(1) Imperceptible information hiding technology uses the autocorrelation and statistical redundancy of source data to embed secret information into digital carrier, which does not affect the subjective quality of the original carrier and is not easily perceived by observers. If the carrier is an image, the modification should be invisible to the human visual system; If the carrier is sound, the human auditory system should not hear this change.
The embedding of secret information should not change the subjective quality of the original digital carrier, but also change its statistical law, which makes it very difficult to check the existence of secret information in the secret carrier file with statistical inspection tools.
(2) Robustness Robustness reflects the anti-interference ability of information hiding technology. It means that after hiding information, digital media can recover secret information and maintain the integrity and reliability of the original information under the condition of ensuring low bit error rate, although it has undergone many unintentional or intentional signal processing in the transmission process. Also known as self-recovery or error correction. The processing of hidden information generally includes digital-to-analog and analog-to-digital conversion; Resampling, requantization and low-pass filtering; Shear and displacement; Lossy compression coding is applied to the image, such as transform coding and vector quantization. Low-frequency amplification of audio signals and so on.
(3) When hiding capacity information hiding technology is applied to covert communication, in order to improve communication efficiency, it is often hoped that each digital carrier file can carry more secret data. Hiding capacity is an index reflecting this ability, which refers to the maximum number of bits that a digital carrier can hide secret information on the premise that it is still imperceptible after hiding secret data.
With the development of digital hiding technology, higher and more specific requirements are put forward for its technical performance in specific applications. In general information hiding methods, these features are conflicting and contradictory. For example, some methods have large hiding capacity, but poor robustness; Some methods are robust, but not easy to detect; Some methods have poor robustness, but less computation, and so on. We should choose various performances according to actual needs, so as to find the most suitable information hiding method. Information hiding technology plays an important role in many aspects of information security system, which can be summarized as the following aspects:
(1) The information hiding technology of data security communication can be applied to data security communication. Both parties hide secret information in a digital carrier and transmit it through an open channel. In military, commercial, financial and other aspects, such as military intelligence, sensitive data in e-commerce, secret agreements and contracts between negotiators, online banking information and other information transmission, information hiding technology has a wide application prospect.
(2) Neither party can deny what he has done or that he has received the other party's information, which is an important link in the information system. Information hiding technology can hide their identity tags in the carrier to be sent, thus confirming their identity.
(3) Copyright protection of digital works and copyright protection of piracy tracking is one of the important problems that information hiding technology tries to solve. With the deepening of digital technology, people will enjoy more and more digital services, such as digital libraries, digital movies, digital news and so on. This kind of digital works is easy to modify and copy, and its copyright protection has become an urgent practical problem. Using robust digital watermarking technology in information hiding can effectively solve this kind of problem. While distributing works to users, service providers hide the identity information of service providers and users in the works in the form of watermarks, which can not be removed theoretically. When a digital work is found to be illegally disseminated, the illegal disseminator can be tracked through the extracted identification information.
(4) Integrity, authenticity identification and content recovery: A recovery watermark based on all the information of the work and an authentication watermark based on the content of the work can be embedded in the digital work. The authentication watermark can identify the integrity and authenticity of the digital work, locate the tampered area, and the tampered area can be recovered through the recovery watermark.