s-Note is an App for iPhone/iPad that allows the user hiding a note, with attachment files, into an image picked from the photo library. The files might include a list of contacts, calendar events or documents.
s-Note is distributed to all end users in all countries defined by the US Bureau of Industry and Security (BIS), the Agence Nationale de la sécurité des systèmes (ANSSI) and associated classification reports.
The hiding mechanism leverages on a mix of steganography and cryptography techniques. The encryption process requires the user to select an image from his/her photo library, digit a password, type the note, eventually attach files, and save it. Images that contain notes must not be modified, resized or filtered in order to preserve the integrity of the note itself. In the time of the Internet, s-Note allows anyone to hide, a place that anyone looks at and no one can watch into: an image, its private data.
s-Note exploits the standard AES cryptography algorithm to encrypt user info and a modified version of the F5 steganography algorithm to inject them into an image.
The note size is limited by image capacity. As well known in the literature, the F5 algorithm limits are the message size, while it decreases the detection possibility: so it is even hard to understand if an image contains a message.