A multi-authority attribute ring signature supporting dynamic policies and dual anonymity for zero-trust networks

Why digital trust needs a rethink

As more of our work and personal lives move into the cloud, the old idea of a secure “inside” and dangerous “outside” of a company network is breaking down. Modern “zero-trust” security assumes that every request, from every device and user, must be checked continuously. This paper introduces a new way to prove who you are and what you’re allowed to do—without revealing your identity or sensitive details—so digital systems can stay secure while better protecting privacy.

From ID cards to flexible digital badges

Traditional security systems often rely on fixed credentials, like usernames, passwords, or static digital certificates. A newer approach uses attributes—facts about a person, such as being a manager, working in finance, or belonging to a hospital’s staff—to decide who can access what. Attribute-based signatures let someone sign a digital message only if their attributes match a rule, such as “Manager AND Finance” or “Doctor OR Nurse.” However, existing schemes tend to be rigid: when access rules change, users need new keys, and it is hard to keep both the signer and their specific attributes fully hidden.

Why decentralization and anonymity are so hard

At the same time, decentralized identity (DID) systems are shifting control away from big central identity providers toward individual users. In these systems, different organizations—like HR, health, or finance departments—may each issue their own digital badges or attributes. In a zero-trust world, a gateway might ask for different combinations of these badges from day to day. Existing tools struggle to keep up: many cannot flexibly mix attributes from multiple authorities, some reveal which attributes were used, and others become too slow or heavy for phones and other modest devices when strong privacy is required.

A new way to sign without giving yourself away

The authors propose a new kind of digital signature called a multi-authority attribute ring signature. “Multi-authority” means that many independent organizations can each hand out attribute keys, without needing to coordinate every time. “Ring signature” means that a message appears to have been signed by someone in a group, but it is impossible for an outsider to tell who exactly did it. In this scheme, a user can locally combine the attribute keys they already hold to meet whatever rule a verifier chooses on the fly—say, “employee in finance” today and “member of the security team OR internal auditor” tomorrow—without returning to the issuing authorities for new keys.

Hiding both the signer and their attributes

The central innovation is what the authors call dual anonymity. Not only is the real signer hidden within a group of possible signers, but the exact subset of attributes used is also concealed. The verifier learns only that “someone in this group met the policy,” not who it was or which badges they relied on. This is achieved by carefully blending together keys and cryptographic operations built on the Chinese SM9 standard, which is optimized for efficiency. The authors provide formal mathematical proofs that, under widely used security assumptions, attackers cannot forge signatures or uncover the signer’s identity or attributes, even if they can adaptively request keys and signatures during an attack.

Speeding up privacy for real-world networks

Beyond theory, the paper evaluates how fast the new scheme runs compared with well-known SM9-based ring signature systems. The authors analyze the number of heavy operations the computer must perform and then implement all schemes using an open-source cryptographic library. Their tests show that, for large groups of possible signers, their method cuts certain expensive operations by about 30 percent during signing. In practical terms, when a ring contains over a thousand users, generating a signature is more than three times faster than a standard baseline and about one and a half times faster than the best recent alternative, while verification speed at the server side remains comparable.

What this means for safer digital systems

For everyday users, this work points toward login and access systems where you can prove you are allowed to do something without exposing who you are or which of your roles or memberships you are using. For organizations building zero-trust networks and DID-based services, the proposed scheme offers a way to let multiple departments or companies issue their own attributes, while gateways flexibly define and update policies. Although current signatures still grow with the size of the user group, the authors outline future work aimed at keeping signature size fixed even as networks scale. Overall, the scheme moves us closer to secure-by-design digital infrastructure where strong privacy and strong access control reinforce each other rather than compete.

Citation: Chen, J., Zhou, X., Fu, W. et al. A multi-authority attribute ring signature supporting dynamic policies and dual anonymity for zero-trust networks. Sci Rep 16, 9441 (2026). https://doi.org/10.1038/s41598-026-40089-2

Keywords: decentralized identity, zero trust security, anonymous authentication, ring signatures, attribute-based cryptography