Making the Distribution Subsystem Secure

This report presents how the Distribution Subsystem is made secure. A set of different security threats to a shared data programming system are identifed. The report presents the extensions nessesary to the DSS in order to cope with the identified security threats by maintaining reference security. A reference to a shared data structure cannot be forged or guessed; only by proper delegation can a thread acquire access to data originating at remote processes. Referential security is a requirement for secure distributed applications. By programmatically restricting access to distributed data to trusted nodes, a distributed application can be made secure. However, for this to be true, referential security must be supported on the level of the implementation

On Active Attack Detection in Messaging with Immediate Decryption

The widely used Signal protocol provides protection against state exposure attacks through forward security (protecting past messages) and post-compromise security (for restoring security). It supports immediate decryption, allowing messages to be re-ordered or dropped at the protocol level without affecting correctness. In this work, we consider strong active attack detection for secure messaging with immediate decryption, where parties are able to immediately detect active attacks under certain conditions. We first consider in-band active attack detection, where participants who have been actively compromised but are still able to send a single message to their partner can detect the compromise. We propose two complementary notions to capture security, and present a compiler that provides security with respect to both notions. Our notions generalise existing work (RECOVER security) which only supported in-order messaging. We also study the related out-of-band attack detection problem by considering communication over out-of-band, authenticated channels and propose analogous security notions. We prove that one of our two notions in each setting imposes a linear communication overhead in the number of sent messages and security parameter using an information-theoretic argument. This implies that each message must information-theoretically contain all previous messages and that our construction, that essentially attaches the entire message history to every new message, is asymptotically optimal. We then explore ways to bypass this lower bound and highlight the feasibility of practical active attack detection compatible with immediate decryption

Steady: A Simple End-to-End Secure Logging System

We present Steady: an end-to-end secure logging system engineered to be simple in terms of design, implementation, and assumptions for real-world use. Steady gets its name from being based on a steady (heart)beat of events from a forward-secure device sent over an untrusted network through untrusted relays to a trusted collector. Properties include optional encryption and compression (with loss of confidentiality but significant gain in goodput), detection of tampering, relays that can function in unidirectional networks (e.g., as part of a data diode), cost-effective use of cloud services for relays, and publicly verifiable proofs of event authenticity. The design is formalized and security proven in the standard model. Our prototype implementation (about 2,200 loc) shows reliable goodput of over 1M events/s (about 160 MiB/s) for a realistic dataset with commodity hardware for a device on a GigE network using 16 MiB of memory connected to a relay running at Amazon EC2

Secure and Privacy-Preserving Average Consensus

Average consensus is fundamental for distributed systems since it underpins key functionalities of such systems ranging from distributed information fusion, decision-making, to decentralized control. In order to reach an agreement, existing average consensus algorithms require each agent to exchange explicit state information with its neighbors. This leads to the disclosure of private state information, which is undesirable in cases where privacy is of concern. In this paper, we propose a novel approach that enables secure and privacy-preserving average consensus in a decentralized architecture in the absence of any trusted third-parties. By leveraging homomorphic cryptography, our approach can guarantee consensus to the exact value in a deterministic manner. The proposed approach is light-weight in computation and communication, and applicable to time-varying interaction topology cases. A hardware implementation is presented to demonstrate the capability of our approach.Comment: 7 pages, 4 figures, paper is accepted to CPS-SPC'1

Two-tier blockchain timestamped notarization with incremental security

Digital notarization is one of the most promising services offered by modern blockchain-based solutions. We present a digital notary design with incremental security and cost reduced with respect to current solutions. A client of the service receives evidence in three steps. In the first step, evidence is received almost immediately, but a lot of trust is required. In the second step, less trust is required, but evidence is received seconds later. Finally, in the third step evidence is received within minutes via a public blockchain.Comment: Accepted for presentation at the 2nd Distributed Ledger Technology Workshop (DLT 2019), Pis

Strongly Unforgeable Signatures Resilient to Polynomially Hard-to-Invert Leakage under Standard Assumptions

A signature scheme is said to be weakly unforgeable, if it is hard to forge a signature on a message not signed before. A signature scheme is said to be strongly unforgeable, if it is hard to forge a signature on any message. In some applications, the weak unforgeability is not enough and the strong unforgeability is required, e.g., the Canetti, Halevi and Katz transformation. Leakage-resilience is a property which guarantees that even if secret information such as the secret-key is partially leaked, the security is maintained. Some security models with leakage-resilience have been proposed. The hard-to-invert leakage model, a.k.a. auxiliary (input) leakage model, proposed by Dodis et al. at STOC\u2709 is especially meaningful one, since the leakage caused by a function which information-theoretically reveals the secret-key, e.g., one-way permutation, is considered. In this work, we propose a generic construction of digital signature strongly unforgeable and resilient to polynomially hard-to-invert leakage which can be instantiated under standard assumptions such as the decisional linear assumption. We emphasize that our instantiated signature is not only the first one resilient to polynomially hard-to-invert leakage under standard assumptions, but also the first one which is strongly unforgeable and has hard-to-invert leakage-resilience

KeyForge: Mitigating Email Breaches with Forward-Forgeable Signatures

Email breaches are commonplace, and they expose a wealth of personal, business, and political data that may have devastating consequences. The current email system allows any attacker who gains access to your email to prove the authenticity of the stolen messages to third parties -- a property arising from a necessary anti-spam / anti-spoofing protocol called DKIM. This exacerbates the problem of email breaches by greatly increasing the potential for attackers to damage the users' reputation, blackmail them, or sell the stolen information to third parties. In this paper, we introduce "non-attributable email", which guarantees that a wide class of adversaries are unable to convince any third party of the authenticity of stolen emails. We formally define non-attributability, and present two practical system proposals -- KeyForge and TimeForge -- that provably achieve non-attributability while maintaining the important protection against spam and spoofing that is currently provided by DKIM. Moreover, we implement KeyForge and demonstrate that that scheme is practical, achieving competitive verification and signing speed while also requiring 42% less bandwidth per email than RSA2048

VCKSCF: Efficient Verifiable Conjunctive Keyword Search Based on Cuckoo Filter for Cloud Storage

Searchable Symmetric Encryption(SSE) remains to be one of the hot topics in the field of cloud storage technology. However, malicious servers may return incorrect search results intentionally, which will bring significant security risks to users. Therefore, verifiable searchable encryption emerged. In the meantime, single-keyword query limits the applications of searchable encryption. Accordingly, more expressive searchable encryption schemes are desirable. In this paper, we propose a verifiable conjunctive keyword search scheme based on Cuckoo filter (VCKSCF), which significantly reduces verification and storage overhead. Security analysis indicates that the proposed scheme achieves security in the face of indistinguishability under chosen keyword attack and the unforgeability of proofs and search tokens. Meanwhile, the experimental evaluation demonstrates that it achieves preferable performance in real-world settings