In the recent past,the storage of images and data in the cloud has shown rapid growth due to the tremendous usage of multimedia applications.In this paper,a modulated version of the Ikeda map and key generation algorithm are proposed,which can be used as a chaotic key for securely storing images in the cloud.The distinctive feature of the proposed map is that it is hyperchaotic,highly sensitive to initial conditions,and depicts chaos over a wide range of con-trol parameter variations.These properties prevent the attacker from detecting and extracting the keys easily.The key generation algorithm generates a set of sequences using a designed chaos map and uses the harmonic mean of the gen-erated sequences as the seed key.Furthermore,the control parameters are modi-fied after each iteration.This change in the control parameters after each iteration makes it difficult for an attacker to predict the key.The designed map was tested mathematically and through simulations.The performance evaluation of the map shows that it outperforms other chaotic maps in terms of its parameter space,Lya-punov exponent,bifurcation entropy.Comparing the designed chaotic map with existing chaotic maps in terms of average cycle length,maximum Lyapunov exponent,approximate entropy,and a number of iterations,it is found to be very effective.The existence of chaos is also proved mathematically using Schwartz’s derivative theorem.The proposed key generation algorithm was tested using the National Institute of Standards and Technology(NIST)randomness test with excellent results.
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