KR20080016038A - A method and an apparatus for exchanging message - Google Patents

Abstract

A method and an apparatus for exchanging messages are provided to transmit and receive messages safely between a host and a security module by using a public key-based algorithm and to exchange messages with confidentiality, without the necessity of using a complicated algorithm, by transmitting an encoding or decoding key to the other side. A host and a security module respectively transmit device certificates to each other, including their respective public keys. The host creates a digital signature with its own private key and transmits it to the security module. The security module also creates a digital signature with its own private key and transmits it to the host. The host and the security module respectively decode the received digital signatures using the public keys contained in the received device certificates and execute mutual authentication. Afterwards, if the security module encodes a message using the public key received from the host and transmits it to the host, the host decodes the encoded message using its own private key.

Description

A method and an apparatus for exchanging message

1 is a conceptual diagram of a broadcast network in digital cable broadcasting

2 is an element characteristic diagram that a host and a security module include for exchanging messages between the security module and the host according to the present invention.

3A-3C illustrate an example of a certificate that includes a public key

4 is a message exchange method for providing confidentiality in accordance with the present invention.

5 is an embodiment of a message exchange method according to the present invention.

6 is an embodiment of a configuration of a broadcast receiver according to the present invention.

* Brief description of the main parts of the drawing *

600: host 630: control means

700: security module

The present invention relates to a message exchange method in a broadcast receiving device and a broadcast receiving device, and more particularly, to a message exchange method using a public key encryption method.

Digital broadcasting is a general term for broadcasting transmitted digitally. In the United States, it was decided to adopt digital for the next generation of televisions called ATV (Advanced television). In Europe, many projects such as Sweden's HD DIVINE, UK's SPECTRE, and France's DIAMOND are active. Such digital broadcasting is being actively researched in each country by the next generation method linked with B-ISDN or computer network.

As broadcast contents are digitized as described above, the protection of broadcast contents is also a big issue. In order to protect digital broadcast contents in a digital broadcast receiving apparatus, there is a need for a limited reception apparatus in which only a user authorized to watch the digital broadcasting contents can be viewed.

Therefore, the broadcaster encrypts the digital broadcast content secretly and transmits the digital broadcast content to the digital broadcast receiving device. The digital broadcast reception device may decrypt the encrypted digital broadcast content using the secret key, and the authorized user may watch the digital broadcast content. This series of processes is performed through the limited reception device in the digital broadcast reception device. Therefore, the limited reception device is an essential device in the digital broadcast reception device.

In addition, the cable broadcast receiver is an open cable method in which a POD (Point Of Deployment) module including a conditional access (CA) system is separated from a main body. The POD module, for example, uses a PCMCIA card and is capable of being mounted / removed in the main slot of the cable broadcast receiver. Therefore, the POD module is also called a cable card. The main body into which the POD module is inserted is also referred to as a host. For example, a digital built-in TV or a digital ready TV may be a host. The host and the POD module may be referred to as a cable broadcast receiver.

The cable broadcast provides various information to a specific user who has paid the cost. However, there is a possibility that broadcast content may be provided to a user who does not pay a fee through hacking or the like. To solve this problem, we need a security module.

In order for scramble and descramble to operate normally between the security module and the host, the same scramble key and the descramble key are required.

In the security module and the host, decryption is possible only by using a descramble key paired with a scramble key used for encryption. However, the security module and the host generated the same scrambled key descrambled key using the same algorithm, respectively. Therefore, due to a complicated algorithm, the execution speed is slow, there is a problem that the device cost is high.

The present invention is to solve the above problems, an object of the present invention to provide a method and device for securely exchanging messages between devices using a public key encryption scheme.

Another object of the present invention is to provide a method and an apparatus for receiving a reception, which can be performed without using a complicated algorithm by providing a method for securely exchanging previously stored encryption and decryption keys.

In order to achieve the above object, the present invention provides a method of exchanging messages in a host and a security module, the method comprising: providing a device certificate of the host from the host to the security module; Encrypting and distributing the encrypted message to the host, wherein the host receiving the encrypted message deciphers the encrypted message with the host's private key. To provide.

The device certificate includes a public key, and the security module encrypts the message using the public key of the device certificate.

The message may be an encryption key for encrypting a broadcast signal or a decryption key for decrypting the broadcast signal.

The encryption key for encrypting the broadcast signal is a value previously stored in the security module.

Encryption and reverse encryption of the message is characterized by using a public key encryption scheme.

The symmetric key encryption method is characterized in that the RSA method.

The host and the security module are characterized in that it is supported on an open cable application platform (OCAP).

According to another embodiment of the present invention, the present invention provides a method of exchanging messages in a host and a security module, the method comprising: providing a device certificate of the security module from the security module to the host; Encrypting the message in a secure manner and distributing the message to the secure module, wherein the secure module that receives the encrypted message includes encrypting the encrypted message with a private key of the host. It provides a message exchange method.

According to another embodiment of the present invention, the present invention provides at least two multimedia devices, wherein the at least two multimedia devices distribute the public key to the counterpart device, encrypt the message with the received public key, and distribute the public key. A device for distributing an encrypted message to a device and receiving the encrypted message includes a control unit for decrypting by using a private key of the device and restoring the message.

Therefore, according to the present invention, by using a public key based algorithm, the host and the security module can securely send and receive messages, and can safely transmit an encryption key or decryption key to an external device, without using a complicated algorithm. You can exchange messages with confidentiality in the host and security modules.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention that can specifically realize the above object will be described.

1 conceptually illustrates a broadcast network in digital cable broadcasting. Referring to FIG. 1, a cable headend or a plant may receive a broadcast signal through various communication networks.

The headend may transmit the cable broadcast received through the various communication networks to the cable broadcast receiver through the network including the node. The cable broadcast receiver may receive a broadcast signal transmitted from the headend or transmit a specific signal to the headend. In this case, the transmission and reception may be made through a cable network as shown in FIG. 1 capable of transmitting data in both directions.

The host may be connected to other peripheral devices such as digital televisions, DVD players, Digicams, set-top boxes, and the like in various types of interfaces.

Meanwhile, as described above, the host may receive and process an OCAP based service provided from the headend.

In other words, the host can download OCAP-Java applications such as monitor applications, various applications, and EPGs transmitted from the headends located at remote locations through the cable network and run them on their systems.

At this time, the receiver receiving the broadcast is installed with a security module for security. Therefore, the broadcast receiver is composed of a host and a security module. The host and the security module encrypt and receive a broadcast signal or other data for security.

2 is an element included in the host and the security module for the exchange of messages between the security module and the host according to the present invention.

Referring to FIG. 2, the security module includes a root CA certificate, a manufacturer CA certificate, a card device certificate, and a card private key. The host includes a root CA certificate, a manufacturer CA certificate, a host device certificate, and a host private key. In this specification, the security module and the cable card are used in the same sense, and are embodiments of the module for security, and are not limited to the cable card.

The security module and host store the device certificate and private key, and exchange digital signature data and certificates with each other when connecting. Based on the exchanged data, the host determines the validity of the card device certificate and verifies the electronic signature data sent from the card. Algorithms used are X.509 v3 and RSA (Rivest Shamir Adleman), respectively. In other words, a mutual authentication process is required.

For security, a process of encrypting and decrypting the actual data is required along with a mutual authentication process for determining the validity of the certificate.

The present invention provides a method and apparatus for encrypting and decrypting data using a public key based algorithm.

Digital signatures are a technique used to verify the identity of the creator of an electronic document and whether the electronic document has been tampered with. Public key based algorithms include Diffid-Hellman, DSA, and RSA. In the embodiment of the present invention will be described using the RSA algorithm. However, the scope of the present invention is not limited by this embodiment. To use a public key-based algorithm, you basically need a private key and its corresponding public key. The public key is usually distributed in a device certificate. It also uses the X.509 method to avoid the risk of hacking. In addition, two RSA public and RSA private keys are used for both mutual authentication and secure message transmission.

3A-3C illustrate a certificate that includes a public key.

The certificate includes a field indicating information of the corresponding product, and a field indicating a public key and information about the certificate.

Referring to FIG. 3A, C, O, and OU fields in a device certificate may indicate information of a corresponding product, and CN may be used as an ID of the corresponding product. Valid Period may indicate the validity period of the certificate. For example, C = KR, O = LG Electronics Inc., OU = DMB can be indicated.

In FIG. 3B, examples of C = US, O = VeriSign, OU = DMB_CA, and CN = VeriSign Mfg CA can be given.

Referring to Figure 3c, the certificate for the highest authentication period may be an example of C = US, O = VeriSign, CN = VeriSign Mfg Root CA.

Public key encryption can be encrypted using both public and private keys. Encrypting with a private key and decrypting it with a public key ensures integrity, and encrypting with a public key and decrypting it with a private key can provide confidentiality. The present invention provides a method and apparatus for electronic signature, signature data verification and secure message exchange using two pairs of public and individual keys.

The host and the security module form an electronic signature for the digital signature, and the encryption side uses its private key. The generated digital signatures are exchanged with each other and then decrypted with the other party's public key and compared with the original. At this time, SHA-1 or MD5 algorithm can be used to increase the execution speed.

After the integrity of the digital signature is verified, the message exchange between the host and the security module encrypts and sends a message to each other for confidentiality, and the receiving device decrypts it. At this time, the encryption key used for the encryption at the transmitting side and the decryption key used for the encryption at the receiving side should be paired. Currently there is no method of transmitting or receiving a message that maintains confidentiality between the security module and the host. Instead of transmitting an encryption key or decryption key, the same encryption is performed using a complex algorithm in each of the host and the security module to generate the same key. Key and decryption keys can be generated. However, this can increase the algorithm, which can cause a problem of slowing down execution.

4 illustrates a message exchange method for providing confidentiality in accordance with the present invention. According to the present invention, it is possible to exchange security messages.

Referring to FIG. 4, there is a message to be transmitted between the host and the security module. The message is encrypted with a public key received from the counterpart device, and the encrypted message is distributed to the counterpart device. The device receiving the encrypted message performs decryption with its own private key to restore the original message.

In this case, the message may be a broadcast signal itself, or may be an encryption key or a decryption key. By securely exchanging encryption keys or decryption keys, the host and the security module do not need to generate the same encryption key and decryption key by separate processes. Therefore, the key previously stored in the security module (or host) can be used as an encryption and decryption key, and it can be encrypted with the public key of the counterpart and transmitted to the counterpart stably.

The algorithm for encrypting the message with the private key and decrypting it with the public key ensures integrity, since the private key is not distributed, so if the digital signature is decrypted with the received public key, it is encrypted by the subject that sent the public key. It becomes clear. Therefore, integrity is guaranteed.

On the other hand, since the message can be encrypted with the received public key, the encrypted message can be distributed, and the message can only be decrypted with the private key of the subject. The decryption cannot be performed by other devices. This ensures the confidentiality of the message.

5 illustrates in detail the message exchange method according to the present invention.

The exchange of messages takes place between A and B devices. In this case, step 1 is a device certificate exchange step of device A and device B, step 2 is a mutual authentication step, step 3 is a message exchange step. Device A and device B may be target devices for exchanging messages, such as a digital television, a mobile phone, or a PDA. In the present specification, embodiments of device A and device B will be described as security modules and hosts. In other words, A device is a security module and B device is a host.

The exchange of messages may be from device A to device B or from device B to device A. This can happen at the same time or only one side.

The host distributes the device certificate to the security module, and the security module distributes the device certificate to the host. The device certificate contains a public key (step 1).

The security module and the host generate a digital signature with their private key and send it to the counterpart respectively. At this time, the device receiving the digital signature decrypts the digital signature using the public key extracted from the device certificate received from the other party to perform mutual authentication (step 2).

The security module and the host encrypt a message to be sent to the partner using the public key received from the partner. The encrypted message is directly distributed to the counterpart device, and the device receiving the encrypted message decrypts the encrypted message using its own individual key and restores the message (step 3).

Although described herein as an embodiment, it is possible to transmit and receive secure messages between mutual devices. That is, it is possible to send a security message from the host to the security module, or from the security module to the host. In addition, a security message can be transmitted and received by the present invention not only between the host and the security module, but also between multimedia devices such as a mobile phone and a PDA.

6 shows a configuration of an embodiment of a broadcast receiver according to the present invention.

Referring to FIG. 6, first, the stream broadcast signal transmitted from the headend is received by the host 600, which is transmitted to the security module 700. Hereinafter, a description will be given of a cable card which is an embodiment of a security module. The present invention is not limited to the cable card. The broadcast signal subjected to the limited reception process in the cable card 700 is transmitted to the host 600 to allow the viewer to watch the broadcast.

Processing of the broadcast signal will be described with reference to the configuration of FIG. 6.

The digital broadcast reception device includes a host 600 and a cable card 700.

The host 600 includes a tuner 602, a demultiplexer 604, an audio decoder 606, a video decoder 608, an audio processor 609, a video processor 610, an additional information processor 612, and a CAS (Conditional). Access System) module 614, key input unit 616, card interface unit 618, storage unit 620, and the control means 630.

The tuner 602 tunes to a broadcast channel selected by a user. When the user changes the viewing channel, the corresponding frequency is selected. The selected frequency enters a VSB or QAM converter (not shown) and is converted into a digital signal.

The demultiplexer 604 demultiplexes the time multiplexed transport stream into demultiplexed, that is, video, audio and side information signals.

The audio decoder 606 expands / restores the audio signal separated by the demultiplexer 604 and converts the audio signal to be output through the audio processor 209, and the video decoder 608 separates the video signal separated by the demultiplexer 604. Extend / Restore.

The video processor 610 converts the video signal output from the video decoder 608 into luminance and color signals to be displayed on a screen, and the additional information processor 612 separates the additional information signal separated by the multiplexer 604. Analyze

The CAS module 614 extracts an Entitlement Control Message (ECM) PID and a Local Transport Stream ID (LTSID) from the information analyzed by the additional information processor 612.

A command desired by a user is input to the key input unit 616, and the control unit 630 controls the operation of each unit of the digital broadcasting system. The control means 630 is also responsible for the copy restriction process that is responsible for the limited reception function between the cable card 700 and the host 600. The control means 630 classifies the received digital broadcast signal into a main stream and an extra stream, determines whether to scramble, and descrambles the scrambled stream.

The storage unit 620 stores and extracts necessary information according to the control signal of the control means 630, and in the present invention, information of the stream in which the scramble is determined is stored by the control signal of the control means. .

The cable card 700 is inserted into the card interface unit 222. The card interface unit may be located inside the host, may be located in the security module 700, or may exist together in both.

Hereinafter, the control means 630 and the cable card 700 will be described in detail.

The control means 630 and the cable card 700 are responsible for encrypting and decrypting the message. The control means 630 is responsible for encrypting and decrypting the host described above.

That is, the control means 630 provides the host device certificate to the cable card 700, and the cable card 700 provides the card device certificate to the control means 630. In addition, it extracts the public key from the provided device certificate, performs encryption, and sends an encrypted message to the device that received the device certificate. The device receiving the encrypted message decrypts the encrypted message using a private key paired with the distributed public key and restores the message. The recovered message may be an encryption key for encrypting the broadcast signal or a decryption key for decrypting the broadcast signal. Therefore, by safely transmitting the encryption key or the decryption key to the external device, the actual broadcast signal can be encrypted using the received encryption key, and the decryption can be executed.

In this embodiment, however, the descrambling module is provided in the cable card, and the cable card is attached to and detached from the host. The broadcast signal from the broadcast station is descrambling through the descrambling module of the cable card and provided to the user. However, according to the exemplary embodiment, the descrambling module is provided inside the host without a cable card, and the descrambling module may be configured to be downloaded from a broadcasting station. That is, the descrambling module downloaded from the broadcasting station or the like may have a different configuration to be stored in a predetermined memory in the host.

As an example of a method for downloading the descrambling module, when a security processor pre-embedded in the set-top is connected to a network, a CA (Conditional Access) image may be automatically downloaded from the headend. However, it is natural that the difference in configuration does not change the scope of the present invention.

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and changes without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present invention.

According to the invention described above

First, using a public key based algorithm, the host and the security module can send and receive messages securely.

Second, as the encryption key or the decryption key can be securely transmitted to the counterpart device, the host and the security module can exchange messages with confidentiality without using a complicated algorithm.

Claims (11)

In the message exchange method in the host and security module, Providing a device certificate of the host from the host to the security module; Encrypting a message with the provided device certificate in the security module and distributing the message to the host; And the host receiving the encrypted message deciphers the encrypted message with the host's private key. The method of claim 1, The device certificate includes a public key, The security module encrypts the message using the public key of the device certificate. The method of claim 1, The message is an encryption key for encrypting a broadcast signal or a decryption key for decrypting a broadcast signal in the security module. The method of claim 3, wherein And an encryption key for encrypting the broadcast signal is a value previously stored in the security module. The method of claim 1, Encrypting and de-encrypting the message using a public key encryption method. The method of claim 5, The symmetric key encryption method is a message exchange method characterized in that the RSA method. The method of claim 1, The host and the security module are supported on an open cable application platform (OCAP). In the message exchange method in the host and security module, Providing a device certificate of the security module from the security module to the host; Encrypting a message with the provided device certificate at the host and distributing the message to the security module; Receiving the encrypted message and encrypting the encrypted message with the host's private key. At least two multimedia devices; The at least two multimedia devices distribute the public key to the counterpart device, encrypt the message with the received public key, distribute the encrypted message to the counterpart device that distributed the public key, and the device that receives the encrypted message And a control unit for restoring the message by decrypting using the private key. The method of claim 9, The multimedia apparatus is a message exchange device, characterized in that the security module is installed for the security of the broadcast signal and the host receiving the broadcast signal. The method of claim 9, The message is one of an encryption key for encrypting a broadcast signal or a decryption key for decrypting an encrypted broadcast signal.

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