Patent Publication Number: US-2012042393-A1

Title: User terminal, method and system for transmitting digital content

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from and the benefit of Korean Patent Application No. 10-2010-0078113, filed on Aug. 13, 2010, which is hereby incorporated by reference for all purposes as if fully set forth herein. 
     BACKGROUND 
     1. Field 
     Exemplary embodiments of the present invention relate to a user terminal, a method and a system for transmitting digital content. 
     2. Discussion of the Background 
     Digital content may include various kinds of content, for example, e-books, downloadable music/movie files and the like. An e-book, also known as an electronic book, is a digital book which is recorded in an electronic recordable medium. A user may purchase an e-book and download the content of the book in a user terminal. A content provider may apply digital rights management (DRM) to e-books. In particular, the content provider generally does not permit liquidity in DRM. Thus, the user cannot share digital content with other users or assign the digital content to other users. This inconvenience may occur for companies as well as for individuals. 
     SUMMARY OF THE INVENTION 
     Exemplary embodiments of the present invention provide a user terminal, a method, and a system for transmitting digital content in which a user may purchase digital content such as e-books and apply, to the digital content, various kinds of functions including re-purchasing, sharing, assigning, and the like. 
     Additional features of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. 
     An exemplary embodiment of the present invention discloses a user terminal to transmit digital content provided by a content provider, and may include a digital rights management (DRM) unit to change DRM information; a content processing unit to encode the provided digital content having the changed DRM information; and a communication unit to transmit the encoded digital content to a first external terminal. 
     Another exemplary embodiment of the present invention discloses a method to transmit digital content, including changing digital rights management (DRM) information of digital content provided by a digital content provider; encoding the digital content having the changed DRM information; and transmitting the encoded digital content to a first external terminal. 
     Another exemplary embodiment of the present invention discloses a system for transmitting digital content, including a digital content provider to provide digital content; and a user terminal to receive the digital content from the digital content provider, to change digital rights management (DRM) information of the received digital content, and to transmit the digital content having the changed DRM information; and a first external terminal to receive the digital content having changed DRM information. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. Other features and aspects will be apparent from the following detailed description, the drawings, and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and together with the description serve to explain the principles of the invention. 
         FIG. 1  depicts an illustrative system for transmitting digital content according to an exemplary embodiment. 
         FIG. 2  depicts an illustrative structure of digital content having an initial digital rights management (DRM) area according to an exemplary embodiment. 
         FIG. 3  depicts an illustrative DRM area according to an exemplary embodiment. 
         FIG. 4  depicts an illustrative DRM area according to an exemplary embodiment. 
         FIG. 5  depicts an illustrative DRM area according to an exemplary embodiment. 
         FIG. 6  depicts an illustrative DRM area according to an exemplary embodiment. 
         FIG. 7  depicts an illustrative DRM area according to an exemplary embodiment. 
         FIG. 8  depicts an illustrative DRM area according to an exemplary embodiment. 
         FIG. 9  is a flowchart illustrating a method for transmitting digital content by a first user terminal according to an exemplary embodiment. 
         FIG. 10  is a flowchart illustrating a method for purchasing and transmitting digital content based on DRM information extension according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
     The invention is described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure is thorough, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the size and relative sizes of layers and regions may be exaggerated for clarity. Like reference numerals in the drawings denote like elements. 
     It will be understood that, although the terms first, second, third etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention. 
       FIG. 1  depicts an illustrative system for transmitting digital content according to an exemplary embodiment. 
     Referring to  FIG. 1 , the system  5  for transmitting digital content may include a digital content provider  100 , a first user terminal  200  and a second user terminal  300 . Although  FIG. 1  shows two user terminals, the first user terminal  200  and the second user terminal  300 , aspects of the present invention are not limited to a specific number of user terminals. A user of the first user terminal  200  may be identical to or different from a user of the second user terminal  300 . 
     The first user terminal  200  may purchase digital content from the digital content provider  100  and transmit the purchased digital content to an external terminal, here, second user terminal  300 . The digital content may be transmitted from the first user terminal  200  to the second user terminal  300  without intervention of the digital content provider  100 . Although described as purchased, digital content may be provided to or received by the first user terminal as a gift or loan. 
     To enable digital content transmission without intervention of the digital content provider  100 , the digital content provider  100  may add a digital rights management (DRM) area to the digital content and record DRM information related to purchasing in the DRM area. The first user terminal  200  may change the DRM information of the purchased digital content and transmit the digital content having the changed DRM information to the second user terminal  300 . According to an exemplary embodiment, digital content may have a broad range of application using DRM information extension. For example, DRM information extension may be a series of processes for changing DRM information of purchased digital content through a user terminal to rent, transfer or assign the digital content of the user terminal to an external terminal. 
     The digital content provider  100  may include a content managing unit  110 , a DRM generating unit  120 , an encoding unit  130 , a provider communication unit  140 , and a provider control unit  150 . 
     The content managing unit  110  may store and manage a plurality of available digital content sales. The content managing unit  110  may store and manage digital content in the form of a file. 
     The DRM generating unit  120  may generate DRM information using a purchase condition of the first user terminal  200 . Specifically, the DRM generating unit  120  may generate DRM information including a selling condition of the digital content and a purchase condition of the digital content. The generated DRM information may be added to the digital content. 
       FIG. 2  depicts an illustrative structure of digital content having an initial DRM area according to an exemplary embodiment. 
     Referring to  FIG. 2 , the structure of digital content may include a content area  21  and an initial DRM area  22 , and the initial DRM area  22  may include a seller area  23  and a purchaser area  24 . 
     The content area  21  is an area for digital content purchased by a purchaser. For example, if the purchaser purchases an e-book, the content area  21  may have the content of the e-book recorded therein. 
     The initial DRM area  22  is an area for DRM information generated by the DRM generating unit  120 . A selling condition may be recorded in the seller area  23  and a purchase condition may be recorded in the purchaser area  24 . The seller area  23  may not be changeable by the DRM unit  240  of the first user terminal  200  whereas the purchaser area  24  may be changeable by the DRM unit  240 . 
     The selling condition may be set by a manager for each digital content, regardless of the purchase condition. The manager may be a manager of the digital content provider  100  or an owner of rights. A user may purchase digital content under the selling condition. The selling condition may be changed by the manager of the digital content provider  100 . The selling condition may be selectively changed by the manager in response to a request of a purchaser or according to the purchase condition of digital content. 
     Specifically, at least one of detailed information of digital content, the number of licenses of digital content, a transmissible number of digital content, a copyable number of digital content, and an assignable number of digital content may be recorded in the seller area  23 . 
     The purchase condition may be set by a user that purchased digital content. At least one of information of a first purchaser of digital content, information of a current owner of digital content, the number of currently owned licenses of digital content, the number of currently withdrawable licenses of digital content, a transmissible number of digital content, a copyable number of digital content, an assignable number of digital content, and a rental period of digital content may be recorded in the purchaser area  24 . 
     Information recorded in the seller area  23  and the purchaser area  24  is described with reference to Table 1. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Information 
                 Description or Example 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 Seller area 
                 Detailed information of digital 
                 General information including product 
               
               
                   
                 content 
                 ID (title, serial number), writer, price, 
               
               
                   
                   
                 name of selling place, and the like 
               
               
                   
                 Number of licenses of digital 
                 Purchase quantity of identical digital 
               
               
                   
                 content 
                 content 
               
               
                   
                 Transmissible number of digital 
                 Maximum number of digital content 
               
               
                   
                 content 
                 transmittable by a first purchaser 
               
               
                   
                 Maximum transmissible number 
                 Maximum transmittable depth number 
               
               
                   
                 per time of digital content 
                 of digital content (for example, 1 
               
               
                   
                   
                 depth denotes a case where a first 
               
               
                   
                   
                 purchaser transmits digital content to a 
               
               
                   
                   
                 first user, and 2 depth denotes a case 
               
               
                   
                   
                 where the first user transmits the 
               
               
                   
                   
                 digital content to a second user) 
               
               
                   
                 Copyable number of digital 
                 Maximum copyable number of digital 
               
               
                   
                 content 
                 content by a first purchaser 
               
               
                   
                 Assignable number of digital 
                 Maximum assignable number of 
               
               
                   
                 content 
                 digital content by a first purchaser 
               
               
                 Purchaser area 
                 Information of first purchaser of 
                 Identity information of a first user 
               
               
                   
                 digital content 
                 terminal or a first user of digital 
               
               
                   
                   
                 content 
               
               
                   
                 Information of a current owner of 
                 A current owner is a first user when a 
               
               
                   
                 digital content 
                 first purchaser transmits digital 
               
               
                   
                   
                 content to the first user 
               
               
                   
                 Number of currently owned 
                 Number of licenses changes 
               
               
                   
                 licenses of digital content 
                 depending on the number of 
               
               
                   
                   
                 transmission of digital content. 
               
               
                   
                 Number of currently 
                 Number of digital content transmitted 
               
               
                   
                 withdrawable licenses of digital 
                 to an external terminal 
               
               
                   
                 content 
               
               
                   
                 Transmissible number of digital 
                 Decrease when digital content are 
               
               
                   
                 content 
                 transmitted to an external terminal 
               
               
                   
                 Copyable number of digital 
                 Decrease when digital content are 
               
               
                   
                 content 
                 copied to an external terminal 
               
               
                   
                 Assignable number of digital 
                 Decrease when digital content are 
               
               
                   
                 content 
                 assigned to an external terminal 
               
               
                   
                 Rental period of digital content 
                 Unlimited or until x day, x month, x 
               
               
                   
                   
                 year 
               
               
                   
               
            
           
         
       
     
     In Table 1, the number of licenses is a purchased quantity of identical digital content, for example, the number of licenses is three when three identical e-books are purchased. That is, the first user terminal  200  may obtain three licenses from the digital content provider  100  in one download. This is similar to the concept that multiple identical books may be purchased in a brick and mortar bookstore. The DRM information of Table 1 may be information for a single digital content. 
     Referring again to  FIG. 1 , the encoding unit  130  may encode digital content having DRM information generated by the DRM generating unit  120 . The encoding unit  130  may encode digital content using certification information of the first user terminal  200  in response to a purchase request of a purchaser. The certification information may include at least one of a unique number and a personal certificate of the first user terminal  200 , and the unique number of the first user terminal may be, for example, an international mobile equipment identity (IMEI) number. The IMEI number may be a serial number of the first user terminal  200  assigned by a manufacturer. 
     The provider communication unit  140  may transmit the encoded digital content from the encoding unit  130  to the first user terminal  200  via a communication network  10 . 
     The provider control unit  150  may control the operation of the digital content provider  100  using a control program, software, a processor, etc. For example, the provider control unit  150  may perform a charging process using certification information, and may control the encoding unit  130  to encode the digital content using the certification information if the charging process is completed. 
     The first user terminal  200  may further include a communication unit  210 , a memory unit  220 , a display unit  230 , a DRM unit  240 , a content processing unit  250 , a memory managing unit  260  and a control unit  270 . 
     The first user terminal  200  may purchase digital content from the digital content provider  100  and transmit the purchased digital content to the second user terminal  300 . 
     The communication unit  210  may support a wired or wireless communication between the digital content provider  100  and the first and second user terminals  200  and  300 , respectively. For example, the communication unit  210  may receive the purchased digital content from the digital content provider  100 . 
     The control unit  270  may control the operation of the first user terminal  200  using a control program, software, a processor, etc. 
     The memory unit  220  may store the digital content purchased from the digital content provider  100  in the form of a file. Throughout the specification, the term “digital content” is used interchangeably with “file,” for convenience. In addition, the memory unit  220  may store various kinds of programs for operating the first user terminal  200 . 
     The display unit  230  may display a user interface (UI) used to provide various functions of the first user terminal  200 , the current status of the first user terminal  200 , etc. In particular, the display unit  230  may display a file list of digital content stored in the memory unit  220 . In this instance, the file list may include effective files. For example, if digital content stored in the memory unit  220 , however, is not available in the first user terminal  200  as the digital content was transmitted to the second user terminal  300 , a file name of the digital content may not be displayed. In this instance, ‘transmission’ may be an operation related to movement of digital content, for example, transfer, copying, assignment, and the like. The transmitted digital content may be withdrawn from the second user terminal  300 . 
     The DRM unit  240  may change DRM information of digital content. The DRM unit  240  may change DRM information based on the initial DRM area  22  in  FIG. 2  that is added to the digital content if the digital content are purchased. 
     The DRM unit  240  may analyze information in the seller area  23  of the DRM area  22  included in the purchased digital content, that is, a selling condition, and manage a file transmission condition. The file transmission condition may be included in a purchase condition, or may be the purchase condition. If digital content, that is, a file is transmitted to the second user terminal  300 , the DRM unit  240  may change the purchase condition stored in the purchaser area  24 , and store DRM information including the changed purchase condition in the digital content. Also, if the digital content transmitted to the second user terminal  300  is withdrawn, the DRM unit  240  may again change the DRM information of the withdrawn digital content. 
     The content processing unit  250  may encode or decode digital content received by the communication unit  210 . The content processing unit  250  may decode digital content using certification information. If the digital content provider  100  encoded the digital content using a unique number of the first user terminal  200 , the content processing unit  250  may decode the digital content using the unique number. 
     The content processing unit  250  may analyze information received from the second user terminal  300 , for example, if the purchased digital content are transmitted to the second user terminal  300 . The information of the second user terminal  300  may be a unique number and/or a personal certificate of the second user terminal  300 . The content processing unit  250  may encode the digital content including DRM information changed by the DRM unit  240  using the information received from the second user terminal  300 . 
     The memory managing unit  260  may store, delete, and change the status of the digital content, for example, if DRM information is changed by the DRM unit  240  or the digital content are encoded by the content processing unit  250 . In particular, if the encoded digital content is transmitted to the second user terminal  300 , the memory managing unit  260  may perform a locking operation to disable usage of the corresponding digital content in the first user terminal, and set the status of the digital content as DISABLE. Also, if the digital content is withdrawn from the second user terminal  300 , the memory managing unit  260  may release the locking of the digital content and set the status of the digital content as ENABLE. 
     Hereinafter, a DRM area before and after being changed is described with reference to  FIGS. 3 to 5 . 
     Digital content, which is first purchased by and stored in an exemplary first user terminal, may be referred to as first digital content, and the first digital content is transmitted to an exemplary second user terminal. The first digital content stored in the second user terminal may be referred to as second digital content. The DRM unit of an exemplary first user terminal changes the DRM information of the first digital content if the first digital content is transmitted. The first digital content having DRM information changed by the exemplary DRM unit may be referred to as “first prime digital content.” The DRM information of the second digital content may be also changed by an exemplary DRM unit. In this instance, the DRM information of the second digital content may be different from the DRM information of the first prime digital content. 
       FIG. 3  depicts an illustrative DRM area according to an exemplary embodiment.  FIG. 3  illustrates an example of DRM information in a seller area  31  and a purchaser area  32  of an initial DRM area  30  that is added to digital content when the digital content is purchased. The initial DRM area  30  may be produced by the digital content provider  100 , included in the digital content and transmitted to the first user terminal  200 . Accordingly, purchasing of the digital content is completed. 
     The selling condition recorded in the seller area  31  shows that the number of purchasable licenses of the digital content is ‘1’, the digital content is unlimitedly transmittable and transmittable at the maximum to two persons per time, and is assignable. 
     The purchase condition recorded in the purchaser area  32  shows that a purchaser of the digital content is a ‘Terminal  1 ’, a current owner of the digital content is the ‘Terminal  1 ’, the number of currently owned licenses is ‘1’, the number of currently withdrawable licenses is ‘0’, a sequentially transmissible number of the digital content is ‘2’, and a rental period of the digital content is unlimited. 
     If the number of currently withdrawable licenses is ‘0’, the digital content has not yet been transmitted to another user terminal. If the sequentially transmissible number is ‘2’, the digital content may be transmitted at maximum to two users. Thus, if a user A transmits the digital content to a user B, the sequentially transmissible number is decreased to ‘1’. If the user B transmits the same digital content to a user C, the sequentially transmissible number is decreased to ‘0’ and the digital content may not be transmitted any longer and is should be withdrawn. The rental period may be set by a user of a terminal possessing the digital content. However, aspects of the present invention need not be limited thereto, such that, a sequentially transmissible number of ‘2,’ if transmitted from user A to user B, may be provide user B with the right to transmit the digital content to two users. In addition, the two users, which received digital content from B, may be provided with the right to transmit the digital content to two users each. 
       FIG. 4  depicts an illustrative DRM area included in digital content transmitted from an exemplary first user terminal to an exemplary second user terminal, as taught herein. The DRM information of  FIG. 4  may be DRM information resulting from the change of DRM information stored in the initial DRM area  30  of  FIG. 3 . 
     Referring to  FIG. 4 , a DRM area  40  of digital content transmitted to the exemplary second user terminal may have a seller area  41  and a purchaser area  42 . The seller area  41  may be the same as when the digital content is first purchased by the exemplary first user terminal. 
     The purchaser area  42  shows that the purchaser of the digital content is ‘Terminal  1 ,’ and a current owner is ‘Terminal  2 .’ The number of currently owned licenses and the number of currently withdrawable licenses is ‘1’ and ‘0’, respectively, because the digital content is rented from the first user terminal. The purchase condition of the purchaser area  42  may be a purchase condition resulting from change of the purchase condition of the purchaser area  32  by the DRM unit  240  of the first user terminal. 
     The sequentially transmissible number is ‘1,’ and if the purchase condition is the result of a change in the purchase condition of area  32 , the second user terminal may transmit the digital content to an external terminal once. 
     If the first user terminal sets a rental period and transmits the digital content to the second user terminal, the digital content stored in the second user terminal may be deleted at the expiration of the rental period. After the rental period expires, the state of the digital content previously set as DISABLE by the first user terminal may be changed to ENABLE, making the digital content available to the first user terminal. Because the rental period of the digital content is set as Oct. 1, 2010 in  FIG. 4 , the second user terminal should return the digital content to the first user terminal on or by Oct. 1, 2010. 
       FIG. 5  depicts an illustrative DRM area according to an exemplary embodiment. 
       FIG. 5  depicts an illustrative DRM area in an exemplary first user terminal when the digital content is transmitted to an exemplary second user terminal. For example, the changed DRM information of  FIG. 5  may be information included in the digital content stored in the first user terminal  200 . 
     Referring to  FIG. 5 , as the digital content is transmitted to the second user terminal, a DRM area  50  of the digital content stored in the first user terminal may have a seller area  51  and a purchaser area  52 . The seller area  51  may be the same as if a user of the first user terminal initially purchases the digital content. 
     The purchaser area  52  shows that a purchaser of the digital content is ‘Terminal  1 ’ and a current owner is ‘Terminal  2 .’ The number of currently owned licenses is ‘0’ and the number of currently withdrawable licenses is ‘1’ indicating that the digital content was rented or transmitted to a second user terminal. The purchase condition of the purchaser area  52  may be a purchase condition resulting from the change of the purchase condition of the purchaser area  32  of  FIG. 3  by an exemplary DRM unit. 
     The first user terminal may no longer transmit the digital content because the number of currently owned licenses is ‘0.’ 
     If a rental period is unlimited, the transmitted digital content should be removed from the first terminal, and if the digital content is transmitted to the second user terminal, the digital content stored in the first user terminal may be deleted. Conversely, if a rental period is set for a predetermined time, the digital content stored in the first user terminal may not be deleted, but may be in a DISABLE state, i.e., in a locked state, as described above. The DISABLE state is to prepare for a situation in which the digital content may not be normally withdrawn from the second user terminal. 
     If the first user terminal assigns the digital content to the second user terminal, the digital purchaser of  FIG. 4  and  FIG. 5  may be changed to a ‘Terminal  2 ’ and the digital content in the first user terminal may be deleted. 
     A DRM area to be changed, if a plurality of licenses are purchased, and the digital content transmitted to a plurality of external terminals is described with reference to  FIG. 6  to  FIG. 8 . 
       FIG. 6  depicts an illustrative DRM area according to an exemplary embodiment. 
       FIG. 6  depicts an illustrative initial DRM area  60  that is added to digital content if the digital content is purchased. The initial DRM area  60  may be made by an exemplary digital content provider, included in the digital content, and transmitted to an exemplary first user terminal. 
     The selling condition recorded in the seller area  61  shows that the number of purchasable licenses of the digital content is ‘10’, the digital content is transmissible unlimitedly, transmissible at a maximum to two persons at a time, and is assignable. 
     The purchase condition recorded in the purchaser area  62  shows that a purchase of the digital content is a ‘Terminal  1 ’, a current owner of the digital content is ‘ARRAY’, the number of currently owned licenses is ‘10’, the number of currently withdrawable licenses is ‘0’, a sequentially transmissible number is ‘2’, and the rental period of the digital content is unlimited. 
       FIG. 7  depicts an illustrative DRM area according to an exemplary embodiment.  FIG. 7  depicts an illustrative DRM area included in the digital content transmitted from an exemplary first user terminal to an exemplary second user terminal. 
     A DRM area  70  of the digital content transmitted to the second user terminal may have a seller area  71  and a purchaser area  72 . The seller area  71  may be the same as if the first user terminal initially purchased the digital content. The purchaser area  72  shows that a purchaser of the digital content is ‘Terminal  1 ,’ and a current owner is ‘Terminal  2 .’ The number of currently owned licenses is ‘1’ and the number of currently withdrawable licenses is ‘0.’ The sequentially transmissible number is ‘1’ and a rental period is set to expire on Oct. 1, 2010. 
       FIG. 8  depicts an illustrative DRM area according to an exemplary embodiment.  FIG. 8  illustrates an example of changed DRM information of the digital content stored in an exemplary first user terminal if the digital content is transmitted to an exemplary second user terminal. 
     Referring to  FIG. 8 , a DRM area  80  of the digital content stored in a first user terminal may have a seller area  81  and a purchaser area  82 . The seller area  81  may be the same as when the first user terminal initially purchased the digital content. The purchaser area  82  shows that a purchaser of the digital content is ‘Terminal  1 ,’ and a current owner an ‘Array.’ In an exemplary embodiment, the Array may include multiple terminals, for example, ten terminals, one of which may be “Terminal  2 .” The number of currently owned licenses is ‘9’ and the number of currently withdrawable licenses is ‘1.’ The sequentially transmissible number is ‘2’ and a rental period is unlimited. As digital content (for example, one e-book) is rented to a second user terminal as shown in  FIG. 8 , the digital content stored in the first user terminal should be deleted or changed to a DISABLE state. Also, if a rental period is unlimited, the digital content stored in the first user terminal should be deleted. 
     However, if a plurality of licenses are purchased as shown in  FIG. 6 , the digital content may not be deleted from the first user terminal until the number of currently owned licenses decreases to ‘0’, and the purchase condition of the digital content may be changed as follows. 
     As shown in  FIG. 6 , a current owner of the initial DRM information is an Array having 10 licenses. If the digital content is transmitted to the second user terminal of the Array, the current owner may be changed to a ‘Terminal  2 ’ and the number of currently owned licenses and the number of currently withdrawable licenses may be changed to ‘9’ and ‘1’, respectively. If the digital content is transmitted to an external terminal, the number of currently owned licenses may decrease and the number of currently withdrawable licenses may increase as shown in  FIG. 8 . If the number of currently owned licenses becomes ‘1’, it indicates that the digital content was transmitted nine times. 
     In this instance, if the digital content with a predetermined rental period is transmitted once or more, the digital content may not be deleted from the first user terminal and may maintain a DISABLE state. Also, if the digital content is assigned to the second user terminal, the number of currently owned licenses and the number of currently withdrawable licenses may be adjusted and the rights corresponding to the digital content may be given to the second user terminal. The second user terminal may rent or assign the assigned digital content to an external terminal in the same way as the first user terminal. 
       FIG. 9  is a flowchart illustrating a method for transmitting digital content by a first user terminal according to an exemplary embodiment of the present disclosure. Although depicted as being performed serially, those skilled in the art will appreciate that at least a portion or portions of the method of  FIG. 9  may be performed contemporaneously, or in a different order than presented in  FIG. 9 . 
     A first user terminal, which may transmit digital content using DRM information extension and extended DRM information, may be the exemplary first user terminal  200  described with reference to  FIG. 1 . The method of  FIG. 9  may be performed by the control unit  270  of the first user terminal  200  of  FIG. 2  or by a processor. A digital content provider and a second user terminal may be the digital content provider  100  and the second user terminal  300  of  FIG. 1 , respectively. 
     In operation  900 , the first user terminal sends a purchase request, to the digital content provider. 
     In operation  905 , the digital content provider requests certification information from the first user terminal. 
     In operation  910 , the first user terminal transmits a unique number of the first user terminal or a personal certificate, or a combination thereof, as the certification information to the digital content provider. 
     In operation  915 , the digital content provider performs a certifying and charging process using the certification information. 
     In operation  920 , the digital content provider generates DRM information, by way of example DRM information using a purchase condition established by the user of the first user terminal. 
     In operation  925 , the digital content provider encodes the digital content including the DRM information generated in operation  920  and transmits the encoded digital content to the first user terminal. Accordingly, the sale and purchase of the digital content is completed. 
     In operation  930 , the first user terminal stores the purchased digital content in the first user terminal. 
     In operation  935 , the second user terminal requests the first user terminal transmit the digital content. In this instance, transmission is an operation related to movement of digital content, for example, transfer, copying, assignment, etc. 
     In operation  940 , the first user terminal requests certification information from the second user terminal. 
     In operation  945 , the second user terminal transmits a unique number of the second user terminal or a personal certificate, or a combination thereof, as the certification information to the first user terminal. 
     In operation  950 , the first user terminal performs a certification process using the certification information received from the second terminal, checks the DRM information, and determines whether the digital content is transmissible. In operation  950 , the first user terminal may change DRM information of digital content to be stored in the first user terminal and DRM information of digital content to be transmitted to the second user terminal, if the digital content is transmissible. The DRM information may be changed based on the purchase condition, for example, the number of licenses at the time of purchasing, the number of currently owned licenses, assignability, etc. 
     In operation  955 , the first user terminal transmits the digital content having the changed DRM information to the second user terminal. 
     In operation  960 , the first user terminal determines if the digital content transmission of operation  955  failed. 
     In operation  965 , if the operation  960  determined the transmission was a failure, the first user terminal recovers the DRM information changed in operation  950  to a previous state. 
     In operation  970 , if the first user terminal receives a transmission complete report from the second user terminal, the first user terminal determines transmission of the digital content was successful. 
     In operation  975 , the first user terminal determines if operation  955  was an assignment of the transmitted digital content. 
     In operation  980 , if the operation  975  determines the transmission of the digital content was an assignment of the digital content to the second terminal, the first user terminal may delete the digital content stored in operation  930 . 
     In operation  985 , if the operation  975  determines the transmission of the digital content was a rental of the digital content, the first user terminal may set the state of the digital content stored in operation  930  as DISABLE and may apply the DRM information changed in operation  950  to the digital content stored in operation  930 . 
     In step  990 , the first user terminal transmits usage permission to the second user terminal if a license transfer is completed. Accordingly, the DRM information of the digital content transmitted to the second user terminal is extended, so that the second user terminal may use the digital content. 
     In operation  995 , the digital content is withdrawn from the second user terminal if a rental period of the DRM information extended in operation  990  expires. Operation  995  may not be performed if transmission of the digital content in operation  955  is assignment of the digital content. 
       FIG. 10  is a flowchart illustrating a method for purchasing and transmitting digital content based on DRM information extension according to an exemplary embodiment. Although depicted as being performed serially, those skilled in the art will appreciate that at least a portion or portions of the method of  FIG. 10  may be performed contemporaneously, or in a different order than presented in  FIG. 10   
     In an exemplary embodiment, the digital content provider, first user terminal, second user terminal, third user terminal and fourth user terminals may respectively be the digital content provider  100 , the first user terminal  200 , the second user terminal  300  and external terminals with reference to  FIG. 1  to  FIG. 9 . 
     In operation  1010 , the first user terminal informs the digital content provider of desired digital content to retrieve and requests to purchase the retrieved digital content. A user of the first user terminal may establish a purchase condition for the retrieved digital content, by way of example, the number of licenses of the digital content is one, a transmissible number of the digital content is five, the digital content is assignable, etc. 
     In operation  1020 , the digital content provider generates DRM information using the purchase condition set by the user of the first user terminal, and transmits the digital content including the generated DRM information to the first user terminal. The digital content provider certifies and encodes the digital content, using certification information of the first user terminal, and transmits the encoded digital content to the first user terminal. 
     In operation  1030 , the first user terminal transmits the purchased digital content to the second user terminal. In this instance, the first user terminal may transmit the purchased digital content for rental. The first user terminal checks certification information of the second user terminal, determines whether to change the DRM information, and if the digital content is transmissible. If the digital content is transmissible, the first user terminal encodes the digital content using the certification information from the second user terminal, and transmits the encoded digital content to the second user terminal. The digital content stored in the first user terminal may be deleted or set to a DISABLE state, and the second user terminal may use the digital content. 
     In operation  1040 , the digital content is withdrawn and returned to the first user terminal if the rental period of the digital content transmitted to the second user terminal expires. 
     In operation  1050 , the first user terminal may transmit the digital content to multiple terminals. In this instance, the digital content stored in the first user terminal may not be deleted, but the DRM information of the digital content may be changed. 
     In other words, in operation  1050 , the first user terminal may transmit the purchased digital content to the third user terminal based on the DRM information. The first user terminal may assign the digital content to the third user terminal if an ‘assignable’ purchase condition is included in the DRM information generated and transmitted in operation  1020 . 
     In operation  1060 , the third user terminal transmits the assigned digital content to the fourth user terminal. 
     In operation  1070 , the digital content may be returned to the third user terminal if the rental period of the digital content transmitted to the fourth user terminal expires. The digital content stored in the fourth user terminal may be deleted, and the DRM information (for example, the number of currently owned licenses) of the digital content stored in the third user terminal may be changed accordingly. 
     Exemplary embodiments of the present disclosure may include transfer and purchase of programs purchased from application stores as well as digital content, such as e-books, music files and movie files. For example, the programs purchased from application stores may be transmitted or withdrawn according to aspects of the present disclosure. Also, exemplary embodiments of the present disclosure may be applied to various kinds of content depending on a file encoding range. 
     Exemplary embodiments according to aspects of the present disclosure may be recorded in non-transitory, computer-readable media including program instructions to implement various operations embodied by a computer. The media may also include, alone or in combination with the program instructions, data files, data structures, and the like. The media and program instructions may be those specially designed and constructed for the purposes of the present invention, or they may be of the kind well-known and available to those having skill in the computer software arts. 
     Exemplary embodiments of the present disclosure provide a user terminal, a method, and a system for transmitting digital content, in which a user may provide other users with digital content purchased by the user from a digital content provider. In this instance, the user may change digital rights management (DRM) information of the digital content without intervention of the digital content provider and transmit the digital content having the changed DRM information to the other users, thus providing digital content to other users more conveniently. 
     Furthermore, exemplary embodiments of the present disclosure provide a user terminal, a method, and a system for transmitting digital content, in which digital content may be transmitted between user terminals. Digital content transmission may be made under a concept of transfer and withdrawal as opposed to unauthorized copying, thereby increasing management efficiency of the digital content. 
     In addition, exemplary embodiments of the present disclosure provide a user terminal, a method and a system for transmitting digital content, in which a digital content provider may set various conditions including transmissibility of digital content, the number of licenses of digital content, a rental period of digital content and the like. The method and the system for transmitting digital content may allow competition between digital content providers, leading to a more active digital content market. For example, a company A may provide digital content at a low price and having limited transmissibility, and a company B may provide digital content at a high price and having unlimited transmissibility. 
     It will be apparent to those skilled in the art that various modifications and variation can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.