Copyright protection of 1
With the rapid development of communication technology, the problem of information security has become very prominent, and the copyright protection of digital works (such as computer art, scanned images, digital music, video and three-dimensional animation) has become a hot spot at present. Because it is very easy to copy and modify a digital work, and it can be exactly the same as the original work, the creator has to use some methods that seriously damage the quality of the work to increase the copyright mark, but this obviously visible mark is easy to be tampered with. The appearance of digital watermarking is based on the principle of data hiding, which makes the copyright sign invisible or inaudible, which does not damage the original and achieves the purpose of copyright protection. In other words, digital watermarking technology directly embeds some tag information related or unrelated to multimedia content, but it does not affect the use value of the original content and is not easy to be perceived or noticed by people. Through these hidden information in multimedia content, people can confirm the creator and buyer of the content and check whether the information is true and complete. Digital audio watermarking technology is an important research direction of information hiding technology.
The information to be kept secret is embedded in the audio through a special algorithm without affecting the normal listening effect (that is, it has auditory transparency), so that people cannot detect and destroy such information. You can extract it in the same way on the computer when you want to use it. Through the information hidden in audio content, we can judge whether the object is protected, monitor the spread of protected data, identify the authenticity, solve copyright disputes and provide authentication evidence for the court. At present, digital audio watermarking technology has the function of tracking illegal copies, but it can't prevent piracy. Technically, when you buy a sound work, you need to enter your basic information during the process of invoicing, and even the payee can take photos of the buyer and embed this information in the song. Of course, this involves privacy issues, so this information can only be used in the case of piracy and copyright protection, not in other cases. This is the same reason that telecom companies need customer information. If there is piracy in the market, the judiciary will buy one, extract the watermark inside, and know who the source of distribution is. If this can be legally realized, people will have to go through one more procedure to buy audio works, just like going to the hospital to register and going to the telecom to call and fill out a form. It may take some time for people to recognize this procedure and crack down on piracy.
2 digital signature
Digital signature is based on public key encryption system, and the operation mode involved in digital signature generation is called hash function, also known as "hash function". Hash function is actually a mathematical calculation process. This calculation process is based on a calculation method that creates a digital expression or a compressed form of information in the form of "hash function value" or "hash function result" (usually called "information summary" or "information identification"). In the case of secure hash function (sometimes called one-way hash function), it is actually impossible to deduce the original information from the known hash function results. Therefore, the function of hash function can make the software operate on less and predictable data to generate digital signatures, while maintaining a high degree of correlation with the original information content, effectively ensuring that the information has not been modified after digital signature.
The so-called digital signature is a digital string that can only be generated by the sender of the information and cannot be forged by others. It is also a proof of the authenticity of the information sent by the sender. When signing a document or any other information, the signer must first accurately define the scope of the content to be signed. Then, the hash function in the signer's software will calculate the unique hash function result value of the signature information (for practical purposes). Finally, the signer's private password is used to convert the hash function result value into a digital signature. The generated digital signature is unique to both the signature information and the private password used to create the digital signature.
A digital signature (the digital signature of the result of the message hash function) is attached to the message and stored and transmitted together with the message. However, it can also be stored and transmitted as a single data unit, as long as it can maintain a reliable connection with the corresponding information. Because a digital signature is unique to the information it signs.
3 digital fingerprint
Digital fingerprinting technology is a new digital product copyright protection technology developed in recent years. Digital fingerprinting is a kind of copyright protection technology for digital works. It makes use of the redundancy and randomness that are common in digital works to introduce certain errors into each distributed copy of data, making the copy unique, so that when illegal redistributed copies are found, dishonest original buyers can be traced according to the errors in the copies.
Generally speaking, the introduced error refers to the information related to the user and a purchase process. When the publisher discovers the illegally released authorization information, he can track the illegally released users according to the information. Digital fingerprint system can be divided into two parts: algorithm and protocol. The algorithm includes fingerprint coding, decoding, embedding, extraction and data distribution strategy, while the protocol part specifies how entities interact to realize data distribution and tracking system with various features.
4 broadcast monitoring
The watermarking system developed by Korea Broadcasting Corporation Institute of Technology (KBS TRI) embeds copyright information into the uncompressed video stream before MPEG-2 compression, and detects the watermark in the received video without the original video. Using security key to generate watermark and watermark embedding location. The intensity of embedding watermark in each pixel is determined by the human invisible visual system. The watermarking technology of KBS meets the requirements of invisibility, robustness and security. Watermark in broadcast content can identify the original broadcaster and detect illegal copying and unauthorized reuse of the content.
For standard definition video, the information embedded as a watermark in the video is a 64-bit copyright identifier; For HD video, it is 128 bit copyright identifier. The watermark bits of the copyright identifier are generated by the security key used for the security of the watermarking system. In digital TV transmission, watermark is embedded in the spatial domain of video sequence before MPEG-2 compression. Therefore, the watermark must be able to withstand MPEG-2 compression. The imperceptibility of watermark is determined by the watermark strength. For imperceptibility, we want the watermark strength to be as low as possible, and for robustness, we want the watermark strength to be as high as possible. Therefore, the design of watermarking system always compromises between imperceptibility and robustness. Therefore, according to the human visual system, the watermark intensity is designed to be different at each pixel. Watermark detection in the transmitted MPEG-2 stream. The detection algorithm needs more than 30 frames of video. Illegal users can carry out various attacks on digital content containing watermarks. Therefore, the watermarking system of KBS company is designed to meet the requirements of robustness.
With the progress of information technology and digital technology, the copyright protection of digital TV content becomes more and more important in the communication environment of digital TV. Watermarking technology is considered as the most feasible solution for terrestrial digital TV.
5. Secure communication
Digital watermarking technology can also be applied to the secure communication of information. Secure communication plays an important role in intelligence, military and other fields. The system must ensure that the two parties can communicate normally and the communication content will not be stolen by the enemy. Traditionally, secure communication is mainly realized by cryptographic technology. Therefore, for the sake of national security, all countries spare no effort to develop their own cryptographic technology to ensure the security of confidential communication. With the development of network technology, ordinary users also hope that their communication on the network will not be eavesdropped by the third party, so cryptographic technology has stepped out of the military black box and is more and more used in the network. However, even well-designed cryptographic algorithms may still be cracked by the enemy. What's more, it is difficult for us to detect that the password has been cracked, and it will be extremely dangerous to continue to use this password to send information. On the other hand, if the enemy detects the ciphertext transmitted on the channel, even if it cannot be cracked in a short time, it will deliberately destroy our communication channel and prevent our communication. If our intelligence personnel collect information abroad, it is easy to expose their identities by sending files through passwords. Therefore, secret communication should not only meet the basic requirements of confidentiality, but also be extremely concealed and difficult to be detected.
With the development of the Internet, people all over the world can easily send emails and various documents through the Internet, which is very open and unsafe. If we can hide secret information in some common files, such as pictures, MP3, WAV. The carrier of information hiding can be regarded as the communication channel, the information to be hidden can be regarded as the signal to be transmitted, and the embedding and extraction of information can be regarded as the modulation and demodulation process in communication respectively.
Because it is difficult to detect the existence of digital watermark information in multimedia data, some important information can be hidden in ordinary multimedia data during transmission, so as to avoid being eavesdropped and monitored by third parties. When transmitting through the ordinary internet, it will be difficult for the enemy to find the existence of secret information, so they will not actively destroy the communication channel, thus ensuring the communication security.