Article Preview
TopIntroduction
Data security is considered as one of the major challenges in today’s present electronic communications. The assurance of data security can be sustained and achieved in the secrecy of its existence. In insecure communication, information hiding techniques have an important role in protecting confidential information from unauthorized access.
Steganography and watermarking are two common techniques of information hiding systems (see Figure 1), steganography is applied in confidential communication, wherein watermarking a visible or an invisible mark that is embedded to identify the ownership of the copyright (Artz, 2001). The major goal of watermarking is disabling the removability and the replacement of the watermark, while in steganography it is the concealment of a message’s presence (Chugh, 2013). Watermarking is used in identifying ownership of the copyright such as Web page art and audio files, which entails embedding a unique piece of information within a medium. Steganography is the art and science of confidential covert communication, where secret data storage is done by embedding secret data into an innocuous medium such as images, which will escape detection and be retrieved with minimum distortion at the destination (Prema& Natarajan, 2013).
Figure 1. Disciplines of information hiding (Wandell,1995)
Steganography is a word with Greek origins that means “secret writing.” Steganography is a contemporary technique that has been used for centuries. In old eras, Greeks have used different techniques to hide secret messages such as tattooing trusted slaves’ heads and using wax covered tablets and using music scores, a method invented by Gaspar Schott, where the letters would match to specific musical notes on musical sheets (Rabah, 2004; Katzenbeisser & Petitcolas, 2000). In modern times steganography media are not limited, almost all digital file formats can be used, but formats with high degree of redundancy are more appropriate than others, since the redundancy of the bits makes it harder to detect any alteration in a medium. Image and audio files comply with this requirement (Wandell,1995; Katzenbeisser & Petitcolas, 2000). In modern times steganography media are not limited, almost all digital file formats can be used, but formats with high degree of redundancy are more appropriate than others, since the redundancy of the bits makes it harder to detect any alteration in a medium. Image and audio files comply with this requirement (Wandell, 1995; Brabin & Sadasivam, 2009).
TopSteganography Techniques
Two of the main steganography techniques are spatial and frequency domain as indicated in Figure 2. Spatial domain techniques substitute redundant parts of a cover with a secret message, wherein frequency domain secret information is embedded in a transform space of the signal.
Figure 2. Steganography techniques (Prema & Natarajan, 2013)
Spatial Domain Techniques
Spatial domain methods operate directly on pixels offering fine concealment while giving a great capability of hiding information. As a result, these methods are frequently employed in steganography tools. It can reach high capacity, but it is not robust against simple modifications and is easy to detect (Chen et al., 2008).
Least Significant Bit (LSB)
LSB’s intelligibility and simplicity is what makes it commonly used. It uses insignificant bits of the cover image’s values to embed the payload. The LSBs of the cover image are replaced by the MSBs of the payload [8]. As LSB embedding takes place on noise, it can easily be modified, and destroyed, by further compression, filtering, or a less than perfect format or size conversion (Chanu et al., 2012).