RITM: Revocation in the Middle

Abstract

Abstract-Although TLS is used on a daily basis by many critical applications, the public-key infrastructure that it relies on still lacks an adequate revocation mechanism. An ideal revocation mechanism should be inexpensive, efficient, secure, and privacypreserving. Moreover, rising trends in pervasive encryption pose new scalability challenges that a modern revocation system should address. In this paper, we investigate how network nodes can deliver certificate-validity information to clients. We present RITM, a framework in which middleboxes (as opposed to clients, servers, or certification authorities) store revocation-related data. RITM provides a secure revocation-checking mechanism that preserves user privacy. We also propose to take advantage of content-delivery networks (CDNs) and argue that they would constitute a fast and cost-effective way to disseminate revocations. Additionally, RITM keeps certification authorities accountable for the revocations that they have issued, and it minimizes overhead at clients and servers, as they have to neither store nor download any messages. We also describe feasible deployment models and present an evaluation of RITM to demonstrate its feasibility and benefits in a real-world deployment.

BlockPKI: An Automated, Resilient, and Transparent Public-Key Infrastructure

“…Short-lived, multisigned certificates greatly reduce the need for a revocation system, but do not completely suppress it. Given that designing a satisfactory revocation system has proven to be an extremely challenging task [25,38,39], we consider it to go beyond the scope of this paper. Nevertheless, the security of BlockPKI can be further improved by combining it with any existing revocation scheme.…”

Let's Revoke: Scalable Global Certificate Revocation

“…One approach is through a middlebox. Revocation in the Middle (RITM) [8] is one such strategy that distributes revocation information to middleboxes throughout the Internet via a CDN. As the middlebox intercepts traffic, it checks each certificate's revocation status and appends this status to the connection as part of a TLS extension.…”

“…For CRLs and OCSP these requirements are highly variable depending on the usage of certificates by a given client, though average costs can be established for both of these strategies. For 7 While other revocation strategies also allow clients to adopt a hard-fail policy (such as OCSP Must-Staple [25] and RITM [8]), no other previously proposed strategy can do so without adding new entities in the PKI ecosystem or forcing relatively high numbers of servers to change their configurations and key management practices.…”

“…Among these concerns are scalability [2]- [4], privacy [5], page loading delays [5], and susceptibility to downgrade attacks [2], [5], [6]. The remaining strategies have other debilitating weaknesses, such as requiring significant infrastructure changes [7], [8] or opening new attack surfaces [9]. Due to these critical issues, certificate revocation is ignored by most clients, leaving many computers and mobile devices vulnerable to attack [10].…”

Investigating Secure Implementation of Government Web based Systems in Tanzania

“…They scanned over the whole Internet and found misconfigured trust relationships between certificate chains that can be exploited. Other studies such as [15], [32] have also analysed the aspect of HTTPS certificate validation and revocation and found several issues that can allow attackers to interfere with the security provided by HTTPS.…”