# Decentralized Pub/Sub's Missing Link: The Role-Based Access Control Challenge

The growing demand for decentralized systems has exposed a critical gap in publish/subscribe (pub/sub) architectures: the lack of robust role-based access control (RBAC) without sacrificing decentralization. This technological hurdle continues to force organizations to choose between security and true distributed operations.


## The Current Landscape

Traditional pub/sub systems rely heavily on centralized brokers to manage access control[1]. While these systems effectively handle message routing and filtering, they create single points of failure and trust bottlenecks that contradict the principles of decentralization[2].


### The RBAC Dilemma

Current implementations face two fundamental challenges:

**Trust Management**
- Brokers must maintain and verify role assignments
- Access control policies must be consistently enforced across distributed nodes
- Role hierarchies become complex to manage without central authority[1]

**Scalability Concerns**
- Content-based routing optimizations conflict with fine-grained access control
- Dynamic policy updates create significant overhead
- Cross-domain role verification remains problematic[5]

The Technical Challenge
Industry experts have long considered building a decentralized pub/sub system with fine-grained access control to be a major open problem. Current solutions face a fundamental dilemma: they either sacrifice security for decentralization or vice versa.
“The middleware community has long been expecting pub/sub systems where publishers can define by whom and how their data can be accessed, preferably not just role-based but also attribute-based,” notes a recent IEEE study.
Current Market Solutions Fall Short
Existing implementations struggle with two critical limitations:
Security Compromises
• Systems relying on non-cryptographic trusted domains
• Centralized architectures that create single points of failure
• Solutions that violate core pub/sub decoupling principles
Technical Barriers
• Publishers cannot encrypt data using subscriber keys due to pub/sub’s decoupling nature
• Broker-based encryption risks exposing all historical publications if a single broker is compromised

## A Promising Solution


The emergence of Decentralized Identity standards, particularly Verifiable Credentials and Presentations, offers a potential breakthrough. This approach would:

**Leverage Verifiable Presentations**
- Encode role assertions as verifiable credentials
- Use presentation requests to enforce access control at subscription time
- Enable peer-to-peer verification without central authorities[4]

**Enable Dynamic Access Control**
- Allow for credential-based channel subscriptions
- Support fine-grained attribute-based access control
- Maintain privacy through selective disclosure[3]

The integration of decentralized identity with pub/sub systems could finally bridge the gap between security requirements and decentralization goals, though significant implementation challenges remain. As one industry expert noted, this convergence represents the next frontier in distributed systems architecture.

Sources
[1] [PDF] Role-Based Access Control for Publish/Subscribe Middleware ... https://www.eecg.utoronto.ca/debs03/papers/belokosztolski_etal_debs03.pdf
[2] What is Pub/Sub Architecture? - GeeksforGeeks https://www.geeksforgeeks.org/what-is-pub-sub/
[3] [PDF] SSIBAC: Self-Sovereign Identity Based Access Control https://www.dpss.inesc-id.pt/~mpc/pubs/SSIBAC__Self_Sovereign_Identity_Based_Access_Control.pdf
[4] Linked Verifiable Presentation - Decentralized Identity Foundation https://identity.foundation/linked-vp/
[5] [PDF] Access Control in Publish/Subscribe Systems https://www.doc.ic.ac.uk/~prp/doc/research/DEBS08PSAC.pdf
[6] Decentralized Identity: Verifiable Credentials Deep Dive https://techcommunity.microsoft.com/blog/microsoftsecurityandcompliance/decentralized-identity-verifiable-credentials-deep-dive/3690641