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One of the important problems arising in designing and practical implementation of cryptosystems is provide countermeasures against side-channel attacks. When implemented on a specific physical device, the algorithms, strength of which from the purely mathematical point of view is without great doubt, often employ weaknesses to such attacks.A fault analysis attack is one of the options of the side-channel attack on a cryptosystem. Its essence is that the attacker has an active influence on a physical device that provides computation (for example, a smart card). Faults caused by influence are then analysed in order to restore security information that is stored inside the device. These attacks are often significantly more efficient than passive side-channel attacks.The fault analysis attacks were proposed over 20 years ago. Since then, attacks have been successfully built owing to implementation of a number of symmetric and asymmetric crypto-algorithms. Also, a number of different methods for active influence on computation have been proposed, using specific physical effects and characteristics of the computing environment. Approaches to counteracting such types of attacks are also actively developing. For this, both physical and purely mathematical methods are used. However, it should be noted that cryptographic hash functions, and more complex crypto-schemes containing them as components (for example, some message authentication codes and digital signatures), are slightly presented in these papers.It is important to note that practical implementation of a specific attack requires that a combination of the following factors is available: a possibility of a specific physical impact on computation, an adequate mathematical model of such physical impact and a purely mathematical component of the attack that is a specific algorithms for introducing faults and further analysis of the results. At the same time, the solution of each of these problems separately is of independent theoretical value.The paper results do not involve the physical component of attack, aiming only at mathematics. In other words, a proposal is to present the specific algorithms for introducing faults and further analysis of the results. In this case, a specific fault model is considered known and specified. Several such models have been considered, based on the similar ones previously proposed for other algorithms.As an object of study, two standards to form message authentication codes have been selected: HMAC and NMAC. These standards can be based on any cryptographic hash function that provides the required level of security. The paper examines four examples of widely used hashes: MD5, MD4, SHA-1, SHA-0.The main results of the paper are as follows:- built specific algorithms for introducing faults in computation and their further analysis, allowing to discover secret information (secret keys);- finding and validation of estimates of such attacks (in terms of the number of introduced faults and the work factor of further analysis) for various combinations of parameters (algorithms and fault models); - shown that attacks timing can be reasonable.

The paper presents anew mathematical method for parasitic signal analyzing. NICV (Normalized Inter-Class Variance) method allows reducing considerably of computing and time expenditure in carrying out side channel attacks. To analyze NICV efficiency mathematical statistics methods and theory of probability were used. The paper presents an algorithm implementing NICV within a developed software package. The main shortcomings of the existing solutions have been taking into consideration during development of the new software: architecture of the presented software is easily extensible for adding new tools; unified format is used for all processing data. NICV was tested on the first round of 64-bit Data Encryption Standard algorithm. To assess the effectiveness two attacks based on differential power analysis and correlation power analysis have been simulated. Another advantage of the package is flexibility in adding of new methods for processing, saving, both original information and its new statuses in the database after carrying out signal processing.Side-Channel Attacks (SCA) are considered as a serious threat for data protected by cryptographic devices. Therefore such devices must be tested for resistance to these attacks. It should be taken into account that SCA are very powerful tool but they require significant computation capacity, especially in case of countermeasures. Presented software package program can help to analyze cryptographic devices on resistance to SCA and implemented NICV method allows decreasing of time and computation costs.