A study of methods used to improve encryption algorithms robustness

Encryption algorithms are commonly used to ensure data confidentiality and integrity in different communication systems and networks [1]. Public or private encryption keys can be used, depending on the specific of each service and application. One of the most performing public encryption algorithms is RSA (Rivest-Shamir-Adleman) [2]. Some private encryption algorithms, also called symmetric algorithms, are DES (Data Encryption Standard), TDES (Triple DES) and AES (Advanced Encryption Standard) [3]. These algorithms use different length of the encryption keys, from 64-bits up to 256-bits. Longer encryption keys increase the robustness of the algorithms against the brute force attack. The correlation between the plain-text and the cipher-text can be exploited by the attackers to deduce the encryption key or, directly, the original data. Therefore it is important to reduce the correlation between the initial message and the encoded version of it using enlarged data structures for block encryption algorithm, longer encryption key sequences and non-linear operations. The major goal of this paper is the study of correlation in different cases of modified encryption techniques.