Steganography is a solution for covert communication and blockchain is a p2p network for data transmission, so the benefits of blockchain can be used in steganography. In this paper, we discuss the advantages of blockchain in steganography, which include the ability to embed hidden data without manual change in the original data, as well as the readiness of the blockchain platform for data transmission and storage. By reviewing the previous four steganography schemes in blockchain, we have examined their drawback and shown that most of them are non-practical schemes for steganography in blockchain. We have proposed two algorithms for steganography in blockchain, the first one is a high-capacity algorithm for the key and the steganography algorithm exchange and switching, and the second one is a medium-capacity algorithm for embedding hidden data. The proposed method is a general method for steganography in each blockchain, and we investigate how it can be implemented in two most popular blockchains, Bitcoin and Ethereum. Experimental result shows the efficiency and practicality of proposed method in terms of execution time, latency and steganography fee. Finally, we have explained the challenges of steganography in blockchain from the steganographers' and steganalyzers' point of view.

Introducing the Transaction cost economics (TCE), the article, as its main concerns, tries to explain the method of making the concept of Transaction cost operational and applying it in empirical studies. In this paper, the writer tries to provide some answers to these questions: How do followers of institutionalism and Transaction cost economists use this concept in practice and empirical studies? And basically, do they have any coherent method to deal with subject matters of economics or that institutional approach is only story telling?New institutional economics (NIB)are divided into two main areas; institutional environment and institutional arrangement. TCE is related to the institutional arrangement and Williamson has related it into governance structure. Coase's article entitled "The Nature of the Firm" is the beginning of this approach which emphasizes the firm must be considered as a governance structure, rather than a production function or a technological construction. TCE tends to make the concept of Transaction cost operational and for achieving this purpose, uses the idea of firm as a governance structure and develop "discriminating alignment" hypothesis.

Nowadays, information plays an important role in organizations. Sensitive information is often stored in databases. Traditional mechanisms such as encryption, access control, and authentication cannot provide a high level of confidence. Therefore, the existence of Intrusion Detection Systems in databases are necessary. In this paper, we propose an intrusion detection system for detecting attacks in both database Transaction level and inter-Transaction level (user task level). For this purpose, we propose a detection method at Transaction level, which is based on describing the expected Transactions within the database applications. Then at inter-Transaction level, we propose a detection method that is based on anomaly detection and uses data mining to find dependency and sequence rules. The main advantage of this system, in comparison with the previous database intrusion detection systems, is that it can detect malicious behaviors in both Transaction and inter-Transaction levels.Also, it gains advantages of a hybrid method, including specification-based detection and anomaly detection, to minimize both false positive and false negative alarms. In order to evaluate the accuracy of the proposed system, some experiments have been done. The experiment results demonstrate that the true positive rate (recall metric) is higher than 80%, and the false positive rate is lower than 10% per different data sets and choosing appropriate ranges for support and confidence thresholds. The experimental evaluation results show high accuracy and effectiveness of the proposed system.

oubt in the Transaction” occurs when the definite conclusion of the two parties of the Transaction concern to uncertain parts of two or more than to things. The majority Shiite jurisprudents, as well as some jurists have prohibited the uncertainty in Transaction and considered it to be harmful for reasons such as consensus, invoking to some narrations, the impossibility of availability of uncertain thing, ambiguity, risk, non-applicability of such Transactions, foolishness of this act, analogous to uncertain compromising, and incorrectness of the concluding of the contract. Iran’ s civil law, following the majority, has necessitated “ the defined subject” for the correctness of the Transaction. By criticizing the reasons of the prohibition of doubting in Transaction, and also by referring to reasons such as generalities, invoking to the traditions regarding marriage, uncertain testament and vow, the present article has determined the validity of the Transaction that its subject is uncertain and made possible spreading its validity to the assumption that the collection that consists of the things that have different prices. And in the end, it has suggested two solutions of stipulation and drawing lots for determining the subject of the Transaction.

The main axis of this writing and what causes dispute are that in some cases after the fact of two or more successive Transactions towards the object of Transaction, the transferor of ownership measures for termination of base Transaction. Lawyers and tribunals have not consensus in confronting such a case and concerning the circumstances of possession of first purchaser and consecutive possessors, so they issue contradictory judgments that will harm the rights of the third party beneficiary. Hesitation about set of related articles to this subject in civil code especially article 454 and also scrutiny in scholars and lawyers make it clear that legislature follows opinions of lawyers and scholars that separate legal options and contractual options from each other and makes his possessions not operative but it should be noted about executing legal options by beneficiary of an option that the above-mentioned possession is in lieu of property destruction of contract subject due to validity of possessions by the customer. Therefore, vendor is merely entitled of counterfeit. We tried to consider that various promises and divergence of Islamic jurisprudence and subjected law are classified according to nature of aforesaid possession. They are analyzed by explaining foundations and their side effects and relying on legal provisions and rules and they are also explained correctly. So, the influence of the present analyze on application step (judicial precedent) is undeniable.

I am going to assess shortcomings of Transaction Cost Economics (TCE) of Oliver Williamson My argument is that this analysis suffers from misidentification of the relevant problem of the theory, analytical incoherence, inconsistent empirical support and methodological defects. In formulating Coase's fundamental idea, Williamson accepts an efficient equilibrium which occurs once forever, thus he can not identify the main 'problem of organization theory and he can not explain the evolution of organization and society as a whole. His analytical problem originates from rationality presumption. He accepts rationality IS bounded and as a consequence all contracts are incomplete. But he argues that rationality is not so bounded that agents are not able to choose the best and less costly incomplete contracts via their farsightedness. Despite the well-known claim that TCE are supported by vast empirical studies, deep reviews of literature show that empirical evidence does not corroborate TCE hypothesis who wholeheartedly. Even if this claim is true and TCE hypothesis and predictions are confirmed by empirical data, (1) this does not mean Transaction costs are minimized and (2) deriving policy implication for improving organization and society is impossible yet. From methodological point of view, this approach assumes Systems are close, and establish fix relations among variables. From this instrumental point of view reality is constrained to empirical and observable areas, and because of this view understanding observed reality and casual power of unobservable reality is impossible.

The "option contracts" are among means being used in the stock market today. This kind of contract can be corrected through certain contracts such as "Jealeh" and "Solh" contracts. It's correction based on independent contract is devoid of any fault, though it's linkage with some other contracts like "Insurance" as well as Representation is faciny challenge. It should be said, however That there exist general conditions relevant to the contracts in this kind of interaction and is devoid of any fault from this point of view. The payment of the right of condition can be corrected for the cause of ebra. On the subject of the linkage between papers of the tansaction option are can refer to the suggestion of participation and representation and all possible defects can be repelled. The verdicts related to the papers like ownership (possession), interest and so, are compatible with the religious law.