Digital Watermarking Digital Information Protection Technology

The so-called digital watermarking technology is to embed certain information representing the identity of the copyright owner into the protected information in a certain way. When a copyright dispute arises, the digital watermark is extracted by a corresponding algorithm to verify the ownership of the copyright and ensure The legitimate interests of copyright owners avoid the threat of illegal piracy. The protected information can be any kind of digital media such as images, sounds, videos, or general electronic documents. Digital watermarking is a digital signal embedded in a digital product. The existence of a watermark should be based on the principle of not destroying the appreciation value and use value of the original data.

Digital watermarking process

The following describes a process of adding a digital watermark. Suppose there is a digital photographic image. In order to identify the author's ownership of the work, the method of adding a visible mark to the original image may be used, but this may harm the integrity of the image. Therefore, the digital watermark embedding technique can be used to identify the author as a logo. Invisible data (digital watermarking) is hidden in the original image, achieving the purpose of not only indicating the ownership but also harming the subjective quality and integrity of the image. Water-saturated images can maintain the original image format and other information without affecting the reproduction and processing of normal information. From the subjective quality point of view, the difference between the two images is negligible and can not be detected with the naked eye. Only the specific decoder can extract hidden information from it. This technology is an important application branch of digital hidden technology.

Digital watermarking technology does not directly prevent copying. Instead, it illegally copies and disseminates information by verifying the ownership of the product. It uses legal means to impose sanctions on it, and indirectly eliminates attempts by pirates to copy illegally, thus protecting intellectual property rights. effect. Another use of digital watermarking is to identify the authenticity of the data. The images taken by digital cameras and digital video recorders are not yet available as forensic evidence because they are easily tampered with. If a watermark is embedded in an evidence photograph, any modification made to the photograph destroys the watermark, and special detection software can detect where the photograph has been altered.

The basic features of digital watermarking

Digital watermarks have many features. Because it is often used as a sign of copyright, it is different from the usual information hiding and secret communication (secret communication is focused on maximally hiding and transmitting information), it needs to have the following characteristics: Invisibility that can not see the number The existence of a watermark.

Robustness means that the digital watermark is not destroyed when the protected information undergoes certain modifications, such as transmission, JPEG compression, filtering, and geometric transformation of the image such as translation, expansion, rotation, and cropping.

The method of adding a watermark and detecting a watermark to security is absolutely confidential to an unauthorized third party and cannot be easily deciphered. Even if detected by a hacker, it cannot be read (the digital watermark needs to be encrypted).

Digital watermarking can be divided into many specific categories based on specific application areas, such as robust watermarks for copyright protection, fragile watermarks used to protect data integrity, and annotated watermarks used to indicate data content. Among them, the robust watermark for copyright protection is currently the hotspot. Robust watermarks need the strongest robustness and need to resist malicious attacks.

Digital watermarking general model

Digital watermarking technology includes two processes: embedding, detection, and extraction. The design of the embedding stage mainly solves two problems: one is the generation of digital watermarks, which can be a string of pseudo-random numbers, or it can be generated by encrypting the information related to the authors such as strings, icons, etc.; second, the embedding algorithm, the embedding scheme The goal is to make digital watermarking a good compromise between invisibility and robustness.

The detection phase is mainly to design a detection algorithm corresponding to the embedded process. The result of the detection is either the original watermark (such as a string or icon, etc.) or the test result based on statistical principles to determine the presence or absence of the watermark. The goal of the detection scheme is to minimize the probability of misjudgments and missed determinations.

In order to increase the unpredictable difficulty of removing watermarks for attackers, most of the current watermarking schemes use keys when they are added and extracted. Only those who master the keys can read the watermarks.