[Paper Review] PKI Scalability Issues

Adam Slagell, Rafael Bonilla|ArXiv.org|Sep 9, 2004

Advanced Database Systems and Queries13 references8 citations

TL;DR

This paper investigates scalability challenges in Public Key Infrastructure (PKI), focusing on enrollment and certificate revocation in PKIX, SPKI, and PGP systems. It evaluates solutions like delta CRLs, CRS, CRTs, and real-time protocols (OCSP, SCVP), concluding that CRS and CRTs offer scalable, succinct revocation proofs, while depender graphs enable fault-tolerant, distributed revocation with balanced communication overhead.

ABSTRACT

This report surveys different PKI technologies such as PKIX and SPKI and the issues of PKI that affect scalability. Much focus is spent on certificate revocation methodologies and status verification systems such as CRLs, Delta-CRLs, CRS, Certificate Revocation Trees, Windowed Certificate Revocation, OCSP, SCVP and DVCS.

Motivation & Objective

• To analyze scalability limitations in traditional PKI systems, particularly in certificate enrollment and revocation.
• To evaluate emerging solutions such as delta CRLs, CRS, CRTs, and real-time protocols (OCSP, SCVP) for improved scalability.
• To assess the feasibility of depender graphs for fault-tolerant, distributed certificate revocation in dynamic environments.
• To explore the applicability of these systems in military and coalition-based scenarios requiring interoperability and resilience.
• To identify future research directions, including role-based cryptosystems, PKI translators, and formal modeling of PKI components.

Proposed method

• Analyzes PKIX, SPKI, and PGP as representative PKI models, focusing on certificate lifecycle management.
• Evaluates traditional CRLs and their variants (e.g., delta CRLs) for revocation scalability and proof efficiency.
• Examines CRS (Certificate Revocation Status) and CRTs (Certificate Revocation Trees) as scalable alternatives providing succinct validity proofs.
• Reviews real-time services like OCSP, SCVP, and DVCS for on-demand certificate status validation.
• Proposes depender graphs as a fault-tolerant, distributed mechanism for propagating revocation information with minimal global state.
• Compares communication overhead and trust assumptions across systems, emphasizing load balancing and fault tolerance.

Experimental results

Research questions

• RQ1 How do traditional CRL-based revocation systems scale with increasing numbers of certificates and users?
• RQ2 To what extent do CRS and CRTs reduce communication and storage overhead compared to conventional CRLs?
• RQ3 Can real-time protocols like OCSP and SCVP provide scalable, low-latency alternatives to periodic CRL updates?
• RQ4 How effective are depender graphs in enabling scalable, fault-tolerant certificate revocation without centralized coordination?
• RQ5 What are the practical implications of these systems in military and coalition-based PKI deployments?

Key findings

• Traditional CRLs scale poorly due to large message sizes and lack of succinct validity proofs, especially in large-scale deployments.
• Delta CRLs improve scalability by reducing update sizes but still do not provide compact proofs of validity for end users.
• CRS and CRTs offer significantly more scalable revocation by enabling succinct, cryptographically verifiable proofs of certificate status.
• Depender graphs provide fault tolerance and load balancing by distributing revocation propagation across nodes with minimal global state, though they require trust in parent nodes.
• Real-time protocols like OCSP and SCVP enable on-demand validation and support centralized policy enforcement, improving usability and security in enterprise settings.
• Translators between PKI systems (e.g., PKIX, PGP, SPKI) can enable interoperability, though they introduce complexity in trust and key management.