Payload Encoding for Secure Extraction Process in Multiple Frequency Domain Steganography

Abstract

In this paper, we used a new technique for payload encoding in hided text in a bitmap image. The technique based on using an index of the dictionary representing the characters of the secret messages instead of the characters themselves. The technique uses multiple frequency domains for embedding these indexes in an arbitrary chosen bitmap image. By using discrete cosine transform DCT, discrete wavelets transform DWT, and a combination of both of them. We test the technique in a software package designed specially for implementing this technique, and we got very good results in terms of capacity of hiding, imperceptibility which are the most two important properties of steganography, the time of hiding the text, and the security issues, especially by using a new approach in payload encoding that gives the technique a powerful behavior in both encoding and extracting sides. Imperceptibility; improved by increasing PSNR (between 106.58 and 122.28 db), security; improved by using an encrypted Stego-key and secret message by the dictionary, capacity; improved by a factor = 1.3 by encoding the secret message characters with 6-bits only and embedding the secret message in all three color components RGB, efficiency; improved by having a embedding/ extraction time in msec (for example 256x256 Lena image it is 638 msec, in the worst case).