Lattice-Based Encryption Scheme Promises Quantum-Safe Cloud Storage With Faster Performance

Every day, hospitals, banks, and governments hand over enormous troves of sensitive records to cloud providers, trusting mathematical locks to keep prying eyes away. The locks most widely used today, however, share a fatal flaw: a sufficiently powerful quantum computer could shatter them. A team of researchers in India now reports a new encryption scheme designed to survive that quantum threat while running fast enough for real-world cloud storage, and while letting administrators strip access from users the moment their privileges expire.

The study, published in the journal Cluster Computing, introduces what the authors call EQR-MCPABE, short for an efficient and quantum-resistant multi-authority ciphertext-policy attribute-based encryption scheme. The work was carried out by Sravya Gudipati and R. Padmavathy of the National Institute of Technology Warangal, together with Syam Kumar Pasupuleti of the Quantum-Safe Cryptography Lab at the Institute for Development and Research in Banking Technology in Hyderabad. Gudipati and Pasupuleti contributed equally to the research.

Attribute-based encryption is a family of techniques that rethinks who holds the keys to a piece of data. Instead of encrypting a file for one specific recipient, the data owner encrypts it under a policy written in terms of attributes, such as department, clearance level, or role. Only users whose credentials satisfy the policy can decrypt the content. In the ciphertext-policy variant, the encryptor dictates the policy, which makes the approach a natural fit for fine-grained access control in cloud environments where files may be read by many different people over long periods.

Multi-authority versions of the scheme add another layer of practicality. Rather than relying on a single trusted authority to issue every key, a dangerous single point of failure, multiple independent authorities each manage their own set of attributes. A hospital might have one authority for medical roles and another for administrative clearances, and no single entity can reconstruct a user’s full secret key. This decentralization has made multi-authority ciphertext-policy attribute-based encryption, or MCP-ABE, one of the most promising building blocks for privacy-preserving cloud applications.

Yet nearly all of the classical MCP-ABE schemes rest on number-theoretic assumptions, problems such as factoring and computing discrete logarithms that Shor’s algorithm, running on a future quantum computer, is known to solve efficiently. That looming vulnerability has pushed cryptographers toward lattice-based constructions, whose security rests on problems like Learning with Errors that have resisted both classical and quantum attack strategies for nearly two decades. Lattice problems involve finding short vectors in high-dimensional geometric structures, and no known quantum algorithm breaks them.

Existing lattice-based MCP-ABE schemes, however, carry a heavy computational burden. Most are built on the Learning with Errors problem or its ring-based variant, Ring-LWE, and they rely on Gaussian sampling algorithms, procedures that draw random values from a bell-shaped distribution over a lattice. Gaussian sampling is notoriously expensive and delicate to implement correctly, and it has historically been a major source of inefficiency in lattice cryptography. On top of that, many of these schemes lack effective attribute revocation, the ability to cleanly remove a user’s access when attributes change, which is essential for any system handling dynamic organizations where people join, leave, and change roles constantly.

The new scheme sidesteps both problems. EQR-MCPABE is constructed from module lattices, a middle ground between general lattices and ideal lattices that offers a balance of security confidence and efficiency. Module lattices have gained prominence in post-quantum cryptography; the standardized key-encapsulation mechanism CRYSTALS-Kyber, selected by standards bodies for quantum-safe encryption, is itself built on module lattices. Crucially, the new construction avoids Gaussian sampling algorithms altogether, which the authors identify as the key to reducing computation cost while preserving resistance to quantum attacks.

Revocation is handled through a server-assisted mechanism. Instead of forcing every authority to reissue keys whenever an attribute must be revoked, the scheme delegates part of the revocation workload to the cloud server, allowing access to be cut off efficiently without imposing a heavy burden on users or authorities. The design achieves both forward and backward security, meaning that a revoked user cannot read data encrypted after the revocation, and cannot recover data encrypted before it either, closing the window that poorly designed revocation systems often leave open.

On the theoretical side, the authors prove that EQR-MCPABE is secure against chosen-plaintext attacks under the Module-LWE assumption, the module-lattice analogue of the Learning with Errors problem. Chosen-plaintext security is a standard formal guarantee: an adversary who can obtain encryptions of messages of their choosing still cannot extract information about other encrypted content. Grounding the proof in Module-LWE ties the scheme’s security to a well-studied lattice problem, aligning it with the assumptions underpinning the leading post-quantum standards.

Performance analysis presented in the paper shows that the scheme outperforms existing lattice-based MCP-ABE constructions, a result the researchers attribute largely to the elimination of Gaussian sampling and the efficiency of the module-lattice setting. As organizations worldwide begin the long migration to quantum-safe cryptography, work like this points toward access-control systems that can protect fine-grained, multi-authority cloud data not just against today’s attackers, but against the quantum machines of tomorrow, without the performance penalties that have kept earlier lattice-based designs out of practical deployment.

Subject of Research: A quantum-resistant multi-authority attribute-based encryption scheme for secure cloud storage

Article Title: Efficient and quantum-resistant multi-authority CP-ABE with attribute revocation for cloud Storage

Article References: Gudipati, S., Pasupuleti, S. K., & Padmavathy, R. (2026). Efficient and quantum-resistant multi-authority CP-ABE with attribute revocation for cloud Storage. Cluster Computing, 29(15), Article 849. https://doi.org/10.1007/s10586-026-06660-2

Image Credits: AI Generated

DOI: 10.1007/s10586-026-06660-2

Keywords: cryptography, post-quantum cryptography, lattice-based cryptography, cloud storage, attribute-based encryption, Module-LWE, attribute revocation, access control, multi-authority encryption, quantum computing, data security, Efficient