Introduction 2. Information embedding and extraction Fishing Spoon,Fishing Lure Spoon,Fishing Spinner Noeby Fishing Tackle Co., Ltd. , http://www.fishings-sofine.com
Today's world is in the era of network information, and the rapid development of digitization and network technology has brought about tremendous changes in all walks of life. The traditional printing industry is also undergoing a digital and networked revolution. From the prepress, printing, and post-press printing stages, the new remote printing format using digital printing technology and equipment is quietly emerging and quickly transmitted through the Internet and online. Developed. In foreign countries, the popularization and application of the Internet in the printing industry has evolved from a simple web page for companies providing information and receiving services to the provision of network services; application software developed according to the characteristics and needs of the printing industry has been successful; online remote real-time proofing Internet-based printing platemaking and remote printing controls have been used in production practice. However, in this huge digital network, it will inevitably involve the transmission of images. These texts and images that exist in the form of digits on the network can be quickly copied, modified, deleted, and added, which can easily lead to some malicious destruction. . Therefore, how to effectively protect the online transmission of graphic data has become an urgent issue.
At present, most network security protection measures are implemented through traditional encryption technologies. It encrypts multimedia data files such as images, sounds, and texts to form encrypted files. Most people cannot recognize them. Only the person who knows the password can see or listen to it. To encrypt the meaningful information. Although the encrypted file appears garbled when it is opened illegally, it can achieve the purpose of encryption, but on the other hand, it can easily cause the curiosity and attention of the illegal destroyer, increasing the possibility of being cracked; in addition, once the encrypted file is cracked, its content It is completely destroyed. With the increasingly prominent network security problems, traditional encryption technologies have increasingly exposed many deficiencies. Therefore, an emerging research field, information hiding technology, has emerged.
Information hiding
1. What is information hiding
Information hiding is a brand new field of research that spans multiple disciplines such as digital signal processing, image processing, speech processing, pattern recognition, digital communications, multimedia technology, and cryptography. It hides a meaningful message in another message called a cover (such as an ordinary picture) and gets a Stego Cover. The unlawful person does not know whether this general information hides other information. Information, and even if it is known, it is difficult to extract or remove hidden information. The carrier used can be text, images, sounds and video. To increase the difficulty of cracking, it is also possible to combine encryption and concealment techniques, ie, encrypt the information to obtain ciphertext, and then hide the ciphertext in the carrier. It is more of a layer of protection than a simple password-encryption method, changing the message that needs to be protected from "invisible" to "invisible."
According to different protection objects, information hiding can be classified into secret technology and watermark technology. The secret technology is mainly used for confidential communication, and it needs to protect the hidden information; the watermark technology is mainly used for copyright protection to achieve the purpose of authenticating the authenticity. The ultimate protection is the carrier, for example, the number, serial number, text, Copyright information such as image logos are embedded in multimedia data to serve as copyright protection, as well as the security of documents and tickets.
1) Stealth Technology
Stealth technology is an important sub-discipline of information hiding and an ancient technology. In history, Steganography has gradually formed two major branches in its development: Semantic Steganography and Stealth Technology. For example, the ancient Tibetan poetry is a kind of hidden secret; the secretive technique of technology is the main branch of information steganography. Its development is accompanied by the development of information technology, from the ancient use of animal's body and waxing on wood chips. Invisible ink and microfilm used in modern times, spread-spectrum communications used in modern times, hidden secrets of online multimedia data, etc. It is mainly used for the secure communication of information, such as the network distribution of military orders, military maps, and network transmission of military secrets.
2) Digital Watermarking Technology
Traditional watermarks are implemented on paper by the papermaking process, and digital watermarks are implemented digitally on digital products. It is a new type of information anti-counterfeiting technology proposed in 1994. The basic idea is to embed secret information in products such as digital images, audio and video, in order to protect the copyright of digital products or to prove the authenticity of products. At present, digital watermarking technology has become the fastest-growing hotspot technology in the field of multimedia information security research. Its application mainly involves digital intellectual property protection, e-commerce and so on.
2. Typical algorithms for information hiding
The current typical algorithms for information hiding are divided into spatial domain hiding algorithms and transform domain hiding algorithms according to different embedded domains.
1) Spatial domain hiding algorithm
The airspace method directly changes the value of an image element, typically by adding hidden content to the luminance or chrominance of the image element. Like the LSB algorithm, it hides the information by adjusting the least significant bit of the pixel data of the pseudo-carrying body so that the hidden information is hard to find by the sight. The feature of the airspace class algorithm is that only a small, undetectable change to the hidden carrier can hide a large amount of information, and the calculation speed is faster. However, from the basic principle, the information hidden by the algorithm is extremely fragile. If the carrier image has slight changes, the hidden information may be lost.
2) Transform domain hiding algorithm
The transform domain hiding algorithm uses some kind of mathematical transformation to represent the image in the transform domain (eg, frequency domain), by adding certain transform domain coefficients of the image to add the information to be hidden, and then using the inverse transform to generate an image with other information hidden. . Common transform domain algorithms are: DCT-based transform domain algorithm, DWT-based transform domain algorithm. The transform domain algorithm has good robustness (refers to the ability to avoid the loss of hidden information due to some modification of the image file), and has certain resistance to image compression, filtering and noise in the transmission process, and some algorithms It also has practical significance by combining current image and video compression standards (such as JPEG, MPEG, etc.).
Image Information Hiding Software
At present, relevant software for information hiding in the world has been continuously introduced, and in a few years, a few companies that have applied digital watermarking technology have emerged. However, the existing steganography software is mostly used for secure communication, and most of its hidden information is text; digital watermarks are mostly used in the online copyright protection of multimedia products and online image security. Watermarks are usually some simple signs or serial numbers. , often using binary watermarks or watermarks with simple colors and patterns. Specialized techniques for researching and decorating prints with rich colors, delicate details, and complex patterns are rare. In order to meet the requirements of the digital network development of printing technology, we proposed the idea of ​​developing the software for printing images using the information hiding technology combined with the traditional cryptography technology. Through this software, the image can be encrypted and hidden and sent from the Internet to another party. The other party uses the software to input a password to extract and decrypt images. In this way, the security of online print image transmission is achieved. The following are the design ideas and technical points of the software development.
1. Encryption of information (images)
In order to increase the strength of the print image file against attacks, the image is first encrypted, so that even if the attacker has mastered the information hiding embedding and extraction algorithm, it can not open or see the original image of the hidden image.
From the perspective of the current development of encryption technology, a symmetric cryptography algorithm or a public key cryptography algorithm can be used to directly encrypt an image file or scramble the image (that is, the order of the image information is disordered to make it disorganized and unrecognizable). Only the person who owns the key can see and use the image. Because the private key cryptographic algorithm is difficult to manage the key, the public key cryptographic algorithm runs very slowly and is not suitable for encrypting data with a large amount of data. If these two algorithms are combined, the symmetric cryptographic algorithm is first used for encryption. The image then transmits the communication key through the public key cryptography algorithm, which not only solves the key management problem, but also guarantees the running speed.
Due to the large volume of printed image information to be hidden, the spatial domain method is suitable. According to the research theory of information hiding, we can see that, under the premise of being invisible (hidden information cannot be seen or heard artificially), the more hidden information is, the worse the robustness is, or when certain robustness is ensured. The more information that is hidden, the harder it is to make senseless. In order to hide information on the basis of guaranteeing imperceptibility, to achieve a certain degree of robustness, it is possible to combine human visual characteristics with less information embedded in parts or colors that are sensitive to the human eye; parts that are insensitive to the human eye or Color embedded more information.
3. Performance analysis and detection
Imperceptibility is the most basic requirement for image information hiding. At the same time, information hiding must have a certain degree of robustness. Therefore, these two properties need to be analyzed and tested: Robustness can be detected by using the existing StirMark software; imperceptibility can be measured by testing peak signal-to-noise ratio (PSNR, a measure based on pixel distortion) To initially evaluate, because PSNR can not fundamentally reflect the embedded performance of information hiding, it must also be combined with subjective visual effects to evaluate comprehensively.
Because the development of information hiding technology is not perfect at present, China's digital networked printing still lags far behind developed countries. Now it is proposed that the use of information hiding technology to the online security transmission scheme of printing images can only be in the preliminary stage of discussion. The specific issues need to be resolved, but in the long run, we believe that this technology will be of great significance in solving the security problems in the networking and digitalization of printing and related industries.
Source: Ke Yin Media