Chaos-Based Key Stream Generator Based on Multiple Maps Combinations and its Application to Images Encryption

In recent years, growing number of cryptosystems based on chaos have been proposed. However, most of themencounter some problems such as: low level of security and small key space. The key stream generator is the key design issueof an encryption system. It directly determines security and efficiency, but most of the proposed key streams are binary valued, and suffer from short period and limited key space. In this paper, we propose an n-ary key stream generator, based onhierarchical combination of three chaotic maps. We demonstrate that the produced key streams have good statisticalproperties, such as uniform distribution, δ-like auto-correlation function, near-zero cross-correlation and very heightsensitivity to initial conditions, under precision restricted condition. An image cryptosystem is constructed using the proposedapproach and proven to be enough secure to resist various attacks. Complexity is analysed and an effective acceleration ofchaos-based image cryptosystems is shown to be achievable