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Text hiding using Discrete Cosine Transformation (DCT)

By Razis Shamsudin and Nik Shahidah Afifi Md Taujuddin

Abstract

Steganography comes from the Greek words steganos, roughly translating as “covered writing”. Steganographic techniques allow one party to communicate information to another without a third party even knowing that the communication is occurred. The ways to deliver these “secret messages” is vary greatly. “The goal of steganography is to hide messages inside other harmless messages in a way that it does not allow any enemy to even detect that there is a second secret message present.” Steganography is a process that involves hiding a message in an appropriate carrier for example an image or an audio file. The carrier can then be sent to a receiver without anyone else knowing that it contains a hidden message. There are various technique being used in hiding the message using steganography practice, namely digital watermarking, least significant bit (LSB), fractal codes, masking and filtering, algorithms and transformations, Discrete wavelet transformation, Discrete Cosine Transformation and many more. This project will implement Discrete Cosine Transformation (DCT) as steganography technique in hiding text into an image. The process start with divides up the image into 8 by 8 pixel blocks, and then calculates the discrete cosine transform (DCT) of each block. A quantizer rounds off the DCT coefficients according to the quantization matrix. This step produces the "lossy" nature of Joint Photography Expert Group (JPEG) , but allows for large compression ratios. JPEG's compression technique uses a variable length code on these coefficients, and then writes the compressed data stream to an output file (.jpg). The purpose of this project is to develop a prototype software system that can hide a text into an image using Discrete Cosine Transformation (DCT) technique. It means that various algorithms and transformations are applied on the image to hide the text or messages. The system is build by using Matlab 7.6

Topics: TA1001-1280 Transportation engineering
Year: 2010
OAI identifier: oai:eprints.uthm.edu.my:2067

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