Abstract:
The present disclosure relates to a 5th-Generation (5G) or pre-5G communication system to be provided to support a higher data rate than a 4th-Generation (4G) communication system like Long Term Evolution (LTE). The present invention provides a method for encrypting a multimedia content comprising: encrypting multimedia contents including a plurality of variants and a plurality of samples; and transmitting the encrypted multimedia contents, wherein the plurality of variants correspond to the samples included in the multimedia contents, respectively, and are configured with reference to a predetermined number of samples, and each of the plurality of variants is configured with reference to a combination of different samples.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
       [0001]    This application is a U.S. National Stage application under 35 U.S.C. §371 of an International application filed on Jul. 13, 2015 and assigned application number PCT/KR2015/007251, which claimed the benefit of a Korean patent application filed on Jul. 15, 2014 in the Korean Intellectual Property Office and assigned Serial number 10-2014-0089234, the entire disclosure of which is hereby incorporated by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure relates to a method and apparatus for encrypting and decrypting multimedia content. 
       BACKGROUND ART 
       [0003]    To satisfy demands for wireless data traffic having increased since commercialization of 4th-Generation (4G) communication systems, efforts have been made to develop improved 5th-Generation (5G) communication systems or pre-5G communication systems. For this reason, the 5G communication system or the pre-5G communication system is also called a beyond-4G-network communication system or a post-long term evolution (LTE) system. 
         [0004]    To achieve a high data rate, implementation of the 5G communication system in an ultra-high frequency (mmWave) band (e.g., a 60 GHz band) is under consideration. In the 5G communication system, beamforming, massive multi-input multi-output (MIMO), full dimensional MIMO (FD-MIMO), an array antenna, analog beamforming, and large-scale antenna technologies have been discussed to alleviate a propagation path loss and to increase a propagation distance in the ultra-high frequency band. 
         [0005]    For system network improvement, in the 5G communication system, techniques such as an evolved small cell, an advanced small cell, a cloud Radio Access Network (RAN), an ultra-dense network, a Device to Device (D2D) communication, a wireless backhaul, a moving network, cooperative communication, Coordinated Multi-Points (CoMPs), and interference cancellation have been developed. 
         [0006]    In the 5G system, Advanced Coding Modulation (ACM) schemes including hybrid Frequency-Shift Keying (FSK) and Quadrature Amplitude Modulation (QAM) Modulation (FQAM) and Sliding Window Superposition Coding (SWSC), and advanced access schemes including Filter Bank Multi Carrier (FBMC), Non-Orthogonal Multiple Access (NOMA), and Sparse Code Multiple Access (SCMA) have been developed. 
         [0007]    Meanwhile, a communication system is continuously evolving to provide various services to users, and representative service types are a broadcast service and a personal data service. 
         [0008]    The broadcast service means a service provided over the wireless Internet, and information related to the broadcast service includes high-speed large-volume information. The personal data service means a service provided to a specific user, and security is important to the personal data service, because personal information may leak when the service is provided. 
         [0009]    However, at present, there is no way to fundamentally prevent and solve information leakage and thus research on the way is needed. 
       DETAILED DESCRIPTION OF THE INVENTION 
     Technical Problem 
       [0010]    The present disclosure proposes a method and apparatus for configuring multimedia content to facilitate detection of falsification of the multimedia content. 
         [0011]    The present disclosure proposes a method and apparatus for encrypting multimedia content which is configured to facilitate detection of falsification of the multimedia content. 
         [0012]    The present disclosure also proposes a method and apparatus for detecting a subject that falsifies multimedia content if the multimedia content is falsified. 
       Technical Solution 
       [0013]    A method for encrypting multimedia content proposed in an embodiment of the present disclosure includes encrypting multimedia content including a plurality of variants and a plurality of samples and transmitting the encrypted multimedia content, in which the plurality of variants correspond to samples in included the multimedia content, respectively, and are configured with reference to a predetermined number of samples, and each of the plurality of variants is configured with reference to a combination of different samples. 
         [0014]    A method for decrypting multimedia content proposed in an embodiment of the present disclosure includes receiving encrypted multimedia content including a plurality of variants and a plurality of samples, detecting and decrypting one of the plurality of variants, comparing a picture related to the decrypted variant with an original picture before being encrypted, and detecting that the multimedia content is falsified, if the picture related to the decrypted variant is different from the original picture, in which the plurality of variants correspond to samples included in the encrypted multimedia content, respectively, and are configured with reference to a predetermined number of samples, and each of the plurality of variants is configured with reference to a combination of different samples. 
         [0015]    An apparatus for encrypting multimedia content proposed in an embodiment of the present disclosure includes a controller configured to encrypt multimedia content including a plurality of variants and a plurality of samples and a transceiver configured to transmit the encrypted multimedia content, in which the plurality of variants correspond to samples in included the multimedia content, respectively, and are configured with reference to a predetermined number of samples, and each of the plurality of variants is configured with reference to a combination of different samples. 
         [0016]    An apparatus for decrypting multimedia content proposed in an embodiment of the present disclosure includes a transceiver configured to receive encrypted multimedia content including a plurality of variants and a plurality of samples and a controller configured to detect and decrypt one of the plurality of variants, to compare a picture related to the decrypted variant with an original picture before being encrypted, and to detect that the multimedia content is falsified, if the picture related to the decrypted variant is different from the original picture, in which the plurality of variants correspond to samples included in the encrypted multimedia content, respectively, and are configured with reference to a predetermined number of samples, and each of the plurality of variants is configured with reference to a combination of different samples. 
         [0017]    Other aspects, advantages, and key features of the present disclosure will be processed together with the attached drawings, and will be apparent to those of ordinary skill in the art from the following detailed description disclosing various embodiments of the present disclosure. 
         [0018]    Before undertaking the DETAILED DESCRIPTION OF THE INVENTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document. 
         [0019]    The terms “include” and “comprise,” as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like. The term “controller” means any device, system or part thereof that controls at least one operation, and such a device may be implemented in hardware, firmware or software, or some combination of at least two of the same. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases. 
       Advantageous Effects 
       [0020]    The present disclosure proposes a method for configuring multimedia content including variants configured with reference to different samples, thereby easily detecting falsification of the multimedia content and easily detecting a subject that falsifies the multimedia content. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0021]      FIG. 1  illustrates an example of encryption of plaintext multimedia content; 
           [0022]      FIG. 2  illustrates an example of decryption of ciphertext multimedia content; 
           [0023]      FIG. 3  illustrates an example where a variant is introduced to encryption and decryption of multimedia content; 
           [0024]      FIG. 4  illustrates an example where variants are configured for some of samples included in multimedia content; 
           [0025]      FIG. 5  illustrates an example where a new variant pattern is generated by mixing variant patterns of multimedia content decrypted with two different licenses; 
           [0026]      FIG. 6  illustrates an example where variants for samples included in multimedia content are configured according to an embodiment of the present disclosure; 
           [0027]      FIG. 7  illustrates an example where variants for samples included in multimedia content are configured according to another embodiment of the present disclosure; 
           [0028]      FIG. 8  illustrates an example where a new variant pattern is generated by mixing variant patterns that form a secret variant relationship; 
           [0029]      FIG. 9  illustrates an example where a decryption device decrypts a variant that forms a secret variant relationship; 
           [0030]      FIG. 10  is a flowchart illustrating a method, performed by an encryption device, for encrypting multimedia content according to an embodiment of the present disclosure; 
           [0031]      FIG. 11  is a flowchart illustrating a method, performed by a decryption device, for decrypting multimedia content according to an embodiment of the present disclosure; 
           [0032]      FIG. 12  is a block diagram illustrating an internal structure of an encryption device that encrypts multimedia content according to an embodiment of the present disclosure; and 
           [0033]      FIG. 13  is a block diagram illustrating an internal structure of a decryption device that decrypts encrypted multimedia content according to an embodiment of the present disclosure. 
       
    
    
     MODE FOR CARRYING OUT THE INVENTION 
       [0034]    Hereinafter, embodiments of the present disclosure will be described in detail with reference to the attached drawings. Moreover, a detailed description of well-known functions or elements associated with the present disclosure will be omitted if it unnecessarily obscures the subject matter of the present disclosure. Further, the terminologies to be described below are defined in consideration of functions in the present disclosure and may vary depending on a user&#39;s or operator&#39;s intention or practice. Therefore, the definitions should be made based on the contents throughout the entire description of the present disclosure. 
         [0035]    Various changes may be made to the present disclosure and the present disclosure may have various embodiments which will be described in detail with reference to the drawings. However, the embodiments according to the concept of the present disclosure are not construed as limited to specified disclosures, and include all changes, equivalents, or substitutes that do not depart from the spirit and technical scope of the present disclosure. 
         [0036]    It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a component surface” includes reference to one or more of such surfaces. 
         [0037]    Although the terms such as “first” and “second” used in the various exemplary embodiments of the present disclosure may modify various elements of the various exemplary embodiments, these terms do not limit the corresponding elements. These terms may be used for the purpose of distinguishing one element from another element. For example, a first element may be named as a second element without departing from the right scope of the various exemplary embodiments of the present disclosure, and similarly, a second element may be named as a first element. The term “and/or” includes a combination of a plurality of related provided items or any one of the plurality of related provided items. 
         [0038]    The terms used in the various exemplary embodiments of the present disclosure are for the purpose of describing particular exemplary embodiments only and are not intended to be limiting. The singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. The term “include” or “has” used in the exemplary embodiments of the present disclosure is to indicate the presence of features, numbers, steps, operations, elements, parts, or a combination thereof described in the specifications, and does not preclude the presence or addition of one or more other features, numbers, steps, operations, elements, parts, or a combination thereof. 
         [0039]    All of the terms used herein including technical or scientific terms have the same meanings as those generally understood by an ordinary skilled person in the related art unless they are defined other. The terms defined in a generally used dictionary should be interpreted as having the same meanings as the contextual meanings of the relevant technology and should not be interpreted as having ideal or exaggerated meanings unless they are clearly defined in the various exemplary embodiments. 
         [0040]    An electronic device according to various embodiments of the present disclosure may be a device including a communication function. For example, an electronic device may include a smartphone, a tablet personal computer (PC), a mobile phone, a video phone, an electronic-book (e-book) reader, a desktop PC, a laptop PC, a netbook computer, a workstation, a server, a personal digital assistant (PDA), a portable multimedia player (PMP), an MP3 player, a mobile medical equipment, a camera, and a wearable device (e.g., a head-mounted device (HMD), electronic clothing, an electronic bracelet, an electronic necklace, an electronic appcessory, an electronic tattoo, or a smart watch. 
         [0041]    According to some embodiments, the electronic device may be a smart home appliance having a communication function. For example, the smart home appliance may include a TV, a digital video disk (DVD) player, audio equipment, a refrigerator, an air conditioner, a vacuum cleaner, an oven, a microwave oven, a washer, a drier, an air cleaner, a set-top box, a TV box (e.g., HomeSync™ of Samsung, TV™ of Apple, or TV™ of Google), a game console, an electronic dictionary, a camcorder, and an electronic frame. According to various embodiments of the present disclosure, the electronic device may include various medical equipment (for example, magnetic resonance angiography (MRA), magnetic resonance imaging (MRI), computed tomography (CT), an imaging device, or an ultrasonic device), a navigation system, a global positioning system (GPS) receiver, an event data recorder (EDR), a flight data recorder (FDR), a vehicle infotainment device, electronic equipment for ships (e.g., a navigation system and gyro compass for ships), avionics, a security device, an industrial or home robot, and so forth. 
         [0042]    According to some embodiments, the electronic device may include a part of a furniture or building/structure having a communication function, an electronic board, an electronic signature receiving device, a projector, and various measuring instruments (for example, a water, electricity, gas, or electric wave measuring device). 
         [0043]    The electronic device according to various embodiments of the present disclosure may be one of the above-listed devices or a combination thereof. It will be obvious to those of ordinary skill in the art that the electronic device according to various embodiments of the present disclosure is not limited to the above-listed devices. 
         [0044]    A method and apparatus proposed in an embodiment of the present disclosure are applicable to various communication systems such as an Institute of Electrical and Electronics Engineers (IEEE) 802.11 communication system, an IEEE 802.16 communication system, a digital multimedia broadcasting (DMB) service, a digital video broadcasting-handheld (DVB-H) service, and a mobile broadcasting service such as an Advanced Television Systems Committee-Mobile/Handheld (ATSC-M/H) service, a digital video broadcasting system such as an Internet protocol television (IPTV) service, an Moving Picture Experts Group (MPEG) media transport (MMT) system, an evolved packet system (EPS), an Long Term Evolution (LTE) communication system, an LTE-Advanced (LTE-A) communication system, a high-speed downlink packet access (HSDPA) mobile communication system, a high-speed uplink packet access (HSUPA) mobile communication system, a 3rd-Generation (3G) Project Partnership 2 (3GPP2) high rate packet data (HRPD) mobile communication system, a 3GPP2 wideband code division multiple access (WCDMA) mobile communication system, a 3GPP2 code division multiple access (CDMA) mobile communication system, a mobile Internet protocol (IP), and so forth. 
         [0045]      FIG. 1  illustrates an example of encryption of plaintext multimedia content. 
         [0046]    Referring to  FIG. 1 , plaintext multimedia content including a plurality of samples is encrypted with a predetermined media key. That is, the plurality of samples included in the plaintext multimedia content, e.g., S1  101 , S2  103 , S3  105 , S4  107 , and S5  109  are encrypted to M1*  111 , M2*  113 , M3*  115 , M4*  117 , and M5*  119 , respectively, by using the media key. 
         [0047]    Two encryption schemes, that is, a symmetric encryption scheme and an asymmetric encryption scheme may be used for the encryption. The symmetric encryption scheme means that encryption and decryption are performed using an identical media key, and the asymmetric encryption scheme means that different media keys are used for encryption and decryption. It is assumed that the symmetric encryption scheme is used in  FIG. 1 . 
         [0048]      FIG. 2  illustrates an example of decryption of ciphertext multimedia content. 
         [0049]    Referring to  FIG. 2 , ciphertext multimedia content including a plurality of samples are decrypted using a media key used for encryption of the ciphertext multimedia content. That is, a plurality of samples included in the ciphertext multimedia content, e.g., M1  211 , M2  213 , M3  215 , M4  217 , and M5  219  are decrypted to S1*  201 , S2*  203 , S3*  205 , S4*  207 , and S5*  209 , respectively, by using the media key used for encryption of the ciphertext. It is assumed that the symmetric encryption scheme is used in  FIG. 2 . 
         [0050]    The symmetric encryption scheme that performs encryption and decryption using the identical media key is economical because of high encryption speed and small volume due to its simple algorithm. However, the symmetric encryption has vulnerable security. That is, if the media key leaks, then the multimedia content leaks, and in this case, there is no way to identify who leaks the multimedia content. 
         [0051]    Thus, a scheme that introduces a variant to some of samples included in the ciphertext multimedia content has been proposed. The variant is used to decrypt the ciphertext, and the variant is set differently according to a license granted to users. The multimedia content decrypted using the variant differs from user to user according to a combination of variants. Therefore, when a variant is introduced to the ciphertext multimedia content, users may be specified based on the decrypted multimedia content. 
         [0052]      FIG. 3  illustrates an example where a variant is introduced to encryption and decryption of multimedia content. 
         [0053]    Referring to  FIG. 3 , plaintext multimedia content including a plurality of samples is encrypted with a predetermined media key. 
         [0054]    In  FIG. 3 , it is assumed that the symmetric encryption scheme is used and the encrypted multimedia content includes encrypted samples and a plurality of variants. It is also assumed that a key identifier (KID) issued to a user A is 21, a KID issued to a user B is 22, and a KID issued to a user C is 23. The KID is a license granted to a user and is used to decrypt a variant. 
         [0055]    A plurality of samples included in plaintext multimedia content, e.g., S1  301 , S2  303 , S3  305 , S4  307 , and S5  309  are encrypted to M1*  311 , M2*  313 , M3*  315 , M4*  317 , and M5*  319 , respectively, by using a predetermined media key. The encrypted multimedia content further includes variants M2-1**  321 , M2-2**  323 , and M2-3**  325  in addition to the encrypted samples M1*  311 , M2*  313 , M3*  315 , M4*  317 , and M5*  319 . 
         [0056]    To decrypt M2-2**  323 , the user B identifies a KID issued to the user B by referring to a variant location vloc. The user B identifying a KID 22 issued to the user B identifies a location of the variant M2-2**  323  decryptable with the KID issued to the user B by referring to variant metadata Vmet*. The user B performs partial decryption with respect to M2-2**  323  by using vbrKID included in Vmet*, such that M2-2**  323  is partially decrypted to, e.g., M2-2*. Then, the user B performs full decryption with respect to the partially decrypted M2-2* by using the KID included in Vmet*, such that M2-2* is decrypted to, e.g., S2. 
         [0057]      FIG. 4  illustrates an example where variants are configured for some of samples included in plaintext multimedia content. 
         [0058]    Referring to  FIG. 4 , (a) illustrates plaintext multimedia content including samples S1  401  through S5  409 , and (b) illustrates an example where variants are configured for samples S2  403 , S4  407 , and S5  409  among the samples S1  401  through S5  409 . In (b), the sample S2 is configured with variants S2-1  411 , S2-2  413 , and S2-3  415 , the sample S4 is configured with variants S4-1  421 , S4-2  423 , and S4-3  425 , and the sample S5 is configured with variants S5-1  431 , S5-2  433 , and S5-3  435 . 
         [0059]    Assuming that multimedia content shown in (b) is decrypted multimedia content, variants for the respective samples S2, S4, and S5 may implement various patterns based on combinations of the variants. The variant patterns implemented by the combinations of the variants may be used to track a user, and in case of leakage of the multimedia content, a person who leaks the multimedia content may be identified based on the variant patterns. 
         [0060]    Each variant pattern may be implemented by a combination of one of S2-1  411 , S2-2  413 , and S2-3  415  and one of S5-1  431 , S5-2  433 , and S5-3  435 , and in this case, a total of 27 variant patterns may be implemented. In the following embodiment of the present disclosure, variant patterns implemented in this way will be expressed by arranging combined variants, and for convenience, a variant pattern will be expressed merely by an index of each sample. According to a variant pattern expression method of the present disclosure, for example, a variant pattern S2-1  411 -S4-1  421 -S5-2  433  is expressed like (1-1-2), a variant pattern S2-3  415 -S4-1  421 -S5-1  431  is expressed like (3-1-1), and a variant pattern S2-1  411 -S4-1  421 -S5-1  431  is expressed like (1-1-1). 
         [0061]      FIG. 5  illustrates an example where a new variant pattern is generated by mixing variant patterns of multimedia content decrypted with two different licenses. 
         [0062]    Referring to  FIG. 5 , ciphertext multimedia content  500  is assumed to be decrypted according to a license A  510  and a license B  520 . It is assumed that a variant pattern of the multimedia content decrypted according to the license A  510  is (1-1-2), and a variant pattern of the multimedia content decrypted according to the license B  520  is (3-1-1). 
         [0063]    In this case, a hacker may know which samples among samples included in multimedia content are configured as variants, and variant patterns decrypted with two different licenses may be mixed to generate a new variant pattern. That is, the hacker may mix the variant pattern (1-1-2) with the variant pattern (3-1-1) to generate a new variant pattern (1-1-1). 
         [0064]    In this case, assuming that a variant pattern of multimedia content decrypted according to a license C is the same as the variant pattern (1-1-1) generated by the hacker, the user granted with the license C may be misunderstood as the hacker who leaks the multimedia content. As a result, the hacker may escape from pursuit. 
         [0065]    Thus, the following description of the present disclosure will provide a scheme for configuring a variant to prevent the hacker from escaping from pursuit, if variant patterns decrypted with two different licenses are mixed to falsify media content. 
         [0066]      FIG. 6  illustrates an example where variants for samples included in multimedia content are configured according to an embodiment of the present disclosure. 
         [0067]    Referring to  FIG. 6 , multimedia content is assumed to include samples S1  601  through S9  615 . 
         [0068]    A sample S5  607  is configured with reference to the samples S1  601  and S9  615 , a sample S3  605  is configured with reference to the samples S1  601  and S5  607 , a sample S7  611  is configured with reference to the samples S5  607  and S9  615 , a sample S6  609  is configured with reference to the samples S5  607  and S7  611 , and a sample S8  613  is configured with reference to the samples S7  611  and S9  615 . 
         [0069]    Variants S4-1  617 , S4-2  619 , and S4-3  621  for a sample S4 are configured with reference to different samples. That is, the variant S4-1  617  is configured with reference to the samples S2  603  and S3  605 , the variant S4-2  619  is configured with reference to the samples S2  603  and S5  607 , and the variant S4-3  621  is configured with reference to the samples S3  605  and S5  607 . As such, by configuring the variants S4-1  617 , S4-2  619 , and S4-3  621  with different combinations of samples referred to, when the variants S4-1  617 , S4-2  619 , and S4-3 are decrypted, bitstreams have different characteristics even though the decrypted samples look identical visually. 
         [0070]      FIG. 7  illustrates an example where variants for samples included in multimedia content are configured according to an embodiment of the present disclosure. 
         [0071]    Referring to  FIG. 7 , multimedia content is assumed to include samples S1  701  through S9  713 . 
         [0072]    A sample S5  707  is configured with reference to the samples S1  701  and S9  713 , a sample S3  705  is configured with reference to the samples S1  701  and S5  707 , a sample S7  711  is configured with reference to the samples S5  707  and S9  713 , and a sample S6  709  is configured with reference to the samples S5  707  and S7  711 . 
         [0073]    That is, the variant S4-1  715  for the sample S4 is configured with reference to the samples S2  703  and S3  705 , the variant S4-2  717  is configured with reference to the samples S2  703  and S5  707 , and the variant S4-3  719  is configured with reference to the samples S3  705  and S5  707 . Hereinbelow, a group of a plurality of variants configured for a particular sample will be referred to as a variant group. That is, the variants S4-1  715 , S4-2  707 , and S4-3  719  belong to a variant group for the sample S4. 
         [0074]    The variants S4-1  715 , S4-2  707 , and S4-3  719  belonging to the variant group for the sample S4 may be referred to by variants belonging to a variant group for another sample. That is, a variant S8-1  721  for a sample S8 is configured with reference to the variant S4-1  715  and the sample S7  711 , a variant S8-2  723  is configured with reference to the variant S4-2  717  and the sample S6  709 , and a variant S8-3  725  is configured with reference to the variant S4-3  719  and the sample S7  711 . 
         [0075]    As such, the variants S8-1  721 , S8-2  723 , and S8-3  725  are configured with reference to the variants S4-1  715 , S4-2  707 , and S4-3  719 , respectively. Hereinbelow, a relationship where a variant belonging to a particular variant group refers to a variant belonging to another variant group will be called a hidden variant relationship. That is, the variants S8-1  721 , S8-2  723 , and S8-3  725  are configured with reference to the variants S4-1  715 , S4-2  717 , and S4-3  719 , respectively. 
         [0076]    The variants S8-1  721 , S8-2  723 , and S8-3  725  may freely refer to variants belonging to different variant groups, respectively, but may not overlappingly refer to a particular variant belonging to the another variant group. For example, the variants S8-1  721  and S8-2  723  may not overlappingly refer to the identical variant S4-1  715 . In this way, variants belonging to different variant groups, e.g., the variants S4-1  715 , S4-2  717 , and S4-3  719  may be referred to by the variants S8-1  721 , S8-2  723 , and S8-3  725 , respectively, only once. 
         [0077]      FIG. 8  illustrates an example where a new variant pattern is generated by mixing variant patterns that form a secret variant relationship. 
         [0078]    Referring to  FIG. 8 , ciphertext multimedia content  800  is assumed to be decrypted according to a license A  810  and a license B  820 . It is assumed that a variant pattern of the multimedia content decrypted according to the license A  810  is (1-1-2), and a variant pattern of the multimedia content decrypted according to the license B  520  is (3-1-1). 
         [0079]    If a variant pattern is implemented with a combination of one of variants 1-1, 1-2, and 1-3 for a sample S1, one of variants 2-1, 2-2, and 2-3 for a sample S2, and one of variants 3-1, 3-2, and 3-3 for a sample S3, the variant 3-2 that implements a variant pattern of multimedia content decrypted according to a license A  810  is assumed to form a hidden variant relationship with the variant 1-1. It is also assumed that the variant 3-1 that implements a variant pattern of multimedia content decrypted according to a license B  820  forms a hidden variant relationship with the variant 1-3. 
         [0080]    In this case, a hacker may know which samples among samples included in multimedia content are configured as variants, and variant patterns decrypted with two different licenses may be mixed to generate a new variant pattern. That is, the hacker may mix the variant pattern (1-1-2) with the variant pattern (3-1-1) to generate a new variant pattern (1-1-1). 
         [0081]    However, the variant 3-1 that implements the variant pattern (1-1-1) generated by the hacker has a wrong reference relationship as shown in the drawing, resulting in image distortion, etc., during reproduction of related multimedia content. Moreover, in spite of no visual problem, bitstreams may be configured differently. That is, the variant 3-1 has a hidden variant relationship with the variant 1-3, but the variant pattern (1-1-1) generated by the hacker has a wrong reference relationship because the variant 3-1 does not refer to the variant 1-3. 
         [0082]    Thus, the apparatus for detecting falsification of media content may detect that a reference relationship of the variant 3-1 is wrong. The apparatus may also recognize that the variant 1-1 that implements the variant pattern (1-1-1) is one of variants that configure a variant pattern decrypted according to the license A  810 . In this case, even if assuming that the variant pattern of the multimedia content decrypted according to the license C is the same as the variant pattern (1-1-1) generated by the hacker, the apparatus may recognize that the user granted with the license C is not the hacker who leaks the multimedia content. 
         [0083]      FIG. 9  illustrates an example where a decryption device decrypts a variant that forms a secret variant relationship. 
         [0084]    Referring to  FIG. 9 , it is assumed that a variant S8-1  901  is configured with reference to a variant S4-1  903  and a sample S7  905  and the variant S8-1  901  forms a hidden variant relationship with the variant S4-3  907 . 
         [0085]    The decryption device uses a result of the sample S4 having a reference relationship for decrypting the variant S8-1  901 , that is, a decrypted picture. The variant S8-1  901  that implements the variant pattern (1-1-1) refers to the variant S4-1  903 , but forms a secret variant relationship with the variant S4-3  907 , such that the decryption device decrypts the variant S8-1  901  by referring to the variant S4-3  907  and the sample S7  905 . 
         [0086]    However, the decrypted picture of the variant S4-1  903  and the decrypted picture of the variant S4-3  907  have referred to different pictures, and thus bitstreams thereof are also different. Moreover, the decrypted picture of the variant S8-1  901  decrypted referring to the variant S4-1  903  and the sample S7  905  and the decrypted picture of the variant S8-1  901  decrypted referring to the variant S4-3  907  and the sample S7  905  are also different. 
         [0087]      FIG. 10  is a flowchart illustrating a method, performed by an encryption device, for encrypting multimedia content according to an embodiment of the present disclosure. 
         [0088]    Referring to  FIG. 10 , in operation  1000 , the encryption device configures a plurality of variants for at least one of samples included in transmitted multimedia content. In operation  1002 , the encryption device encrypts the multimedia content including the plurality of variants and the plurality of samples. 
         [0089]    In operation  1004 , the encryption device transmits the multimedia content encrypted in operation  1002 . 
         [0090]      FIG. 11  is a flowchart illustrating a method, performed by a decryption device, for decrypting multimedia content according to an embodiment of the present disclosure. 
         [0091]    Referring to  FIG. 11 , in operation  1100 , a decryption device receives encrypted multimedia content. In operation  1102 , the decryption device detects and decrypts one of the variants included in the received multimedia content. Herein, the detected variant is assumed to have been configured with reference to one variant and one sample, and may be, for example, the variant S8-1 of  FIG. 9 . 
         [0092]    In operation  1104 , the decryption device compares a decrypted picture, that is, a picture related to the decrypted variant S8-1 with the original picture before being encrypted, and if the picture related to the decrypted variant is the same as the original picture before being encrypted, the decryption device goes to operation  1106 . In operation  1106 , the decryption device detects that the multimedia content received in operation  1100  has not been falsified. 
         [0093]    If the picture related to the decrypted variant is not the same as the original picture before being encrypted in operation  1104 , the decryption device goes to operation  1108 . In operation  1108 , the decryption device detects that the multimedia content received in operation  1100  has been falsified. If the decryption device detects that the multimedia content has been falsified, it is reasonable that there exists at least one license used for leakage of the multimedia content. 
         [0094]    In operation  1110 , the decryption device detects a variant that forms a secret variant relationship with the variant S8-1 detected in operation  1102 . The variant that forms the secret variant relationship with the variant S8-1 may be, for example, the variant S4-3 of  FIG. 9 . 
         [0095]    In operation  1112 , the decryption device decrypts other variants S4-1 and S4-2 in the variant group including the variant S4-3. In operation  1114 , the decryption device compares a picture related to each of the decrypted variants S4-1 and S4-2 with the original picture before being encrypted to detect the original variant S4-1 to which the variant S8-1 refers. 
         [0096]    Meanwhile,  FIGS. 10 and 11  illustrate operation processes of the encryption device and the decryption device, and various modifications may be made to  FIGS. 10 and 11 . For example, consecutive operations are shown in  FIGS. 10 and 11 , but those operations described with  FIGS. 10 and 11  may overlap, may be performed in parallel, may be performed in different orders, or may be performed multiple times. 
         [0097]      FIG. 12  is a block diagram illustrating an internal structure of an encryption device  1200  that encrypts multimedia content according to an embodiment of the present disclosure. 
         [0098]    Referring to  FIG. 12 , the illustrated encryption device  1200  may include a transceiver  1202  and a controller  1204 . 
         [0099]    The controller  1204  controls an overall operation of the encryption device  1200 . In particular, the controller  1204  controls an overall operation related to encryption according to an embodiment of the present disclosure. Herein, the overall operations related to encryption are the same as those described above with reference to  FIGS. 3 through 10 , and thus will not be described in detail at this time. 
         [0100]    The transceiver  1202  transmits various messages under control of the controller  1204 . Herein, various messages transmitted by the transceiver  1202  are the same as those described above with reference to  FIGS. 3 through 10 , and thus will not be described in detail at this time. 
         [0101]      FIG. 13  is a block diagram illustrating an internal structure of a decryption device  1300  that decrypts encrypted multimedia content according to an embodiment of the present disclosure. 
         [0102]    Referring to  FIG. 13 , the illustrated decryption device  1300  may include a transceiver  1302  and a controller  1304 . 
         [0103]    The controller  1304  controls an overall operation of the decryption device  1300 . In particular, the controller  1304  controls an overall operation related to decryption according to an embodiment of the present disclosure. Herein, the overall operations related to decryption are the same as those described above with reference to  FIGS. 3 through 9 , and  FIG. 11 , and thus will not be described in detail at this time. 
         [0104]    The transceiver  1302  transmits various messages under control of the controller  1304 . Herein, various messages transmitted by the transceiver  1302  are the same as those described above with reference to  FIGS. 3 through 9  and  FIG. 11 , and thus will not be described in detail at this time. 
         [0105]    While embodiments of the present disclosure have been described, various changes may be made without departing the scope of the present disclosure. Therefore, the scope of the present disclosure should be defined by the appended claims and equivalents thereof, rather than by the described embodiments. 
         [0106]    The apparatus and method for encrypting and decrypting multimedia content according to an embodiment of the present disclosure may be implemented by hardware, software, or a combination of hardware and software. Such arbitrary software may be stored, for example, in a volatile or non-volatile storage device (e.g., a ROM, etc.), a memory (e.g., a RAM, a memory chip, a memory device, or a memory IC), or a machine (e.g., computer) recordable optical or magnetic storage medium (e.g., a CD, a DVD, a magnetic disc, a magnetic tape, etc.) regardless of its ability to erase or rewrite. It can be seen that the graphic screen update method according to the present disclosure may be implemented by a computer or a portable terminal which includes a controller and a memory, and the memory is an example of a machine-readable storage medium which is suitable for storing a program or programs including instructions for implementing the embodiment of the present disclosure. 
         [0107]    Accordingly, the present invention includes a program that includes a code for implementing the apparatus and method set forth in the appended claims of the specification and a machine (computer, etc.) readable storage medium for storing the program. Furthermore, the program may be electronically transferred by an arbitrary medium, such as a communication signal transmitted through a wired or wireless connection, and the present invention appropriately includes equivalents of the program. 
         [0108]    In addition, the apparatus for encrypting and decrypting multimedia content according to the embodiment of the present invention, may receive the program from a program providing device that is connected thereto in a wired or wireless manner, and may store the received program. The program providing device may include a memory for storing a program including instructions for instructing the graphic processing apparatus to execute a preset method, information necessary for the method, a communication unit for performing wired or wireless communication with the graphic processing apparatus, and a controller for transmitting a corresponding program to the graphic processing apparatus at the request of the apparatus or automatically.