Abstract:
The invention proposes methods and devices for managing domains. The domains comprise a plurality of member devices, and the method comprises the steps of: storing (S 500,  S 501 ), by a first domain manager (M 1 ), domain management information (P 1,  P 2,  P 3,  P 4  and P 5 ) in said plurality of member devices; and obtaining (S 510,  S 511 ), by a second domain manager (M 2 ), said domain management information from at least one of said plurality of member devices. In comparison with the prior art, where the domain management information is maintained in the domain authority, the embodiment decreases the work load of the domain authority and provides conveniences.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to domain management, and particularly to managing domain management information. 
       BACKGROUND 
       [0002]    Currently, people might own several consumer electronics devices such as PCs, smart phones, audio/video players and other portable devices. Content provided by content providers, such as music provided by an on-line music provider, can be shared on these devices via a “domain” built among them. The domain usually has a domain manager that is responsible for various domain operations, such as security authentication requests (logging in, checking permissions, etc.), maintaining and enforcing the domain policy. And it uses much domain management information for managing the domain, for example the list of member devices, the domain policy, and domain secrets such as private keys of the domain manager, root certificate and pin code of the domain. 
         [0003]    The domain management information should be maintained. For example, the domain manager might be replaced because, for example, the device bearing the domain manager is lost or damaged, and the new domain manager should acquire domain management information to manage the domain. Taking domain secrets as an example, traditionally, the new domain manager determines new domain secrets, such as the public keys and the private keys, and rebuilds the domain management message. This is not a highly efficient scheme, because it cannot make good use of the previous domain management information. According to a solution proposed by US2008/0052388A1, the previous domain manager stored the domain management information in a domain authority of the domain, such as the authorizing server of the content provider, so that the new domain manager can retrieve domain management information from the domain authority. 
       SUMMARY OF THE INVENTION 
       [0004]    According to the prior art, the domain management information is maintained by the domain authority. The drawbacks of the prior art include that: 
         [0005]    (1) the load on the domain authority is heavy since it maintains the management information of the domains all over the country or the globe. And the management information, such as the member device list, sometimes takes up a relatively large amount of storage space; and 
         [0006]    (2) the previous as well as the new domain manager need to be on-line to exchange the domain management information with the domain authority. 
         [0007]    Thus, it would be advantageous to provide a method of maintaining the domain and a device that reduces the workload of the domain authority. It would also be advantageous to maintain the domain management information in a more convenient manner, for example off-line. 
         [0008]    To achieve at least one of these objects, in a first aspect of the invention, there is provided a method of managing a domain comprising a plurality of member devices, the method comprising the steps of: storing, by a first domain manager, domain management information in said plurality of member devices; obtaining, by a second domain manager, said domain management information from at least one of said plurality of member devices. 
         [0009]    In this aspect, the domain management information is stored in the member devices of the domain, instead of in the domain authority. Thus, the working load on the domain authority is decreased. And the domain manager can obtain the domain management information from the member devices off-line without accessing the on-line domain authority, which is more convenient. 
         [0010]    In some cases, the domain management information comprises management information that needs to be kept accessible only for domain managers, such as domain secrets. Thus, it is advantageous to maintain the confidentiality of this part of the domain management information. To this end, in a preferred embodiment of the first aspect, said storing step comprises the sub-steps of:
       generating a plurality of pieces of data from at least part of said domain management information, such that at least two pieces of data which are different from each other are required for recovering said at least part of said domain management information;   distributing said plurality of pieces of data to said plurality of member devices respectively;
           wherein said obtaining step comprises the sub-steps of:   
           receiving at least two pieces of data which are different from each other from at least two of said plurality of member devices;   recovering said at least part of said domain management information from the received at least two pieces of data.       
 
         [0016]    In this embodiment, the management information, such as domain secrets, is distributed among the member devices. Only the domain manager can collect the pieces and recover the management information. Thus, the security of this embodiment is higher. 
         [0017]    In a preferred embodiment, the number of pieces of data that are generated is larger than the number of pieces of data that are required for recovering the management information, which means that the domain manager need not collect all the pieces of data in order to recover the management information, and thus the robustness of this embodiment is increased. 
         [0018]    In a preferred embodiment, said generating step comprises the sub-steps of:
       constructing a polynomial, wherein said at least part of said domain management information is configured to be a coefficient of a term of the polynomial;   generating said plurality of pieces of data by using said constructed polynomial;
 
wherein the number of pieces of data that are received in the receiving step is not less than the number of the terms of the polynomial;
 
and said recovering step calculates said coefficient according to the received pieces of data.
       
 
         [0021]    In another embodiment, said generating step splits said at least part of said domain management information into a plurality of pieces of data;
       said receiving step receives the plurality of pieces of data;   and said recovering step combines the received pieces of data into said at least part of said domain management information.       
 
         [0024]    In these embodiments, the operations necessary to share the management information are relatively simple and efficient; thus, the overhead for maintaining the domain is low. 
         [0025]    In another preferred embodiment, the first domain manager is the previous domain manager of the domain and said second domain manager supersedes said first domain manager as the new domain manager of the domain, and the method further comprises, before said obtaining step, the steps of:
       authenticating, by a domain authority of the domain, the second domain manager;   authenticating, by said at least one of said plurality of member devices, the second domain manager.       
 
         [0028]    In this embodiment, the new domain manager needs to be authenticated before being able to obtain the management information stored by the previous domain manager. Thus, the security of this embodiment is relatively high. 
         [0029]    Correspondingly, in a second aspect, there is provided a method of managing a domain by a domain manager of the domain, and the domain comprises a plurality of member devices, wherein the method comprises: storing domain management information in said plurality of member devices. 
         [0030]    In a third aspect, there is provided a method of managing a domain by a domain manager of the domain, the domain comprising a plurality of member devices in which domain management information is stored, wherein the method comprises the step of: obtaining said domain management information from at least one of said plurality of member devices. 
         [0031]    In a fourth aspect, there is provided a device for managing a domain, the domain comprising a plurality of member devices, wherein the device comprises: a first unit for storing domain management information in said plurality of member devices. 
         [0032]    In a fifth aspect, there is provided a device for managing a domain, the domain comprising a plurality of member devices in which domain management information is stored, wherein the device comprises: a second unit for obtaining said domain management information from at least one of said plurality of member devices. 
         [0033]    These and other features of the present invention will be described in detail in the embodiment part. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]    Features, aspects and advantages of the present invention will become apparent from reading the following description of non-limiting embodiments with the aid of the appended drawings. In the drawings, same or similar reference numerals refer to the same or similar steps or means. 
           [0035]      FIGS. 1 and 2  respectively show a schematic view of the domain before and during superseding the domain manager; 
           [0036]      FIG. 3  shows a block diagram of a device  30  for managing a domain by the previous domain manager as shown in  FIG. 1 , according to an embodiment of the invention; 
           [0037]      FIG. 4  shows a block diagram of a device  40  for managing a domain by the new domain manager as shown in  FIG. 2 , according to an embodiment of the invention; 
           [0038]      FIG. 5  shows a flowchart of the method of managing a domain, according to an embodiment of the invention; 
           [0039]      FIG. 6  shows a registration procedure of the domain manager. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0040]    A method of managing a domain comprising a plurality of member devices, the method comprising the steps of:
       storing, by a first domain manager, domain management information in said plurality of member devices;   obtaining, by a second domain manager, said domain management information from at least one of said plurality of member devices.       
 
         [0043]    A scenario in which a new domain manager supersedes a previous domain manager is described by way of example. As shown in  FIGS. 1 and 2 , the domain O comprises a plurality of member devices D 1 , D 2 , D 3 , D 4  and D 5 . As shown in  FIG. 1 , domain manager M 1  is the previous domain manager. And as shown in  FIG. 2 , domain manager M 1  crashed, for example, and needs to be superseded by the new domain manager M 2 . It should be noted that, in this example, the invention is not limited in terms of domain topology and in terms of the scenario of the superseding domain manager. 
         [0044]    With reference to  FIG. 1  to  FIG. 5 , the concept of the invention will be elucidated by describing the devices and the methods according to embodiments of the invention. 
         [0045]    As shown in  FIG. 3 , the device  30  for managing a domain comprises: a first unit  300  for storing domain management information in said plurality of member devices. 
         [0046]    As shown in  FIG. 4 , the device  40  for managing a domain comprises: a second unit  400  for obtaining said domain management information from at least one of said plurality of member devices. 
         [0047]    Initially, the domain manager Ml was authorized to act as the domain manager of this domain O by the corresponding domain authority. 
         [0048]    At a later stage, in step S 50 , the first unit  300  of the device  30  in the domain manager Ml stores domain management information in the member devices D 1 , D 2 , D 3 , D 4  and D 5 . 
         [0049]    In one embodiment, some domain management information, such as a list of member devices, could be stored in duplication in each of the member devices D 1 , D 2 , D 3 , D 4  and D 5  by the first unit  300 . And the new domain manager could obtain this information from at least any one of the member devices. 
         [0050]    In another embodiment, domain secrets in the domain management information, such as domain policy, pin code as well as private keys, could be managed in a more secure way. The first unit  300  further comprises a first subunit  3000  and a second subunit  3001 . 
         [0051]    In step S 500 , the first subunit  3000  generates a plurality of pieces of data, for example  5 , from the domain secret such that at least two pieces of data which are different from each other are required for recovering the domain secret. 
         [0052]    In one preferred embodiment, the first subunit  3000  uses secret sharing techniques to generate the pieces. One of the secret sharing techniques is the polynomial method. According to the polynomial method, the first unit  300  constructs a polynomial, wherein the domain secret is configured to be a coefficient of a term of the polynomial. After that, the first subunit  3000  generates pieces of data by using the constructed polynomial. The principle of the polynomial method is elucidated by means of the following example. 
         [0053]    If it is determined by the domain manager that at least n different pieces are required for recovering the domain secret, a polynomial with n terms can be constructed. For example, in this embodiment, 3 pieces are required for recovering the domain secret, and thus the first subunit  3000  constructs a quadratic polynomial 
         [0000]        f ( x )=( ax   2   +bx+M )mod  p    
         [0000]    where p is a random prime larger than any of the coefficients. The coefficients a and b are chosen randomly; they are kept secret and discarded after the pieces have been distributed. M is the domain secret. The prime p is public. 
         [0054]    The 5 pieces are obtained by calculating the polynomial at 5 different points: 
         [0000]        p   i =( f ( xd   i ), i ), i= 1, 2, 3, 4 and 5 
         [0055]    In other words, the first piece could have two values (f(x 1 ), 1), i.e. the polynomial evaluated at x=1; the second piece could be (f(x 2 ), 2), and so forth. 
         [0056]    Since the quadratic polynomial has three unknown coefficients, a, b, and M, any three pieces can be used to create three equations, while neither one nor two pieces can. And four or five pieces are redundant. 
         [0057]    For example, let M be 10. And f(x) is constructed as follows: 
         [0000]        f ( x )=(7 x   2 +8 x+ 10) mod 11 
         [0058]    where 7, 8 and 11 were chosen randomly. 
         [0059]    The 5 pieces are: 
         [0000]        p   1 =( f (1),1)=(3,1) 
         [0000]        p   2 =( f (2),2)=(10,2) 
         [0000]        p   3 =( f (3),3)=(9,3) 
         [0000]        p   4 =( f (4),4)=(0,4) 
         [0000]        p   5 =( f (5),5)=(5,5) 
         [0060]    In another preferred embodiment, the first subunit  3000  splits the domain secret into at least 3 sections. For example, the domain secret is 10 and 000001010 in binary format. Thus the first section is 000, the second section is 001 and the third section is 010. Each section can be taken as one of the 5 pieces of data. For example, section 1 is duplicated as piece 1 and 2, section 2 is duplicated as piece 3 and 4, and section 5 is taken as piece 5. 
         [0061]    Then, in step S 501 , the second subunit  3001  distributes the generated 5 pieces of data to member devices D 1 , D 2 , D 3 , D 4  and D 5  respectively. As shown in  FIG. 1 , piece P 1  is stored in D 1 , piece P 2  is stored in D 2 , and so forth. In this way, the domain management information has been stored. Practically, the pieces can be sent to the member device via LAN or WLAN supporting this domain. 
         [0062]    In the case that the domain manager M 1  is down. The owner of the domain uses the new domain manager M 2  to supersede the domain manager M 1 . 
         [0063]    Preferably, to increase the security, before obtaining the stored domain management information, the new domain manager M 2  needs to request authentication by the domain authority and the member devices. These authentications can be done in the registration procedure of the new domain manager, and as this procedure does not relate to the essence of the invention, it will be discussed in a later part. 
         [0064]    In step S 51 , the second unit  400  of the device  40  obtains the domain management information from the member devices D 1 , D 2 , D 3 , D 4  and D 5 . 
         [0065]    In the embodiment in which the first unit  300  stores the domain management information in duplication in each of the member devices D 1 , D 2 , D 3 , D 4  and D 5 , the second unit  400  obtains this information from at least any one of the member devices. 
         [0066]    In the preferred embodiment in which the domain manager M 1  generated 5 different pieces from the domain secret and distributed the pieces among the member devices, the second unit  400  comprises a third subunit  4001  and a fourth subunit  4002 . 
         [0067]    In step S 510 , the third subunit  401  receives at least 3 pieces of mutually different data from at least 3 of the member devices D 1 , D 2 , D 3 , D 4  and D 5 . 
         [0068]    In this embodiment, the member device D 3  is turned off Thus, the third subunit  4001  receives pieces P 1 , P 2 , P 4  and P 5 . Please note that the number of pieces of data generated is larger than the number of pieces of data that are required for recovering; thus, the domain manager M 2  does not need to collect all 5 pieces of data in order to recover the domain secret, and thus the robustness of this embodiment is increased. 
         [0069]    Corresponding to the above, in a preferred embodiment the domain manager M 1  uses the polynomial method to generate the pieces. And in step S 511 , the fourth subunit  4002  calculates the coefficient M according to the 3 received pieces of data. Specifically, the fourth subunit  4002  uses any three of the four received pieces, for example P 1 , P 4  and P 5 , and solves the following set of formulas: 
         [0000]        a* 1 2   +b* 1+ M≡ 3(mod 11) 
         [0000]        a* 3 2   +b* 3 +M≡ 9(mod 11) 
         [0000]        a *4 2   +b* 4 +M≡(mod  11) 
         [0070]    And the solution will be a=7, b=8, and M=10. Thus, M is recovered. 
         [0071]    Additional calculations can be done according to other sets of three pieces, such as P 2 , P 4  and P 5 , to recover another M and verify M by comparing the recovered several Ms. 
         [0072]    Corresponding to the above, in another preferred embodiment the domain manager M 1  splits the domain secret into at least 3 sections and takes each section as one of 5 pieces of data. The fourth subunit  4002  combines the received sections 1, 2 and 3 into the domain secret. 
         [0073]    After the domain management information has been obtained, the new domain manager could continue to utilize the domain management information. 
         [0074]    Referring to  FIG. 6 , the following part describes the registration procedure of the new domain manager. 
         [0075]    i. Domain manager owner (DMO) sends request message to supersede domain manager to Domain Authority (DA) using a candidate domain manager (CDM); the request message may include PDM DAID  (ID of the previous domain manager allocated by DA), CDM IID  (Initial ID of the CDM), and a signature on the request by DMO to supersede DM. 
         [0076]    ii. DA verifies signature. If the result of the verification is “pass”, go on to the next step; otherwise, return error message and stop domain manager superseding process. 
         [0077]    iii. DA and CDM authenticate each other. If mutual authentication is “success” and DA identifies that CDM can be a domain manager, go on to the next step; otherwise, error message is returned and domain manager superseding process is stopped. 
         [0078]    iv. DA creates domain management information for CDM, such as CDM DAID  (ID of the CDM allocated by DA), domain management key and authorization certificate for CDM as the domain manager; and creates DM superseding certificate which includes PDM DAID , CDM DAID , the description of DM superseding and signature by DA on the above mentioned information. Alternatively, DA might send the latest domain policy to CDM if DA has ever created more than one domain policy for PDM. 
         [0079]    v. The CDM becomes the new domain manager (NDM) and sends DM superseding certificate with DA signature to each member device. 
         [0080]    vi. Each member device verifies the superseding signature. If verification is “pass”, go on to the next step; otherwise, return error message and stop DM superseding process. 
         [0081]    vii. NDM and each device authenticate each other. If mutual authentication is “success”, each device sends the stored piece to the NDM, and the NDM recovers the domain management information; otherwise, error message is returned and DM superseding process is stopped. 
         [0082]    viii. NDM sends some domain management information, such as domain policy and public keys, to every device. 
         [0083]    ix. Every device verifies domain management information with NDM&#39;s signature. If verification is “pass”, devices accept domain management information updated by NDM and replace the old information; otherwise, return error message. 
         [0084]    x. NDM informs DA that DM superseding process is completed. 
         [0085]    It should be noted that the number of pieces of data and the number of member devices are not necessarily the same. They could be the same, in which case one piece of data is stored into one member device; they could also be different, however, in which case either the data pieces outnumber the member devices or the other way round. In the latter case, one data piece may be stored in more than one member device, or more than one data piece may be stored in one member device. 
         [0086]    It should be noted that the terms domain manager and member device are meant to describe the function of one apparatus in the respective domain, and that this should not be construed as limiting the practical apparatus bearing the domain manager or the member devices. For example, the domain manager may be just a smart phone, and the member devices may be PCs. 
         [0087]    The above units and sub-units can be implemented by way of either software or hardware or a combination thereof. For example, the program codes achieving the functions of these units or sub-units are stored in a memory. These codes are loaded and executed by the CPU or other controller which controls the apparatus bearing the domain manager. In another example, a certain IC chip achieves the functions of these units and sub-units, and the chip can be controlled by the CPU or other controller. Those skilled in the art could implement embodiments of the invention in various ways according to the concept and principle taught by the description. 
         [0088]    Those of ordinary skill in the art could understand and realize modifications to the disclosed embodiments, through studying the description, drawings and appended claims. All such modifications which do not depart from the spirit of the invention are intended to be included within the scope of the appended claims. The word “comprising” does not exclude the presence of elements or steps not listed in a claim or in the description. The word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. In the practice of the present invention, several technical features in the claims can be embodied by one component. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.