نشریه منادی امنیت فضای تولید و تبادل اطلاعات (افتا)
سال ششم شماره 1 (پیاپی 12، پاییز و زمستان 1396)

Doing a joint and secure computation on private inputs (Secure Multiparty Computation) is an interesting problem in the field of information security. The Millionaire problem is the first SMC problem in which two millionaires wish to know who is richer without disclosing their wealth. Then many problems have been defined in the field of secure multiparty computation. In this paper, the problem of secure multiparty summation is considered where a group of users wants to jointly and securely compute the summation value of their private inputs. We have reviewed and compared the related works in this filed; we have also identified the open issues and future works.

In this article, we introduce Time Memory Trade Off attack and a method for finding near collisions in a hash function. By considering hash computations, it is easy to compute a lower bound for the complexity of near-collision algorithms, and to construct matching algorithm. However, this algorithm needs a lot of memory, and uses memory accesses. Recently, some algorithms have been proposed that do not require this amount of memory. They need more hash evaluation, but this attack is actually more practical. These algorithms can be divided in two main group: the first group is based on truncation and the second group is based on covering codes. In this paper, we consider the first group that is based on truncation. For practical implementation, it can be assumed that some memory is available, Leurent [10] showed that it is possible to reduce the complexity significantly by using this memory. In the next step, Sasaki et al. [9] proposed improvement of most popular Time Memory Trade off for K-tree algorithm by using multi-collision based on Helman’s table. As a result, they obtained new trade off curve that for k=4 the tradeoff curve will be . In this article, at the first the methods of TMTO, and then the method of finding near-collision by using TMTO are explained.

validation among Users, Stockholders, and delivering important and various services with high availability are part of import dimensions of local search engines. This paper provided a comprehensive research result on Combination of security control tools with main components of local search engines, like crawler, ranker, Indexer and security requirements Consideration in all phases of software development life cycle. We organize the existing research works on securing local search engines based on combination of security standards relevant to software development life cycle of systems with key components of local search engines to help developers, software project managers for implementing security controls and requirements properly.

Due to the increasing use of smartphones among different groups of users in society as well as various capabilities that mobile devices provide for users, ensuring the security of smartphones is very important. Distribution markets of apps compromises the security of smartphones. Appstores play an important role in ensuring the security of smartphones and, if security requirements will be followed then they can protect users against malware developers. For this purpose, it is essential to identify security risks for this part of the app ecosystems. In this document, security risks raised in the app ecosystem in the field of app distribution markets have been explained.

The use of Wireless Sensors Networks (WSNs) is rapidly growing in the areas of research, application, operation, and commerce. These kind of networks are used for monitoring a desired region of an environment. So, many abilities of these networks, by considering their lower cost, have caused them to be applicable in various areas. WSNs are designed in scale of hundreds to thousands nodes, wherein this great scale is technologically the most challenging issue. One of the most basic and challenging problem is the coverage issue. Security is another important issue. Coverage is the most paramount goal of creating and implementing of WSNs, because coverage is directly related to the degree of quality, method, and durability of the WSNs for recognizing the parameters and defined aims of the regions, and the implementation cost. In this paper, the methods of improving the security of public places (by increasing the coverage of the regions based on the sensors networks) have been investigated. The results indicate that by choosing an appropriate and optimum coverage, it is possible not only to cover the entire region by utilizing the minimum number of sensors, but also it is possible to increase the security of the monitored places of the network by lesser nodes.

Nowadays, with burgeoning of computer networks and content on the internet, the demand is high for watching and searching contents like videos, music, files and documents and search engines, one of the factors that responds to the demands of the users and give them help to reach their goals faster. Also, the search engines, which have many advantages in the mistake design and configured components crawler, indexer and ranking, is malfunction that leads to the disclosure of confidential information users and websites, providing irrelevant and pollution results and non-secure search engines architecture. Therefore, considering the security problems and prospects components in the architecture of search engines, including local search engines is essential. The main parts that should guarantee their security in the architecture of local search engines is inclusion of the crawler (crawl policies, design factors, code injection attacks, crawler availability, crawler database), the indexer (search module, indexer database, indexing mechanisms, design factors) and the ranking (ranking policy, negative Search Engine Optimization (SEO)). The main topics of this article at first the threats and vulnerabilities main components in local search engines are studied, then requirements and security policies is provided for the three major components that leads to local search engines with secure architecture.