Steganography and Secure Communication on Online Social Networks and Online Photo Sharing

On the in Internet today, there are numerous web-sites offering places to store and share images (photos, drawings, cliparts, etc.). Online Social Networks (OSN) and Online Photo Services (OPS) usually offer this type of service making it possible to upload and manage the images they publish. Users can publish their own images as well as add descriptions and tags. By adjusting the personal privacy settings, the images become visible only to authorized users, with it then being possible to add any comments. Generally, OSN/OPS manipulate the published images by resizing, upgrading metadata, compressing, embedding watermarking, and making it difficult to use well-known steganographic methodologies on them. In this paper two new steganographic schemes that mainly take advantage of the published images and survive the OSN/OPS processing before their publication, are proposed and analyzed. Finally, a notification system which uses tags to manage the sent/received information on the secret channel is proposed. This allows for the deletion of the received information as well as a bandwidth increase of the secret channel.