In this paper an improvement of quantum encryption algorithm based on superposition state is proposed. The whole process including the encryption algorithm where the superposition state and bit-swapping are introduced, makes the quantum ciphertext space to expand broadly and allows the transmission of the necessary information and the decryption that is illustrated here. | International Journal of Computer Networks and Communications Security VOL. 3, NO. 7, JULY 2015, 283–290 Available online at: E-ISSN 2308-9830 (Online) / ISSN 2410-0595 (Print) Expand the Quantum Cipher-text Space by Using a Superposition Key Alharith A. Abdullah1, Rifaat Z. Khalaf2 and Mustafa Riza3 1 Department of Computer Engineering, Eastern Mediterranean University, Gazimagusa, North Cyprus, Turkey 2 Department of Mathematics, Eastern Mediterranean University, Gazimagusa, North Cyprus, Turkey 3 Department of Pysics, Eastern Mediterranean University, Gazimagusa, North Cyprus, Turkey E-mail: ABSTRACT In this paper an improvement of quantum encryption algorithm based on superposition state is proposed. The whole process including the encryption algorithm where the superposition state and bit-swapping are introduced, makes the quantum ciphertext space to expand broadly and allows the transmission of the necessary information and the decryption that is illustrated here. Finally, a short security analysis is given to show the difference between the proposed algorithm and its classical counterpart. Keywords: Quantum Cryptography, Quantum Computation, Quantum Encryption Algorithm, Superposition. 1 INTRODUCTION Advance in quantum computation is always considered as threat to the classical encryption systems. The most comprehensive summary in the field of quantum computation is given by [1]. Taking into account the block encryption algorithms; These algorithms are generally very easy to implement and they depend on long keys to ensure an appropriate level of security. Obviously, the length of the key is important to make a brute force attack very diffcult. So a review on the basics of a brute force or extensive search attack is provided. The diffculties of this attacking method are based on the combinatorics. The number of possible keys of a key with a length of n-bit can be easily calculated. So when it is intended to .
