Secure data replication over untrusted hosts

In the Internet age, data replication is a popular technique for achieving fault tolerance and improved performance. With the advent of content delivery networks, it is becoming more and more frequent that data content is placed on hosts that are not directly controlled by the content owner, and because of this, security mechanisms to protect data integrity are necessary. In this paper we present a system architecture that allows arbitrary queries to be supported on data content replicated on untrusted servers. To prevent these servers from returning erroneous answers to client queries, we make use of a small number of trusted hosts that randomly check these answers and take corrective action whenever necessary. Additionally, our system employs an audit mechanism that guarantees that any untrusted server acting maliciously will eventually be detected and excluded from the system

PKI Safety Net (PKISN): Addressing the Too-Big-to-Be-Revoked Problem of the TLS Ecosystem

In a public-key infrastructure (PKI), clients must have an efficient and secure way to determine whether a certificate was revoked (by an entity considered as legitimate to do so), while preserving user privacy. A few certification authorities (CAs) are currently responsible for the issuance of the large majority of TLS certificates. These certificates are considered valid only if the certificate of the issuing CA is also valid. The certificates of these important CAs are effectively too big to be revoked, as revoking them would result in massive collateral damage. To solve this problem, we redesign the current revocation system with a novel approach that we call PKI Safety Net (PKISN), which uses publicly accessible logs to store certificates (in the spirit of Certificate Transparency) and revocations. The proposed system extends existing mechanisms, which enables simple deployment. Moreover, we present a complete implementation and evaluation of our scheme.Comment: IEEE EuroS&P 201