KR20080054033A - Apparatus and method for conditional access - Google Patents

Abstract

A limited reception apparatus and a method thereof are provided to use the same scrambling algorithm, which is used for a limited reception, to prevent duplication. Digital contents are received from the exterior(S400). It is checked whether the inputted digital contents have been set for duplication prevention, and if the digital contents have been set for duplication prevention, DES descrambling is performed(S410,S412,S422,S424). If the digital contents have not been set for duplication prevention, DES descrambling is performed for limited reception coding(S420). The descrambled digital contents are stored in a storage medium after performing DES scrambling(S430,S432,S438,S442). Descrambled digital contents, which have not been stored in the storage unit, are reproduced on a display unit(S440). If a host is connected to an external terminal, it is inquired whether to prevent duplication(S460). DES descrambling is performed on the digital contents to prevent duplication, and the digital contents are outputted(S432,S462).

Description

Apparatus and method for conditional access

1 is a diagram illustrating an internal configuration of a conditional access device in a cable broadcast receiver according to an embodiment of the present invention.

Figure 2 is an exemplary view showing a scrambler / descrambler using Triple DES according to the present invention.

3 is a block diagram showing a conditional access device using Triple DES according to the present invention.

4 is a flowchart illustrating a method of limiting reception using Triple DES according to an embodiment of the present invention.

* Description of the symbols for the main parts of the drawings *

10. Transmitter 11.Scrambler for CAS

20. Cable card 21. Descrambler for CAS

22. Scrambler for Copy Protection 30. Host

31.Display Engine 32.Scrambler for Copy Protection

33. Descrambler for Copy Protection

35.DES scrambler / descrambler 37.Storage

TECHNICAL FIELD The present invention relates to a broadcast receiver, and more particularly, to a limited receiver and a method thereof.

Recently, the technology industry of the content industry has been provided to prevent illegal distribution and duplication of digital content and to consume the content only within the authorized range of authorized users. In addition, the company will focus on developing digital rights management (DRM) -based distribution technology that can be used for a variety of multi-platform terminals such as mobile phones, MP3Ps, STBs (set-top boxes), and digital homes, as well as DRM interworking technologies between these different terminals. In keeping with research. In general, the limited reception service requires an encryption function of a broadcast stream and a management function for checking and authorizing a subscriber's qualification. ATSC and ETSI adopt Triple-DES and DVB common scrambling, respectively, which are used to receive and scramble the scrambled broadcast data. The descrambler of this algorithm must be installed in the user's TV.

Recently, TV broadcasting system has been converted to all-digital transmission method including compression technique of TV signal, and conforming to international standard ISO / IEC 13818-2 for compression of TV signal has become a universal standard for encryption. ought. For example, ETSI established DVB (Digital Video Broadcasting) as the regulation for comprehensive digital broadcasting of European satellite, cable and terrestrial broadcasts.

The limited reception technique for the TV signal can be divided into the following functional aspects. The first is a scrambling technique that transforms the shape of the original program signal, and the second is an entitlement technique that manages the viewing key of each recipient and the related key required for descrambling to restore the modified signal. In the entitlement technology, the entitlement management message (EMM) includes the entitlement control function and the expiration date of the entitlement, including the key used for scrambling and the conditions for acquiring the program in an entitlement control message (ECM). It can be classified into the credential management function. In ECM and EMM, the relevant key necessary for descrambling is encrypted by the appropriate encryption algorithm and transmitted to each receiver.

In order to perform conventional CAS and copy protection, a problem arises in having various scramblers and descramblers. In particular, when viewed from the receiving end, a descrambler for descrambling CAS and copy protected content received from the outside, as well as a scrambler for transmitting to the outside, must be built in. This poses a problem for set-top box manufacturers to have various IPs in their designs.

In particular, since the scrambling algorithm and the corresponding descrambling algorithm are different from each other, when the transmitting end transmits the encrypted data by scrambling using a specific scrambler, the receiving end always performs descrambling using the corresponding descrambler. There is a problem that must be done.

SUMMARY OF THE INVENTION An object of the present invention is to improve an efficient design and use method of CAS and copy protection in order to solve the existing problems for coping with the above-described limited reception (CAS) and copy protection.

In particular, manufacturers related to receivers can efficiently design and use a descrambler for receiving a CAS, a scrambler for a copy protection, and a descrambler, thereby eliminating the need to mount multiple IPs.

The present invention relates to an efficient design for a descrambler and a copy protection required in a conditional access system (CAS) for granting viewing rights only to a user authorized in a digital broadcasting receiver and a method of using the same.

In order to give a right to watch a broadcast to a user authorized in digital TV, an basically required IP called a descrambler is required. Each broadcaster adopts its own CAS to protect the digital contents of the broadcaster, and all CAS adopted by each broadcaster is different, and each CAS company uses a different descrambler. This CAS is a technique used by broadcasters to grant access rights between transmissions and users.

In addition, since the protection of digital content on transmissions such as CAS is not a technology for securely transmitting content between devices or devices, an encryption technology called copy protection is required to securely transfer content between devices. need. This copy protection is used to prevent other users from seeing the copy even when the digital content is transferred between various input and output ports and the digital media such as DVR (Digital Video Recording). .

In the case of CAS, when a broadcaster transmits a broadcast, the technology of a scrambler is required, but from the receiver's point of view, only the descrambler corresponding to the scrambler used by the broadcaster can decode the digital content, thereby enabling access.

Similarly, in the case of copy protection, since digital content to be received from a port such as an input or played on a DVR is scrambled content, a corresponding descrambler is required as in CAS. On the other hand, in order to store content in the DVR or to transmit it securely through an output port or the like, copy protection is required for the content, which requires a scrambler.

According to an aspect of the present invention, there is provided a conditional access device for demodulating a limited reception broadcast signal; A data encryption unit for outputting the demodulated broadcast signal by performing at least one of descrambling and scrambling using one initial substitution data encryption algorithm; A storage unit which stores the scrambled broadcast signal; And a display unit displaying the descrambled broadcast signal.

The data encryption algorithm is characterized in that the Triple DES method.

The apparatus may further include a data connection interface unit for transmitting the scrambled broadcast signal to the outside.

The data encryption unit performs both scrambling and descrambling of the input signal using one initial substitution.

In addition, the present invention provides a method of receiving a broadcast receiver using a data encryption algorithm using one initial substitution, comprising: demodulating the limited reception broadcast signal; Descrambling and outputting the demodulated broadcast signal; Scrambling and storing the output broadcast signal using the data encryption algorithm; And descrambling the stored broadcast signal by using the data encryption algorithm.

The data encryption algorithm is characterized in that the Triple DES method.

The method may further include transmitting the scrambled broadcast signal to the outside using the data encryption algorithm.

The data encryption algorithm is characterized in that scrambling and descrambling are performed in the same order.

According to another aspect of the present invention, there is provided a method of limiting reception, comprising: demodulating encrypted image data; Descrambling and outputting the demodulated image data; Scrambling and storing the output image data using one initial substitution data encryption algorithm; And descrambling the stored image data by using the data encryption algorithm.

The data encryption algorithm is characterized in that the Triple DES method.

The objects, features and advantages of the present invention will be more readily understood by reference to the accompanying drawings and the following detailed description. In describing the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the description thereof will be omitted.

1 is a diagram illustrating an internal configuration of a conditional access device in a cable broadcast receiver according to an embodiment of the present invention.

The transmitter 10 generates and transmits a broadcast signal including a broadcast program and broadcast information. The scrambler for CAS 11 encrypts and outputs a limited reception broadcast signal among the generated broadcast signals.

The cable card 20 is a device that engages with the host 30 to watch digital cable TV and provides user authentication and copy protection. The descrambler for CAS 21 receives the limited reception broadcast signal from the transmitter 10 and performs reverse encryption. The scrambler for Copy Protection 22 encrypts the reverse encrypted broadcast signal using the same limited reception algorithm. At this time, the limited reception algorithm is a data encryption (DES) algorithm using one initial substitution.

The host 30 receives the scrambled broadcast signal for copy protection from the cable card 20 and plays it back through the display unit or is connected to an external device to scramble and output the data. To this end, the host 30 includes a display engine 31, a scrambler for Copy Protection 32, and a descrambler for Copy Protection 33. The descrambler for Copy Protection 33 descrambles and outputs the scrambled broadcast signal transmitted from the cable card 20 using a corresponding data encryption algorithm. The display engine 31 reproduces the broadcast signal from the output descrambled broadcast signal through video / audio signal processing. The scrambler for Copy Protection 32 is connected to an external device (multimedia flare, storage terminal, PMP, etc.) so that the host 30 can scramble the broadcast signal or multimedia data using a corresponding data encryption algorithm for copy protection. do.

2 is an exemplary view showing a scrambler / descrambler using Triple DES according to the present invention.

The encryption algorithm of the limited reception and copy protection according to the present invention uses a Data Encryption Standard (DES) algorithm.

The basic algorithms of encryption used in the Data Encryption Standard (DES) are Permutation and Substitution, which use these two to form a basic step called a round, and these rounds are repeated 16 times to form a single encrypted DES block. Configure

Figure 2a shows the scrambling process of DES, consisting of 16 rounds of repetition. Specifically, in the key generator, 8-bit parity bits are first removed from a 64-bit key, and then an operation key (Ki, i = 1, ..., 16) is generated from the remaining 56 bits and used for data encryption. . The 64-bit plaintext block is divided into 32 bits after initial permutation, and the right 32 bits are expanded with the 48-bit key selected from the 56-bit keys to generate a 48-bit value. After 32 bits are made using the substitution algorithm (S-box), the P-box process is performed once more, and finally a new right 32 bits is formed by exclusive-or with the previous left 32 bits. The previous 32-bit value is the new left 32-bit value. The above process is repeated 16 times, and the right 32 bits and the left 32 bits generated at the end are combined to obtain the final encrypted DES block through an inverse permutation process.

The decryption process of FIG. 2B is almost the same as the encryption process, but there are two differences. The shift of the key is done to the right rather than the left, and the number of bits to be shifted is the reverse of encryption. DES has several operation modes to encrypt the entire data by connecting them properly when the length of data to be encrypted exceeds 64 bits. ECB (Electronic CodeBook) mode, Cipher Block Chaining (CBC) mode, CFB Four modes of operation are used: (Clpher FeedBack) mode and OFB (Output FeedBack) mode.

The alternative to DES being vulnerable to certain data is Triple-DES. Triple-DES decrypts the result encrypted with one key with the other key and encrypts the result with the key previously used for encryption. In FIG. 2 (a, b), the structure of Triple-DES uses the same key as the first for the first and third encryptions. This guarantees even more security with a 112-bit key alone. The second encryption uses the DES decrypt module. If you use Key A and Key B as the same, Triple-DES is equivalent to single DES. Therefore, Triple-DES maximizes security while using the module of single DES as it is.

3 is a block diagram showing a conditional access device using Triple DES according to the present invention.

The scrambler / descrambler for limit reception and copy protection according to the present invention uses a data encryption algorithm (DES) using one initial substitution.

In general, scrambling algorithms generally have a reverse process of performing scrambling and descrambling. However, since the DES scrambler / descrambler 35 according to the present invention is performed in the same order in performing scrambling and descrambling, the DES scrambler / descrambler 35 can perform the role of a scrambler even with one descrambler as shown in FIG. You can do that.

According to the characteristics of the DES, the possible applications in FIG. 3 will be described. In the case of CAS, it is possible to use DES or triple DES as a descrambler. That is, when the scrambler in the CAS used by the broadcaster is DES or Tiple DES, it is possible for the receiving end to operate as the DES descrambler and the Triple DES descrambler. In addition, in case of copy protection, DES and Triple DES can be scrambled with externally to enable copy-protected content to be descrambled by the host. In addition, since it is necessary to perform scrambling when the digital content is to be stored or transmitted by connecting to the DVR and external ports, the scrambling is performed using DES and Triple DES, and then stored in storage (Storage, 37) and externally. Transmission is possible.

4 is a flowchart illustrating a limit reception method using triple DES according to an embodiment of the present invention.

Broadcasters use a scrambler to scramble digital content and send it to the receiver in order to transmit the broadcast safely. In this way, the content sent using the scrambling technology is cleared so that only the receiver having the authority from the broadcasting company can descramble the equipment such as the cable card through the descrambler corresponding to the scrambler used by the sender so that the content can be viewed. To restore its contents. In the case of embedded systems, scrambling allows them to be sent safely to other devices. First, the limited reception and copy protection method of performing a data encryption algorithm using one initial substitution according to the present invention receives digital content from the outside (S400). When copy protection is set by determining whether the input digital content is copy protected, DES descrambling is performed (S410, 412, 422, 424). At this time, the data encryption algorithm follows the Triple DES scheme.

In case of digital content for which copy protection is not set, DES descrambling for limited reception decoding is performed (S420). When the descrambled digital content is stored, after the DES scrambling is performed, the descrambled digital content is stored in the storage medium (S430, 432, 438, 442).

The descrambled digital content not stored in the storage is reproduced on the display unit in operation S440. At this time, if the host and the external terminal is connected to the query whether the copy protection (S460). After the DES scrambling for copy protection, digital content is output to the outside (S432, S462).

On the other hand, the terms used in the present invention (terminology) are terms defined in consideration of functions in the present invention, which may vary according to the intention or custom of the skilled person in the relevant field, the definitions of which are used throughout the present invention. Will have to be laid down as a foundation.

The present invention is not limited to the above-described embodiments and may be variously modified and changed by those skilled in the art, which are included in the spirit and scope of the present invention as defined in the appended claims.

The present invention can use the single IP to perform the role of the scrambler and descrambler to reduce the burden of the design having to have each scrambler and descrambler, a variety of applications with one scrambler and the descrambler IP Has the following effect:

First, it has one scrambling algorithm and provides it for use in response to limited reception.

Secondly, it provides the same scrambling algorithm used for conditional reception and can be used for copy protection.

In addition, it provides a single scrambling algorithm to serve as a scrambler and a descrambler.

Claims (10)

In the limited reception method of a broadcast receiver performing a data encryption algorithm using one initial substitution, Demodulating a restricted reception broadcast signal; Descrambling and outputting the demodulated broadcast signal; Scrambling and storing the output broadcast signal using the data encryption algorithm; And Calling the stored broadcast signal and descrambling using the data encryption algorithm. The method of claim 1, And the data encryption algorithm is a triple DES scheme. The method of claim 1, And transmitting the scrambled broadcast signal to the outside using the data encryption algorithm. The method of claim 1, In the data encryption algorithm, scrambling and descrambling are performed in the same order. A demodulator for demodulating a limited reception broadcast signal; A data encryption unit for outputting the demodulated broadcast signal by performing at least one of descrambling and scrambling using one initial substitution data encryption algorithm; A storage unit which stores the scrambled broadcast signal; And And a display unit for displaying the descrambled broadcast signal. The method of claim 5, And the data encryption algorithm is a triple DES scheme. The method of claim 5, And a data connection interface unit for transmitting the scrambled broadcast signal to the outside. The method of claim 5, And the data encryption unit performs both scrambling and descrambling of the input signal using one initial substitution. Demodulating encrypted image data; Descrambling and outputting the demodulated image data; Scrambling and storing the output image data using one initial substitution data encryption algorithm; And Calling the stored image data and descrambling using the data encryption algorithm. The method of claim 9, And the data encryption algorithm is a triple DES scheme.

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