challenges. The development and implementation of post-quantum and future-proofed cryptography can not only be seen as a technological advancement, but also as a complete re-envisioning of the architecture that underpins cybersecurity, allowing for the continued protection of systems that enable digital trust, privacy, and authentication, from both classical and quantum computers.
Architectural image of the Post-Quantum and Future-Proof Cryptography
