KR20100105322A - Dcas, sm, tp and method for certificating security - Google Patents

Abstract

PURPOSE: A DCAS, SM, TP and a method for certificating security are provided to form a safe security environment by using a security protocol module in which mutual authentication and a security channel between a security module and a transmission process module are formed. CONSTITUTION: A security module fairing part transmit a key request message including security module(44-44n) and a transmission process module(46-46n). The security module fairing part receives a key response message including an encoding seed key from a head end. The secure module key generating unit transmits the contents encryption key based on the encoding seed key to the transmittal module. The secure module key generating unit receives the contents encryption key of the transport module. The security module encryption unit compares the contents encryption key with the contents encryption key.

Description

Receiving restriction system, security module, transmission processing module and security authentication method using same {DCAS, SM, TP and method for certificating security}

One aspect of the present invention relates to a security technology, and more particularly, to a security protocol technology in a download-type conditional access system.

This study is derived from the research conducted as part of the IT growth engine technology development project of the Korea Communications Commission. [Task Management Number: 2007-S-007-03, Assignment Name: Downloadable CA System Development]

The Downloadable Conditional Access System (DCAS) allows users to freely purchase set-top boxes (STBs) through retail, regardless of the Multiple System Operators (MSOs) that cable service subscribers subscribe to. Makes it possible. DCAS also ensures that subscribers continue to use paid cable services even if they change their MSOs, without replacing their STBs. DCAS also allows cable operators to replace CAS with another company's products without replacing the STBs already distributed.

The above advantages can be found in applications requiring security, such as Conditional Access System (CAS) applications, Digital Rights Management (DRM) applications or Authorized Service Domain (ASD) applications. Not only do they safely download images from the MSO to the Secure Micro (SM), a security chip in the STB, but also because the MSO allows applications to be installed and replaced online.

In accordance with an aspect, a security protocol technique for ensuring a secure security environment between a security module and a transmission processing module of a download-type reception restriction system is proposed.

According to an aspect of the present invention, there is provided a security authentication method of a security module with a transmission processing module of a security module, the method including: receiving a validation message including an encryption seed key for an identifier pair of the security module and the transmission processing module; Generating a content encryption key based on the key and encrypting the data transmitted to the delivery processing module using the content encryption key.

Meanwhile, the security module according to another aspect encrypts and transmits a key request message including an identifier pair of the security module and the transmission processing module to the headend, and sends a key response message including an encryption seed key for the identifier pair from the headend. The security module pairing unit receives the security module key generation unit based on the encryption seed key, generates a content encryption key and transmits the content encryption key to the transmission processing module, and receives the content encryption key generated by the transmission module. And a security module encryption unit for comparing the content encryption key generated by the security module key generator and encrypting the data transmitted to the transmission processing module.

Meanwhile, when the transmission processing module according to another aspect receives an authentication request message including the authentication information of the security module, the transmission processing module transmits an authentication response message including the authentication information of the transmission processing module to the security module, and sends the security module and the security module to the security module. Transmission processing module pairing unit for receiving the encryption seed key for the identifier pair of the transmission processing module, the transmission processing module key generation unit for generating a content encryption key using the encryption seed key and transmitting to the security module and the content transmitted to the security module If the encryption key is the same as the content encryption key generated in the security module includes a transmission processing module encryption unit for sharing it with each other and encrypting the data transmitted to the security module.

On the other hand, in the download-type receiving limit system according to another aspect, the security device of the set-top box generates a security module content encryption key based on a validation message including an encryption seed key for an identifier pair of the security module and the transmission processing module. Receiving the encryption seed key from the security module and the security module that encrypts the data transmitted to the transmission processing module using the security module content encryption key, and generating the transmission processing module content encryption key using the encryption seed key. And a transmission processing module for encrypting data transmitted to the security module using the encryption key.

According to an embodiment, a secure security environment may be configured through a security protocol that forms mutual authentication and a secure channel between the security module and the transmission processing module.

Furthermore, malicious attacks on the security module and the transmission processing module can be prevented based on the secure mutual authentication and security channel configuration between the security module and the transmission processing module. For example, a hacker may block an attempt to illegally connect a security module with a transmission processing module of another set-top box, or may block a hacked transmission processing module from maliciously attempting to extract security information of the security module.

Furthermore, the security of the application can be strengthened by verifying the integrity of the application running on the security module based on the authentication of the security module and the transmission processing module.

Hereinafter, with reference to the accompanying drawings will be described embodiments of the present invention; In the following description of the present invention, if it is determined that detailed descriptions of related well-known functions or configurations may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. In addition, terms to be described below are terms defined in consideration of functions in the present invention, which may vary according to intention or custom of a user or an operator. Therefore, the definition should be made based on the contents throughout the specification.

1 is a block diagram of a download-type reception limiting system 1 according to an embodiment of the present invention. Referring to FIG. 1, the downloadable reception restriction system 1 includes a certification authority 10, a comprehensive cable broadcasting company 20, and a set top box 40, and the set top box 40 includes a security module 44 and A transfer processing module 46.

The downloadable conditional access system (DCAS) is a security module that allows an application to be installed in the set-top box 40, rather than providing a pay broadcasting service by a CAS operator installing an application on a smart card or a PCMCIA card. (Secure Micro: SM) 44 is mounted. Accordingly, even if the application is renewed through the hybrid fiber coat (HFC) 30 or the multiple system operator (MSO) 20 is changed, the set-top box 40 is continuously replaced. Paid cable service is available.

In the present invention, a multiple system operator (MSO) corresponds to a headend device of the DCAS 1, and the set top box 40 corresponds to a host device of the DCAS 1. In this case, a communication mechanism related to security protocols and procedures for messages transmitted and received between the headend device and the host device is defined as a DCAS security protocol.

The Trusted Authority (TA) 10 is an independent authority and performs authentication roles of the Secure Micro (SM) 44 and the Transport Processor (TP) 46 of the set-top box 40. do. Further, the TA 10 performs initialization on the SM 44 and the TP 46 as well as authentication on the SM 44 and the TP 46. In this case, the local key server (LKS) may replace the TA 10 according to the configuration and operation policy of the DCAS (1).

The multiple system operator (MSO) 20 includes an authentication proxy (AP), a personalization server (PS), and a conditional access system ( CAS ) . The AP acts as an agent of the TA 10, and the PS manages an image of an application to be transmitted to the set top box 40.

The set top box 40, which is a host device, includes an SM 44 and a TP 46. The SM 44 is a security chip that stores and runs applications including CA applications, DRM applications, and ASD applications, and stores and manages various paid viewing credentials. The TP 46, which is a descrambler chip, descrambles and restores broadcast information received through the MSO 20, which is a headend device.

On the other hand, one of the security requirements considered important in DCAS 1 is the security authentication problem between SM 44 and TP 46. This problem is also referred to as a pairing problem between the SM 44 and the TP 46. If pairing is not performed properly, it can cause serious problem in Control Word (CW) hacking. For example, the hacked TP 46 may intercept the CW delivered by the SM 44 via an impersonation attack to the SM 44. In this case, a hacker uses the intercepted CW to watch a paid broadcast without permission.

In addition, when pairing is not performed properly, a paid viewer management problem may occur. For example, a hacker may install a CA application and disconnect the SM 44 storing paying viewing credentials from one set-top box, and then connect to another set-top box without viewing qualifications to watch paying broadcasting. have. This causes business losses because the MSO 20 cannot properly perform the paid subscriber management.

Accordingly, the present invention proposes a security protocol that can solve the mutual authentication and secure channel configuration problem between the SM 44 and the TP 46, which is one of the security requirements of the DCAS (1). By providing a secure security environment between the SM 44 and the TP 46 through the aforementioned security protocol, a user illegally connects the SM 44 with the TP 46 of another set-top box 40 or hacks the TP. It is possible to block the phenomenon in which the 46 46 maliciously extracts the security information of the SM 44.

2 to 4 are flowcharts illustrating a security authentication method between the SM 44 and the TP 46 according to an embodiment of the present invention.

2 to 4, a security authentication method using a security protocol between the SM 44 and the TP 46 includes an initialization step, a pairing step, and a key generation step. First, a local key server LKS may replace TA 10. The headend device includes a TA 10 and an MSO 20, and the set top box as a host device includes an SM 44 and a TP 46. In this case, the MSO 20 targets an authentication proxy (AP) serving as an agent of the TA 10.

Initialization is a step of determining the starting point of the security protocol between the SM 44 and the TP 46. In the pairing step, when the SM 44 transmits identification information of the SM 44 and the TP 46 to the head end, the head end determines the validity of the identification information. In this case, when the identification information of the SM 44 and the TP 46 is valid, the headend manages the SM 44 and the TP 46 as a pair. The headend then sends a validation message including the encryption seed key to the SM 44.

The key generation step is a step in which the SM 44 and the TP 46 generate a content key encryption key (CKEK) to encrypt each other's traffic, thereby encrypting each other's traffic. The CKEK generated at the SM 44 is the same as the CKEK generated at the TP 46 when the SM 44 and the TP 46 are paired. Hereinafter, each step of the security authentication method using the aforementioned security protocol will be described in detail with reference to the accompanying drawings.

2 is a flowchart illustrating an initialization method for security authentication between the SM 44 and the TP 46 according to an embodiment of the present invention.

Referring to FIG. 2, the initialization step is a step of determining a start time of a security protocol between the SM 44 and the TP 46 when a preset initialization condition is met. Here, the initialization condition is that when the power is newly applied or reset to the SM 44 (200), when the new boot (200), the SM 44 in a virgin state (virgin) in a security broadcast message (Security Announce message) from the AP (20) It may be one of the case of receiving 210 or the case of receiving a client update through a download message (DCASDownload message) from the AP 20 in a state in which the SM 44 is not virgin (220). The client may be a CAS client, a DRM client, or an ASD client, but is not limited thereto.

On the other hand, if the above-described initialization condition is met, the SM 44 generates a TPCertReq message 230 including the authentication information (X.509 CERTIFICATE_SM) of the SM 44 and transmits it to the TP 46. . Then, the TP 46 receiving the authentication request message 230 from the SM 44 verifies the certificate signature using the TA root certificate. At this time, if the verification is successful, the TP 46 stores the SM 44 authentication information (X.509 CERTIFICATE_SM) in the nonvolatile memory of the TP 46.

Subsequently, the TP 46 generates and transmits an authentication response message (TPCerRsp message) 240 including the TP 46 authentication information (X.509 CERTIFICATE_TP) to the SM 44. Then, the SM 44 receiving the authentication response message 240 from the TP 46 verifies the certificate signature using the TA root certificate. At this time, if the verification is successful, the SM 44 stores the authentication information (X.509 CERTIFICATE_TP) of the TP 46 in the authentication response message 240 in the nonvolatile memory of the SM 44.

3 is a flowchart illustrating a pairing method for security authentication between the SM 44 and the TP 46 according to an embodiment of the present invention.

Referring to FIG. 3, in the pairing step, the SM 44 transmits the SM 44 identification information SM_ID and the TP 46 identification information TP_ID to the AP 20, and validates the validity at the TA 10. It is a decision step. Specifically, the SM 44 encrypts a KeyRequest message 300 including an identifier pair (KeyPairingID) of the SM 44 and the TP 46 to the TA 10 via the AP 20. send. KeyPairingID is a value obtained by concatenating the SM identifier SM_ID and the TP identifier TP_ID, and is generated by the following equation. For example, the KeyPairingID may be a value obtained by concatenating a SM_ID having a size of 40 bytes and a TP_ID having a size of 8 bytes.

KeyPairingID = SM_ID || TP_ID

Meanwhile, the TA 10 receiving the key request message 300 verifies 310 for the KeyPairingID. Upon verification, the TA 10 is the SM 44 and the TP 46 that the TA 10 receives through the key request message 300 and the ID value issued when the SM 44 and the TP 46 are first generated. Compare the ID values of each other. As a result of the comparison, the TA 10 has ID values of the SM 44 and the TP 46 issued by the TA 10 and IDs of the SM 44 and the TP 46 received through the key request message 300. It is determined that the KeyPairingID value is valid only when it matches exactly.

The TA 10 generates a key response message 320 according to the validity determination result of KeyPairingID. At this time, if the KeyPairingID value is valid, the TA 10 generates a key pairing key (KPK) value, which is a seed encryption key, and transmits a validation message 330 indicating the validity to the SM 44 via the AP 20. . In contrast, if the KeyPairingID value is not valid, the TA 10 displays a status message 340 indicating that it is not valid, for example, a message in which all byte values constituting the KPK are set to 0xff. The transmission is made to the SM 44 via the reference numeral 20.

For example, the seed encryption key KPK has a size of 160 bits and may be generated through the following equation. Where H (m) is the SHA1 value for the message m, PRF (X) msb (Y) is the pseudo random function, X is the seed value of the PRF, and the most significant bit of the PRF result value ( MSB) is taken as the number of bits Y.

KPK = PRF (H (Ki ₁ || Ki ₂ || Ki ₃ || SM_ID || TP_ID || RAND _KPK )) _{msb (1 ~ 160)}

4 is a flowchart illustrating a key generation method for security authentication of the SM 44 and the TP 46 according to an embodiment of the present invention.

Referring to FIG. 4, in a key generation step, a content key encryption key (CKEK) is generated to encrypt traffic between the SM 44 and the TP 46. Since the CKEK is generated using the above-described KPK, the SM 44 and the TP 46 may generate the same CKEK only when the SM 44 and the TP 46 are normally paired. CKEK can be generated through the following equation. That is, the CKEK may be formed using the first bit to the 128th bit in order from the most significant bit MSB of the combined value of the KPK, the SM identifier SM_ID, and the TP identifier TP_ID.

CKEK = (KPK || SM_ID || TP_ID) _{msb (1 ~ 128)}

In detail, upon receiving the successful message from the AP 20, the SM 44 generates a CKEK and a hash message authentication key (HMAC_KEY) (400). The SM 44 generates and transmits a CKEK message (CKEKGenInfo messsage) 410 including KPK and HMAC_KEY to the TP 46. At this time, the CKEK message (CKEKGenInfo messsage) 410 is encrypted with the public key of the TP 46, it is digitally signed with the private key of the SM (44). In contrast, when the SM 44 receives a key response message (KeyResponse message) that fails validation, for example, a message in which all byte values of the KPK are '0xff', the KPK having a value of '0xff' is received. Delivers a CKEK message (CKEKGenInfo messsage) 410 including the TP 46 to the TP 46.

According to an embodiment, the HMAC_KEY generated by the SM 44 is a value obtained by SHA1 of a value obtained by concatenating a random number generated by using the RAND function with SM_ID and TP_ID, and may be formed according to the following equation.

HMAC_KEY = H (RAND _HMAC || SM_ID || TP_ID)

Meanwhile, the TP 46 receives the KPK and the HMAC_KEY through the CKEK message 410 transmitted by the SM 44, and then generates the CKEK. In this case, the CKEK is the same as the CKEK generated in the SM 44 when the SM 44 and the TP 46 are paired in pairs.

The TP 46 then forwards the generated CKEK and CKEK acknowledgment message (CKEKGenInfoCnfm message) 420 including the HMAC_KEY to the SM 44. However, the TP 46 terminates the security protocol when all 20 byte values of the KPK received from the SM 44 are '0xff'. At this time, the CKEKGenInfoCnfm message 420 is encrypted with the public key of the SM 44 and digitally signed with the private key of the TP 46.

Subsequently, the SM 44 receiving the CKEKGenInfoCnfm message 420 checks whether the SM 44 is identical to the CKEK and HMAC_KEY generated by the SM 44 itself. Here, SM 44 shares CKEK and HMAC_KEY with TP 46 if they are identical. The SM 44 encrypts the control word, the ADS content key, and the DRM content key with CKEK and transfers the CKEK to the TP 46.

In this case, encryption may be performed on the DLDU content field of the message, and HMAC authentication may be performed on the ALDU header field and the DLDU content field. Meanwhile, the CKEK message (CKEKGenInfo messsage) 410 may perform RSA encryption and RSA digital signature authentication on the DLDU content field of the message. For example, the RSA encryption may use the RSAES_OAEP method, and the RSA digital signature authentication may use the RSASSA-PSS method, but is not limited thereto.

5 is a structural diagram of a message 500 transmitted to a security protocol according to an embodiment of the present invention.

Referring to FIG. 5, a message 500 transmitted to a security protocol according to an embodiment includes an adaptive layer data unit (ALDU) header field 510, a DCAS layer data unit (DLDU) content field 520, and a hashed HMAC. Message Authentication Code) field 530.

Among the messages described above with reference to FIGS. 2 to 4 except for the TPCertReq message 230, the TPCertRsp message 240, and the CKEKGenInfo message 410, the following requirements are required. AES encryption and HMAC authentication are performed accordingly.

That is, in AES encryption, SM 44 and TP 46 selectively perform AES encryption on important fields such as Control Word (CW) in DLDU content 520 using CKEK as encryption key. . Here, the SM 44 and the TP 46 encrypt data transmitted from each other using a content encryption key. For example, the SM 44 and the TP 46 may use the AES 128 Advanced Encryption Standard 128 Electric Code Block (ECB) scheme. The AES 128 ECB encrypts the factors requiring encryption in the message transmitted between the SM 44 and the TP 46 using the aforementioned CKEK as an encryption key. On the other hand, in the HMAC authentication process, the SM 44 and the TP 46 concatenate 160-bit values HMAC- HMAC-SHA1 with the ALDU header 510 and the DLDU content 520 after the DLDU content 520. do.

6 is a block diagram showing an SM 44 according to an embodiment of the present invention. Referring to FIG. 6, the SM 44 includes a security module pairing unit 600, a security module key generation unit 610, a security module encryption unit 620, and a security module control unit 630.

The security module pairing unit 600 transmits an authentication request message (TPCertReq message) including the authentication information (X.509 CERTIFICATE_SM) of the SM 44 to the TP 46 when the preset initialization condition is met. Receive a TPCertRsp message containing authentication information (X.509 CERTIFICATE_TP) of the TP 46 from 46.

When receiving the authentication response message, the security module pairing unit 600 encrypts the key request message including the identifier pair of the SM 44 and the TP 46 and transmits the encrypted key request message to the headend, and encrypts the seed key for the identifier pair. Receive a key response message from the headend that includes an in key pairing key (KPK). The KPK is a key that generates a pseudo random number sequence using the KeyPairingID value as the seed value when the key pairing identifier (KeyPairingID) value in which the SM 44 identifier SM_ID and the TP identifier TP_ID are valid is valid.

The key response message received by the SM 44 according to the validation of the headend's KeyPairingID value includes the KPK if the KeyPairingID is valid. Corresponds to the message.

Meanwhile, the security module key generation unit 610 generates a CKEK message (CKEKGenInfo messsage) including the content encryption key CKEK and the hash message authentication key HMAC_KEY based on the KPK, and transmits the generated CKEK message (CKEKGenInfo messsage) to the TP 46. Here, the CKEK message (CKEKGenInfo messsage) may be encrypted with the public key of the TP 46 and digitally signed with the private key of the SM 44.

The CKEK may be formed using the first to 128th bits in order from the most significant bit (MSB) of a value in which the KPK and the SM identifier (SM_ID) and the TP identifier (TP_ID) are combined. The HMAC_KEY may be a value obtained by taking SHA1 with respect to a value obtained by concatenating a random number generated by using the RAND function with SM_ID and TP_ID.

Thereafter, when the TP 46 generates CKEK and HMAC_KEY, the security module key generation unit 610 receives a CKEK confirmation message (CKEKGenInfoCnfm message) including the above-mentioned keys from the SM 44. The CKEKGenInfoCnfm message may be encrypted with the public key of the SM 44 and digitally signed with the private key of the TP 46. However, the TP 46 terminates the security protocol when all 20 byte values of the KPK received from the SM 44 are '0xff'.

On the other hand, if the security module encryption unit 620 receives the CKEK confirmation message (CKEKGenInfoCnfm message) through the security module key generation unit 610, it is generated by the SM 44 itself through the security module key generation unit 610 Check that it is the same as one CKEK and HMAC_KEY. Here, if the same, CKEK and HMAC_KEY is shared with the TP 46, and the security module encryption unit 620 encrypts the control word, ADS content key and DRM content key with CKEK to transfer to the TP (44).

The security module controller 630 controls the aforementioned security module pairing unit 600, the security module key generation unit 610, and the security module encryption unit 620.

7 is a diagram illustrating a TP 46 according to an embodiment of the present invention. Referring to FIG. 7, the TP 46 includes a transmission processing module pairing unit 700, a transmission processing module key generation unit 710, a transmission processing module encryption unit 720, and a transmission processing module control unit 730.

The transmission processing module pairing unit 700 receives the authentication request message (TPCertReq message) including the authentication information (X.509 CERTIFICATE_SM) of the SM 44, and receives the authentication information (X.509 CERTIFICATE_TP) of the TP 46. The authentication response message (TPCertRsp message) is transmitted to the SM 44.

Subsequently, when validation of the identifier pair (KeyPairingID) of the SM 44 and the TP 46 received from the SM 44 at the headend is performed, the transmission processing module pairing unit 700 receives the KeyPairingID from the SM 44. Receive a CKEK message (CKEKGenInfo messsage) containing an encryption seed key (KPK) and a hash authentication key (HMAC_KEY) for. KPK is a key for generating a pseudo random number sequence using the KeyPairingID value as a seed value when the KeyPairingID value is valid.

Meanwhile, the transmission processing module key generation unit 710 generates a CKEK using the KPK and HMAC_KEY of the CKEK message received from the SM 44. Subsequently, the transmission processing module key generation unit 710 transmits the generated CKEK confirmation message (CKEKGenInfoCnfm message) including the generated CKEK and HMAC_KEY to the SM 44. However, the transmission processing module key generation unit 710 terminates the security protocol when all 20 byte values of the KPK received from the SM 44 are '0xff'. The CKEKGenInfoCnfm message may be encrypted with the public key of the SM 44 and digitally signed with the private key of the TP 46.

The CKEK may be formed using the first bit to the 128th bit in order from the most significant bit MSB of the combined value of the KPK and the SM identifier SM_ID and the TP identifier TP_ID. The HMAC_KEY may be a value obtained by taking SHA1 with respect to a value obtained by concatenating a random number generated by using the RAND function with SM_ID and TP_ID.

Meanwhile, if the CKEK and HMAC_KEY transmitted to the SM 44 are the same as the CKEK and HMAC_KEY of the SM 44, the transmission processing module encryption unit 720 shares them, and encrypts data transmitted to the SM 44. Hash message authentication is performed on the transmitted message.

The transmission processing module controller 730 controls the aforementioned transmission processing module pairing unit 700, the transmission processing module key generation unit 710, and the transmission processing module encryption unit 720.

In summary, using a security protocol between the SM 44 and the TP 46 according to an embodiment enables the mutual authentication and the establishment of a secure channel to configure a secure security environment. At this time, malicious attacks on the SM 44 and the TP 46 may be blocked. For example, a hacker may illegally block an attempt to connect the SM 44 with the TP 46 of another set-top box, and the hacked TP 46 may block an attempt to maliciously extract the security information of the SM 44. Can be. Further, based on the security authentication between the SM 44 and the TP 46, the integrity of the application implemented on the SM 44 may be verified to enhance security of the application.

The embodiments of the present invention have been described above. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the appended claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

1 is a block diagram of a download-type reception restriction system according to an embodiment of the present invention;

2 is a flowchart illustrating an initialization method for security authentication between a security module and a transmission processing module according to an embodiment of the present invention;

3 is a flowchart illustrating a pairing method for security authentication between a security module and a transmission processing module according to an embodiment of the present invention;

4 is a flowchart illustrating a key generation method for security authentication between a security module and a transmission processing module according to an embodiment of the present invention;

5 is a structural diagram of a message transmitted to a security protocol according to an embodiment of the present invention;

6 is a block diagram showing a security module according to an embodiment of the present invention,

7 is a block diagram showing a transmission processing module according to an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

1: Receive Download System 10: Certificate Authority

20: Comprehensive cable broadcasting service provider 30: Guangdong coaxial mixed network

40, 42, 42n: set-top box 44: security module

46: transmission processing module 600: security module pairing unit

610: security module key generation unit 620: security module encryption unit

630: security module control unit 700: transmission processing module pairing unit

710: transmission processing module key generation unit 720: transmission processing module encryption unit

720: transmission processing module control unit

Claims (20)

In the security authentication method with the transmission processing module of the security module in the download-type reception limit system, Receiving a validation message including an encryption seed key for the identifier pair of the security module and the transmission processing module; And Generating a content encryption key based on the encryption seed key, and encrypting data transmitted to the transmission processing module using the content encryption key. The method of claim 1, The encryption seed key is a key pairing key for generating a pseudo random number sequence using the key pairing identifier value as a seed value when a key pairing identifier value combining the identifier of the security module and the identifier of the transmission processing module is valid. Security authentication method. The method of claim 1, And the content encryption key is a value generated using a combination of the encryption seed key, an identifier of the security module, and an identifier of the transmission processing module. The method of claim 1, And an identifier pair of the security module and the transmission processing module is a key pairing identifier in which an identifier of the security module and an identifier of the transmission processing module are combined. The method of claim 1, And a content encryption key generated by the security module is identical to a content encryption key generated by the transmission processing module when the security module and the transmission processing module are paired. The method of claim 1, wherein receiving the validation message comprises: Encrypting a key request message including an identifier pair of the security module and the transmission processing module and transmitting the encrypted key request message to the headend; And And receiving the validation message from the headend, which is a key response message for the key request message. The method of claim 1, wherein encrypting the data transmitted to the transmission processing module comprises: Generating a content encryption key and a hash authentication key and transmitting a message including the encryption seed key to the delivery processing module; If the transmission processing module generates a content encryption key and a hash authentication key using the encryption seed key, receiving the keys from the transmission processing module; And The received content encryption key and hash authentication key are compared with the content encryption key and hash authentication key of the security module, and if they match, the data transmitted to the transmission processing module is encrypted and hashed for the message transmitted to the transmission processing module. Security authentication method comprising the step of performing a message authentication. The method of claim 7, wherein And said hash authentication key is a value obtained by taking SHA1 for a value obtained by concatenating a random number generated by using a RAND function, an identifier of the security module, and an identifier of the transmission processing module. The method of claim 7, wherein And encrypting the data is performed in a DLDU content field of a message transmitted between the transmission processing modules, and the hash message authentication is performed in the DLDU content field and an ALDU header field of the message. The method of claim 1, wherein encrypting the data transmitted to the transmission processing module comprises: And encrypting the data using a symmetric key encryption algorithm. The method of claim 1, And initializing for security authentication between the security module and the transmission processing module. The method of claim 11, wherein the initializing is performed. Transmitting an authentication request message including authentication information of the security module to the transmission processing module if a preset initialization condition is met; And And receiving an authentication response message including the authentication information of the transmission processing module from the transmission processing module. The method of claim 12, wherein the initialization condition, When the security module is powered on or reset and booted up, the security module receives a security broadcast message from the headend or a client update request from the headend through a download message, characterized in that one of the Security authentication method. In the security module for authenticating the security with the transmission processing module in the download-type reception limit system, A security module pairing that encrypts and transmits a key request message including an identifier pair of the security module and the transmission processing module to a headend, and receives a key response message including an encryption seed key for the identifier pair from the headend. part; A security module key generation unit for generating a content encryption key based on the encryption seed key, transmitting the content encryption key to the transmission processing module, and receiving the content encryption key generated by the transmission module; And And a security module encryption unit for comparing the received content encryption key with a content encryption key generated by the security module key generation unit and encrypting data transmitted to the transmission processing module if they match. The method of claim 14, The encryption seed key is a key pairing key that generates a pseudo-random sequence by using the key pairing identifier value as a seed value when a key pairing identifier value in which the security module identifier and the transmission processing module identifier are combined is valid. Security module. The method of claim 14, The content encryption key is a security module, characterized in that the value generated by using the combined value of the identifier of the encryption module, the identifier of the security module and the transmission processing module. The method of claim 14, The security module key generation unit generates a content encryption key and a hash message authentication key, The security module encryption unit encrypts the data transmitted to the transmission processing module by sharing the generated content encryption key and the hash message authentication key with the content encryption key and the hash message authentication key received from the transmission processing module. And a hash message authentication for a message transmitted to a transmission processing module. In the transmission processing module for authenticating the security with the security module in the download-type reception limit system, Upon receiving an authentication request message including authentication information of the security module, an authentication response message including authentication information of the transmission processing module is transmitted to the security module, and the identifier of the security module and the transmission processing module is transmitted from the security module. A transmission processing module pairing unit which receives an encryption seed key for the pair; A transmission processing module key generation unit generating a content encryption key using the encryption seed key and transmitting the generated content encryption key to the security module; And If the content encryption key transmitted to the security module is the same as the content encryption key generated by the security module, and share it, and a transmission processing module encryption unit for encrypting the data transmitted to the security module, characterized in that it comprises a transmission processing module. The method of claim 18, The encryption seed key is a key pairing key that generates a pseudo-random sequence by using the key pairing identifier value as a seed value when a key pairing identifier value in which the security module identifier and the transmission processing module identifier are combined is valid. Transmission Processing Module. In the security device of the set-top box in the download-type reception limit system, A security module content encryption key is generated based on a validation message including an encryption seed key for an identifier pair of a security module and a transmission processing module, and data transmitted to the transmission processing module is generated using the security module content encryption key. A security module for encrypting; And Receiving the encryption seed key from the security module, generating a transmission processing module content encryption key using the encryption seed key, transmission processing for encrypting data transmitted to the security module using the transmission processing module content encryption key Security device of a set-top box, characterized in that it comprises a module.

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