The Boolean formula satisfiability problem (SAT) plays a fundamental role in many practical applications, but is computationally challenging due to its NP-hard nature. Leveraging cloud computing has become an effective way to address larger-scale instances. This article proposes a secure outsourcing framework for solving Boolean formula SAT, with a focus on preserving the confidentiality of both the Boolean formulas and their solutions. The core innovation of our scheme lies in its robust obfuscation technique, which prevents the original formula from being exposed during outsourcing. This is an essential property when formulas encode sensitive designs, such as advanced digital circuits. Our approach transforms Boolean formulas into systems of equations over the finite field$\mathbf {GF}(2)$, which are then modified through arithmetic operations to generate an obfuscated equivalent. These transformed systems can be solved either by applying linearization techniques in the cloud or by reverting to Boolean form for processing by specialized SAT solvers. Compared to existing methods, our scheme offers enhanced protection by generating obfuscated instances that are indistinguishable from any formula with the same solution space. Moreover, the transformation incurs only linear growth in problem size, ensuring practical efficiency is maintained.

User name and password are the most commonly used user authentication scheme in information systems. Strong passwords are secure but difficult to remember, so many users prefer easy-to-remember passwords. These weak passwords are also easily guessed by attackers, leading to online password guessing attacks, posing a serious security threat to information systems. Providing a reliable user authentication scheme to allow legitimate users to login while preventing online password guessing attacks is a challenge. We define a formal statistical model for the behavior of users and attackers, and differentiate users and attackers according to this model. The proposed solution computes the entropy of the passwords entered by the user and considers the user legitimate only if the entropy does not exceed a threshold. We show that entropy is an effective feature to distinguish legitimate users from attackers. We also show that the proposed user authentication scheme is effective in identifying password guessing attacks, even if the user chooses a common password. The new scheme adds an extra layer of protection to passwords, which is especially important for weak passwords. The scheme is a slight modification of the existing scheme, so it can be easily integrated into existing systems.

An efficient protocol for establishing secret keys for neighboring nodes in a wireless network is presented in this paper. The security of the key generated by our protocol is based on the unpredictability of the noises in binary symmetric communication channels. The two nodes which try to establish a common secret key receive messages from a common source of random bit strings. Due to noises in the communication channel, the messages received by them, and most importantly the messages received by the eavesdropper, are not the same. We show that the two nodes can modify their messages in an efficient way to obtain a common string which contains enough uncertainty to the eavesdropper. Then, a secure universal hash function is applied to compute a secret key for extracting randomness from the common string. We prove that the probability for the eavesdropper to know the value of the key is negligible. One advantage of our proposed protocol is that the secret key rate is better than the known scheme in other models, such as the bounded storage model. Furthermore, our proposed protocol needs only to perform exclusive-or operations and compute hash values. Thus, it is a computationally light-weight protocol and suitable for devices with limited computing resources, such as sensors in sensor networks.