The ability to quickly revoke a compromised key is critical to the security of a public-key infrastructure. Regrettably, most certificate revocation schemes suffer from latency, availability, or privacy issues. The problem is exacerbated by the lack of a native delegation mechanism in TLS, which increasingly leads domain owners to engage in dangerous practices such as sharing their private keys with third parties. We investigate the utility of "proxy certificates" to address long-standing revocation and delegation shortcomings in the web PKI. By issuing proxy certificates, entities holding a regular (non-CA) certificate can grant all or a subset of their privileges to other entities. This fine-grained control on delegating privileges requires no further actions from a CA, yet does not require trust on first use (TOFU). The lifetime of a proxy certificate can be made almost arbitrarily short to curb the consequences of a key compromise. We analyze the benefits of this approach in comparison to alternatives, discussing various use cases and technical implications. We also show that combining short-lived proxy certificates with other schemes constitutes an attractive solution to several pressing problems. Overall, we make the case that the benefits obtained from incorporating proxy certificates into the current PKI substantially outweighs the changes required in practice. Such changes are minimal, and would only be required on the browser end, should a domain owner opt to use proxy certificates.
Recent trends in public-key infrastructure research explore the tradeoff between decreased trust in Certificate Authorities (CAs), resilience against attacks, communication overhead (bandwidth and latency) for setting up an SSL TLS connection, and availability with respect to verifiability of public key information. In this paper, we propose AKI as a new public-key validation infrastructure, to reduce the level of trust in CAs. AKI integrates an architecture for key revocation of all entities (e.g., CAs, domains) with an architecture for accountability of all infrastructure parties through checks-and-balances. AKI efficiently handles common certification operations, and gracefully handles catastrophic events such as domain key loss or compromise. We propose AKI to make progress towards a public-key validation infrastructure with key revocation that reduces trust in any single entity. The current Transport Layer Security (TLS) Public-Key Infrastructure (PKI) is based on a weakest-link security model that depends on over a thousand trust roots. The recent history of malicious and compromised Certification Authorities has fueled the desire for alternatives. Creating a new, secure infrastructure is, however, a surprisingly challenging task due to the large number of parties involved and the many ways that they can interact. A principled approach to its design is therefore mandatory, as humans cannot feasibly consider all the cases that can occur due to the multitude of interleavings of actions by legitimate parties and attackers, such as private key compromises (e.g., domain, Certification Authority, log server, other trusted entities), key revocations, key updates, etc. We present ARPKI, a PKI architecture that ensures that certificate-related operations, such as certificate issuance, update, revocation, and validation, are transparent and accountable. ARPKI efficiently supports these operations, and gracefully handles catastrophic events such as domain key loss or compromise. Moreover ARPKI is the first PKI architecture that is co-designed with a formal model, and we verify its core security property using the TAMARIN prover. We prove that ARPKI offers extremely strong security guarantees, where compromising even n 1 trusted signing and verifying entities is insufficient to launch a man-in-the-middle attack. Moreover, ARPKI’s use deters misbehavior as all operations are publicly visible. Finally, we present a proof-of-concept implementation that provides all the features required for deployment. Our experiments indicate that ARPKI efficiently handles the certification process with low overhead. It does not incur additional latency to TLS, since no additional round trips are required. The recently proposed concept of publicly verifiable logs is a promising approach for mitigating security issues and threats of the current Public-Key Infrastructure (PKI). Although much progress has been made towards a more secure infrastructure, the currently proposed approaches still suffer from security vulnerabilities, inefficiency, or incremental deployment challenges. In this paper we propose PoliCert, a comprehensive log-based and domain-oriented architecture that enhances the security of PKI by offering: a) stronger authentication of a domain's public keys, b) comprehensive and clean mechanisms for certificate management, and c) an incentivised incremental deployment plan. Surprisingly, our approach has proved fruitful in addressing other seemingly unrelated problems such as TLS-related error handling and client server misconfiguration.