  The popularity of Internet usage although increases exponentially, it is
incapable of providing the security for exchange of confidential data between
the users. As a result, several cryptosystems for encryption of data and images
have been developed for secured transmission over Internet. In this work, a
scheme for Image encryption/decryption based on Vector Quantization (VQ) has
been proposed that concurrently encodes the images for compression and shuffles
the codebook and the index matrix using pseudorandom sequences for encryption.
The processing time of the proposed scheme is much less than the other
cryptosystems, because it does not use any traditional cryptographic
operations, and instead it performs swapping between the contents of the
codebook with respect to a random sequence, which resulted an indirect
shuffling of the contents of the index matrix. It may be noted that the
security of the proposed cryptosystem depends on the generation and the
exchange of the random sequences used. Since the generation of truly random
sequences are not practically feasible, we simulate the proposed scheme using
MATLAB, where its operators like rand(method, seed), randperm(n) has been used
to generate pseudorandom sequences and it has been seen that the proposed
cryptosystem shows the expected performance.
