ACM Transactions on Privacy and Security最新文献

Security assessment relies on public information about products, vulnerabilities, and weaknesses. So far, databases in these categories have rarely been analyzed in combination. Yet, doing so could help predict unreported vulnerabilities and identify common threat patterns. In this paper, we propose a methodology for producing and optimizing a knowledge graph that aggregates knowledge from common threat databases (CVE, CWE, and CPE). We apply the threat knowledge graph to predict associations between threat databases, specifically between products, vulnerabilities, and weaknesses. We evaluate the prediction performance both in closed world with associations from the knowledge graph, and in open world with associations revealed afterward. Using rank-based metrics (i.e., Mean Rank, Mean Reciprocal Rank, and Hits@N scores), we demonstrate the ability of the threat knowledge graph to uncover many associations that are currently unknown but will be revealed in the future, which remains useful over different time periods. We propose approaches to optimize the knowledge graph, and show that they indeed help in further uncovering associations. We have made the artifacts of our work publicly available.

Bitcoin uses blockchain technology to maintain transactions order and provides probabilistic guarantees to prevent double-spending, assuming that an attacker’s computational power does not exceed 50% of the network power. In this paper, we design a novel bribery attack and show that this guarantee can be hugely undermined. Miners are assumed to be rational in this setup and they are given incentives that are dynamically calculated. In this attack, the adversary misuses the Bitcoin protocol to bribe miners and maximize their gained advantage. We will reformulate the bribery attack to propose a general mathematical foundation upon which we build multiple strategies. We show that, unlike Whale Attack, these strategies are practical, especially in the future when halvings lower the mining rewards. In the so called ’guaranteed variable-rate bribing with commitment’ strategy, through optimization by Differential Evolution (DE), we show how double spending is possible in the Bitcoin ecosystem for any transaction whose value is above 218.9BTC, and this comes with 100% success rate. A slight reduction in the success probability, e.g. by 10%, brings the threshold down to 165BTC. If the rationality assumption holds, this shows how vulnerable blockchain-based systems like Bitcoin are. We suggest a soft fork on Bitcoin to fix this issue at the end.

The Lightning Network (LN) is a second layer system for solving the scalability problem of Bitcoin transactions. In the current implementation of LN, channel capacity (i.e., the sum of individual balances held in the channel) is public information, while individual balances are kept secret for privacy concerns. Attackers may discover a particular balance of a channel by sending multiple fake payments through the channel. Such an attack, however, can hardly threaten the security of the LN system due to its high cost and noticeable intrusions. In this work, we present a novel non-intrusive balance tomography attack, which infers channel balances silently by performing legal transactions between two pre-created LN nodes. To minimize the cost of the attack, we propose an algorithm to compute the optimal payment amount for each transaction and design a path construction method using reinforcement learning to explore the most informative path to conduct the transactions. Finally, we propose two approaches (NIBT-RL and NIBT-RL-β) to accurately and efficiently infer all individual balances using the results of these transactions. Experiments using simulated account balances over actual LN topology show that our method can accurately infer (90%sim 94% ) of all balances in LN with around 12 USD.

Group signatures and their variants have been widely used in privacy-sensitive scenarios such as anonymous authentication and attestation. In this paper, we present a new post-quantum group signature scheme from symmetric primitives. Using only symmetric primitives makes the scheme less prone to unknown attacks than basing the design on newly proposed hard problems whose security is less well-understood. However, symmetric primitives do not have rich algebraic properties, and this makes it extremely challenging to design a group signature scheme on top of them. It is even more challenging if we want a group signature scheme suitable for real-world applications, one that can support large groups and require few trust assumptions. Our scheme is based on MPC-in-the-head non-interactive zero-knowledge proofs, and we specifically design a novel hash-based group credential scheme, which is rooted in the SPHINCS+ signature scheme but with various modifications to make it MPC (multi-party computation) friendly. The security of the scheme has been proved under the fully dynamic group signature model. We provide an implementation of the scheme and demonstrate the feasibility of handling a group size as large as 2⁶⁰. This is the first group signature scheme from symmetric primitives that supports such a large group size and meets all the security requirements.

DeepFake data contains realistically manipulated faces - its abuses pose a huge threat to the security and privacy-critical applications. Intensive research from academia and industry has produced many deepfake/detection models, leading to a constant race of attack and defense. However, due to the lack of a unified evaluation platform, many critical questions on this subject remain largely unexplored. (i) How is the anti-detection ability of the existing deepfake models? (ii) How generalizable are existing detection models against different deepfake samples? (iii) How effective are the detection APIs provided by the cloud-based vendors? (iv) How evasive and transferable are adversarial deepfakes in the lab and real-world environment? (v) How do various factors impact the performance of deepfake and detection models?

To bridge the gap, we design and implement DEEPFAKER, a unified and comprehensive deepfake-detection evaluation platform. Specifically, DEEPFAKER has integrated 10 state-of-the-art deepfake methods and 9 representative detection methods, while providing a user-friendly interface and modular design that allows for easy integration of new methods. Leveraging DEEPFAKER, we conduct a large-scale empirical study of facial deepfake/detection models and draw a set of key findings: (i) the detection methods have poor generalization on samples generated by different deepfake methods; (ii) there is no significant correlation between anti-detection ability and visual quality of deepfake samples; (iii) the current detection APIs have poor detection performance and adversarial deepfakes can achieve about 70% ASR (attack success rate) on all cloud-based vendors, calling for an urgent need to deploy effective and robust detection APIs; (iv) the detection methods in the lab are more robust against transfer attacks than the detection APIs in the real-world environment; (v) deepfake videos may not always be more difficult to detect after video compression. We envision that DEEPFAKER will benefit future research on facial deepfake and detection.

Network traffic classification has many applications, such as security monitoring, quality of service, traffic engineering, etc. For the aforementioned applications, Deep Packet Inspection (DPI) is a popularly used technique for traffic classification because it scrutinizes the payload and provides comprehensive information for accurate analysis of network traffic. However, DPI-based methods reduce network performance because they are computationally expensive and hinder end-user privacy as they analyze the payload. To overcome these challenges, bit-level signatures are significantly used to perform network traffic classification. However, most of these methods still need to improve performance as they perform one-by-one signature matching of unknown payloads with application signatures for classification. Moreover, these methods become stagnant with the increase in application signatures. Therefore, to fill this gap, we propose OptiClass, an optimized classifier for application protocols using bit-level signatures. OptiClass performs parallel application signature matching with unknown flows, which results in faster, more accurate, and more efficient network traffic classification. OptiClass achieves twofold performance gains compared to the state-of-the-art methods. First, OptiClass generates bit-level signatures of just 32 bits for all the applications. This keeps OptiClass swift and privacy-preserving. Second, OptiClass uses a novel data structure called BiTSPLITTER for signature matching for fast and accurate classification. We evaluated the performance of OptiClass on three datasets consisting of twenty application protocols. Experimental results report that OptiClass has an average recall, precision, and F1-score of 97.36%, 97.38%, and 97.37%, respectively, and an average classification speed of 9.08 times faster than five closely related state-of-the-art methods.