  Information security is one of the most challenging problems in today's
technological world. In order to secure the transmission of secret data over
the public network (Internet), various schemes have been presented over the
last decade. Steganography combined with cryptography, can be one of the best
choices for solving this problem. This paper proposes a new steganographic
method based on gray-level modification for true colour images using image
transposition, secret key and cryptography. Both the secret key and secret
information are initially encrypted using multiple encryption algorithms
(bitxor operation, bits shuffling, and stego key-based encryption); these are,
subsequently, hidden in the host image pixels. In addition, the input image is
transposed before data hiding. Image transposition, bits shuffling, bitxoring,
stego key-based encryption, and gray-level modification introduce five
different security levels to the proposed scheme, making the data recovery
extremely difficult for attackers. The proposed technique is evaluated by
objective analysis using various image quality assessment metrics, producing
promising results in terms of imperceptibility and security. Moreover, the high
quality stego images and its minimal histogram changeability, also validate the
effectiveness of the proposed approach.
