  In Present era, information security is of utmost concern and encryption is
one of the alternatives to ensure security. Chaos based cryptography has
brought a secure and efficient way to meet the challenges of secure multimedia
transmission over the networks. In this paper, we have proposed a secure
Grayscale image encryption methodology in wavelet domain. The proposed
algorithm performs shuffling followed by encryption using states of chaotic map
in a secure manner. Firstly, the image is transformed from spatial domain to
wavelet domain by the Haar wavelet. Subsequently, Fisher Yates chaotic
shuffling technique is employed to shuffle the image in wavelet domain to
confuse the relationship between plain image and cipher image. A key dependent
piece-wise linear chaotic map is used to generate chaos for the chaotic
shuffling. Further, the resultant shuffled approximate coefficients are
chaotically modulated. To enhance the statistical characteristics from
cryptographic point of view, the shuffled image is self keyed diffused and
mixing operation is carried out using keystream extracted from one-dimensional
chaotic map and the plain-image. The proposed algorithm is tested over some
standard image dataset. The results of several experimental, statistical and
sensitivity analyses proved that the algorithm provides an efficient and secure
method to achieve trusted gray scale image encryption.
