An intermediate approach to spritz and RC4

Abstract

Spritz is a recently announced sponge-based stream cipher intended to be a drop-in replacement for RC4. It is more secure, more complex and more versatile than RC4 but, unfortunately, it cannot compete with it in terms of performance. In this paper we analyze the modification of RC4 to include some of the concepts from Spritz in order to make a hybrid that is faster than Spritz and more secure than RC4, which has been attacked recently, especially in terms of short term biases in its output. We analyze the performance and statistical randomness of this hybrid, that we call RC4itz, and compare it to AES in output feedbackmode, RC4 and Spritz. RC4itz presents good characteristics and is an interesting tradeoff between the security of Spritz and the speed of RC4.