Abstract—By employing the characteristics of the basic structure (keystream), Stream ciphers designers attempt to create algorithms that have advanced features from security and speed point of view. They take into consideration the state-of-the-art scientific and technical developments to design more advanced algorithm versions. This research proposes the design of a new efficient and secure stream cipher, named BloStream which proves to be more secure than conventional stream ciphers that commonly implement Exclusive-OR (XOR) for mixing. The proposed algorithm encompasses two major components. The first part involves the Pseudo Random Number Generator (PRNG), exhausting Rabbit algorithm. And the second part involves a nonlinear invertible round function (combiner), depending on Rijndael-like function algorithm, to perform the encryption/decryption processes. This new construction strengthens the weak XOR combiner. The proposed cipher is not only a random number generator but also a self-synchronizing stream cipher in such a way that the cipher text influences its internal functioning. The proposed algorithm utilizes 16-bytes secret key to encrypt the plaintext which is a multiple of 16-bytes up to 264bytes length. The evaluation of BloStream performance, in terms of implementation aspects and security properties as well as the statistical test for keystream and comparison with similar systems revealed that, BloStream was more efficient, faster, and securer than the conventional stream ciphers.

Index Terms—Stream ciphers, rabbit cipher, Rijndael-like function, combiner algorithm, PRNG.

Ali H. Kashmar is with School of Mathematical, Sciences Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor DE, Malaysia. He is also with College of Science, University of Baghdad, Baghdad, Iraq (email: Kashmar992000@yahoo.dk).
Eddie S. Ismail is with School of Mathematical, Sciences Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor DE, Malaysia.
Firdaus M. Hamzah is with Uint Pengajian Asas Kejuruteraan, Faculty Kejuruteraan and Alam Bina, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor DE, Malaysia.
Haider F. Abdul Amir is with School of Science and Technology, Universiti Malaysia Sabah, 88400 Kota Kinabalu, Sabah, Malaysia.

Cite: Ali H. Kashmar, Eddie S. Ismail, Firdaus M. Hamzah, Haider F. Abdul Amir, "Design a Secure Hybrid Stream Cipher," International Journal of Applied Physics and Mathematics vol. 5, no. 3, pp. 153-166, 2015.