Navid Abapour

In recent years, establishing secure visual communications has turned into one of the essential problems for security engineers and researchers. However, only limited novel solutions are provided for image encryption, and limiting visual cryptography to only limited schemes can bring up negative consequences, especially with emerging quantum computational systems. This paper presents a novel algorithm for establishing secure private visual communication. The proposed method has a layered architecture with several cohesive components, and corresponded with an NP-hard problem, despite its symmetric structure. This two-step technique is not limited to gray-scale pictures, and furthermore, it is relatively secure from the theoretical dimension.

In the last few years, due to the benefit of solving large-scale computational problems, researchers have developed multi-cloud infrastructures. The trust-related issue in multiclouds includes more complicated content and new problems. A new trust management framework for multi-cloud environments is proposed in this article. The proposed framework used a combination of objective and subjective trust values to calculate the cloud service provider’s trust values. This new framework can identify and rectify fake feedback from other feedbacks. Another advantage of this framework is applying fuzzy rules to calculate trust values. Two main components of the proposed framework are simulated in this paper. The simulation results confirm the important role of applied components. Also, this paper proposed a framework compared with other frameworks (feedback-based model, SLA-based model, and multi-cloud model). Simulation results show the proposed framework increased trust values more than other models. Also, compared with other models, our framework gives better mean trust values.

With the increasing integration of crowd computing, new vulnerabilities emerge in widely used cryptographic systems like the RSA cryptosystem, whose security is based on the factoring problem. It is strongly advised to avoid using the same modulus to produce two pairs of public-private keys, as the cryptosystem would be rendered vulnerable to common modulus attacks. Such attacks can take two forms: one that aims to factorize the common modulus based on one key pair and the other that aims to decrypt certain ciphertexts generated by two public keys if the keys are co-prime. This paper introduces a new type of common modulus attack on the RSA cryptosystem. In our proposed attack, given one public-private key pair, an attacker can obtain the private key corresponding to a given public key in RSA decryption. This allows the adversary to decrypt any ciphertext generated using this public key. It is worth noting that the proposed attack can be used in the CRT model of RSA. In addition, we propose a parallelizable factoring algorithm with an order equivalent to a cyclic attack in the worst-case scenario.