RU2258315C1 - Method for forming and checking of message certified with watermark - Google Patents

Abstract

FIELD: computer science.

SUBSTANCE: previously for sender and receiver a binary series of digital watermark k-bit long is formed as well as binary series of secret key, message is certified at sender side using binary series of digital watermark and secret key, certified message is sent to receiver, where authenticity of received message is checked using binary series of digital watermark and secret key.

EFFECT: higher reliability, higher efficiency.

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Description

The invention relates to the field of telecommunications and information technology, in particular to a technique for protecting the authenticity of messages, such as speech, sound, music, television, facsimile, etc. converted to digital form. messages. A genuine message is understood to mean a message in which there are no unauthorized changes to its content and its sender (author) is identified. Unauthorized changes to the content and authorship of a message can be made by an attacker in the process of transferring and storing a message generated by the sender. The task of the message recipient is to establish the fact that the content of the received message corresponds to the content of the message sent by the sender and that the sender is the author of the received message. The technical result achieved by the implementation of the claimed technical solution is to develop a method for generating and verifying a message authenticated with a digital watermark, which increases the security of a message authenticated by a digital watermark of the sender from the deliberate actions of an attacker to change the content of the message and its authorship.

The proposed method for generating and verifying a message certified by a digital watermark can be used to establish the authenticity of speech, sound, music, television, fax, etc. multimedia messages transmitted and stored in modern information and telecommunication systems. The multimedia information converted by the sender to the digital form during transmission and storage can easily be modified by the attacker and transferred to the recipient in a modified form. This attacker strategy is called a message spoofing attack. Also, an attacker, not waiting for a message to be sent by the legal sender, can re-generate a false message and transfer it to the recipient on behalf of the sender. This attacker strategy is called a message simulator attack. In addition, the attacker can intercept the message transmitted by the legal sender and replace the sender’s signature in it with his own, appropriating the copyright of this message. Such an attacker’s action strategy is called a message spoofing attack. The listed actions of the attacker can be easily implemented on digital multimedia messages using common audio, video, graphic and other editors. Moreover, the recipient of distorted information cannot detect the fact of distortion of its content and authorship. Therefore, for speech, sound, music, television, fax, etc. messages transmitted via communication channels or recorded on such media as audio or video tapes, CD or DVD disks, floppy disks, etc., it is required to establish the absence of intentional distortions in them and their authorship.

Known methods for establishing the authenticity of multimedia messages recorded on audio or video tapes, CDs and floppy disks. These methods use unique technological features of the media. For example, the authenticity of a message is established if the reader detects a bad sector label in the desired location on the disk of the message to be protected. Known methods for establishing the authenticity of multimedia messages recorded on audio or video tapes, CDs and floppy disks are described, for example, in the book: V. Zhelnikov. Cryptography from papyrus to computer. - ABF, 1996, page 218. However, verifying the authenticity of messages based on the use of unique technological features of the media of these messages is fundamentally incapable of establishing the absence of intentional distortions in these messages and their authorship when they are rewritten from carriers with unique technological features to the media of these features not having.

Therefore, it is advisable to build methods for establishing the authenticity of multimedia messages based on embedding their authentication information in the messages themselves, without using any binding to the unique technological or other features of the media of these messages. In recent years, such methods have been developed within the framework of steganographic methods of information protection and have received the name of methods for generating and verifying a message authenticated with a digital watermark. These methods are described, for example, in the book: V.G. Gribunin, I.N. Okov, I.V. Turintsev. Digital steganography. M .: Solon-R, 2002, page 6-17. The main idea of these methods is to embed in the certified multimedia message a special label - a digital watermark (CEH) of the sender (author) of the message using a secret key. This CEH is a unique identifier of the sender and uniquely identifies the sender of the message when the recipient retrieves this CEH from the received message using a secret key. The fact of extracting this CEH from the received message using the secret key also allows the recipient to make sure that the content of the message authenticated by this watermark is not changed or formed as a result of malicious actions. By analogy with watermarks certifying the authenticity of banknotes on paper, these identifiers are called the digital watermark of the message. Digital watermarks of messages can be visually perceptible, for example, an image of a registered trademark of a manufacturer or an image of a sender's face, and visually not perceptible, for example, a binary sequence registered as a personal identification number (PIN) of a sender of a multimedia message.

Embedding a sender’s digital watermark in a certified multimedia message is possible by using a secret key unknown to a potential attacker. At the verification stage, a digital watermark is extracted from the received multimedia message using the same secret key, which is compared with the digital watermark of the message sender, and if they coincide, a decision is made about the authorship of this message and the absence of distortions in it. An attacker who knows the digital watermark of the sender of the message, but does not know his secret key, is not able to generate a multimedia message certified by the digital watermark of the sender, which, when verified, the recipient recognizes as genuine.

Known methods for generating and verifying a digitally authenticated message are described, for example, in the book: Johnson N., Jajodia S. "Steganalysis of Images Created Using Current Steganographic Software" .// Proceeding of the Workshop on Information Hiding, 1998. They are preliminary formation for the sender and recipient of the binary sequence of a digital watermark with a length of 64 bits. The binary sequence of a digital watermark is the same for any multimedia message authenticated by the sender. To assure the sender of the message, starting from the first sample, the next samples of the message are read into the next block of samples with a length of 64 samples. The next block of samples is converted by a discrete cosine transform method into 64 discrete cosine transform coefficients. Coefficients are rounded to integer values. From the first to the last bit, the i-th bit is read, where i = 1, 2, ..., 64, the binary sequence of the digital watermark. Starting from the first to the last coefficient of the discrete cosine transform, the next coefficient is read in which its least significant bit is replaced with the i-th bit of the binary sequence of the digital watermark, the converted value of the next coefficient of the discrete cosine transform is read into the next output block of coefficients with a length of 64 coefficients. When the next output block of coefficients is filled, it is transformed by the inverse discrete cosine transform method into 64 counts of the next block of a certified message, which is transmitted to the recipient. Read the next 64 samples of the message and re-read the binary sequence of the digital watermark and perform the subsequent actions until then, until the next samples of the message. To verify the authenticity of the message received by the recipient, starting from the first sample, the received next message samples are read into the next block of received samples with a length of 64 samples. The next block of received samples is converted by a discrete cosine transform method into 64 received discrete cosine transform coefficients. The values of the received coefficients are rounded to integer values. From the first to the last bit, the i-th bit is read, where i = 1, 2, ..., 64, of the binary sequence of the digital watermark and, from the first to the last, the next discrete cosine transform coefficient is accepted, in which it the least significant bit is compared to the i-th bit of the binary sequence of the digital watermark. If all the least significant bits of the received next coefficients coincide with the corresponding i-th bits of the binary sequence of the digital watermark, then the next block of received samples is considered authentic. Then, the next received message samples are read into the next block of received samples with a length of 64 samples, after which the steps to check the next block of received samples are repeated until the received next message samples arrive.

In the known methods for generating and checking a message certified by a digital watermark, replacing the least significant bit of the next coefficients of the discrete cosine transform of the next block of samples by the i-th bits of the binary sequence of the digital watermark leads to a slight change in the value of the next samples of the message of this block. If, for example, a message authenticated by a digital watermark is a grayscale image, then these methods of generating and checking a message authenticated by a digital watermark lead to relatively small changes in the brightness of each of the 64 pixels of the next image block, which is visually inconspicuous and practically does not reduce the image quality.

A disadvantage of the known methods for generating and verifying a message authenticated by a digital watermark is the low security of the message authenticated by the sender's digital watermark from the deliberate actions of the attacker to change the content of the message and its authorship.

If you intentionally change the content of a message authenticated by the sender's digital watermark, the attacker can change any bits of the next discrete cosine transform coefficients of the next sample blocks of this message, except for the least significant bits of these coefficients. Since the least significant bits of the next coefficients of the discrete cosine transform of the next blocks of samples of the modified message are not changed by the attacker, the recipient of the modified message, performing the described verification steps, erroneously recognizes the received message as genuine. Thus, the attacker has the ability to convert the message, certified by the digital watermark of the sender, into a false message. Therefore, the known methods do not provide the security of the message, authenticated by the sender's digital watermark, to a message spoofing attack.

With a different strategy of actions, an attacker who knows at least one arbitrary message authenticated by the sender’s digital watermark can generate a false message favorable to him, and replace the least significant bits of the next discrete cosine transform coefficients of the next sample blocks of this message with the corresponding bits of the digital watermark binary sequence legal sender. When the recipient verifies the authenticity of the received message, the least significant bits of the next coefficients of the discrete cosine transform of the next blocks of samples of the received message coincide with the corresponding bits of the binary sequence of the sender's digital watermark, that is, the recipient of the received false message will be erroneously considered authentic. Thus, the attacker has the ability on behalf of the sender to successfully impose arbitrary false messages to the recipient. Therefore, the known methods do not ensure the security of the message, authenticated by the digital watermark of the sender, to an attack simulating the message.

In the third strategy of actions, an attacker can replace the least significant bits of the next coefficients of the discrete cosine transform of the next blocks of message samples, authenticated by the sender's digital watermark, with the corresponding bits of the binary sequence of his digital watermark, without changing the other bits of the next DCT coefficients. An attacker, like a legitimate sender, can be the same potential author of messages in an information and telecommunication system and, in accordance with known methods, a unique binary sequence of his digital watermark is formed for an attacker. The recipient of the message with the changed authorship, performing the verification steps described in the known methods using the binary sequence of the digital watermark of the attacker, mistakenly recognizes the attacker as the author of the received message. Thus, an attacker is able to appropriate the authorship of an arbitrary message from a legitimate sender. Therefore, the known methods do not provide the security of the message, certified by the digital watermark of the sender, to the attack of substitution of authorship.

The closest in technical essence to the claimed method for generating and verifying a message certified with a digital watermark is the method described in US Patent 5613004 IPC ⁶ H 04 L 009/20 of 03/18/97. The method is a prototype for generating and verifying a message certified by a digital watermark, which consists in preliminary forming for the sender and recipient of the binary sequence a digital watermark label with a length of m bits, a binary sequence of a digital watermark with a length of k bits, and a binary sequence of a secret key with a length of k bits. Pre-set the number of bit matches of the binary sequence of the digital watermark label and the number of bit matches of the binary sequence of the digital watermark to zero. To assure the sender of the message, starting from the first to the mth character, the next bit of the binary sequence of the digital watermark label and the binary sequence of the next message count are read. In the binary sequence of the next sample of the message, the least significant bit is replaced with the next bit of the binary sequence of the digital watermark label, and the converted binary sequence of the next sample of the message is transmitted to the recipient as certified. After that, the i-th one is sequentially read, where i = 1, 2, ..., k, the bit of the binary sequence of the secret key, the i-th bit of the binary sequence of the digital watermark and the binary sequence of the next message count. If the i-th bit of the binary sequence of the secret key takes a single value, then the low-order bit of the binary sequence of the next sample of the message is replaced by the i-th bit of the binary sequence of the digital watermark and the converted binary sequence of the next sample of the message is transmitted to the recipient as certified. If the i-th bit of the binary sequence of the secret key takes a value of zero, the binary sequence of the next sample of the message is transmitted without change to the recipient as certified. Then again, starting from the first to the mth character, the next bit of the binary sequence of the digital watermark label and the binary sequence of the next message count are read and the subsequent actions are performed until the binary sequences of the next message samples arrive.

To verify the authenticity of the message received by the recipient, the received binary sequence of the next message count is read and, starting from the first to the mth character, the next bit of the binary sequence of the digital watermark label. The least significant bit of the received binary sequence of the next sample of the message is compared with the next bit of the binary sequence of the digital watermark label and if they match, the number of matches of the bits of the binary sequence of the digital watermark label is increased by one, otherwise this number is set to zero and the received binary sequence of the next sample is read messages and re-read, starting from the first to the mth character, the next bit of the binary sequence and a digital watermark and perform the following steps after him. If the number of matches of the bits of the binary sequence of the digital watermark label has reached the value m, then the received binary sequence of the next sample of the message and the i-th one are read, where i = 1, 2, ..., k, the bit of the binary sequence of the secret key and the i-th bit binary sequence digital watermark. If the i-th bit of the binary sequence of the secret key is equal to a single value, then the least significant bit of the received binary sequence of the next sample of the message is compared with the i-th bit of the binary sequence of the digital watermark and, if they match, the number of matches of the bits of the binary sequence of the digital watermark is increased by a unit value, after reading the k-th bit of the binary sequence of the digital watermark, the number of matches of the bits of the binary sequence of the digital watermark cp NIWA with the number of individual bit values of the binary sequence a private key and when they are equal the received binary sequence m + k successive samples messages considered authentic, then repeat for authentication action of the next group of m + k received successive samples messages before completion of reception of all sample messages.

The disadvantage of the prototype of the claimed method of generating and checking a message authenticated with a digital watermark is the low security of the message, authenticated by the sender's digital watermark, from the deliberate actions of the attacker to change the content of the message and its authorship. If you intentionally change the content of a message authenticated by a sender’s digital watermark, the attacker can change any bits except the low-order bits of an arbitrary number of successive samples of the authenticated message. Since the least significant bits of the next samples of the modified message are not changed by the attacker, the recipient of the modified message, by performing the described verification steps, erroneously recognizes the received message as genuine. Thus, the attacker has the ability to convert the message, certified by the digital watermark of the sender, into a false message. Therefore, the prototype of the claimed method does not ensure the security of the message, certified by the digital watermark of the sender, to the attack of spoofing the message.

With a different strategy of actions, an attacker who knows the binary sequence of the sender’s digital watermark can generate a false message consisting of successive samples, and replace the low-order bits of the binary sequence of successive samples of the false message with the least significant bits of the binary sequence of successive samples of the message, authenticated by the sender’s digital watermark. The recipient of such a false message, performing the described verification steps, erroneously recognizes the received message as genuine. Thus, the attacker has the ability on behalf of the sender to successfully impose arbitrary false messages to the recipient. Therefore, the prototype of the claimed method does not ensure the security of the message, certified by a digital watermark of the sender, to an attack simulating a message.

In the third strategy of actions, an attacker can replace the low-order bits of the binary sequence of the next samples of a message authenticated by the sender's digital watermark with the next bits of the binary sequence of his digital watermark and the next bits of the binary sequence of his digital watermark. In this case, the attacker keeps the remaining bits of the binary sequence of successive samples of the message unchanged, that is, the content of the message does not change. An attacker, like a legitimate sender, can be the same potential author of messages in an information and telecommunication system and, in accordance with the prototype of the proposed method, a unique binary sequence of a digital watermark label with a length of m bits, a binary sequence of a digital watermark of length k bits and a binary sequence of a secret key of length k bits. The recipient of the message with the changed authorship, performing the verification steps described in the prototype method using a binary sequence of a digital watermark label with a length of m bits, a binary sequence of a digital watermark with a length of k bits, and a binary sequence of a secret key with a length of k bits, an attacker mistakenly recognizes the attacker as the author of the received message . Thus, an attacker is able to appropriate the authorship of an arbitrary message from a legitimate sender. Therefore, the prototype of the claimed method does not ensure the security of the message, certified by a digital watermark of the sender, to the attack of the substitution of authorship.

For all the intentional actions described by the attacker, he does not need to know the binary sequence of the secret key of length k bits.

The specified disadvantage of the prototype of the claimed method for generating and verifying a message authenticated with a digital watermark occurred due to the fact that the binary sequence of a digital watermark embedded in the message does not depend on the message being authenticated and the binary sequence of the secret key.

The aim of the invention of the claimed technical solution is to develop a method for generating and checking a message authenticated with a digital watermark, which ensures increased security of the message authenticated with a digital watermark of the sender from intentional actions by an attacker to change the message content and authorship.

, где Р_под - допустимая вероятность принятия подлинной группы из k очередных отсчетов сообщения, являющейся не подлинной.This goal is achieved by the fact that in the known method of generating and verifying a message verified with a digital watermark, the message consists in preliminarily generating for the sender and recipient a binary sequence of a digital watermark of length k bits and a binary sequence of a secret key, the message is authenticated at the sender using binary sequences of digital watermark sign and secret key. A certified message is transmitted to the recipient, where the authenticity of the received message is verified using binary sequences of a digital watermark and a secret key. Additionally, a hash function with a binary output value is formed previously for the sender and recipient, and the minimum allowable number K _{min of} genuine message samples in a group of k sequentially received is set. . The minimum allowable number K _{min of} genuine message samples in a group of k sequentially received is established from the condition

, where P _sub is the admissible probability of accepting a genuine group of k successive samples of a message that is not genuine.

, а действие

означает округление значения -log₂P_ош до ближайшего целого, причем соответствующим первому биту двоичной последовательности цифрового водяного знака у отправителя сообщения принимают первый отсчет из k последовательно принятых двоичных последовательностей очередных отсчетов сообщения.To assure the sender of the message, the i-th one is sequentially read, where i = 1, 2, ..., k, the bit of the binary sequence of the digital watermark and the binary sequence of the next sample of the message, which is hashed using the binary sequence of the secret key according to the previously generated hash function . After that, the hashed value is compared with the i-th bit of the binary sequence of the digital watermark and, if they match, the binary sequence of the next sample of the message is transmitted to the recipient as certified, and if they do not match, the binary sequence of the next sample of the message is sequentially converted by changing its least significant bits. To convert the binary sequence of the next sample of a message by changing its least significant bits, one, two, three, and so on, the least significant bits are sequentially changed. Then, after each conversion, the converted binary sequence of the next sample of the message is hashed using the binary sequence of the secret key according to the previously generated hash function, the hashed value is compared with the i-th bit of the binary sequence of the digital watermark, and the conversion of the binary sequence of the next sample of the message is performed until the hashed value of the converted binary sequence of the next count of messages the i-th bit of the binary sequence of the digital watermark, after which the last converted binary sequence of the next sample of the message is transmitted to the recipient as certified. After verifying the binary sequence of the next sample of the message using the kth bit of the binary sequence of the digital watermark, the i-th bit of the binary sequence of the digital watermark is read out again, starting from the first to the k-th, and the binary sequence of the next sample of the message and the following it acts until binary sequences of successive samples of the message arrive. At the message recipient, a sample corresponding to the first bit of the binary digital watermark sequence of the message sender is preliminarily selected from among the received binary sequences of subsequent samples of the message. To select the next message sample corresponding to the first bit of the binary digital watermark sequence from the sender of the message, the maximum allowable probability P _{Osh of} erroneous allocation of this sample is preliminarily set, the binary sequences of the next message samples received by the receiver are hashed using the binary secret key sequence according to the previously generated hash function hashed values are compared sequentially with by creating, starting from the first, the bit values of the binary sequence of the digital watermark until m in a row matches them, where

, and the action

means rounding the value of -log ₂ P _Ош to the nearest integer, and the first sample of k consecutively received binary sequences of subsequent samples of the message is received from the message sender corresponding to the first bit of the binary digital watermark sequence.

Then, to verify the authenticity of the message received by the recipient, k binary sequences of successive samples of the message are successively received, hashed using the binary secret key sequence using the pre-formed hash function, and each i-th hashed value is compared with the i-th bit of the binary digital watermark sequence. The number K _{c of} hashed binary sequences of the next message samples is calculated from k received samples that match the values of the corresponding bits of the digital watermark binary sequence, and for K _c ≥K _{min, the} received k binary sequences of the next message samples are considered authentic, and then the verification steps are repeated. the authenticity of the next group of k binary sequences of the next samples of the message and so on until the reception of all binary sequences of the next samples is completed The messages.

The indicated new set of actions performed due to the unpredictable dependence of all bits of the binary sequences of the next samples of the digital watermarked message on the corresponding bits of the digital watermark binary sequence of length k bits and the binary secret key sequence allows the security of the message certified by the sender's digital watermark to the deliberate actions of the attacker to modify the content of the message and its authorship a. This unpredictability when the binary sequence of the secret key is unknown to the attacker is ensured by hashing the binary sequence of the next sample of the message using the binary sequence of the secret key according to a preformed hash function with a binary output value. A preformed hash function with a binary output value for an attacker is indistinguishable from a random function, that is, the probability of correctly determining its output value when the binary sequence of the secret key is unknown to the attacker is ½, that is, equal to the probability of random guessing.

A pre-generated hash function with a binary output value must satisfy the following requirements:

1) The binary output value of the hash function equally depends on each bit of the binary sequences of the subsequent samples of the message and each bit of the binary sequence of the secret key.

2) Knowing the description of the hashing function and the binary sequences of the next samples of the authenticated message, the attacker is not able to calculate the binary sequence of the secret key.

3) Knowing the description of the hash function, the attacker is not able to correctly generate the output value of the hash function with a probability substantially greater than ½ for binary sequences of the next samples of the selected message, without knowing the binary sequence of the secret key.

. Выбором соответствующего значения K_min можно обеспечить сколь угодно малую допустимую вероятность Р_доп при рассматриваемой атаке подмены сообщения. Например, при K_min=20 вероятность успешной атаки подмены сообщения не превышает одной миллионной: Р_доп≤2^-20. Поэтому указанная новая совокупность выполняемых действий позволяет повысить защищенность сообщения, заверенного цифровым водяным знаком отправителя, к атаке подмены сообщения.If the binary sequence of the secret key is unknown to the attacker, he cannot change the next message samples in the message verified by the sender with a digital watermark so that the recipient of the modified message, by performing the verification steps described, mistakenly acknowledges the received message as authentic. When an attacker changes one successive sample of a certified message, the probability that the hashed value of the binary sequence of one successive message sample changed by an attacker matches the corresponding bit of the binary sequence of the digital watermark is ½. In a group of k consecutively received message samples, to recognize them authentic, at least K _min hashed values of binary sequences of the next message samples changed by the attacker with the corresponding bits of the digital watermark binary sequence must match. Therefore, the probability of accepting a genuine group of k successive samples of a message that is not genuine is

. By choosing the appropriate value of K _min it is possible to provide an arbitrarily small permissible probability P _add for the message substitution attack under consideration. For example, with K _min = 20, the probability of a successful message spoofing attack does not exceed one millionth: P _add ≤2 ^-20 . Therefore, this new set of actions performed can increase the security of the message, certified by the sender's digital watermark, to the message spoofing attack.

. Следовательно, вероятность принятия подлинной группы из k очередных отсчетов сообщения, являющейся не подлинной, равна

. Выбором соответствующего значения K_min можно обеспечить сколь угодно малую вероятность Р_доп при рассматриваемой атаке имитации сообщения. Например, при К_min=30 вероятность успешной атаки имитации сообщения не превышает одной миллиардной. Поэтому указанная новая совокупность выполняемых действий позволяет повысить защищенность сообщения, заверенного цифровым водяным знаком отправителя, к атаке имитации сообщения.Also, if the binary sequence of the secret key is unknown to the attacker and one or more messages authenticated by the sender’s digital watermark are known, the attacker cannot reconfigure a non-authentic message consisting of binary sequences of successive samples so that the receiver of an unauthentic message performs the verification steps described by mistake Recognized the received message as genuine. When an attacker forms a false message with a length of k successive samples, the probability that at least K _min hashed values of binary sequences of successive samples of an invalid message will coincide with the corresponding bits of a binary digital watermark sequence is

. Therefore, the probability of accepting a genuine group of k successive samples of a message that is not genuine is

. By choosing the appropriate value of K _min it is possible to provide an arbitrarily small probability P _add for the message simulation attack under consideration. For example, at K _min = 30, the probability of a successful attack simulating a message does not exceed one billionth. Therefore, this new set of actions performed can increase the security of the message, authenticated by the sender's digital watermark, to an attack simulating a message.

Also, if the binary sequence of the secret key is unknown to the attacker and the message is authenticated by the sender’s digital watermark, the attacker cannot change the authorship of this message to his own. Let the attacker, like the sender, be the same potential author of messages and, in accordance with the claimed method, a unique binary digital watermark sequence with a length of k bits and a binary secret key sequence can be formed previously for the attacker. If the authorship of the message changes, the attacker in each binary sequence of the next message count, certified by the sender’s digital watermark, must replace the least significant bits by which the recipient checks the sender’s digital watermark with the corresponding number of the least significant bits into which the attacker’s digital watermark is embedded. At the same time, the certified message is distorted in several least significant bits of the binary sequence of each successive message sample. At the same time, the quality of speech, sound, music, television, facsimile, etc. messages transmitted over the communication channel or recorded on media such as audio or video tapes, CD or DVD discs, floppy disks, etc., becomes significantly worse. The purpose of an attacker in an attack on the substitution of authorship is to appropriate copyright and property rights to the message, provided that the required quality of the message is maintained. For example, if an attacker replaced the manufacturer’s trademark in his video recorded on a video tape with his own, but there were noises that were clearly perceived by the audience’s organs of vision and hearing, attribution and replication for the purpose of selling such counterfeit products did not make sense. Therefore, this new set of actions performed allows to increase the security of the message, authenticated by the sender's digital watermark, to the attack of substitution of authorship.

The analysis of the prior art carried out by the applicant made it possible to establish that there are no analogues that are characterized by sets of features identical to all the features of the claimed method for generating and verifying a message certified with a digital watermark. Therefore, the claimed invention meets the condition of patentability "Novelty."

The search results for known solutions in this and related fields of technology in order to identify signs that match the distinctive features of the prototypes of the claimed invention showed that they do not follow explicitly from the prior art. From the prior art determined by the applicant, the influence of the provided by the essential features of the claimed invention on the achievement of the specified technical result is not known. Therefore, the claimed invention meets the condition of patentability "Inventive step".

The claimed method is illustrated by figures, which show:

- figure 1 is a timing diagram of the formation of a certified digital watermark message;

- figure 2 is a typical example of the hashing of binary sequences of subsequent samples of a message using a binary sequence of a secret key for a pre-formed hash function;

- figure 3 is a timing chart for checking a received message shifted relative to a message authenticated with a digital watermark;

- figure 4 is a timing diagram of the verification of a received message, synchronized with a digitally authenticated message;

- figure 5 is a graph showing the effect of the proposed method.

The implementation of the claimed method is as follows.

To protect the authenticity of multimedia messages transmitted over modern information and telecommunication networks, authentication information called a digital watermark of the message is embedded in the binary sequences of successive message samples using the binary sequence of the secret key. The binary sequence of the secret key is shown in figure 1 (a). Single bit values in the figures are shown in the form of shaded pulses, zero bit values in the form of unshaded pulses. The binary sequence of the secret key is presented with the requirement that it cannot be calculated by cybercriminals who may be aware of messages authenticated using it. The binary sequence of a digital watermark of length k bits is shown in Figure 1 (b). The binary sequence of the digital watermark of the message sender is registered as a unique identifier of the message sender and the fact of its detection in the received message using the secret key of the sender in the received message clearly indicates the authorship of the message sender who owns this digital watermark and the absence of distortions in the received message. The binary sequence of the digital watermark of the sender (author) of messages can be well known.

Initial messages, such as voice, sound, video, facsimile, etc., the form of which is shown in figure 1 (c), before being certified with a digital watermark, are preliminarily converted to digital form, for example, by pulse-code modulation (PCM) . Known methods for converting speech, sound, video, facsimile, etc. Messages to the digital form are described, for example, in the book: A.G. Zyuko, D.D. Klovsky, M.V. Nazarov, L.M. Fink "Theory of signal transmission." - M.: Radio and Communications, 1980, p. 243. Known conversion methods can be performed in two stages: first, discretization and quantization are performed, and then the sampled and quantized signal is converted into binary sequences of successive message samples.

The type of digital speech, sound, video, facsimile and similar messages discretized with a sampling frequency F = 1 / T, where T is the time interval between successive samples, and quantized by q levels (q = 256) is shown in figure 1 (g) . The first sample has a value equal to 179, the second sample is 185, the kth sample is 180, etc. The type of binary sequences of the next samples of the message shown in figure 1 (d). For q = 256, binary sequences of successive samples of a message consist of 8 bits. The most significant bit of the sequence is written first (on the left in figure 1 (d), the least significant bit is recorded last in the sequence (on the right in figure 1 (d).

Known methods for generating and verifying a message verified by a digital watermark bit by bit embed the binary sequence of the digital watermark in the least significant bits of the sequence of samples of the message, which is described, for example, in the book: A.P. Romancev. A statistical method for revealing the steganographic concealment of information in sound files: Materials of the International Informatization Forum MFI-2000, - M .: ZAO Informsvyazizdat, 2000, p.203-204. Embedding the binary sequence of a digital watermark in the least significant bits of the sequence of samples of speech, sound, video, fax and similar messages practically does not affect the quality of the certified messages.

Attackers may try to destroy digital watermarks embedded in authenticated multimedia messages or make them undetectable for verifying digital watermarks. If an attacker managed to destroy the built-in digital watermark or make it undetectable, then he can impersonate the legitimate author of such a multimedia message.

To determine the reference number of a message, starting from which, when checking a digital watermark, it is necessary to start extracting the binary sequence of the digital watermark, in the known methods of generating a digital watermark, before embedding the digital watermark itself, the binary sequence of the digital watermark mark is embedded in the message. If during the verification of a digital watermark, a binary sequence of a digital watermark label is identified in the message, then the start of the digital watermark embedded in the binary sequence of the message is uniquely determined.

Therefore, if the attacker’s samples of the authenticated message are distorted, in which the binary sequence of the digital watermark mark is embedded, then when checking the digital watermark, the mark will not be detected and, as a result, the digital watermark will not be read. The binary sequence of a digital watermark label is generally well known, and therefore is easily detected and distorted by an attacker in a certified message. An increase in resistance to malicious intentional actions can be achieved by not using a special binary digital watermark label sequence and determining the beginning of the digital watermark binary sequence embedded in the message from the binary digital watermark sequence itself using the secret key known to the recipient of the binary sequence.

If the samples of the certified message are distorted, in which the binary sequence of the digital watermark is embedded, then in the known methods, when checking the binary sequence of the digital watermark extracted from the certified message will not be identified with the binary sequence of the digital watermark of the author (sender) of the message, since they require their matches accurate to bits. Therefore, an increase in resistance to the deliberate actions of an attacker can be achieved by using a digital watermark, which can be identified with a digital watermark of the author (sender) of the message in the presence of distortions in one or more samples of the authenticated message.

In the inventive method, to ensure the formation and verification of a message authenticated by a digital watermark, increasing the security of the message, authenticated by a digital watermark of the legal sender, to the deliberate actions of an attacker to change the content of the message and its authorship, the following sequence of actions is implemented.

The preliminary formation for the sender and receiver of the binary sequence of a digital watermark of length k bits is as follows. Sender's unique digital watermark is selected. A unique binary digital watermark sequence of length k bits of the sender is formed by randomly selecting a sequence of binary characters described, for example, in the book: D. Knut, "The Art of Computer Programming." - M .: Mir, 1977, v.2, p. 22. If the binary sequence of the sender’s digital watermark is 32 bits in length, the probability of its coincidence with the binary sequence of the digital sender of another sender is 2 ^-32 ≈10 ^-9 , which is practically sufficient to ensure the repeatability of digital watermarks of a large number of senders.

Preliminary formation for the sender and recipient of the binary sequence of the secret key is as follows. The binary sequence of the secret key is formed by a random choice of a sequence of binary characters, described, for example, in the book: D. Knut "The Art of Computer Programming". - M .: Mir, 1977, v. 2, p. 22. The length of the binary sequence of the secret key must be at least 64 bits, which is described, for example, in the book by M. D. Smid, D. K. Bransted, "Encryption Standard Data: Past and Future. " TIIER, 1988, v. 76, No. 5, p. 45.

The preliminary generation of a hash function with a binary output value for the sender and receiver is as follows. Known methods for preliminary generation of the hash function are described, for example, in the book by M. D. Smid, D. K. Bransted, “Data Encryption Standard: Past and Future”. TIIER, 1988, v. 76, No. 5, p. 49. They consist in the formation of a hashed function with a secret key using the DES data encryption algorithm in ciphertext feedback mode or in output feedback mode. However, these methods of pre-shaping the hash function generate hash functions with an output value of 64 bits. Therefore, to pre-generate the hash function with a binary output value, it is proposed to convert the output value of 64 bits of the hash function generated in the known methods by modulo 2 calculation. As a result of this conversion, even 64-bit output values will take zero values, and 64-bit odd output values bits will take unit values. Conversion of a binary sequence by calculation modulo 2 is described, for example, in the book of B. A. Kalabekov "Microprocessors and their use in signal transmission and processing systems". - M .: Radio and communications, 1988, p. 10.

, где Р_под - допустимая вероятность принятия подлинной группы из k очередных отсчетов сообщения, являющейся не подлинной. Например, величину допустимой вероятности принятия подлинной группы из k очередных отсчетов сообщения, являющейся не подлинной, устанавливают равной Р_под=2^-32, что рекомендуется в книге Г.Симмонс "Обзор методов аутентификации информации". ТИИЭР, 1988, - т.76, №5, стр. 116. Следовательно, величину К_min целесообразно установить не менее 32.The preliminary establishment for the sender and recipient of the minimum allowable number K _{min of} genuine samples of a message in a group of k sequentially received is as follows. The minimum allowable number K _{min of} genuine message samples in a group of k sequentially received is set to

, where P _sub is the admissible probability of accepting a genuine group of k successive samples of a message that is not genuine. For example, the value of the admissible probability of accepting a genuine group of k successive samples of a message that is not genuine is set to P _under = 2 ^-32 , which is recommended in the book by G. Simmons "Overview of Information Authentication Methods". TIIER, 1988, v. 76, No. 5, p. 116. Therefore, it is advisable to set the K _min value to at least 32.

To assure the sender of the message using binary sequences of a digital watermark of length k bits and a secret key, the i-th one is sequentially read, where i = 1, 2, ..., k, the bit of the binary sequence of the digital watermark and the binary sequence of the next message count. Known methods for sequentially reading bits of a binary sequence of a digital watermark and a binary sequence of the next message count are described, for example, in the book by B. A. Kalabekov "Microprocessors and their use in signal transmission and processing systems". - M .: Radio and communications, 1988, p. 70.

The read binary sequence of the next sample of the message is hashed using the binary sequence of the secret key according to a preformed hash function. To do this, the binary sequence of the next sample of the message is encrypted using the DES data encryption algorithm in ciphertext feedback mode using the binary secret key sequence. The DES data encryption algorithm in ciphertext feedback mode using a binary secret key sequence is described, for example, in the book by M. D. Smid, DK Bransted, “Data Encryption Standard: Past and Future”. TIIER, 1988, v. 76, No. 5, p. 49. Then, the hash function converts the 64-bit output value by modulo 2 calculation. The output value is converted by modulo 2 computation, for example, in the book by B. A. Kalabekov “Microprocessors” and their use in signal transmission and processing systems. " - M.: Radio and Communications, 1988, p. 10. As a result of this conversion, the hashed value will take on a zero value for even output values of 64 bits in length, and will take a single value for odd output values of 64 bits in length.

Figure 2 shows a typical example of the hashing of binary sequences of successive samples of a message using a binary sequence of a secret key from a preformed hash function. The binary sequences of the next message samples, as well as the converted binary sequences of the next message samples correspond to the values of the next message samples from 0 to 255. The hashed value of the binary sequences of the next message samples take a zero or one value with a probability close to 1/2.

Then, the hashed value of the binary sequence of the next sample of the message is compared with the i-th bit of the binary sequence of the digital watermark. Known methods for comparing the hashed value of the binary sequence of the next sample of the message with the i-th bit of the binary sequence of the digital watermark are described, for example, in the book: W. Peterson, E. Weldon "Error Correcting Codes". M .: Mir, 1976, p. 52. The result of comparison may be their coincidence or mismatch. If the hashed value matches the i-th bit of the binary sequence of the digital watermark, the binary sequence of the next sample of the message is transmitted to the recipient as certified. Methods of transmitting to the recipient as a certified binary sequence the next count of the message are known and described, for example, in the book: A.G. Zyuko, D.D. Klovsky, M.V. Nazarov, L.M. Fink "Theory of signal transmission." - M.: Radio and Communications, 1986, p. 11.

An example of the obtained hashed values is shown in figure 1 (e). Let the unit hashed value be formed when hashing the binary sequence of the first sample of the message. It is compared with the value of the first bit of the binary sequence of the digital watermark and, if they match, the binary sequence of the first sample of the message is transmitted to the recipient as a certified binary sequence of the first sample of the message. An example of a certified binary sequence of subsequent samples of the message shown in figure 1 (l).

In case of mismatch, the binary sequence of the next sample of the message is sequentially converted by changing its least significant bits. To convert the binary sequence of the next sample of a message by changing its least significant bits, one, two, three, and so on, the least significant bits are sequentially changed. The sequential change of one, two, three, and so on of the least significant bits of a binary sequence of the next message count can be performed by sequentially inverting one, two, three, and so on of the least significant bits of a given binary sequence. Known methods for inverting one, two, three, and so on the least significant bits of the binary sequence of the next message count are described, for example, in the book of B. A. Kalabekov "Microprocessors and their use in signal transmission and processing systems." - M .: Radio and communications, 1988, p. 19.

After each conversion, the converted binary sequence of the next sample of the message is hashed using the binary sequence of the secret key according to the previously generated hash function, the hashed value is compared with the i-th bit of the binary sequence of the digital watermark, and the conversion of the binary sequence of the next sample of the message is performed until the hashed value of the converted binary sequence of the next count of messages with the i-th bit of the binary sequence of the digital watermark, after which the last converted binary sequence of the next sample of the message is transmitted to the recipient as certified.

For hashing using a binary secret key sequence using a previously generated hash function, the converted binary sequence of the next sample of the message is encrypted using the DES data encryption algorithm in ciphertext feedback mode using the binary secret key sequence. The DES data encryption algorithm in ciphertext feedback mode using a binary secret key sequence is described, for example, in the book by M. D. Smid, DK Bransted, “Data Encryption Standard: Past and Future”. TIIER, 1988, v. 76, No. 5, p. 49. Then, the hash function converts the 64-bit output to a modulo 2 calculation. As a result of this conversion, the hashed value will take a value of zero for even 64-bit output values and will take a single value with odd output values of 64 bits.

Then, the hashed value of the transformed binary sequence of the next message sample is compared with the i-th bit of the binary sequence of the digital watermark. Known methods for comparing a hashed value with the i-th bit of a binary sequence of a digital watermark are described, for example, in the book: W. Peterson, E. Weldon “Error Correcting Codes”. M .: Mir, 1976, p. 52. If the hashed value coincides with the i-th bit of the binary sequence of the digital watermark, the last converted binary sequence of the next sample of the message is transmitted to the recipient as certified, otherwise the binary sequence of the next sample of the message is continued to be converted. The methods for transmitting to the recipient, as a certified transformed binary sequence, the next message count are known and described, for example, in the book: A.G. Zyuko, D.D. Klovsky, M.V. Nazarov, L.M. Fink "Theory of signal transmission". - M.: Radio and Communications, 1986, p. 11.

An example of the obtained hashed values is shown in figure 1 (e). Let, as shown in figure 1 (e), when hashing the binary sequence of the second sample of the message formed a single hashed value. It does not match the value of the second bit of the binary sequence of the digital watermark. Therefore, the binary sequence of the second sample of the message is sequentially converted. For this, the unit value of the least significant bit of the binary sequence of the second sample of the message is changed to zero, as shown in figure 1 (g). The hashed value of the transformed binary sequence of the second sample of the message is zero, that is, it coincides with the second bit of the binary sequence of the digital watermark. Then, the transformed binary sequence of the second sample of the message is transmitted to the recipient as a certified transformed binary sequence of the second sample of the message.

Let, as shown in figure 1 (e), when hashing the binary sequence of the k-th sample of the message, a null hashed value is generated. It does not match the value of the kth bit of the binary sequence of the digital watermark. Therefore, the binary sequence of the kth sample of the message is sequentially converted. For this, the zero value of the least significant bit of the binary sequence k-ro of the message count is changed to a single value, as shown in figure 1 (g). The hashed value of the transformed binary sequence of the k-th sample of the message is zero, that is, again does not coincide with the k-th bit of the binary sequence of the digital watermark. Then, the zero value of the penultimate one (according to FIG. 1 (e)) of the significant bit of the binary sequence of the kth sample of the message is changed to a unit value, as shown in FIG. 1 (s). The hashed value of the binary sequence of the kth message count converted in this way is single, that is, it coincides with the kth bit of the binary sequence of the digital watermark. Then, the last transformed binary sequence of the kth sample of the message is transmitted to the recipient as certified.

The probability of a mismatch between the hashed value of the binary sequence of the next message sample and the i-th bit of the binary sequence of the digital watermark is ½. After converting the binary sequence of the next sample of the message by changing its one least significant bit, the probability of the hashed value of the converted binary sequence of the next sample of the message not matching with the i-th bit of the binary sequence of the digital watermark is 1/4. After sequentially changing one, two, three, and so on, the least significant bits of the binary sequence of the next sample of the conversion message of the binary sequence of the next sample of the message, the probability of a mismatch of the hashed value of the converted binary sequence of the next sample of the message with the i-th bit of the binary sequence of the digital watermark is 2 ^{-η- 1} , where η is the number of sequentially changed least significant bits of the binary sequence of the next sample with communication. Choosing the appropriate value of the number η, one can practically guarantee the coincidence of the hashed value of the transformed binary sequence of the next sample of the message with the i-th bit of the binary sequence of the digital watermark.

After verifying the binary sequence of the next sample of the message using the kth bit of the binary sequence of the digital watermark, the i-th bit of the binary sequence of the digital watermark is read out again, starting from the first to the k-th, and the binary sequence of the next sample of the message and the following it acts until binary sequences of successive samples of the message arrive. The number of binary sequences of successive samples of a message can be arbitrarily large. With the growth of its length, the number of successive groups of k binary sequences of successive samples of the message also increases proportionally, in each of which the recipient checks the authenticity of the received message. Therefore, the longer the message, the more difficult it is for an attacker to change its content or authorship. If an attacker divides the certified message into several parts, then, by assuring the sender of each next group of k binary sequences of subsequent samples of the message, the recipient of any part of the certified message with a length of at least k binary sequences of next samples can verify its authenticity. Since the value of k is no more than dozens of binary sequences, an attacker is practically not able to divide the certified message into parts shorter than k binary sequences of subsequent samples, due to the fact that such short fragments of speech, sound, music, television, facsimile, etc. .P. messages do not carry significant information for their potential recipients.

At the message recipient, a sample corresponding to the first bit of the binary digital watermark sequence of the message sender is preliminarily selected from among the received binary sequences of subsequent samples of the message. To highlight the next sample of the message corresponding to the first bit of the binary sequence of the digital watermark from the sender of the message, the maximum allowable value of the probability P _{er of} erroneous allocation of this sample is preliminarily set. The probability value of _Osh can be set, for example, of the order of 10 ^-1 ... 10 ^-2 . If, as a result of transmission channel errors or deliberate distortions of the authenticated message by the attacker, the recipient cannot select the sample corresponding to the first bit of the binary sequence of the digital watermark from the message sender in the next group of k binary sequences of the next message samples, the receiver will search for the required sample in the next group of k binary sequences of successive samples of the message, and so on, until the desired sample is selected. The probability of non-allocation of the required sample in β consecutive groups of k binary sequences of the next samples of the message is equal to P ^β _Osh . Since with increasing β the probability Р ^β _osh very quickly approaches zero, the recipient is guaranteed to select the next sample of the message corresponding to the first bit of the binary digital watermark sequence of the message sender with a length of not more than β of several consecutive groups of k binary sequences of next samples messages.

The binary sequences of successive samples of messages received by the recipient are hashed using the binary sequence of the secret key according to a previously generated hash function. For hashing using a binary secret key sequence using a pre-generated hashing function, the received binary sequence of the next sample of the message is encrypted using the DES data encryption algorithm in ciphertext feedback mode using the binary secret key sequence. The DES data encryption algorithm in ciphertext feedback mode using a binary secret key sequence is described, for example, in the book by M. D. Smid, DK Bransted, “Data Encryption Standard: Past and Future”. TIIER, 1988, v. 76, No. 5, p. 49. Then, the output value of 64 bits in length hash functions are transformed by calculation modulo 2.

, a действие

означает округление значения -log₂P_ош до ближайшего целого, причем соответствующим первому биту двоичной последовательности цифрового водяного знака у отправителя сообщения, принимают первый отсчет из m последовательно принятых двоичных последовательностей очередных отсчетов сообщения. Известные способы сравнения хэшированного значения принятой двоичной последовательности очередного отсчета сообщения с i-ый битом двоичной последовательности цифрового водяного знака описаны, например, в книге: У.Питерсон, Э.Уэлдон "Коды, исправляющие ошибки". М.: Мир, 1976, стр. 52.The hashed values of the received binary sequences of successive samples of the message are compared sequentially with the corresponding ones, starting from the first, the values of the bits of the binary sequence of the digital watermark until m in a row matches them, where

, a action

means rounding the value of -log ₂ P _Ош to the nearest integer, and the first sample of m consecutively received binary sequences of successive samples of the message is received corresponding to the first bit of the binary digital watermark sequence of the message sender. Known methods for comparing the hashed value of the received binary sequence of the next sample of a message with the i-th bit of the binary sequence of a digital watermark are described, for example, in the book: W. Peterson, E. Weldon "Error Correcting Codes". M.: Mir, 1976, p. 52.

Then, to verify the authenticity of the message received by the recipient, k binary sequences of successive samples of the message are sequentially received. Known methods for sequentially receiving k binary sequences of subsequent samples of a message are described, for example, in the book by U. Peterson, E. Weldon, “Error Correcting Codes”. - M .: Mir, 1976, p. 11.

The received binary sequences of successive message samples are hashed using the binary sequence of the secret key according to a preformed hash function. For hashing using a binary secret key sequence using a pre-generated hashing function, the received binary sequence of the next sample of the message is encrypted using the DES data encryption algorithm in ciphertext feedback mode using the binary secret key sequence. The DES data encryption algorithm in ciphertext feedback mode using a binary secret key sequence is described, for example, in the book by M. D. Smid, DK Bransted, “Data Encryption Standard: Past and Future”. TIIER, 1988, v. 76, No. 5, p. 49. Then, the output value of 64 bits in length hash functions are transformed by calculation modulo 2.

Each i-th hashed value of the received binary sequence of the next sample of the message is compared with the i-th bit of the binary sequence of the digital watermark. Known methods for comparing each i-th hashed value with the i-th bit of a binary sequence of a digital watermark are described, for example, in the book: W. Peterson, E. Weldon “Error Correcting Codes”. - M .: Mir, 1976, p. 52. The result of comparing the values may be their coincidence or mismatch.

The number K _{from the} hashed binary sequences of the next message samples is calculated from the k received samples that match the values of the corresponding bits of the binary digital watermark sequence. The number K _{c is} calculated as the arithmetic sum of cases of coincidence of the hashed binary sequences of the next message samples from k received samples with the values of the corresponding bits of the binary digital watermark sequence. The calculated value of K _c can range from zero to k inclusive.

When the condition K _c ≥K _{min is} fulfilled, the accepted k binary sequences of successive samples of the message are considered authentic. If this inequality is not satisfied, the authenticity of the accepted k binary sequences is not confirmed.

Let, as shown in figure 4 (e), the authenticity of the received k binary sequences of successive samples of the message is verified. The hashed value of the received binary sequence of the first sample of the message, shown in figure 4 (g), coincides with the value of the first bit of the binary sequence of the digital watermark, so the number K _{c is} set to a single value: K _c = 1, as shown in figure 4 (h) .

The following k-1 received binary sequences of successive message samples are processed similarly. Let, as shown in figure 4 (h), after receiving k binary sequences of subsequent samples of the message, the condition K _c ≥K _min is satisfied. Therefore, the received k binary sequences of subsequent samples of the message are considered authentic, as shown in figure 4 (s).

Then, the actions to verify the authenticity of the next group of k binary sequences of the next samples of the message are repeated, and so on until all the binary sequences of the next samples of the message have been received. If during authentication all accepted k binary sequences of subsequent samples of the message are recognized as authentic, then all received message is considered authentic.

Verification of the theoretical background of the claimed method for generating and verifying a message certified with a digital watermark was verified by its analytical studies.

. На фигуре 5 показана зависимость P_неподл от значения К_min. Из фигуры 5 видно, что минимально допустимое число К_min должно быть установлено таким, чтобы выполнялось соотношение P_неподл≤P_доп.The probability of accepting a genuine group of k successive message samples that are genuine is

. The figure 5 shows the dependence of P _nepodl from the value of K _min . From figure 5 it is seen that the minimum allowable number K _min must be set so that the ratio P _unsupported ≤P _add .

The studies confirm that when using the proposed method for generating and verifying a message authenticated with a digital watermark, it is possible to increase its security against the deliberate actions of attackers to change the content of the message and its authorship.

Claims (4)

1. A method for generating and checking a message authenticated by a digital watermark, which consists in the fact that a binary sequence of a digital watermark of length k bits and a binary sequence of a secret key are formed for the sender and recipient, the message is authenticated at the sender using binary sequences of a digital watermark and secret key, transmit the certified message to the recipient, where they verify the authenticity of the received message using binary sequences of qi A watermark and a secret key, characterized in that, in addition, a hashing function with a binary output value is additionally generated for the sender and recipient and the minimum admissible number K _{min of} genuine message samples in a group of k consecutively received is set, for verification from the sender of the message, i- d, where i = 1, 2, ..., k, the bit of the binary sequence of the digital watermark and the binary sequence of the next sample of the message, which is hashed using two the sequence of the secret key according to the previously generated hash function, after which the hashed value is compared with the ith bit of the binary sequence of the digital watermark and, if they match, the binary sequence of the next sample of the message is transmitted to the recipient as authenticated, and if they do not match, the binary sequence of the next sample of the message is sequentially converted by changing its low-order bits, then after each conversion, the converted binary sequence The integrity of the next message count is hashed using the binary sequence of the secret key according to a previously generated hash function, the hashed value is compared with the ith bit of the binary sequence of the digital watermark, and the binary sequence of the next message count is converted until the hashed value of the converted binary sequence of the next message count matches i-bit of the binary sequence of the digital watermark, by Then, the last converted binary sequence of the next message count is transmitted to the recipient as certified, and after the binary sequence of the next message count is verified using the kth bit of the binary sequence of the digital watermark, the ith bit is read out again, starting from the first to the kth the binary sequence of the digital watermark and the binary sequence of the next sample of the message and perform the subsequent actions until the binary the sequence of the message samples, and the recipient of the message is preliminarily allocated from the binary sequences of the message samples the sample corresponding to the first bit of the binary sequence of the digital watermark from the message sender, after which k binary sequences of message samples are received in sequence to verify the authenticity of the message received, hash them using a binary secret key sequence in advance tionary formed hashing function and each ie hash value is compared with i-th bit of the binary sequence of digital watermark calculated number K _c hashed binary sequences regular messages samples from the k received samples, matched with the values of the corresponding bits of the binary sequence a digital watermark, and by _c ≥K _min k binary sequences taken regular readings posts considered authentic, and then repeat the steps to verify the authenticity of another Rupp of k binary sequences of successive samples posts and so on until the end of reception of all binary sequences of successive samples of the message. 2. The method according to claim 1, characterized in that for converting the binary sequence of the next sample of the message by changing its least significant bits, one, two, three, and so on least significant bits are successively changed. 3. The method according to claim 1, characterized in that the minimum allowable number K _{min of} genuine message samples in a group of k sequentially received is established from the condition

, where P _sub is the admissible probability of accepting a genuine group of k successive samples of a message that is not genuine. 4. The method according to claim 1, characterized in that to highlight the next sample of the message corresponding to the first bit of the binary sequence of the digital watermark from the sender of the message, the maximum allowable value of the probability P _{Osh of} erroneous highlighting of this sample, the binary sequences of successive samples of the message received by the recipient, are pre-set hashed using a binary sequence of the secret key according to a pre-formed hash function, hashed values of cp accrue sequentially with the corresponding ones, starting from the first, the bit values of the binary sequence of the digital watermark until m in a row matches them, where

and action

means rounding the value of -log ₂ P _Ош to the nearest integer, and the first sample of k consecutively received binary sequences of subsequent samples of the message is received from the message sender corresponding to the first bit of the binary digital watermark sequence.

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