Information hiding - A survey

Information-hiding techniques have recently become important in a number of application areas. Digital audio, video, and pictures are increasingly fur nished with distinguishing but imperceptible marks, which may contain a hid den copyright notice or serial number or even help to prevent unauthorized copying directly. Military communications systems make increasing use of tr affic security techniques which, rather than merely concealing the content of a message using encryption, seek to conceal its sender, its receiver, or its very existence. Similar techniques are used in some mobile phone syste ms and schemes proposed for digital elections. Criminals try to use whateve r traffic security properties are provided intentionally or otherwise in th e available communications systems, and police forces try to restrict their use. However, many of the techniques proposed in this young and rapidly ev olving field can trace their history back to antiquity, and, many of them a re surprisingly easy to circumvent. In this article, we try to give an over view of the field, of what we know, what knows, what does not, and what are the interesting topics for research.