The Enduring Impact of Proven Cryptography Methods
One of the top honors a cryptographic researcher can earn is a Test-of-Time Award, which certifies that their work, over time, has proven foundational to advancing understanding in the field. Dr. Brent Waters, NTT Research’s Cryptographic & Information Security (CIS) Lab director, recently earned his seventh and eighth Test-of-Time Awards.
At the 2025 International Conference on Practice and Theory in Public Key Cryptography (PKC) in Røros, Norway, the International Association for Cryptologic Research (IACR) awarded NTT Research Cryptography & Information Security (CIS) Lab Director Brent Waters a Test-of-Time Award for his groundbreaking work published in PKC 2009.
The paper, titled “Signing a Linear Subspace: Signature Schemes for Network Coding” and co-authored by Dan Boneh of Stanford University, David Freeman of Universiteit Leiden and Jonathan Katz of the University of Maryland, explored two signature schemes to provide resilience to tampering by malicious nodes. By leveraging the two signature schemes alongside network coding to prevent malicious modification of data, the two signature schemes can be viewed as signing linear subspaces in the sense that a signature on V authenticates exactly those vectors in V.
With the continued, widespread adoption of wireless technologies, network coding has become a critical function in improving throughput and robustness against random network failures. This 2009 paper offered a novel approach to network coding that leverages two signature schemes to protect against the malicious modification of packets – a strategy that continues to prove to be effective in today’s cyber threat landscape.
Following Waters’ 2025 PKC Test-of-Time Award, Waters was awarded his eighth Test-of-Time Award at the 2025 International Conference on Applied Cryptography and Network Security (ACNS), for the paper titled “Secure Conjunctive Keyword Search over Encrypted Data.” Co-authored by Phillipe Golle and Jessica Staddon of the Palo Alto Research Center, this paper explored protocols that allow for conjunctive keyword queries on encrypted data and provided the first searchable encryption system that had more advanced searching beyond simple keyword matching. Their work showed how bilinear maps could be used as a tool in building more complex computations of encrypted data, forming the base for applications that followed, including traitor tracing and support for quadratic functions over encrypted data among several others.
Waters’ latest Test-of-Time Awards join an enduring list of accolades, many of which stem from his critical research on Attribute-Based Encryption (ABE)—one of Waters’ most enduring contributions to the field. A use case for ABE is a concept NTT called “SpillProof.” At Upgrade 2025, NTT Research’s annual R&D summit, researchers demonstrated how SpillProof protects privacy by leveraging ABE to encrypt data at the pixel level within a video feed, enabling fine grained, role-based access to the data.
Under the leadership of Waters, the CIS Lab continues to be a driving force for transformative advancements across the cryptographic industry. Since assuming the role of director in 2022, Waters has continued building the CIS Lab team with renowned theoretical cryptographers across top universities and institutions. Waters attributes the success of the CIS Lab to fostering a space of collaboration where industry experts sitting at the intersection of mathematics and computer science can come together and kick off conversations that begin small but can evolve to shape future research that could lead to industry breakthroughs.
While the cyber threat landscape continues to evolve in complexity and scale, the impact of proven cryptographic strategies continues to be strong. Waters’ recognition through the PKC 2025 and the ACNS 2025 Test-of-Time Awards underscores the importance of critical research focusing on long-term solutions to securing digital infrastructure. As organizations seek to improve their cybersecurity posture, ongoing contributions by cryptographic leaders including Waters and the CIS Lab will be critical to shaping a more secure future.