RU2633185C2 - Method of creating digital photos protected from forgery, and device for its implementation - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: method of creating digital photos that are protected from forgery, includes exposing the CCD-matrix of a digital camera or a smartphone and processing the exposed data to convert to one of the most common digital image formats and supplementing with the data on the survey condition. For the combined aggregate data thus obtained, a hash function is calculated, an electronic digital signature (ES) is created and stored as a single digital image file of a conventional format in the built-in or external memory of the camera or the smartphone. For each exposed photo, a separate asynchronous process is launched before shooting the next one, in the operative memory of the camera or the smartphone, performing data on the location and time of shooting, forming an electronic digital signature and then recording the generated signed electronic document in the form of a digital image file on a medium.

EFFECT: enhancing the protection of digital photos.

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Description

The invention relates to the field of digital photography, namely, the use of an electronic signature in a digital camera to confirm the authenticity of the image and service data, and can be used to create legally significant digital photographs.

A digital camera is a device that is a type of camera in which the photosensitive material is a matrix on charge-coupled devices (CCD) or several CCD arrays from which the signal is presented, processed and stored in the device in digital form. The functions of a digital camera can be additionally implemented in various electronic and other devices, such as a cell phone, smartphone, etc.

Currently, there is a problem associated with the relative ease and simplicity of falsifying an image obtained with a digital camera, as well as related auxiliary data (shooting time, coordinates, type of camera, etc.). If earlier the verification of the authenticity of a photograph was realized by presenting its negative on film, then with the advent of digital cameras the problem was complicated due to the availability of editing the photograph using image editors.

Currently, there are no special technical methods for verifying the authenticity of a photograph taken with a digital camera.

There is a method of confirming the authorship of a photograph, or rather an artistic image, based on the inclusion in the digital image of the so-called digital watermarks (CEH), which is a kind of steganographic data processing [1]. CEHs are embedded in special procedures in a digital image and visible or invisible on it or those signs. CEH allows you to verify authorship or perform another function of marking a digital photograph. However, this method of protection has the disadvantage that in the case of a fake digital watermark in no way indicates that the photograph corresponds to the real situation that should have been captured. This is due to the fact that there is an uncontrolled time interval between reading a photograph from the camera’s memory and processing it in order to implement the CEH. In addition, the procedures for embedding CEHs, as a rule, do not have the necessary resistance to steganalysis, since cryptographic procedures are not used.

There is also a known method of crypto-processing of any digital data, including the available digital image, using computer technology, as a result of which, for example, according to GOST P 34.10-2012 [2] and GOST P 34.11-2012 [3] the image data is signed by the so-called digital electronic signature (EP).

An electronic digital signature is information in electronic form, attached to other information in electronic form (electronic document) or otherwise associated with such information. In essence, an electronic signature is the requisite of an electronic document, which allows to establish the absence of distortion of information in an electronic document from the moment of electronic signature generation and to verify that the signature belongs to the holder of the electronic key certificate. The value of props is obtained as a result of cryptographic conversion of information using the private key of electronic signature [2]. Enhanced ES allows you to determine not only the author of the document, but check the document for changes.

However, there is also a significant drawback to the method of certifying with the help of electronic signature, namely, that between the step of reading a photograph from the camera’s memory (one device) and the stage of supplying it with an electronic document as an electronic document (on another device) there is an uncontrolled stage when the digital image arbitrary distortion introduced.

Currently, forensic algorithms have gained distribution of hash value calculation algorithms, in particular MD5, SHA-1 [5] or GOST P 34.11-2012 [3]. The algorithm determines the length of the hash value, which can be 128, 256, 384, 512 or more bits. For ease of use, the hash value is not represented in binary, but in hexadecimal. In electronic document management, the result of applying a hash function, called a message digest, acts as one of the elements of electronic signature. A simplified scheme of its use is as follows. For a message (electronic document) using electronic means, the message digest is calculated using the well-known algorithm, which is then transmitted along with the message. The recipient of the message, in turn, calculates the digest of the message for the received electronic document and compares it with the existing one. If they match, then the message (electronic document) did not change during transmission. In electronic document management, the message digest serves as a benchmark for comparison, which confirms the immutability of the message.

This method, which should be considered as an integral part of the general procedure for electronic digital signature, also has a disadvantage in that this procedure does not provide for the control of the invariability of the photo document in the time interval between its creation and the formation of electronic signature, which leaves the possibility of deliberate changes to it.

Known software-implemented digital method of protection against counterfeiting and a device for implementing the method [4], related to methods and devices based on the execution of certain programs in a computer system for digitally generating encrypted or encoded images of characters in printed form. The method and system provide combining the original image with a latent image, and the encrypted latent image becomes visible only when viewed through a special decoder lens. Digital processing allows you to encrypt various hidden images according to various parameters. Hidden images can be encoded in separate complementary colors of the original visible image, at different angles relative to each other. The disadvantage of this method is that it is not the original document itself that is protected, but only its “hard” copy, which does not prevent the introduction of changes to the original and, accordingly, the duplication of distorted printed images.

The known method, which is the closest to the proposed one and therefore selected as a prototype, consists in the fact that in order to increase the information content and reliability of the image, the digital data of the generated photograph is supplemented by some service data characterizing the shooting conditions. For example, the JEITA CP-3451 (EXIF) standard [6] (EXIF - Exchangeable Image File Format) allows you to add additional information (metadata) to images and other media files, commenting on this file and describing the conditions and methods of its receipt, authorship etc. The EXIF standard also allows you to save the coordinates of the shooting location received from the GPS receiver and allows for wide development, as a rule, cameras add information specific to a particular camera to the file: camera manufacturer, model, copyright information, shutter speed, aperture, etc. You can read / process these parameters using publicly available image viewers (photo organizers), graphic programs, and special programs for working with metadata.

This method is implemented by the following sequence of actions: initialize the device (supply power, load the operating system and special software modules); exhibiting a photosensor (CCD); Using special software modules (software) loaded into the RAM, data on the exposure of each element of the photosensor (CCD pixel) in the so-called RAW format (raw from the English raw; can exist as separate files * are read from the photosensor. raw); place them in the RAM of the camera (device) or cache of its processor; process raw data according to the conversion algorithms implemented in the mentioned special software modules into one of the generally accepted compressed image formats, for example, JPG; generate and add service data of these compressed formats; form and add additional data to the resulting image file according to the JEITA CP-3451 (EXIF) standard, and then save it as an image file on an internal or external storage medium.

The structure of a JPEG file with a digital image and additional information is shown in FIG. one.

In FIG. 1 JPEG file is presented as a sequence of segments, each of which begins with a marker consisting of two bytes, the first of which has the value “FF”, and the second determines the type of segment. Next in two bytes is the size of the segment.

The structure of the APP 1 application segment containing EXIF data for the image is shown in FIG. 2.

This prototype method also has the disadvantage that both the image data and the additional information contained in the digital image file are not protected and can be easily deleted or changed.

Thus, all these analogue methods and the prototype method have a common drawback - there is a certain time interval during which the digital original may be distorted, which will then be “approved” and presented in counterfeit-protected copies. In turn, this casts doubt on the legal significance of the documents submitted.

Therefore, there is an urgent need to develop a method for forming legally significant digital photographs and a device that implements it, eliminating the possibility of modifying image data and service data, that is, creating a protected digital image file in a digital camera during its formation.

To eliminate this drawback, a method and device for its implementation, combining the functions of digital photography and signing of photographs of a qualified EP, are proposed. In this case, the formation of the electronic signature and the signing of the photograph is carried out in the RAM of the device after it is read from the photosensor and processed by the processor of the device until it is saved as a file on an internal or external storage medium.

The aim of the invention is to increase confidence in digital photographs by protecting their counterfeiting and detecting photomontage, and the technical task is to develop a method and device that implements the supply of image data and service data with an electronic signature directly in a digital camera in the process of generating a digital photograph before recording it to external memory or device memory

This goal is achieved by the fact that in the known prototype method of obtaining a digital photograph containing additional information [6], significant changes have been made, consisting in the fact that between the steps of generating aggregate data and storing them on an internal or external storage medium in the form of a generally accepted graphic file of a format, for example, JPEG, the stage of processing in the operational memory of the received service data and the digital image of the camera for signing it by a qualified electronic signature is additionally included [2].

This is achieved by the fact that the composition of the software and / or hardware of the camera is supplemented by special software or hardware and software, for example, in the form of a specialized coprocessor, a module under which the camera processor calculates the hash function [3] of the file and generates ES [2].

The signed file is written to the external or built-in storage medium of the camera according to one of the selected methods of linking the electronic signature (see Fig. 3).

Technical and organizational basis. When creating a digital signature, the mechanism of asymmetric encryption is used when the secret key is registered in special software that implements the creation of a digital photograph. An unclassified key can be obtained and used by any user (person or organization) who wants to verify the truth of both the image and the data accompanying it. The private and public keys, as well as the parameters of the ES scheme that implement the encryption procedure in accordance with state standards, are issued by authorized bodies, in particular, certification authorities.

Demonstration of the feasibility. To implement the proposed method, a hardware-software device has been developed, which is a digital camera or smartphone operating under the Android operating system, the software of which is used as an application software tool "EP Creator" [7], created using the Android API. When you turn on the camera, this software tool intercepts the control of the processor of the camera (smartphone), not allowing you to save data to external or internal storage devices. For each exposed photograph in the device’s RAM, a separate asynchronous process is started (Fig. 4), which makes it possible to enter data on the place and time of the survey, form the electronic signature and then record the generated signed electronic document in the form of a JPEG file on a medium. In the developed hardware-software device, method 4 is used to bind the ES to the graphic file (Fig. 3), where the key "_ECK_S1_S2" is added to the standard file name, where S1 and S2 are hexadecimal representations of the pair of numbers that make up the ES [2]. At the end of the file recording process automatically ends and frees up the device’s RAM.

Asynchrony eliminates the wait for the processing of the current photograph to complete before taking the next one. The number of simultaneously running asynchronous processes is determined by the available RAM of the smartphone (camera), the resolution of the photographs, the speed of the CPU and the speed of recording to an internal or external storage medium. The timing diagram of the program when executed at time t1, ..., t11 at several, for example eleven, parallel-sequential images is shown in FIG. four.

The resulting file is available for copying and viewing by standard means that support the file system of the storage medium and JPEG format. Any change (editing, renaming, changing the size and resolution of the image, conversion to another graphic format, etc.) of the file contents, including the additional information and signature elements entered, leads to the compromise of the electronic signature. For verification of the undistorted image and related data paired with the “EP Creator” program, the “Verifier” program (written in Java) has been developed that runs on a PC running MS Windows and upon presentation of a photo document for verification either confirms the reliability of the declared EP or denies it , and also displays information about the place and time of shooting stored in the photo.

When formulating the invention and compiling the description, the following sources of patent and scientific and technical information were taken into account:

1. Gribunin V.G., Okov I.N., Turintsev I.V. Digital steganography - M.: SOLON-PRESS. - 2009 .-- 265 p. ISBN: 5-98003-011-5.

2. GOST P 34.10-2012 - The processes of formation and verification of electronic digital signatures.

3. GOST P 34.11-2012 - Information technology. Cryptographic information security. Hash function.

4. RF patent 2176823 G09C 5/00, G06K 19/00, H04N 1/44. Software-implemented digital anti-counterfeiting method and device for implementing the method.

5. Shalkevich VV Ensuring the reliability of digital photographs // Law and Order, 2008, No. 1 (5) (http://www.law.bsu.by/pub/11/shalkevich_1.pdf).

6. Standard of Japan Electronics and Information Technology Industries Association JEITA CP-3451. Exchangeable image file format for digital still cameras: Exif Version 2.2. - 2002. (http://www.exif.org/Exif2-2.PDF).

7. Baushev S.V., Unhealthy H.B. The program of creation in a digital camera or other device equipped with a function of digital photography, electronic digital signature of the generated image and service data. - Certificate of state registration of a computer program No. 20144611607 of 02/06/2014

Claims (7)

1. A method of creating digital photographs protected from counterfeiting, consisting in exposing the CCD matrix of a digital camera or smartphone and processing the exposed data to convert into one of the generally accepted digital image formats, and supplementing with data on the shooting condition, characterized in that for the images thus obtained the combined aggregate data calculate the hash function, form an electronic digital signature (ES) and save them as a single digital image file of a generally accepted format in the internal or external the memory of the camera or smartphone, for each exposed photograph, before taking the next one, a separate asynchronous process is launched in the RAM of the camera or smartphone, making data on the location and time of the shooting, the formation of an electronic digital signature and the subsequent recording of the generated signed electronic document in the form of a digital image file to the media. 2. A device for creating digital photographs protected from counterfeiting, containing RAM, a processor, a CCD matrix, running an operating system and / or software or hardware-software modules that implement exposure of a photosensor (CCD matrix); reading from the photosensor data on the exposure of each element of the photosensor (pixel of the CCD); placing them in RAM or processor cache; processing this data according to the conversion algorithms into one of the generally accepted compressed image formats, overhead data of these compressed formats are generated and added; form and add to the resulting image file the data of the conditions for obtaining the image, characterized in that the software is supplemented with a software or hardware-software module, under the control of which (which) the processor performs cryptographic processing (calculates the hash function of the image data and data of the conditions for obtaining the image) and forms an EF, after which the combined data array containing image data, added data, as well as EF data, is recorded on an external or built-in medium devices in the form of a graphic file of a generally accepted format, and for each exposed photograph, before taking the next one, a separate asynchronous process is started in the RAM, making data about the location and time of the survey, generating an electronic digital signature and subsequent recording of the generated signed electronic document in the form of a digital image file to the media. 3. The device according to claim 2, characterized in that the electronic signature is embedded in the video data or in one of the fields of the EXIF segment or another segment of the service information of the main body of the image file. 4. The device according to claim 2, characterized in that the electronic signature is embedded in the name of the image file. 5. The device according to p. 2, characterized in that the EP is embedded in the data container containing the image file. 6. The device according to claim 2, characterized in that the electronic signature is stored separately from the signed image file. 7. The device according to any one of paragraphs. 2-6, characterized in that it is a digital camera or smartphone.

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