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Traditional covert transmission (CT) approaches have been hindering CT application while blockchain technology offers new avenue. Current blockchain-based CT approaches require off-chain negotiation of critical information and often overlook the dynamic session keys updating, which increases the risk of message and key leakage. Additionally, in some approaches the covert transactions exhibit obvious characteristics that can be easily detected by third-parties. Moreover, most approaches do not address the issue of decreased reliability of message transmission in blockchain attack scenarios. Bitcoin- and Ethereum-based approaches also have the issue of transaction linkability, which can be tackled by Monero-based approaches because of the privacy protection mechanisms in Monero. However, Monero-based CT has the problem of sender repudiation. In this paper, we propose a novel Monero-Based CT approach (MBCT), which enables on-chain session key dynamically updating without off-chain negotiation. MBCT can assure non-repudiation of transmission participants, confidentiality of keys, reliability of message transmission and less observable characteristics. There are achieved by the three components in MBCT, namely, a sender authentication method, a dynamically on-chain session key updating method and a state feedback method. We implement MBCT in Monero-0.18.1.0 and the experiment results demonstrate its high embedding capacity of MBCT.

The Virtual Machine (VM)-based Trusted-Execution-Environment (TEE) technology, like AMD Secure-Encrypted-Virtualization (SEV), enables the establishment of Confidential VMs (CVMs) to protect data privacy. But CVM lacks ways to provide the trust proof of its running state, degrading the user confidence of using CVM. The technology of virtual Trusted Platform Module (vTPM) can be used to generate trust proof for CVM. However, the existing vTPM-based approaches have the weaknesses like lack of a well-defined root-of-trust, lack of vTPM protection, and lack of vTPM's trust proof. These weaknesses prevent the generation of the trust proof of the CVM. This paper proposes an approach to generate the trust proof for AMD SEV-based CVM so as to ensure its security by using a secure vTPM to construct Trusted Complete Chain for the CVM (T3CVM). T3CVM consists of three components: 1) TR-Manager, as the well-defined root-of-trust, helps to build complete trust chains for CVMs; 2) CN-TPMCVM, a special CVM provides secure vTPMs; 3) CN-CDriver, an enhanced TPM driver. Our approach overcomes the weaknesses of existing approaches and enables trusted computing-based applications to run seamlessly in the trusted CVM. We perform a formal security analysis of T3CVM, and implement a prototype system to evaluate its performance.

Processing sensitive data and deploying well-designed Intellectual Property (IP) cores on remote Field Programmable Gate Array (FPGA) are prone to private data leakage and IP theft. One effective solution is constructing Trusted Execution Environment (TEE) on FPGA-SoCs (FPGA System on Chips). Researchers have integrated this type TEE with Trusted Platform Module (TPM)-based trusted boot, denoted as FPGA-SoC tbTEE. But there is no effort on secure and trusted runtime customization of FPGA-SoC TEE. This paper extends FPGA-SoC tbTEE to build Runtime Customizable TEE (RCTEE) on FPGA-SoC by additive three major components (our work): 1) CrloadIP, which can load an IP core at runtime such that RCTEE can be adjusted dynamically and securely; 2) CexecIP, which can not only execute an IP core without modifying the operating system of FPGA-SoC TEE, but also prevent insider attacks from executing IPs deployed in RCTEE; 3) CremoAT, which can provide the newly measured RCTEE state and establish a secure and trusted communication path between remote verifiers and RCTEE. We conduct a security analysis of RCTEE and its performance evaluation on Xilinx Zynq UltraScale+ XCZU15EG 2FFVB1156 MPSoC.

Stubborn mining attack greatly downgrades Bitcoin throughput and also benefits malicious miners (attackers). This paper aims to quantify the impact of block receiving delay on stubborn mining attack severity in imperfect Bitcoin networks. We develop an analytic model and derive formulas of both relative revenue and system throughput, which are applied to study attack severity. Experiment results validate our analysis method and show that imperfect networks favor attackers. The quantitative analysis offers useful insight into stubborn mining attack and then helps the development of countermeasures., Comment: arXiv admin note: text overlap with arXiv:2302.00210

Fully homomorphic encryption (FHE) has experienced significant development and continuous breakthroughs in theory, enabling its widespread application in various fields, like outsourcing computation and secure multi-party computing, in order to preserve privacy. Nonetheless, the application of FHE is constrained by its substantial computing overhead and storage cost. Researchers have proposed practical acceleration solutions to address these issues. This paper aims to provide a comprehensive survey for systematically comparing and analyzing the strengths and weaknesses of FHE acceleration schemes, which is currently lacking in the literature. The relevant researches conducted between 2019 and 2022 are investigated. We first provide a comprehensive summary of the latest research findings on accelerating FHE, aiming to offer valuable insights for researchers interested in FHE acceleration. Secondly, we classify existing acceleration schemes from algorithmic and hardware perspectives. We also propose evaluation metrics and conduct a detailed comparison of various methods. Finally, our study presents the future research directions of FHE acceleration, and also offers both guidance and support for practical application and theoretical research in this field., Comment: 18 pages, 7 figures

GHOST, like the longest-chain protocol, is a chain selection protocol and its capability in resisting selfish mining attack has been validated in imperfect blockchains of Bitcoin and its variants (Bitcoin-like). This paper explores an analytical-model-based method to investigate the impact of stubborn mining attack in imperfect GHOST Bitcoin-like blockchains. We first quantify chain dynamics based on Markov chain and then derive the formulas of miner revenue and system throughput. We also propose a new metric, "Hazard Index", which can be used to compare attack severity and also assist attacker in determining whether it is profitable to conduct an attack. The experiment results show that 1) An attacker with more than 30% computing power can get huge profit and extremely downgrade system throughput by launching stubborn mining attack. 2) A rational attacker should not launch stubborn mining attack if it has less than 25% computing power. 3) Stubborn mining attack causes more damage than selfish mining attack under GHOST. Our work provides insight into stubborn mining attack and is helpful in designing countermeasures.