The security provided by the block cipher algorithms is a top modern approached issue within the specific researches. The security assessment of a block algorithm involves the assessing and testing of components, the statistical testing of algorithm and last, but not least, the cryptanalysis. This paper intends to approach a part of this issue by presenting one of the security assessment stages, namely the component analysis, together with the statistical testing of the block cipher. The

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... ical testing may be considered as a first step in the security assessing of a block algorithm. The statistical testing of randomness of the block cipher represents an essential phase, both, for the research-development process, and for the assessment process applied to the cryptographic primitives, taking into account that the block algorithms are used on a large scale in cryptographic applications. Assessing them, from a cryptographic point of view, is a highly complex task, which cannot be efficiently accomplished by formal methods. This paper presents several statistical methods of carrying out a security assessment on a block algorithm.