New application methods for word-oriented cryptographic primitives

Modern software oriented symmetric ciphers have become a key feature in utilizing word-oriented cryptographic primitives. Using the output sequence, in the order of its generation, of a word-oriented cryptographic primitive in the same way as traditional bit-oriented primitives, we can expose the intrinsic weakness of these primitives, especially for word-oriented linear feedback shift registers, T-functions, and so on. Two new methods for using word-oriented cryptographic primitives are presented in this paper, that is, the extracted state method and cascading extracted coordinate method. Using a T-function as an example, we research the different cryptographic properties of the output sequences of the original method and the two proposed methods, focusing mainly on period, linear complexity, and k-error linear complexity. Our conclusions show that the proposed methods could enhance at low cost the cryptographic properties of the output sequence. As a result, since the new methods are simple and easy to implement, they could be used to design new word-oriented cryptographic primitives.