KR100533154B1 - Cording/Decording Method by using Symmetric Key in Digital Rights Management System - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

The present invention relates to an encryption / decryption method using a symmetric key in a digital rights management system and a computer-readable recording medium having recorded thereon a program for realizing the method.

2. The technical problem to be solved by the invention

An object of the present invention is to provide an encryption / decryption method using a symmetric key in a digital rights management system and a computer-readable recording medium having recorded thereon a program for realizing the method.

3. Summary of the Solution of the Invention

The present invention provides an encryption / decryption method in a digital rights management system, the content providing apparatus comprising: a random value generating step of generating a random value through a random value generating unit; Generating a key recognizer for generating a symmetric key (decryption key) for decryption in the authentication apparatus; Encrypting content by generating a symmetric key (encryption key) according to a predetermined symmetric key algorithm using the random value, the key recognizer, and the identifier of the content providing device provided through the authentication device; And content registration information including the key identifier, the random value, and the identifier of the content providing apparatus, to the authentication apparatus so that the authentication apparatus can decrypt the content encrypted in the encryption step. A decryption step of generating and decrypting a symmetric key (decryption key) according to a key algorithm.

4. Important uses of the invention

The present invention is used for the protection and management of intellectual property rights such as audio, video, e-book, software, etc. in digital format.

Description

Encryption / Decryption Method by Using Symmetric Key in Digital Rights Management System

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the field of information protection technology, and in particular, digital rights management (DRM) that prevents illegal use of digital content having the same quality as the original and protects and manages the rights of content creators after infinite copying. An encryption / decryption method using a symmetric key in a system and a computer-readable recording medium having recorded thereon a program for realizing the method.

The terms used in the present invention are defined as follows.

Digital Rights Management (DRM) refers to a function that protects and manages the rights of digital content creators.

License refers to data that contains the decryption key used to decrypt the encrypted content and the contents specifying the right (number, duration) of the content.

Metadata means data describing data. For example, content metadata is data that contains additional description of the content.

DRM Clearinghouse is a system that performs license issuance, statistical function, billing, financial settlement and settlement to solve encrypted contents by packager, and plays a key role of DRM system.

A packager is a device that performs a series of tasks of attaching a header containing a Uniform Resource Locator (URL), a commerce vendor information, and the like, after encrypting content by using an encryption key.

Unlike analog content, digital content retains the same quality as the original after several copies. When digital content having such characteristics meets the Internet communication media, copies of the same quality as the original can be propagated infinitely rapidly. That's why content owners (e.g., Hollywood filmmakers) who have invested so much capital and effort are reluctant to digitize their content and commercialize it on the Internet. This climate eventually leads to disadvantages in that content consumers (users) cannot receive high quality content.

Currently, the method used to protect digital content provided by the Internet is a content access control method, which enables users to access and use content after subscribing to a content seller or a service provider and paying a content service price. Content security processing is performed by using a billing authentication method in addition to the login method. However, such a content access control method, when a digital file is stored in a hard disk of a personal computer (Personal Computer) at a content service site (shopping mall) and then played back, the user pays a fee and secures the content once. If you then copy the downloaded file to your relatives or colleagues, the content protection device will no longer work. Therefore, login-based digital protection is inevitably dependent on the conscience of the user.

To secure this flaw, DRM technology has emerged. This DRM technology first converts the content into a digital file format via an encoder in the form of DRM packaging. The content is encrypted using an encryption key here. Users can copy and distribute this encrypted content at will, but a decryption key is necessary to use the encrypted content. In addition, the player is required to play the decrypted content. The player plays a role in controlling the use of digital content in addition to the decoding function. That is, the user can use the content only within the content usage right concluded with the shopping mall at the time of downloading the content.

That is, digital content copyright protection encrypts digital content using an encryption key and then pays a fair price to the user who uses the content when using the content. Accordingly, the digital content copyright management system receiving the just payment notice delivers the decryption key to the user.

Therefore, in the digital rights management system, the management and distribution of keys is very important. Also, if the information exchanged inside the management system is exposed to the outside of the system, the rights management system has a problem that can expose the loophole in content protection. have.

The present invention has been proposed to solve the above problems, by generating a key recognizer for cryptographic key management, adds stability of key management to encryption and decryption, and requires signing for information exchange between devices. It is an object of the present invention to provide an encryption / decryption method using a symmetric key in a digital rights management system having improved exchange stability, and a computer-readable recording medium storing a program for realizing the method.

In order to achieve the above object, the present invention provides an encryption / decryption method in a digital rights management system, the content providing apparatus comprising: a random value generating step of generating a random value through a random value generating unit; Generating a key recognizer for generating a symmetric key (decryption key) for decryption in the authentication apparatus; Encrypting content by generating a symmetric key (encryption key) according to a predetermined symmetric key algorithm using the random value, the key recognizer, and the identifier of the content providing device provided through the authentication device; And content registration information including the key identifier, the random value, and the identifier of the content providing apparatus, to the authentication apparatus so that the authentication apparatus can decrypt the content encrypted in the encryption step. And a decryption step of generating and decrypting a symmetric key (decryption key) according to a key algorithm.

On the other hand, the present invention, the digital rights management system having a processor, the content providing apparatus, the random value generating function for generating a random value through the random value generating unit; A key recognizer generation function for generating a key identifier for generating a symmetric key (decryption key) for decryption in the authentication apparatus; An encryption function for encrypting content by generating a symmetric key (encryption key) according to a predetermined symmetric key algorithm using the random value, the key recognizer, and the identifier of the content providing device provided through the authentication device; And content registration information including the key identifier, the random value, and the identifier of the content providing apparatus, to the authentication apparatus so that the authentication apparatus can decrypt the content encrypted in the encryption step. A computer-readable recording medium having recorded thereon a program for realizing a decryption function for generating and decrypting a symmetric key (decryption key) according to a key algorithm is provided.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating an embodiment of a digital rights management system to which the present invention is applied and an operation method thereof.

As shown in FIG. 1, the digital rights management (DRM) system to which the present invention is applied in order to prevent the illegal use while allowing the copying of the digital content, encrypts the digital content using an encryption key, and then encrypts the encryption key and the encryption. The packager 12 of the content provider for registering the metadata of the digital content, the packager that receives and manages the metadata, and interworks with the payment gateway 14 DRM Clearinghouse (license issuing device) 11 for issuing and managing a license to solve the corresponding digital content encrypted with (12), and upon requesting the user to play the content, the user's license is examined and the DRM Request the license issuance to the clearing house (11), and decrypt the corresponding digital content provided by the content provider using the issued license A content player 16 is included.

The digital rights right (DRM) system is largely comprised of a DRM clearing house (license issuing device) 11, a packager 12, and a content player 16 with a DRM function.

The content provider / seller's packager 12 uses an encoder to convert other types of digital content into a file format that the packager 12 can recognize.

The packager 12 includes a file (content) from the encoder, content metadata containing various information (title, artist name, etc.) about the content, a content provider metadata containing information of the content provider, and the content. After packaging the encryption key required for packaging as an input value, the packaged content registration file required for registering the packaged content and package as the DRM clearing house 11 is exported as a result value.

The packager 12 adds a header to the content passed through the encoder, which includes content metadata, information related to encryption / decryption, and a link to a website where a license for a decryption key and a right of the packaged content can be issued. Uniform Resource Locator) consists of a set of metadata that can contain information values necessary for operation in the DRM system.

When the DRM function-embedded content player 16 requests the user to play the content, the user's license is examined and the DRM clearing house 11 issuing a license, and the licensed web server and packaged by the content provider are issued. The digital content provided by the content DB 13 is decoded only in the terminal PC provided with the content.

The DRM clearing house (license issuing device) 11 is a key element of the digital rights management (DRM) system, and is a decryption key necessary for decrypting the content encrypted by the content provider / seller's packager 12 at the content consumer (content user) end. And licenses containing information such as usage rights that can restrict the use of decrypted content. In addition, each time the license is issued, it is linked with the financial institution 14.

The operation of the digital rights management (DRM) system will now be described in more detail with reference to FIG. 1.

First, a DRM service applicant (content author, provider / seller) who wants to receive digital content copyright management and protection service registers with the DRM clearing house 11 using a web user interface (1).

After that, the manager of the DRM clearing house 11 sends a confirmation mail after processing the registration of the DRM service applicant (2). At this time, a variety of information is delivered to the reply mail, the message sign key (Sign Key) used to sign the unique ID of the DRM service applicant and all messages sent between the DRM clearing house 11 from the DRM service applicant in the future Contains information such as value, packager 12 that can package DRM content, website address, and DRM service usage guide. In addition, all transmission messages have a text format and more preferably use Extensible Markup Language (XML), but are not limited thereto.

Next, the DRM service applicant installs the packager 12 according to the procedure sent by e-mail, and then packages all contents to be sold using the DRM service through the packager 12 using the displayed information of FIG. 2. (3).

Subsequently, the DRM service applicant (content author, content provider / seller) registers the packaged content in the DRM clearing house 11 (4). This content registration procedure is performed as follows. At this time, the packaged content is placed in the web server of the content provider and the packaged content database 13, and only the package content registration file is signed with a message sign key, and then transmitted to the DRM clearing house 11. Here, the method used for encrypting and decrypting content uses a symmetric key method. In other words, the same key used for encryption is also used for decryption. Therefore, the key value used for encryption is sent to the DRM clearing house 11 using the message signing key, and the key used for encryption is again used for decryption of the content when a license issuance is requested from the content user (DRM function-embedded content player 16). do.

Thereafter, the content user searches for the desired content on the site of the content provider and makes a purchase request (5). In this case, the contract is signed with the content provider on the right to use the content, that is, how many times it will be played or how long (period: unlimited, days) to view, and whether to allow copying to another medium (CD or portable device). . In this case, the charge for the content purchase request may impose a usage fee on the content user in the DRM clearing house 11 having a function of linking with the content provider site itself or the financial institution 14 (6-1, 6-6). 2). Smaller content providers can earn more from small capital given to use the financial settlement function of the DRM clearing house 11 rather than have their own financial settlement and settlement functions, and the DRM clearing house 11 can settle financial settlements. You can make a profit by adding a fee.

Thereafter, the content user pays with her preferred payment method (7). Examples include credit cards, bank transfers, and cell phone payments.

Then, the financial institution 14 notifies the content provider and the DRM clearing house 11 of the payment result of the content user (8-1, 8-2).

Next, the content provider / seller (shopping mall) notified of the payment processing result from the financial institution 14 requests the license issuance processing to the DRM clearing house 11 (9). At this time, the information is transmitted together with the content usage rights, content ID, and the user's unique information using the PC or operating system to play the content.

In response, the DRM clearing house 11 sends the license to the content user (consumer) (10). The content provider then sends the content to the content user (consumer) (11). Here, the license delivery process 10 may be performed before the content delivery process 11.

Subsequently, the DRM clearing house 11 periodically sends a transaction statement to the content provider 12. In addition, if necessary, the content provider may access the DRM clearing house 11 to check his / her registration status, content registration contents, transaction details, and the like (13).

As described above, the procedure of obtaining a license after a consumer (content user) purchases content from a shopping mall (content provider) site has been described. However, if the user A (content user) copies the content from the consumer B who already owns the content, and the validity (period, number of times) of the customer's content license C is terminated, the content protection is as follows. The same process can be used for copyright protection.

First, the DRM function-embedded content player 16 in the user's PC checks whether a content license exists, and then checks the validity (operation, etc.) of the license itself and the right to use the content embedded therein (a).

As a result of the investigation, if the content is valid, the content is played, and if the license expires, the license server URL in the content header is searched to enter a license agreement (b-1, b-2).

That is, if the license server URL is designated as a shopping mall (content provider) site that provided / sells the content, a license agreement is established between the content user and the shopping mall (b-1), and the content is used by the shopping mall (content provider). (C-1), the user pays the content usage fee to the financial institution 14 associated with the shopping mall as his preferred payment method (d), and the financial institution 14 sends the content user to the shopping mall. Notifies that the payment has been completed (e-1), and requests the DRM clearing house 11 to issue a license in the shopping mall which has received the payment notice (f). In this case, when the shopping mall goes bankrupt, a dead link occurs and this content no longer has vitality.

On the other hand, when the license server URL is set to the DRM clearing house 11, a license agreement is entered into between the content user and the DRM clearing house 11 (b-2), and the DRM clearing house 11 is responsible for using the content to the content user. If the user charges the charge (c-2), and the user pays the content fee to the financial institution 14 associated with the shopping mall as his preferred payment method (d), the financial institution 14 pays the content user to the shopping mall. Notify that the completion of the DRM clearing house 11 (e-2). In this case, it is not necessary to pay attention to the bankruptcy of the small shopping mall, and there is an advantage that content distribution (copying) between content users is possible regardless of the period.

As such, the content user may enter into a content use contract with the shopping mall or the DRM clearing house 11 (b-1, b-2).

Then, the DRM clearing house 11 receives a license issuance request from a shopping mall (content provider) (f) or a payment confirmation notification from the financial institution 14 (e-2). . At this time, the DRM clearing house 11 provides a transaction history to the shopping mall (content provider) (h). In addition, if necessary, the content provider may access the DRM clearing house 11 to check his or her registration status, content registration contents, transaction details, etc. (i).

2 is a block diagram of an embodiment of a digital rights management system for generating and operating an encryption key according to the present invention.

Unlike the general digital rights management system of FIG. 1, the present invention provides another new feature to the symmetric key scheme for protecting digital contents.

The symmetric key generator 22 according to the present invention includes a random seed value from the random generator 21 and a key ID and a DRM clearing house from the key ID generator 23. 11) At the time of registration 2, the content provider ID received from the DRM clearing house 11 is taken as an input value, and a content encryption and decryption key are generated.

Here, the notable fact of the present invention is that Key ID plays an important role in generating (retrieving) the decryption key in the DRM clearing house 11, so that randomness and non-redundancy are required. The random seed value is also used for generation.

In addition, the packager 25 encrypts and packages the content using the encryption key from the symmetric key generator 22, and the DRM clearing house 11 such as a key ID and a content provider (content providing device) ID. After adding the information necessary for key generation to the header, the information is packaged in the form of a registration file and transmitted to the DRM clearing house 11 through a message signing process through a message signer 27. That is, the packager 25 packages two pieces of information, one of which is the content itself, and the other of which is a content registration file including key information.

The packaged content that has passed through the packager 25 is stored in the content storage server 26 of the content provider (content providing device), which is another result of the packager 25 downloaded to the consumer PC when the consumer purchases the content information. The registered content registration file contains information related to the content (title, artist name) and information (Key ID, content provider ID, random seed) necessary for recovering the encryption key of the content provider in the DRM clearing house 11, etc. have.

The content provider (content providing device) generates a content registration file packaged through the packager 25 in a private key (Private Key: generator 214 of FIG. 2), which is given when registering the DRM clearing house 11. 1) Sign and send to the DRM clearing house 11 by using the (signed in step 10 of FIG. 1).

Meanwhile, the DRM clearing house 11 receiving the signed packaging content registration file message checks the integrity of the delivered message using the message verifier 28. That is, check whether the information is signed with the private key given to the content provider at the time of registration.

When the tampering of the received message is confirmed, the database 211 of the DRM clearing house 11 is extracted by extracting and extracting information (Key ID, content provider ID, random seed) necessary to generate a decryption key through the message parser 29. Store in

In order to use the encrypted digital copyrighted content, the user decides to purchase the packaged content at the shopping mall, enters into a content use contract with the shopping mall company, and signs this information again using a private key for signing, Send to clearing house (11). The DRM clearing house 11 extracts usage rights through the integrity check and message parser in the same way as the signed packaging content registration file is processed, and the DRM clearing house 11 displays the fields associated with the packaging content in the database 211 of the DRM clearing house 11. Record it.

The DRM clearing house (license issuing device) 11 is required to generate a decryption key among the information related to the content determined to be purchased by the consumer in the database 211 of the DRM clearing house 11 according to the license issuance request of the shopping mall (Key ID, content provider ID, random seed) and content usage rights fields are found and sent to the license generator 210. The license generator 210 issues a license using the symmetric key generation algorithm shared with the shopping mall and transmits the license to the content user 216. The DRM content player 217 in the user's PC uses the unique information of the user in the license to investigate that the license has been delivered to the correct user, and decrypts the content using the decryption key included in the license to meet the usage rights. Service content to users. Through this process, copyright protection of digital contents is protected.

3 is a structural diagram of an embodiment of a packaged content registration file according to the present invention.

As shown in FIG. 3, the packaged content registration file according to the present invention includes a key ID 31 for generating a symmetric key (decryption key) in the DRM clearing house 11, and a decryption key of the packaged content. Web site link (URL: Uniform Resource Locator) information (32) that can be licensed for use rights, metadata set (33, 34) and sign value (Sign) that can contain information values necessary for operation in DRM system. (39).

By receiving the content registration file containing the above information, the DRM clearing house 11 may generate a symmetric key (decryption key) and provide a license to a user who wants to use digital content.

As described above, the method of the present invention may be implemented as a program and stored in a recording medium (CD-ROM, RAM, floppy disk, hard disk, magneto-optical disk, etc.) in a computer-readable form.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the spirit of the present invention for those skilled in the art to which the present invention pertains, and the above-described embodiments and accompanying It is not limited by the drawings.

As described above, the present invention has an effect of increasing the stability of key management in encryption and decryption by generating a key recognizer for encryption key management in a digital rights management system as compared with the conventional technology.

In addition, the present invention has an excellent effect of increasing the stability of the information exchange by requiring signing for authentication in the information exchange between the devices in the digital rights management system.

1 is a diagram illustrating an embodiment of a digital rights management system to which the present invention is applied and a method of operating the same.

2 is a block diagram of an embodiment for encryption / decryption in the digital rights management system according to the present invention;

3 is a structural diagram of one embodiment of a packaged content registration file according to the present invention;

* Explanation of symbols on the main parts of the drawing

11: DRM Clearinghouse 12: Packager

13: Web server and content DB 14: Financial institutions

15: license storage unit 16: content player

Claims (4)

In the encryption / decryption method in the digital rights management system, A random value generating step of generating, by the content providing device, a random value through the random value generating unit; Generating a key recognizer for generating a symmetric key (decryption key) for decryption in the authentication apparatus; Encrypting content by generating a symmetric key (encryption key) according to a predetermined symmetric key algorithm using the random value, the key recognizer, and the identifier of the content providing device provided through the authentication device; And The content registration information including the key identifier, the random value, and the identifier of the content providing apparatus is transmitted to the authentication apparatus so that the authentication apparatus can decrypt the content encrypted in the encryption step, the predetermined symmetric key. Decoding step to generate and decrypt symmetric key (decryption key) according to the algorithm Encryption / decryption method using a symmetric key in a digital rights management system comprising a. The method of claim 1, The key recognizer in the key recognizer generation step, Encryption / decryption method using a symmetric key in the digital rights management system, characterized in that for generating using the random value generated in the random value generation step. The method of claim 1, Delivery of content registration information in the decoding step, Digital signing using a private key assigned to the content providing device when registering a service to the content providing device, thereby enabling the authentication device to verify a message from the content providing device. Encryption / decryption method using a symmetric key in a digital rights management system, characterized in that. In a digital rights management system having a processor, A random value generating function for generating, by the content providing apparatus, a random value through the random value generating unit; A key recognizer generation function for generating a key identifier for generating a symmetric key (decryption key) for decryption in the authentication apparatus; An encryption function for encrypting content by generating a symmetric key (encryption key) according to a predetermined symmetric key algorithm using the random value, the key recognizer, and the identifier of the content providing device provided through the authentication device; And The content registration information including the key identifier, the random value, and the identifier of the content providing apparatus is transmitted to the authentication apparatus so that the authentication apparatus can decrypt the content encrypted in the encryption step, the predetermined symmetric key. Decryption function to generate and decrypt symmetric key (decryption key) according to the algorithm A computer-readable recording medium having recorded thereon a program for realizing this.