CA2506146C - Improved subset difference method for multi-cast rekeying - Google Patents
Improved subset difference method for multi-cast rekeying Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
- H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
- H04L9/0816—Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
- H04L9/0819—Key transport or distribution, i.e. key establishment techniques where one party creates or otherwise obtains a secret value, and securely transfers it to the other(s)
- H04L9/083—Key transport or distribution, i.e. key establishment techniques where one party creates or otherwise obtains a secret value, and securely transfers it to the other(s) involving central third party, e.g. key distribution center [KDC] or trusted third party [TTP]
- H04L9/0833—Key transport or distribution, i.e. key establishment techniques where one party creates or otherwise obtains a secret value, and securely transfers it to the other(s) involving central third party, e.g. key distribution center [KDC] or trusted third party [TTP] involving conference or group key
- H04L9/0836—Key transport or distribution, i.e. key establishment techniques where one party creates or otherwise obtains a secret value, and securely transfers it to the other(s) involving central third party, e.g. key distribution center [KDC] or trusted third party [TTP] involving conference or group key using tree structure or hierarchical structure
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
- H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
- H04L9/0816—Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
- H04L9/0819—Key transport or distribution, i.e. key establishment techniques where one party creates or otherwise obtains a secret value, and securely transfers it to the other(s)
- H04L9/0822—Key transport or distribution, i.e. key establishment techniques where one party creates or otherwise obtains a secret value, and securely transfers it to the other(s) using key encryption key
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
- H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
- H04L9/0891—Revocation or update of secret information, e.g. encryption key update or rekeying
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L2209/00—Additional information or applications relating to cryptographic mechanisms or cryptographic arrangements for secret or secure communication H04L9/00
- H04L2209/60—Digital content management, e.g. content distribution
Abstract
An improved subset-difference method is provided. The improved method uses the value of a current content key to help generate the requisite difference keys.
The requisite difference keys are then used to encrypt the next content key which will be delivered only to users who are supposed to remain in the group.
Users who have the current content key are then able to generate the requisite difference keys which they can then use to decrypt the next content key. Using the decrypted next content key, the users are then able to continue to receive contents. Since previously revoked users do not have the current content key, they are unable to determine the next content key and thus are prevented from receiving future contents.
The requisite difference keys are then used to encrypt the next content key which will be delivered only to users who are supposed to remain in the group.
Users who have the current content key are then able to generate the requisite difference keys which they can then use to decrypt the next content key. Using the decrypted next content key, the users are then able to continue to receive contents. Since previously revoked users do not have the current content key, they are unable to determine the next content key and thus are prevented from receiving future contents.
Description
IMPROVED SUBSET DIFFERENCE METHOD FOR MULTI-CAST
REKEYING
BACKGROUND OF THE INVENTION
[0001] The present invention generally relates to multicasting in a network, and more specifically, to a method and system for providing improved multicast key management in a network.
REKEYING
BACKGROUND OF THE INVENTION
[0001] The present invention generally relates to multicasting in a network, and more specifically, to a method and system for providing improved multicast key management in a network.
[0002] Using modern technologies that are available today, content delivery systems are capable of delivering contents over computer networks to a large number of users. A
typical content delivery system includes a caching server responsible for delivering contents and a large number of clients or client applications that are under the control of the users. For example, a content delivery system may need to support hundreds of thousands, and possibly even millions, of users viewing a single event or program. In some cases, the programs are lengthy in duration and users are interested in only viewing some portion of a program (e.g., Olympics, shopping channel, news etc.). In order to charge users for such programming, it then becomes necessary to support a pay-by-time model. In a pay-by-time model, a user is charged only for the portion of the program that he or she consumed.
typical content delivery system includes a caching server responsible for delivering contents and a large number of clients or client applications that are under the control of the users. For example, a content delivery system may need to support hundreds of thousands, and possibly even millions, of users viewing a single event or program. In some cases, the programs are lengthy in duration and users are interested in only viewing some portion of a program (e.g., Olympics, shopping channel, news etc.). In order to charge users for such programming, it then becomes necessary to support a pay-by-time model. In a pay-by-time model, a user is charged only for the portion of the program that he or she consumed.
[0003] In a secure set-top client, such pay-by-time functionality may be more easily implemented in a secure manner. For example, tamper-proof hardware can be used in the set-top client to report in an accurate manner the amount of time that the client tuned in to a particular program. However, a general personal computer (PC) client cannot be trusted to perform such a task securely. This is because such PC client can be easily hacked. As a result, in order to support pay-by-time functionality with untrusted clients, a program needs to be delivered in a secure manner. One way to assure secure delivery of a program is to divide the program into program segments. There is a unique program segment key associated with each program segment, where the program segment key could be either used to encrypt the content within that program segment directly or it can be used to encrypt multiple content keys. A user that is authorized for a particular program segment will get the corresponding program segment key and will use it to decrypt the multiple content keys that are in turn used to decrypt the content within the program segment for viewing. In this manner, users that decide to leave a multicast or broadcast program would simply not be given more program segment keys for the following program segments, while the remaining users would continue receiving new program segment keys to allow them to continue viewing.
[0004] One straight-forward approach to support pay-by-time key management is to individually deliver the next program segment key to each user that remains in the multicast or broadcast group. This approach presents a number of problems. For example, for large multicast groups, this approach requires delivering program segment keys well ahead of time to ensure that such keys are delivered in time for each user. Even then, pay-by-time system scalability is severely limited by re-keying and the size of each program segment must be sufficiently large to insure that subsequent program segment keys can be delivered in time.
[0005] A number of multicast re-keying approaches have been proposed in an attempt to solve the foregoing problem. Many of these approaches are efficient at revoking a few users at a time from a multicast group and are based on the assumption that users leave at a constant rate. However, in practical situations, a large number of users may leave and users cannot be expected to leave a multicast group on a constant basis. To the contrary, user departure rate tends to fluctuate widely over the course of a program. For example, a large number of users tend to all want to leave a multicast group after some logical portion of the program is over (e.g., a specific Olympic event). Hence, these existing approaches still do not provide sufficient scalability that would efficiently accommodate varying user departure rate, such as, when a large number of users decide to leave a multicast group within a short period of time (e.g., within the same program segment).
[0006] In one of the proposed multicast key management schemes commonly known as the subset-difference method, each user is placed as a leaf into a binary tree and is given a subset of keys in that tree that depends on the user's position in that tree.
The first time that a subgroup of users needs to be revoked from the group, the overhead of removing such subgroup of users from the group is proportional to the size of the to-be-revoked subgroup.
This appears to provide as much scalability as can be expected. However, as time goes on and additional users leave the group, the overhead of removing such subsequent users becomes proportional to the number of users that have left the group since the beginning of the event. Consequently, as more and more users leave the group, the ability to revoke users from the group will likely degrade to an unacceptable level.
The first time that a subgroup of users needs to be revoked from the group, the overhead of removing such subgroup of users from the group is proportional to the size of the to-be-revoked subgroup.
This appears to provide as much scalability as can be expected. However, as time goes on and additional users leave the group, the overhead of removing such subsequent users becomes proportional to the number of users that have left the group since the beginning of the event. Consequently, as more and more users leave the group, the ability to revoke users from the group will likely degrade to an unacceptable level.
[0007] For purposes of illustration and simplicity herein, it should be understood that a user can be either a person or a client or client application or device that is under the control of a user.
[0008] Fig. 1 is a simplified schematic diagram illustrating a set of users belonging to a particular multicast group that have been arranged into a binary tree according to the subset-difference method. The binary tree has a number of nodes V1 - V15 and a number of leaves V16 - V31. The leaves of the tree V16 - V31 represent the actual users and the leaves that are shaded, V18, V19, V21, V24, V25, V26 and V27, correspond to users that are to be revoked from the group.
[0009] The binary tree is further divided into subtrees that are rooted at nodes V4, V5 and Vg. Each of these subtrees contains an inner subtree, where an inner subtree includes only the to-be-revoked leaves. For example, for a subtree rooted at node V4, there is an inner subtree rooted at node V9 that contains only the to-be-revoked leaves, V18 and V19.
[0010] The main idea of the subset-difference method is to have a key for each of the outer subtrees that is known to everyone in the outer subtree but not known to anyone inside the inner (revoked) subtree. This key is designated as LI,j. For example, for the outer subtree rooted at node V4, this outer subtree including node Vg and leaves V16 and V17, there is a key L4,9 that is known only to leaves V16, V17 but not to leaves V18, V19. In this example, in order to revoke leaves V18, V19, V21, V24, V25, V26 and V27, a new content key (CK) is sent out encrypted using the following difference keys: L4,9, L5,21 and 1,3,6.
[0011] Keys LI,J are generated as follows. First, each inner node VI
in the tree is assigned a unique and independent label LABEL'. Then, a "difference label" for the left child of VI is derived using an one-way function GL: GL(LABELI). Similarly, for the right child of VI, a difference label GR(LABELI) is created. Next, in order to compute a difference label LABELLJ for an outer subtree rooted at node VI and an inner subtree rooted at node V,J, one has to start with the original label LABEL' for node VI and then derive the difference label by applying functions GL and GR multiple times, depending on the path between VI
and Vj. For example, label LABEL3,28 = GL(GL,(GR(LABEL3))). The key LiJ is then computed by simply applying another one-way function Gm to the difference label LABELI,J, i.e., LI,J =
Gm(LABEW.
in the tree is assigned a unique and independent label LABEL'. Then, a "difference label" for the left child of VI is derived using an one-way function GL: GL(LABELI). Similarly, for the right child of VI, a difference label GR(LABELI) is created. Next, in order to compute a difference label LABELLJ for an outer subtree rooted at node VI and an inner subtree rooted at node V,J, one has to start with the original label LABEL' for node VI and then derive the difference label by applying functions GL and GR multiple times, depending on the path between VI
and Vj. For example, label LABEL3,28 = GL(GL,(GR(LABEL3))). The key LiJ is then computed by simply applying another one-way function Gm to the difference label LABELI,J, i.e., LI,J =
Gm(LABEW.
[0012] When a particular leaf "u" is first initialized (i.e., when joining a multicast), this leaf "u" receives the following labels: for every VI ancestor of leaf "u", leaf "u" receives LABEL1,3, LABEL1,4, LABEL1,10,LABEL1,23, LABEL2,4, LABRL2,10, LABEL2,23, LABEL5,10, LABEL5,23, LABELii,23 The foregoing is graphically illustrated in Fig. 2.
[0013] Referring back to Fig. 1, in order to revoke the indicated leaves (Vis, V19, V21) V24, 1125, V26 and V27), as previously mentioned, the new content key is sent out encrypted using L4,9, L5,21 and L3,6. In order for V22 to obtain the new content key, V22 derives L5,21 from LABEL5,10 (which it was given during initialization) as follows:
L5,21 = Gm(LABEL5,21) = Om(G1(LABEL5,1o)) Log(N) + (Log(N)-1) + (Log(N)-2) + +1 = Log(N) * (Log(N)+1)/2 The foregoing can be simplified to 0(log(N)2), where 0(N) is the number of messages required for one rekeying for N users participating in the multicast. For example, with N = 8 million ¨ 223, each user joining a multicast would get initialized with two hundred and
L5,21 = Gm(LABEL5,21) = Om(G1(LABEL5,1o)) Log(N) + (Log(N)-1) + (Log(N)-2) + +1 = Log(N) * (Log(N)+1)/2 The foregoing can be simplified to 0(log(N)2), where 0(N) is the number of messages required for one rekeying for N users participating in the multicast. For example, with N = 8 million ¨ 223, each user joining a multicast would get initialized with two hundred and
[0014] One main problem with the subset-difference method is that once some users in the group are revoked, none of the inner node labels and none of the difference keys are modified. As a result, in order to insure that the previously revoked users do not receive any more content keys, these users have to be counted as to-be-revoked users during each
[0015] It would be impractical to modify the inner node labels during each rekeying
[0016] In addition to this problem, since each user of the group has to be initialized with a considerable amount of keying material which in the worst case scenario could amount to several Kbytes, it would be impractical to initialize each user joining a multicast with all of the necessary labels at the time s/he joins the multicast.
[0017] Hence, it would be desirable to provide an improved subset-difference method that is able to improve multicast key management in a network to allow for more efficient revocation of users from a group and conversely rekeying of remaining users.
BRIEF SUMMARY OF THE INVENTION
BRIEF SUMMARY OF THE INVENTION
[0018] An improved subset-difference method is provided. The improved method uses the value of a current content key to help generate the requisite difference keys. The requisite difference keys are then used to encrypt the next content key which will be delivered only to users who are supposed to remain in the group. Users who have the current content key are then able to generate the requisite difference keys which they can then use to decrypt the next content key. Using the decrypted next content key, the users are then able to continue to receive contents. Since previously revoked users do not have the current content key, they are unable to determine the next content key and thus are prevented from receiving future contents.
[0019] In an exemplary application, the present invention can be deployed in systems that rely on secure information delivery where the information is encrypted using a common group key. Such systems include, for example, multicast or broadcast content delivery systems.
[0020] The exemplary method of the present invention provides a number of advantages and/or benefits. For example, in order to rekey a group, only 0(r) messages are needed, where r is the number of users to be revoked, as compared to the subset-difference method, where 0(R) messages are needed to accomplish the same task, only that R is the number of users that have been revoked from the very beginning of a multicast.
[0021] Reference to the remaining portions of the specification, including the drawings and claims, will realize other features and advantages of the present invention.
Further features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described in detail below with respect to accompanying drawings, like reference numbers indicate identical or functionally similar elements.
BRIEF DESCRIPTION OF THE DRAWINGS
Further features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described in detail below with respect to accompanying drawings, like reference numbers indicate identical or functionally similar elements.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Fig. 1 is a simplified schematic diagram illustrating a set of users of a particular multicast that have been arranged into a binary tree according to the subset-difference method; and
[0023] Fig. 2 is a simplified schematic diagram illustrating initialization of a leaf in a binary tree according to the subset-difference method.
DETAILED DESCRIPTION OF THE INVENTION
DETAILED DESCRIPTION OF THE INVENTION
[0024] The present invention in the form of one or more exemplary embodiments will now be described. According tolone exemplary method of the present invention, the subset-difference method as described above is improved such that the overhead of removing members from a multicast group is proportional only to the size of the next set of members that want to leave the group.
[0025] The exemplary method modifies the subset-difference method to achieve the foregoing improvement as follows. Assume that the current content key is CKp and the next content key that is to be sent out during revocation of some leaves in the tree is Cl(p+1. Then, the difference key LI,j is computed as follows:
= Gm(LABELLJ, Cl<p) During the next rekeying, difference keys are changed to the following values:
= Gm(LABELLj, CKp+1) Also, the content key will be changed to CKp-1-2.
= Gm(LABELLJ, Cl<p) During the next rekeying, difference keys are changed to the following values:
= Gm(LABELLj, CKp+1) Also, the content key will be changed to CKp-1-2.
[0026] During the second rekeying, since previously revoked users in the group do not knoW the content key Cl(p+i, they will not be able to generate the correct difference key LLT and therefore they will also not be able to figure out the value of CKp+2.
As a result, any previously revoked user that does not possess a current content key is unable to get the next content key even if it had all the labels in the tree. Hence, during the second rekeying, it is not necessary to revoke the previously revoked leaves again. In other words, only the additional to-be-revoked leaves need to be revoked.
As a result, any previously revoked user that does not possess a current content key is unable to get the next content key even if it had all the labels in the tree. Hence, during the second rekeying, it is not necessary to revoke the previously revoked leaves again. In other words, only the additional to-be-revoked leaves need to be revoked.
[0027] In some situations, a user that previously left the group may re-join subsequently and gets a different position in the tree. In this case, the user will have the difference keys for two different leaves and if that user leaves a second time, it may still be able to get content keys using its difference keys from the first period of membership in the group. In order to avoid this situation of users getting unauthorized content keys, the respective positions of revoked users in the tree are recorded and if a revoked user joins again, it is given the same position as last time when it was in the group.
[0028] With respect to the issue of amount of keying material needed to initialize a user joining a multicast group, the amount of such material can be reduced by not varying the labels for each multicast. The tree with all of its labels for inner nodes is kept relatively static, possibly only changing occasionally like the service keys. In one exemplary embodiment implemented using a Kerberos or ESBroker system, the values of the labels in the tree are globally made the same and are stored in a key distribution center (KDC) database. The KDC database is responsible for maintaining and handing out multicast group keys at a periodic interval. The KDC database would return a complete set of labels along with a ticket granting ticket (TGT) to each caching server and would also return an appropriate subset of the labels to each user along with the user's TGT. As a result, the user's position in he multicast key hierarchy would be determined during an initial exchange (AS
Req/Rep) with the KDC database.
Req/Rep) with the KDC database.
[0029] In one exemplary application where pay-by-time events are sold in units of program segments, the exemplary method for rekeying is applied to effect changing program segment keys. A difference key LI,J is computed as follows: LI,J Gm(LABELLJ, PSKp), where PSKp represents the program segment key. In this application, the very first PSKp delivered to a user that joins a group cannot be delivered using the exemplary method, since PSICp_i is not known at that time to this user. Preferably, the first PSICp would be delivered to a user using the same point-to-point protocol (e.g., Kerberos) that is used to verify the identity of this user and check if the user is authorized for the multicast.
[0030] Furthermore, in order to avoid cloning of the set of difference labels. The KDC database can change the set of difference labels on a periodic basis, such as once a month or once every several months, and the different sets of labels could be identified with a predetermined version number for synchronization.
[0031] In one exemplary embodiment, the present invention is implemented in the form of control logic using computer software. Based on the disclosure and teachings provided herein, it will be appreciated by a person of ordinary skill in the art that the present invention can-be implemented in other ways and/or methods including, for example, .
hardware and/or a combination of hardware and software.
hardware and/or a combination of hardware and software.
[0032] It is understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims.
Claims (5)
1. An improvement to a subset-difference method, the subset-difference method using a plurality of difference keys to encrypt a content key which is used for delivery of contents, each of the plurality of difference keys being generated by using a corresponding label, the improvement comprising:
generating during a first rekeying each of the plurality of difference keys L
I,J
by applying a one-way function G M to the corresponding current label, LABEL
I,J and a first current content key, CK P;
generating during a next rekeying each of the plurality of difference keys L
I,J
by applying a one-way function G M to the corresponding current label, LABEL
I,J and the next current content key, CK P+1; and wherein a next sequential content key, CK P+2, generated by applying a one-way function G M to the corresponding current label, LABEL I,J and content key, CK P+1, is used to ensure continued delivery of contents.
generating during a first rekeying each of the plurality of difference keys L
I,J
by applying a one-way function G M to the corresponding current label, LABEL
I,J and a first current content key, CK P;
generating during a next rekeying each of the plurality of difference keys L
I,J
by applying a one-way function G M to the corresponding current label, LABEL
I,J and the next current content key, CK P+1; and wherein a next sequential content key, CK P+2, generated by applying a one-way function G M to the corresponding current label, LABEL I,J and content key, CK P+1, is used to ensure continued delivery of contents.
2. A content delivery system implementing an improvement to a subset-difference method using a plurality of difference keys to encrypt a content key which is used for delivery of contents, the content delivery system being capable of providing multicasting and comprising:
means for generating during a first rekeying each of the plurality of difference keys L I,J by applying a one-way function G M to the corresponding current label, LABEL I,J and a first current content key, CK P;
means for generating during a next rekeying each of the plurality of difference keys L I,J by applying a one-way function G M to the corresponding current label, LABEL I,J and the next current content key, CK P+1; and wherein a next sequential content key, CK P+2, generated by applying a one-way function G M to the corresponding current label, LABEL I,J and content key, CK P+1, is used to ensure continued delivery of contents.
means for generating during a first rekeying each of the plurality of difference keys L I,J by applying a one-way function G M to the corresponding current label, LABEL I,J and a first current content key, CK P;
means for generating during a next rekeying each of the plurality of difference keys L I,J by applying a one-way function G M to the corresponding current label, LABEL I,J and the next current content key, CK P+1; and wherein a next sequential content key, CK P+2, generated by applying a one-way function G M to the corresponding current label, LABEL I,J and content key, CK P+1, is used to ensure continued delivery of contents.
3. The content delivery system of claim 2, wherein the content delivery system includes a plurality of clients under the control of corresponding users, a key distribution center and a caching server; and wherein the key distribution center delivers the corresponding labels that are used to respectively generate the plurality of difference keys to the plurality of clients and the caching server.
4. An improvement to a subset-difference method, the subset-difference method using a plurality of difference keys to encrypt a program segment key which is used for delivery of contents, each of the plurality of difference keys being generated by using a corresponding label, the improvement comprising:
generating during a first rekeying each of the plurality of difference keys L
I,J
by applying a one-way function G M to the corresponding current label, LABEL
I,J and a first current program segment key, PSK P;
generating during a next rekeying each of the plurality of difference keys L
I,J
by applying a one-way function G M to the corresponding current label, LABEL
I,J and the next current program segment key, PSK P+1 ; and wherein a next sequential program segment key, PSK P+2, generated by applying a one-way function G M to the corresponding current label, LABEL I,J
and program segment key, PSK P+1, is used to ensure continued delivery of contents.
generating during a first rekeying each of the plurality of difference keys L
I,J
by applying a one-way function G M to the corresponding current label, LABEL
I,J and a first current program segment key, PSK P;
generating during a next rekeying each of the plurality of difference keys L
I,J
by applying a one-way function G M to the corresponding current label, LABEL
I,J and the next current program segment key, PSK P+1 ; and wherein a next sequential program segment key, PSK P+2, generated by applying a one-way function G M to the corresponding current label, LABEL I,J
and program segment key, PSK P+1, is used to ensure continued delivery of contents.
5. A computer program product comprising a computer readable memory storing computer executable instructions thereon that when executed by a computer perform the method of claim 1.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US10/318,486 | 2002-12-13 | ||
| US10/318,486 US7450722B2 (en) | 2002-12-13 | 2002-12-13 | Subset difference method for multi-cast rekeying |
| PCT/US2003/039294 WO2004056037A1 (en) | 2002-12-13 | 2003-12-10 | Improved subset difference method for multi-cast rekeying |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2506146A1 CA2506146A1 (en) | 2004-07-01 |
| CA2506146C true CA2506146C (en) | 2013-07-09 |
Family
ID=32506358
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2506146A Expired - Fee Related CA2506146C (en) | 2002-12-13 | 2003-12-10 | Improved subset difference method for multi-cast rekeying |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US7450722B2 (en) |
| EP (1) | EP1570600B1 (en) |
| AU (1) | AU2003297834A1 (en) |
| CA (1) | CA2506146C (en) |
| WO (1) | WO2004056037A1 (en) |
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| US7849016B2 (en) * | 2002-12-18 | 2010-12-07 | Vincent So | Internet-based data content rental system and method |
| US7313238B2 (en) * | 2003-01-31 | 2007-12-25 | Hewlett-Packard Development Company, L.P. | Method and system for relating cryptographic keys |
| GB2400526B (en) * | 2003-04-08 | 2005-12-21 | Hewlett Packard Development Co | Cryptographic key update management |
| US7697690B2 (en) * | 2003-07-21 | 2010-04-13 | Hewlett-Packard Development Company, L.P. | Windowed backward key rotation |
| DE60322929D1 (en) * | 2003-12-23 | 2008-09-25 | Motorola Inc | Key update in secure multicast communication |
| JP4690420B2 (en) * | 2004-11-16 | 2011-06-01 | テレフオンアクチーボラゲット エル エム エリクソン（パブル） | Improved key distribution in a system for selective access to information |
| US7813510B2 (en) * | 2005-02-28 | 2010-10-12 | Motorola, Inc | Key management for group communications |
| JP4599194B2 (en) * | 2005-03-08 | 2010-12-15 | 株式会社東芝 | Decoding device, decoding method, and program |
| KR100765750B1 (en) * | 2005-05-09 | 2007-10-15 | 삼성전자주식회사 | Method and apparatus for encrypting/decrypting efficiently according to broadcast encryption scheme |
| KR100708133B1 (en) | 2005-05-25 | 2007-04-17 | 삼성전자주식회사 | Method and apparatus for encrypting/decrypting efficiently according to broadcast encryption scheme |
| KR100708134B1 (en) | 2005-05-25 | 2007-04-17 | 삼성전자주식회사 | Method and apparatus for encrypting/decrypting efficiently according to broadcast encryption scheme |
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| KR101223499B1 (en) * | 2006-09-27 | 2013-01-18 | 삼성전자주식회사 | Method of updating group key and group key update device using the same |
| KR101300843B1 (en) * | 2006-11-29 | 2013-08-29 | 삼성전자주식회사 | Method of generating rekey index and rekey index generator using the same |
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| US20020002678A1 (en) * | 1998-08-14 | 2002-01-03 | Stanley T. Chow | Internet authentication technology |
| EP1075108A1 (en) * | 1999-07-23 | 2001-02-07 | BRITISH TELECOMMUNICATIONS public limited company | Cryptographic data distribution |
| US7065643B1 (en) * | 2000-03-28 | 2006-06-20 | Motorola, Inc. | Network compromise recovery methods and apparatus |
| JP2003535559A (en) * | 2000-06-02 | 2003-11-25 | キネティック サイエンシーズ インコーポレイテッド | Email biometric encryption method |
| TW548983B (en) * | 2000-10-26 | 2003-08-21 | Gen Instrument Corp | Initial viewing period for scalable authorization of streaming multimedia content |
| US7096266B2 (en) * | 2001-01-08 | 2006-08-22 | Akamai Technologies, Inc. | Extending an Internet content delivery network into an enterprise |
| US7684565B2 (en) * | 2001-01-16 | 2010-03-23 | General Instrument Corporation | System for securely communicating information packets |
| US7010125B2 (en) * | 2001-01-26 | 2006-03-07 | Interntional Business Machines Corporation | Method for tracing traitor receivers in a broadcast encryption system |
| US7039803B2 (en) * | 2001-01-26 | 2006-05-02 | International Business Machines Corporation | Method for broadcast encryption and key revocation of stateless receivers |
| US20030126464A1 (en) * | 2001-12-04 | 2003-07-03 | Mcdaniel Patrick D. | Method and system for determining and enforcing security policy in a communication session |
| US7340603B2 (en) * | 2002-01-30 | 2008-03-04 | Sony Corporation | Efficient revocation of receivers |
| US7092527B2 (en) * | 2002-04-18 | 2006-08-15 | International Business Machines Corporation | Method, system and program product for managing a size of a key management block during content distribution |
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2002
- 2002-12-13 US US10/318,486 patent/US7450722B2/en not_active Expired - Fee Related
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2003
- 2003-12-10 EP EP03796905.2A patent/EP1570600B1/en not_active Expired - Fee Related
- 2003-12-10 CA CA2506146A patent/CA2506146C/en not_active Expired - Fee Related
- 2003-12-10 WO PCT/US2003/039294 patent/WO2004056037A1/en not_active Application Discontinuation
- 2003-12-10 AU AU2003297834A patent/AU2003297834A1/en not_active Abandoned
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|---|---|
| EP1570600A1 (en) | 2005-09-07 |
| US7450722B2 (en) | 2008-11-11 |
| WO2004056037A1 (en) | 2004-07-01 |
| CA2506146A1 (en) | 2004-07-01 |
| US20040114762A1 (en) | 2004-06-17 |
| AU2003297834A1 (en) | 2004-07-09 |
| EP1570600B1 (en) | 2016-09-07 |
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