KR100947326B1 - Downloadable conditional access system host apparatus and method for reinforcing secure of the same - Google Patents

Abstract

PURPOSE: A DCAS(Downloadable Conditional Access System) host apparatus for forming a stable secure channel between a transmission processor and an SM module is provided to reinforce internal security of the DCAS host by performing authentication between a transmission processor and an SM module. CONSTITUTION: In case the authentication of a TPD(Transport Processor Driver) is completed, an SM(Secure Micro) boot loader(204) transmits the authentication response to the transmission processor driver. In the transmission processor driver is the authentication response, it is based on in the certificate corresponding to the SM boot loader' and the SM boot loader is certified. In case the cross certification is completed, the secure channel is formed with the security key lock according to 'beforehand, the fixed algorithm between the SM client and transmission processor.

Description

Downloadable Conditional Access System host apparatus and method for reinforcing secure of the same}

The present invention relates to a DCAS host device and a method for enhancing security thereof, and more particularly, to an apparatus and a method capable of preventing duplication of a component included in a DCAS host.

Digital conversion of broadcasting is taking place worldwide, and the digitalization of broadcasting technology and systems has already been completed.

Unlike analog content, digital content can not only be completely copied, but also easy to edit and distribute. Therefore, it is essential to restrict and protect access to content.

For this reason, a conditional access system (hereinafter referred to as "CAS") has been proposed to allow only legitimate subscribers to access the content.

The CAS, in conjunction with the Subscriber Management System (SMS), handles the receipt and playback of specific programs only to authorized subscribers.

In a typical CAS, the headend scrambles content and data using a control word (CW), where the control word is encrypted with an authentication key and the authentication key is encrypted with a distribution key.

Thereafter, the control word and the authentication key are included in a predetermined message (eg, a qualification control message or a qualification management message) and transmitted to the set-top box.

When the set-top box receives the scrambled transport stream (scrambled content), the set-top box decrypts the authentication key with the distribution key and obtains a control word with the decrypted authentication key. The set-top box descrambles the scrambled transport stream through the obtained control word and outputs the signal as a viewable form.

In general, the set-top box has a module for supporting the CAS function in an embedded manner to perform descrambling of the transport stream as described above.

Recently, a core function for descrambling, namely, a downloadable conditional access system (DCAS) method, which provides a CAS client that obtains a control word through a credential control message or a credential management message provided through a data channel, is downloaded from a server. have.

DCAS is a security framework for securely deploying client software of security solutions for the protection of new video systems and media technologies to set-top boxes. The introduction of new CAS and aging CAS on networks of multiple service operators (MSOs) The solution was developed to reduce the difficulty of upgrading.

These DCAS support the use of DCAS hosts, including Data Over Cable Service Interface Specification (DOCSIS) two-way communications, Conditional Access (CA) tunnels using specified DCAS identities, and hardware, software, and Secure Micro (SM) clients that comply with DCAS standards. On the premise.

The DCAS host includes an SM module including an SM boot loader and a DCAS host module including a DCAS manager and an SM driver.

When a scrambled transport stream is received at the headend, the CAS client included in the SM module acquires a control word using the credential control message and the credential management message as described above, and the control obtained from the CAS client. The word is passed to the Transport Processor (TP) via the DCAS Manager.

The transmission processor is a hardware device including a descrambler and performs descrambling (decoding) of the transport stream using the control word transmitted as described above.

In this case, the control word is essential information for decrypting the content and must be transmitted in a state where the secret is guaranteed from the SM module to the transmission processor.

The SM module is a processor that stably provides a DCAS service such as performing a DCAS protocol, generating and storing key and secret information, and storing SM client related data and codes including a CAS client.

Such an SM module may be a secure processor that includes a secure storage medium.

However, since the transfer processor is easier to copy than the SM module and can be modified for illegal use of contents for malicious purposes, it is necessary to determine whether the transfer processor is duplicated in the DCAS host. There is a need to enhance the security of messages that are passed between them.

In particular, the existing open cable-based set-top box stipulates that smart card and POD (Point of Deployment) module containing subscriber information can be separated / mounted from the set-top box.

In accordance with the provision of the POD module, in a conventional open cable-based set-top box, a transport stream (Scrambled Stream) is input to an independent POD module (Point of Deployment) connected with a smart card, and descrambling of the transport stream is performed in the POD module.

Unlike conventional open cable-based set-top boxes, in DCAS, a secure channel between the two is essential because the transmitting processor for descrambling and the CAS client acquiring control words operate on physically different processors.

That is, in the DCAS, important information such as control words must be transferred from the SM modules that are physically separated from each other, so that a secure channel needs to be formed between them.

The present invention, in order to solve the problems of the prior art as described above, proposes a DCAS host device and a method for strengthening the security of the stable security channel is formed between the transmission processor and the SM module in the DCAS.

Another object of the present invention is to provide a DCAS host device and a method for enhancing security thereof, which can enhance internal security without increasing costs.

In order to achieve the above object, according to a preferred embodiment of the present invention, a DCAS host apparatus, comprising: a transport processor for receiving a transport stream from a headend; A transport processor driver controlling the transport processor; A memory for storing a certificate corresponding to the transmission processor; And a Secure Micro Boot-loader for authenticating the transport processor driver based on the certificate. When the authentication is completed, the SM client and the SM are configured using a security key generated according to a preset algorithm. A DCAS host device is provided in which a secure channel is formed between transport processors.

According to another aspect of the present invention, as a method for enhancing security of a downloadable conditional access system (DCAS) host, at least one of a transport processor driver and a secure micro boot-loader for controlling a transport processor may be used. Storing a certificate for; And establishing a secure channel between the Secure Micro (SM) client and the transport processor based on the certificate, wherein the SM client includes a Conditional Access System (CAS) client, a Digital Rights Management (DRM) client, and an ASD ( Provided are a method for enhancing DCAS host security including at least one of Authorized Service Domain) clients.

According to the present invention, since authentication between the transmission processor and the SM module is performed using a predetermined certificate, there is an advantage that the security inside the DCAS host can be enhanced.

In addition, according to the present invention, a security key is generated by combining random numbers generated by the transmission processor and the SM module, respectively, and through this, encryption and decryption of messages transmitted and received between the transmission processor and the SM client can be performed. There are advantages to it.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In describing the drawings, similar reference numerals are used for similar elements.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

 Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, the same reference numerals will be used for the same means regardless of the reference numerals in order to facilitate the overall understanding.

1 is a diagram illustrating a DCAS-based broadcast service providing system according to an exemplary embodiment of the present invention.

As shown in FIG. 1, the system according to the present invention includes a head-end 100, a downloadable conditional access system (DAS) server 102, a certificate management server 104, and a DCAS host 106. can do.

The headend 100 receives content from a content provider and encodes the content in a preset format.

In addition, the headend 100 performs scrambling (encryption) of the content according to a preset conditional access algorithm and transmits the scrambled content to the DCAS host 106.

The DCAS server 102 transmits and receives a predetermined message with the DCAS host 106 and performs authentication of the DCAS host.

Although the DCAS server 102 is shown separately from the headend 100 in FIG. 1, this is for convenience of description only, and it is understood that the DCAS server 102 may belong to an infrastructure of the headend 100. It will be obvious to you.

DCAS server 102 allows only legitimate subscribers to view content through authentication of DCAS host 106.

The DCAS host 106, which has been authenticated through the DCAS server 102, tunes, descrambles, and displays the transport stream received from the headend 100.

Here, the DCAS host 106 downloads the CAS client from the DCAS server 102, including the DCAS host module and the Secure Micro (SM) module, as described below.

When the scrambled transport stream is received from the headend 100, the DCAS host 106 performs descrambling of the transport stream based on the DCAS host module, the SM module, and the CAS client.

In the general DCAS host 106, the control word is obtained from a CAS client included in the SM module, and the obtained control word is transferred to a transport processor (TP) via the SM module and the DCAS host module.

As mentioned above, in the DCAS host 106, the acquisition of control words and descrambling using them operate on physically different processors, and thus must increase security between the SM module and the transmitting processor.

According to an exemplary embodiment of the present invention, the DCAS host 106 stores a certificate for the transport processor or the SM module in a separate memory, and if necessary, a secure channel is established between the transport processor and the SM module based on the stored certificate. To form.

Here, the certificate is provided from the certificate management server 104, and may include the ID, serial number, validity period, etc. of the device to which the certificate is assigned.

In the DCAS host 106 according to the present invention, a certificate including an ID relating to a transmission processor is stored, and when the DCAS host 106 is booted, the SM module determines whether the transmission processor is valid through the above certificate, that is, It is determined whether the transmission processor is a duplicate.

On the other hand, the DCAS host 106 stores a certificate containing an ID for an SM module (more specifically, an SM boot loader), and the transmission processor determines whether the SM module is valid through the above certificate. .

In this case, the validity of the certificate corresponding to the transport processor and the SM module may be determined through a certificate revocation list (CRL) provided by the certificate management server 104.

The certificate revocation list may include information on the ID of the transmission processor or the SM module and the current status of the certificate. The certificate revocation list may further include information on the certificate revocation reason, the certificate issue date, and the issuer.

After the mutual authentication between the transmission processor and the SM module is completed, a secure channel may be formed between the two. After the secure channel is formed, information to be kept confidential may be stably transmitted from the SM module to the transmission processor.

Hereinafter, a detailed configuration of a DCAS host and a security hardening method according to the present invention will be described in detail with reference to FIGS. 2 to 5.

2 is a diagram illustrating a component configuration of a DCAS host according to the present invention.

Referring to FIG. 2, the DCAS host according to the present invention may include an SM module 200, a DCAS host module 210, and a transmission processor 220.

The SM module 200 obtains the control word through the entitlement control message or the entitlement management message and transfers the control word to the DCAS host module 210 and performs a function related to authentication of the DCAS host 106.

The SM module 200 may be provided in the form of an on-board type chip, but is preferably downloaded from the DCAS server 102 or included in an external security processor (eg, a USB dongle type security processor). Can be provided.

The SM module 200 may include a DCAS monitor 202 and an SM boot-loader 204.

The DCAS monitor 202 performs message routing between the SM boot loader 204 or SM client 206 and the SMD (SM Driver) 216 of the DCAS host module 210.

The SM boot loader 204 checks the SM client in a situation where the SM module is driven, and transmits and receives a message for authentication with the DCAS server 102.

The DCAS host module 210 performs routing and network resource management of messages destined for the SM module 200 or messages transmitted from the SM module 200.

The DCAS host module 210 may include a conditional access network handler (CANH) 212, a DCAS manager 214, a SMD 216, and a transmission processor driver (TPD) 218.

The conditional access network handler 212 controls connection establishment with a network capable of supporting CAS, and controls the network processing environment in which a particular network sending a message to the DCAS host 106 is required to process the message.

DCAS manager 214 manages all DCAS functions within DCAS host 106. DCAS manager 214 interfaces with conditional access network handler 212, SMD 216, and transmit processor driver 218, which DCAS manager 214 sends messages from SM module 200 or from SM module 200. Routing, filtering, and queuing of forwarded messages are performed.

The transport processor driver 218 connected to the DCAS manager 214 is software for controlling the transport processor 220 configured as hardware, and transmits the control word obtained from the CAS client among the SM clients 206 to the transport processor 220. do.

Here, the SM client 206 may include a Conditional Access System (CAS) client, a Digital Rights Management (DRM) client, and an Authorized Service Domain (ASD) client, which will be described below based on descrambling of the transport processor 220. As will be described, the description will focus on the establishment of a secure channel between the transport processor 220 and the CAS client.

The transport processor 220 descrambles the transport stream using the control word transmitted through the transport processor driver 218.

According to one preferred embodiment of the present invention, to enhance the security of the DCAS host 106 at low cost, the transport processor driver 218 may be modified to modify the SM client 206 of the transport processor 220 and the SM module 200. Allow secure channels to be established between them.

According to the present invention, a certificate corresponding to the transmission processor 220 is stored in the memory 230 connected to the transmission processor driver 218, and a certificate corresponding to the SM module is stored in the SM boot loader 204.

At this time, the certificate of the SM boot loader 204 may also be stored in the memory 230.

As shown in Fig. 3, the DCAS host 106 has a transport processor driver 218 and an SM boot loader 204 has a certificate (TP_Certi./SM_Certi) having IDs (TP_ID and SM_ID) as Distinguished Names (DNs). .) Is stored, and the transmission processor driver 218 and the SM bootloader 204 perform mutual authentication through the above-described certificate.

Mutual authentication for each counterpart is performed, and when authentication is completed, a secure channel is established between the transmission processor 220 and the CAS client.

4 is a diagram illustrating a module configuration of a transmission processor driver according to the present invention, and FIG. 5 is a diagram illustrating a module configuration of an SM boot loader according to the present invention.

6 is a flowchart illustrating a certificate-based security hardening process according to the present invention.

Hereinafter, the configuration and security enhancement process of the transport processor driver and the SM boot loader will be described in detail with reference to FIGS. 4 to 6.

First, as shown in FIG. 4, the transmission processor driver according to the present invention includes a random number generation module 400, an authentication request module 402, an SM authentication processing module 404, a security key generation module 406, and a decryption module. 408 may include.

On the other hand, as shown in Figure 5, SM boot loader 204 according to the present invention is a TP authentication processing module 500, random number generation module 502, authentication response module 504, security key generation module 506 And secure key delivery module 508.

4 through 6, first, the random number generation module 400 of the transmission processor driver generates a first random number Rand_TP when the DCAS host 106 boots (step 600). The first random number is later used for key sharing for secure channel formation.

The authentication request module 402 sends an authentication request message of the transmitting processor to the SM boot loader 204 (step 602).

The authentication request message may include a first random number generated as described above and a certificate stored in the memory 230, that is, a certificate corresponding to the transmission processor.

The TP authentication processing module 500 of the SM boot loader 204 compares the certificate included in the authentication request message with a pre-stored certificate revocation list and determines whether the certificate is valid (step 604).

If it is determined that the certificate corresponding to the transmission processor is valid, the random number generation module 502 of the SM boot loader 204 generates a second random number Rand_SM (step 606).

The authentication response module 504 of the SM boot loader 204 transmits an authentication response message including a certificate corresponding to the SM boot loader and the second random number generated in step 606 to the transmitting processor driver 218 ( Step 608).

When the authentication regarding the transport processor in the SM boot loader 204 is completed as described above, the SM authentication processing module 404 of the transport processor driver 218 generates a certificate and a certificate revocation list transmitted from the SM boot loader 204. The validity of the certificate is determined (step 610).

When mutual authentication is completed between the transmission processor driver 218 and the SM boot loader 204 through the above-described steps, the security key generation module 406 of the transmission processor driver 218 may have a first random number and a second random number. The first security key is generated using the number (step 612).

The first security key may be generated by calculating the first random number and the second random number through a preset logical operation scheme.

In addition, the security key generation module 506 of the SM boot loader 204 also generates a second security key using the first random number and the second random number (step 614).

Here, since the operation method for generating the second security key may be the same as in operation 612, the first and second security keys generated by the transmission processor driver 218 and the SM boot loader 204 may be the same.

Meanwhile, the security key delivery module 508 of the SM boot loader 204 transfers the generated second security key to the CAS client (step 616).

When a control word is obtained from the entitlement control message and the entitlement management message received from the headend 100, the CAS client generates a secure message using the second security key and transmits it to the transmission processor driver 218 (step). 618).

Here, the security message includes a control word and is a message encrypted through the second security key.

When the security message is received, the decryption module 408 of the transmit processor driver 218 decrypts the security message using the first security key generated in step 612 (step 620).

The control word is extracted by step 620, and the transmit processor driver 218 transfers the extracted control word to the transmit processor 220 (step 622).

The transport processor 220 performs descrambling of the scrambled transport stream via the transferred control word (step 624).

According to the present invention, a secure channel is formed between a transport processor and a CAS client through a certificate, and in particular, a control word requiring security is provided to the transport processor by encrypting / decrypting a security word generated through mutual authentication and a random number. This allows a third party to respond to unauthorized duplication of the transmission processor.

On the other hand, the above has been described mainly for the CAS client of the SM client, it will be apparent to those skilled in the art that a secure channel with the transport processor can be formed in the same manner in the case of the DRM client and ASD client without being limited thereto.

Preferred embodiments of the present invention described above are disclosed for purposes of illustration, and those skilled in the art will be able to make various modifications, changes, and additions within the spirit and scope of the present invention. Additions should be considered to be within the scope of the following claims.

1 is a diagram illustrating a system for providing a DCAS-based broadcast service according to an embodiment of the present invention.

2 illustrates a component configuration of a DCAS host according to the present invention.

3 is a schematic diagram illustrating a mutual authentication process between a transport processor driver and an SM boot loader according to the present invention.

4 is a diagram illustrating a module configuration of a transmission processor driver according to the present invention.

5 is a diagram illustrating a module configuration of an SM boot loader according to the present invention.

6 is a flowchart illustrating a secure channel formation process according to the present invention.

Claims (15)

In the DCAS host device, A transport processor for receiving a transport stream from the headend; A transport processor driver controlling the transport processor; A memory for storing a certificate corresponding to the transmission processor; And Including a SM Boot Loader (Secure Micro Boot-loader) for authenticating the transport processor driver based on the certificate, The SM bootloader transmits an authentication response message to the transport processor driver when authentication of the transport processor driver is completed. The transport processor driver authenticates the SM boot loader based on a certificate corresponding to the SM boot loader included in the authentication response message. When mutual authentication is completed, a secure channel is formed between the SM client and the transmission processor using a security key generated according to a predetermined algorithm. The method of claim 1, The transmission processor driver transmits an authentication request message including the certificate and the first random number to the SM boot loader. The method of claim 2, The SM boot loader determines whether the certificate included in the authentication request message is valid using a certificate revocation list received from a certificate management server. The method of claim 3, And transmitting the authentication response message to the transmission processor driver including a second random number and a certificate corresponding to the SM boot loader. The method of claim 4, wherein The transmission processor driver determines whether the certificate corresponding to the SM boot loader is valid using the certificate revocation list. The method of claim 5, And when the certificate included in the authentication response message is determined to be valid, the transmission processor driver generates a first security key using the first and second random numbers. The method of claim 4, wherein When it is determined that the certificate included in the authentication request message is valid, the SM boot loader generates a second security key using the first and second random numbers, and converts the generated second security key to the SM client. DCAS host device transmitting. The method of claim 7, wherein The SM client includes at least one of a conditional access system (CAS) client, a digital rights management (DRM) client, and an authorized service domain (ASD) client, and transmits a security message to the transport processor driver using the second security key. DCAS host device transmitting. The method of claim 8, And when the SM client is a CAS client, the CAS client transmits a security message obtained by encrypting a control word obtained from a credential control message and a credential management message to the transport processor driver. The method of claim 8, The transmission processor driver, when the security message is received, decrypts the security message using the first security key. delete A method of hardening a downloadable conditional access system (DCAS) host. Storing a certificate of each of a transport processor driver and a secure micro boot-loader for controlling the transport processor; And Forming a secure channel between a Secure Micro (SM) client and the transport processor based on the respective certificate, The SM client includes at least one of a conditional access system (CAS) client, a digital rights management (DRM) client, and an authorized service domain (ASD) client. The method of claim 12, The secure channel forming step, The SM boot loader determines whether a certificate corresponding to the transport processor driver is valid, and uses a first random number transmitted by the transport processor driver and a second random number generated when the certificate is valid, to secure a first security. DCAS host hardening method comprising the step of generating a key. The method of claim 13, The secure channel forming step, Determining, by the transmission processor driver, whether a certificate corresponding to the SM boot loader is valid and generating a second security key using the second random number and the first random number transmitted by the SM boot loader; How to harden DCAS host security. The method of claim 14, The secure channel forming step, Generating, by the SM client, a security message using the second security key; And And transmitting, by the transport processor driver, the security message using the first security key.

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