Active Image Authentication

In this technique, a known authentication code is embedded in the image at the time of image generation or sent with the image for accessing its integrity at the receiving end. Verifying this code authenticates the originality of the image. Active Authentication is further classified into 2 categories: Digital Watermarking and Digital Signatures. Drawbacks of Active image authentication:

• The authentication code needs to be embedded in the image at the time of recording using special equipment thus prior information about the image becomes indispensable.
• This approach requires a digital watermark or a digital signature to be created precisely when the image is recorded, which limits its ability to handle specially equipped digital devices.
• As the majority of the images on the Internet, today don’t have a watermark or a digital signature, which has forced this image authentication method to consider additional techniques –   Digital Watermarking: In this technique a digital watermark is embedded into the image at the time of either image acquisition or in the processing stage. Digital Signatures: Digital signatures embed some secondary information that is usually obtained from the image, at the acquisition end into the image.

Probably one of the most exciting fields in the computing world today is Cyber Forensics. Today, we will be discussing one of the most interesting areas in Cyber Forensics i.e. Multimedia Forensics. Computer Forensics is the practice of collecting, analyzing, and reporting on digital evidence so that it is admissible in the court. Forensic investigators must extract the probative facts from the computers involved and use these facts to create a logical scenario. Multimedia Forensics comes as a second phase, in which scientific methods are used for the analysis of the contents.

In this article, we will be discussing the following topics:

What is Multimedia Forensics?

When applied to the field of multimedia, digital forensics started to face challenges, as multimedia is content that uses a mix of audio, video, images, text. Thanks to the wide adoption of mobile devices, cheaper storage, high bandwidth, online users are generating a humongous amount of data. This growth has pushed digital multimedia in the forefront. The amount of data is so massive that it has surpassed the capabilities of the forensic experts to effectively analyze and process the data. Multimedia forensics has now become an integral part of the Cyber Forensics. Multimedia forensics involves the set of techniques used for the analysis of multimedia signals like audio, video, images. It aims to:

• Reveal the history of digital content.
• Identifying the acquisition device that produced the data.
• Validating the integrity of the contents.
• Retrieving information from multimedia signals.

What are the approaches to Multimedia Authentication?

Internet content is not only limited to text form, it comes in a lot of different varieties, so the forensic approaches developed to analyze them must also vary in scope. The goal here is to analyze images, text, audio, video, in order to generate a piece of logical Forensic evidence. Multimedia Forensics divides its efforts between 2 main approaches – Active Image Authentication and Passive Image Authentication. As you can see from the diagram, Active image authentication, and Passive image authentication are further divided into categories. Let’s get started and discuss each category in detail.