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Assimilation of chaos and cryptography has provided some useful measures to deal the intractable problem of fast and highly secure image encryption. To harness the advantages of the concept in novel way, a gray-scale image encryption algorithm is proposed. The algorithmic operations are applied to plain-image in wavelet domain to obtain indistinguishable and obscured encrypted image. The Haar wavelet filter is used to transform the plain-image from spatial domain to frequency domain. The repositioning of wavelet coefficients within the sub-bands is done according to classical Fisher-Yates shuffle. A piece-wise linear chaotic map is used to carry out a promising key dependent shuffling of frequency coefficients. In addition, the permuted coefficients approximate-band is chaotically modulated to get better the confusion property. The proposed algorithm is tested over some standard images. The results of …