Optimal Untelegraphable Encryption Achieves Indistinguishability and Yields Everlasting Security Without Assumptions

The secure transmission of information remains a fundamental challenge, and researchers continually seek methods to protect data from increasingly sophisticated attacks. Anne Broadbent from University of Ottawa, Eric Culf from Institute for Quantum Computing and University of Waterloo, and Denis Rochette from University of Ottawa, now present a significant advance in this field, achieving an unconditionally secure construction of untelegraphable encryption. This new approach, which restricts an attacker to classical information, establishes a strong foundation for uncloneable encryption and offers potential solutions to long-standing problems in secure communication. The team also demonstrates a crucial link between these encryption types, deriving new limitations and establishing an equivalence in certain scenarios, ultimately paving the way towards achieving indistinguishability for uncloneable encryption without relying on unproven assumptions.

Information, rather than arbitrary quantum states, forms the basis of this research. Scientists have achieved an unconditionally secure construction of untelegraphable encryption (UTE), a specialized encryption method where adversaries are limited to classical information production. This work establishes untelegraphable-indistinguishability security, extending to multi-ciphertext scenarios and bounded collusion-resistant extensions without requiring additional assumptions, and incorporates pseudo-random unitaries to develop an everlasting security model.

Quantum Unclonable Cryptography

This research focuses on uncloneable cryptography, a new approach to security that leverages the laws of quantum physics, specifically the no-cloning theorem, to create codes impossible to break, even with unlimited computing power. While approximate copies are possible, the goal is to design schemes where these copies are insufficient to compromise security, relating to concepts like quantum copy-protection and one-out-of-many encryption. Scientists are investigating the theoretical limits of uncloneable cryptography, establishing separations between cloning and information leakage, and constructing specific cryptographic schemes using uncloneable decryption keys and uncloneable functional encryption. They are also improving efficiency by constructing low-depth quantum circuits and exploring applications to software licensing, alongside rigorous security analysis including device-independent security and analysis in the quantum random oracle model. This work represents a significant effort to move beyond traditional cryptography and explore new security paradigms based on the laws of physics, potentially providing security against adversaries with unlimited computational power. While challenges remain in terms of efficiency and practicality, the research is paving the way for a new generation of secure cryptographic systems.

Untelegraphable and Uncloneable Encryption Connections

The study derives new insights into uncloneable encryption (UE) by leveraging approaches from UTE, establishing connections between the two concepts and obtaining new lower bounds for both. Furthermore, researchers proved an asymptotic equivalence between UTE and UE when the number of adversaries increases, suggesting UTE may offer a new pathway toward achieving indistinguishability security for UE. Experiments demonstrate the conceptual link between UTE and two fundamental principles: the no-cloning theorem and the no-telegraphing principle, establishing their informational equivalence. This connection is crucial for understanding the limits of information transmission and security in quantum cryptography, alongside minimality results demonstrating the optimality of the Haar measure game, a core component of the UTE construction, including one-copy and t-copy approximate minimality.

Indistinguishability for Untelegraphable and Uncloneable Encryption

Researchers have made significant progress in the field of unclonable encryption, specifically focusing on untelegraphable encryption, presenting a construction that achieves indistinguishability without relying on unproven assumptions. They extended this result to scenarios with multiple adversaries and established connections between untelegraphable and unclonable encryption, achieving new lower bounds for both and demonstrating an asymptotic equivalence under certain conditions. This research builds upon existing theoretical foundations and strengthens previous results concerning the limits of cloning and distinguishing quantum states. While the current construction relies on assumptions regarding pseudo-random unitaries, future work will likely focus on refining these constructions and exploring alternative approaches to remove these assumptions and further enhance the efficiency and scalability of unclonable encryption schemes, potentially impacting other areas of quantum cryptography and secure computation.