Federal Agencies May Combine Classical and Quantum-Resistant Algorithms
In a significant move towards securing information against the impending challenges posed by quantum computing, the National Institute of Standards and Technology (NIST) has outlined a strategy for national agencies to transition to post-quantum cryptography. The transition, which includes hybrid solutions combining both quantum and classical algorithms, is crucial to mitigate vulnerabilities in existing cryptographic frameworks and to ensure that sensitive federal assets remain secure.
NIST’s announcement comes amid rising alarm over "harvest now, decrypt later" attacks—an emerging threat where adversaries capture encrypted information with the intent to decrypt it once they gain access to more powerful quantum computers. Their recent report provides guidance on managing the migration from existing, quantum-vulnerable public-key cryptography to safer alternatives, underscoring the urgency of adapting to the rapidly evolving technological landscape.
Beginning in 2027, federal agencies are expected to shift from merely assessing their cryptographic inventories to initiating early migrations. This change is part of a broader directive from the Office of Management and Budget (OMB), which, in June, mandated that agencies reduce their "quantum risk" as aggressively as possible, with a goal of completing substantial migrations by the end of 2030. NIST emphasizes that its guidelines will not only serve federal agencies but also offer a framework that critical infrastructure operators can utilize to enhance their security posture.
NIST has identified several key areas that will benefit from the integration of quantum-resistant algorithms during this transitional phase. These include code signing in software development, asymmetric key user sign-in, data transmission across public networks through Transport Layer Security (TLS) or virtual private networks (VPNs), as well as the signing and encryption of emails and documents. While aspects of user-machine authentication may not require immediate attention due to their resistance to late decryption, the protection of data in transit remains paramount. According to experts from NIST, including Dustin Moody and Ray Perlner, immediate steps must be taken to enhance the security of transportation-layer encryption.
Historically, the journey from algorithm standardization to comprehensive integration within information systems has been long and complex, often taking 10 to 20 years. This prolonged timeline underscores the urgent need for action; NIST warns that the deadlines for transitioning key establishment and digital signature mechanisms leave little margin for error. In preparation, NIST has identified four families of post-quantum digital signature algorithms, classifying them for both general use and specific applications like software and firmware signing.
For key exchanges, NIST has approved a family of quantum-resistant algorithms known as the Module-Lattice-Based Key-Encapsulation Mechanism (KEM). In 2025, NIST selected an alternative KEM algorithm, which is currently pending formal approval. Furthermore, NIST has announced that it will maintain a “deprecated” status for currently risky algorithms. This approach allows organizations to evaluate their own risks and make informed decisions regarding the transition to post-quantum cryptography.
The eventual phasing out of all quantum-vulnerable digital signature algorithms is set to take effect after 2030, with a complete prohibition under NIST standards and guidelines by 2035. This necessitates a carefully planned migration strategy for organizations to eliminate unsafe cryptography methods.
During the initial years of this transition to post-quantum cryptography, NIST anticipates that many organizations will operate on hybrid protocols. The term "hybrid" refers to configurations where both existing and quantum-safe algorithms are utilized concurrently for generating cryptographic keys and digital signatures. This strategy can also involve combining several quantum-resistant options that provide security through different mechanisms.
While hybrid solutions offer a pathway to better security by compensating for cryptographic or implementation flaws inherent in individual algorithms, NIST cautions that they also introduce added complexity to system architectures. This complexity can lead to increased security risks and higher costs, making it imperative for organizations to manage their transitions carefully. NIST notes that these hybrid strategies are generally viewed as temporary measures that will eventually give way to the exclusive use of post-quantum cryptographic tools.
As the landscape of encryption and data security evolves in response to the advancements in quantum computing technology, federal agencies must act swiftly and strategically to safeguard critical assets from potential breaches. The successful implementation of these measures will significantly enhance the resilience of national infrastructures and the integrity of sensitive data.