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l occurrences in an encrypted message play a key role in the reverse mapping [1] of characters, leading to prediction of plain text. Apart from single character, relation between cipher text and plain text in terms of bigrams and trigrams also play vital role [2]. Single letter frequencies of a cryptogram are identical to that of the plaintext in transposition ciphers. In substitution systems, each plaintext letter has one cipher text equivalent. The cipher text letter frequencies may not be identical to the plaintext frequencies always, but the same count will be present in the frequency distribution as a whole. K.W. Lee et.al proposed [3] the cryptanalytic technique of enhanced frequency analysis. This technique uses the combined techniques of monogram frequencies, keyword rules and dictionary checking. The proposed three-tier approach reported to be a mechanized version of cryptanalysis of mono alphabetic simple substitution cipher. Thomas Jakobsen proposed [4] a method for fast cryptanalysis of substitution ciphers. This method explored the knowledge of digram distribution and their mapping in the cipher text.

At present cryptanalysis activity is extended to determination of the language being used, determination of the system being used which involves character frequency distribution, searching for repeated patterns and performing statistical tests, reconstruction of the system's specific https://www.51lunwen.org/uk/ keys and reconstruction of the plain text. Recent approaches [5] in literature are being concentrated on retrieval of plain text, based on the features of the respective language. Certain language characteristics are to be identified for successful cryptanalysis. Extensive statistical analysis of frequency distribution of characters is an additive knowledge while retrieving part of plain text message.

 

Bárbara E. et al presented a method [6] for de-ciphering texts in Spanish using the probability of usage of letters in the language. The frequency of different letters is the clue to the presented de-ciphering. Bao-Chyuan et al proposed [7] a method to improve the encryption of oriental language texts with a case study on Chinese text files which are ideogram based and differ from Latin text. Moreover the number of characters that appear in Chinese are much larger when compared to English. The scheme proposed by Bao reported that large Chinese text can be handled more efficiently. A method for Parisian/Arabic script is proposed [8] with regard to shapes and their position in the word.

 

3.SECURITY MODEL

Every language has certain evaluation parameters in such a way that language primitives are used in the construction process of document. This phenomenon is used for understanding the complexity of the language. These meaningful units are the representative set of language primitives. In case of English 论文代写 the language primitives are represented with the help of one-to-one correspondence between characters and machine codes. Syllables are the primitives in Indic scripts and they are represented in the form of canonical structure (C(C(CV))). Machine representation of canonical structure results in a set of variable length of code points ranging from one to nine. These units are transformed with the help of crypto system. The transformation is done onto a different plane where the mapping is a reversible phenomenon. The correlation between the encrypted units and character code poin本论文由英语论文网提供整理，提供论文代写，英语论文代写，代写论文，代写英语论文，代写留学生论文，代写英文论文，留学生论文代写相关核心关键词搜索。