Ensuring confidentiality of sensitive data is of paramount importance, since data leakage may not only endanger data owners’ privacy, but also ruin reputation of businesses as well as violate various regulations like HIPPA and Sarbanes-Oxley Act. To provide confidentiality guarantee, the data should be protected when they are preserved in the personal computing devices (i.e., confidentiality during their lifetime); and also, they should be rendered irrecoverable after they are removed from the devices (i.e., confidentiality after their lifetime). Encryption and secure deletion are used to ensure data confidentiality during and after their lifetime, respectively. This work aims to perform a thorough literature review on the techniques being used to protect confidentiality of the data in personal computing devices, including both encryption and secure deletion. Especially for encryption, we mainly focus on the novel plausibly deniable encryption (PDE), which can ensure data confidentiality against both a coercive (i.e., the attacker can coerce the data owner for the decryption key) and a non-coercive attacker.

Cryptographic algorithms act as essential ingredients of all secure systems. However, the expected security guarantee from cryptographic algorithms often falls short in practice due to various cryptographic application programming interfaces (API) misuses. While many research studies target cryptographic API misuses in the cases of Java, C/C++ and Python, similar issues within the Go domain are still uncovered. In this work, we design and implement CryptoGo, a static analysis detector leveraging taint analysis technique to automatically identify cryptographic misuse of large-scale Go cryptographic projects. We derive 12 cryptographic rules coupled with Go cryptographic APIs and propose the idea of integrating cryptographic algorithm classification into cryptographic misuse detection for the first time, thus achieving precise detection of Go cryptographic API misuse and practical guidance of selecting appropriate cryptographic algorithms. We conduct five kinds of specific taint analyzers to perform backward or forward taint tracking on the APIs and arguments in the intermediate representation of the Go source code. Running on 120 open source Go cryptographic projects from GitHub, CryptoGo discovered that 83.33% of the Go cryptographic projects have at least one cryptographic misuse. It takes only 86.27 milliseconds per thousand lines of code on average for detection. We also disclose the discovered issues to the developers and collect their feedback. Our findings highlight the poor implementation and weak protection in the current Go cryptographic projects.

Conventional overwriting-based and encryption-based secure deletion schemes can only sanitize data. However, the past existence of the deleted data may leave artifacts in the layout at all layers of a computing system. These structural artifacts may be utilized by the adversary to infer sensitive information about the deleted data or even to fully recover them. The conventional secure deletion solutions unfortunately cannot sanitize them. In this work, we introduce truly secure deletion, a novel security notion that is much stronger than the conventional secure deletion. Truly secure deletion requires sanitizing both the obsolete data as well as the corresponding structural artifacts, so that the resulting storage layout after a delete operation is indistinguishable from that the deleted data never appeared. We propose TedFlash, a Truly secure deletion scheme for Flash-based block devices. TedFlash can successfully sanitize both the data and the structural artifacts, while satisfying the design constraints imposed for flash memory. Security analysis and experimental evaluation show that TedFlash can achieve the truly secure deletion guarantee with a small additional overhead compared to conventional secure deletion solutions.

With the rise of generative artificial intelligence, malware creation has become more accessible, leading to a surge in malware and its variants. Traditional detection methods struggle to keep pace with this evolution. Dynamic analysis, though detailed, is resource intensive and susceptible to variations in computer hardware and simulation environments. Static analysis, on the other hand, faces the challenge of discerning valuable features from an extensive pool, especially for software across diverse architectures. To tackle these issues, we propose a binary sample classification approach based on raw bytes, named CAG-Malconv, which incorporates Convolutional Block Attention Module (CBAM) and Bidirectional Gated Recurrent Unit (BiGRU) to extract byte-level features. We evaluated it on two datasets with 48,000 samples of different file types and families. It outperforms state-of-the-art methods based on advanced features and raw bytes in terms of accuracy (ACC), Area Under the Curve (AUC), F1 score, and recall. Furthermore, it allows for the visualization of raw samples, facilitating the precise identification of malicious components like C&C URLs and encryption loops by analyzing activation patterns in hidden layers, thus streamlining malware investigative procedures.

Data integrity is one of the most critical security concerns for users when using the cloud storage service. However, it is difficult for users to always stay online and frequently interact with storage service providers to ensure continuous data integrity in practice. The existing Proof of Storage-time schemes, enabling verifiable continuous data integrity checking at cost of performance, fail to provide flexible storage period, reliable measurement of storage time, and resistance to the outsourcing attack. In this paper, we propose EnclavePoSt, the first practical Proof of Storage-time via Intel SGX, where the data integrity checking can be automatically executed in a hardware-driven Trusted Execution Environment (TEE), i.e., the enclave, when users are offline. The checking results can be aggregated and efficiently verified by users. Besides, the elapsed time during isolated data integrity checking can be precisely measured, and the storage period is allowed to flexibly change. Lastly, our EnclavePoSt is resistant to the outsourcing attack. The security analysis and evaluations justify that the EnclavePoSt is more practical than previous works.

True Random Number Generator (TRNG) is indispensable in cryptographic algorithms and protocols, and the quality of randomness directly influences the security of cryptographic applications. Multiple theoretical or offline entropy estimation methods have been proposed to evaluate the security of TRNGs, while their ideal assumptions commonly cannot be satisfied due to the perturbation of operating conditions at runtime, which makes it difficult to achieve sufficient entropy for the output of TRNGs in practice. Moreover, the output bitrate of TRNG is another fundamental concern during TRNG practical applications, while popular elementary oscillator-based structure commonly has relatively low output bitrate due to the inherent low sensitivity of entropy extraction to jitter (source of randomness). In this paper, we aim to design a TRNG satisfying both practical security (i.e., on-chip entropy assurance) and high output bitrate simultaneously. In particular, an improved stochastic model and a measurement method are established to quantify the entropy of coherent sampling based TRNG. Moreover, an on-chip entropy assurance module is provided to realize the robustness of the proposed design under various operating conditions. We implement the proposed TRNG in a simulation platform and ASIC chips (with SMIC 130 nm CMOS technology). Experimental results indicate that the generated data has sufficient entropy ( $\geq 0.999$ per bit) under various operating conditions. In addition, all the output can pass the NIST SP800-22 and AIS 31 statistical tests with an output bitrate of 4.2 Mbps, which is equivalent to 2 orders of magnitude faster than that of the elementary oscillator-based TRNG.