KR101494510B1 - Apparatus and method for managing group key, recording medium thereof - Google Patents

Abstract

A group key management apparatus and method and a recording medium therefor are disclosed. A group key management apparatus for group communication, the group key management apparatus comprising: a group key generation unit configured to generate a group key using symmetric keys and random values of n (2 or more natural number) terminal apparatuses belonging to a predetermined group; ; And a transmitter for transmitting the group key to at least one of the terminal devices, wherein the group key is updated when the group member is changed. According to the present invention, there is an advantage that a group key can be efficiently generated and distributed even in an environment where terminal devices join and leave the group from time to time. Further, according to the present invention, there is an advantage that both the forward and backward stability of the group key can be assured.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a group key management apparatus and method,

Embodiments of the present invention relate to a group key management apparatus and method for broadcast communication in a group and a recording medium therefor.

Repetition of excessive data transmission, encryption and decryption processes in the process of updating and distributing a group key for broadcast communication in a group, or design that is not suitable for various devices increases the cost of group key management.

For example, in the case of performing an operation more than necessary for updating a group key or using a public key-based algorithm when distributing a generated group key, much time is required for encryption and decryption, do.

On the other hand, in a group key renewal and management technique based on a hash chain, an inverse hash chain technique can be used to ensure both the forward and backward stability of the group key.

Due to the unidirectionality of the hash function, backward stability of the group key can also be ensured through the reverse hash chain technique.

However, when such a reverse hash chain technique is used, there is a problem that the number of update of the group key is limited.

That is, assuming that the server holds a certain length of hash chain by executing a hash function a predetermined number of times in advance, if the number of group key updates due to the user's group joining is larger than the length of the hash chain, There is a problem that the method can not be used.

Therefore, if the length of the hash chain is increased, a problem of memory waste occurs.

Korean Patent Application Publication No. 10-2005-0047990 (entitled " Dynamic Group Key Management Device and Method Therefor in Wireless LAN System)

According to an aspect of the present invention, there is provided a group key management apparatus and method for efficiently generating and distributing a group key even in an environment where terminal devices join and leave the group from time to time, .

Other objects of the invention will be apparent to those skilled in the art from the following examples.

According to a preferred embodiment of the present invention, there is provided a group key management apparatus for group communication, comprising: a key management unit for managing symmetric keys and random values of n (2 or more natural numbers) A group key generation unit for generating a group key by using the group key; And a transmitter for transmitting the group key to at least one of the terminal devices, wherein the group key is updated when a member of the group is changed.

According to another embodiment of the present invention, there is provided a group key management method for a group key management apparatus for intra-group communication, comprising the steps of: using symmetric keys and random values of n (two or more natural numbers) terminal devices belonging to a predetermined group Generating a group key; And transmitting the group key to at least one of the terminal devices, wherein the group key is updated when a member of the group is changed.

According to another embodiment of the present invention, there is provided a computer-readable recording medium on which a program for performing the group key management method described above is recorded.

According to the present invention, there is an advantage that a group key can be efficiently generated and distributed even in an environment where terminal devices join and leave the group from time to time.

Further, according to the present invention, there is an advantage that both the forward and backward stability of the group key can be assured.

1 is a diagram schematically illustrating a state in which a server for group broadcast communication according to an embodiment of the present invention is connected to a plurality of terminal devices for a group key management operation.
2 is a diagram illustrating a group key management apparatus according to an embodiment of the present invention.
3 is a flowchart illustrating a group key management method of a group key management apparatus according to an exemplary embodiment of the present invention.
4 is a diagram schematically illustrating a message exchanged between a group key management apparatus and each terminal apparatus in a group key generating step and a transmitting step according to an embodiment of the present invention.
5 is a diagram schematically showing a message exchanged between a group key management apparatus and each terminal apparatus in a step of updating a group key when a subscription of a terminal apparatus is made to a group according to an embodiment of the present invention; to be.
6 is a diagram schematically showing a message exchanged between a group key management apparatus and each terminal apparatus in the step of renewing a group key when a terminal apparatus is withdrawn from a group according to an embodiment of the present invention; to be.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram schematically illustrating a state in which a server for group broadcast communication according to an embodiment of the present invention is connected to a plurality of terminal devices for a group key management operation.

1, the server 100 is connected to a plurality of terminal devices 200A, 200B, 200C and 200D via a network, and is connected to three terminal devices 200A, 200B and 200C belonging to a predetermined group And generates and distributes a group key for broadcast communication in the group.

The network may include a wired / wireless Internet, a satellite network, a communication network, and a mobile communication network.

The server 100 according to an embodiment of the present invention updates and redistributes a group key when a new terminal device joins a predetermined group or when an existing terminal device withdraws.

To this end, the server 100 generates a group key for broadcast communication in the group using the terminal device information, and transmits the group key encrypted with the symmetric key shared with each terminal device to the corresponding terminal device in the group do.

More specifically, according to an embodiment of the present invention, information on all symmetric keys shared between each terminal device belonging to a group and a server, and a result value of a hash operation on a random value are utilized, , And the random value is modified each time the group key is updated to perform a hash operation, thereby ensuring forward and backward security of the group key.

The server 100 and the first terminal device 200A share a pair of symmetric keys (hereinafter, referred to as a 'first symmetric key'). The server 100 and the plurality of terminal devices share a pair of symmetric keys. The server 100 and the second terminal device 200B share a pair of symmetric keys (hereinafter referred to as a second symmetric key), and the third terminal device 200C and the second terminal device 200B share the same 4 terminal device 200D in the same manner.

The symmetric key encryption algorithm is an algorithm having the same key used for encrypting and decrypting data. The server 100 and the plurality of terminal devices 200A, 200B, 200C, and 200D share each other when exchanging messages It is used for encryption and decryption by using a symmetric key.

For example, if the first terminal device 200A encrypts the information of the group to which the subscriber wants to subscribe using the first symmetric key, which is its own symmetric key, and transmits the encrypted information to the server, Decrypts the received message using the shared first symmetric key and verifies the information of the group.

Similarly, when the second terminal device 200B transmits a join request encrypted with the second symmetric key, which is its own symmetric key, to the server, the server 100 transmits the second symmetric key, which is shared with the second terminal device 200B, And confirms the corresponding group information.

The symmetric key shared between the server and each terminal can be generated when the terminal device is registered with the server or by a Diffie-Hellman technique.

In this way, the server 100 generates and distributes the group key using information on all the symmetric keys shared by the terminal devices in the group, and the result of the hash calculation on the random value, Update the group key according to joining or leaving.

Therefore, according to the present invention, each terminal device can not know the symmetric key of the other terminal devices, the random value generated by the server, or the hash calculation result value of the generated random value, Can be guaranteed.

In addition, the server and each terminal device have an advantage that message exchange can be performed more quickly by encrypting and decrypting the group key with a symmetric key.

Meanwhile, the server 100 according to an embodiment of the present invention operates mainly on group key management for broadcast communication in a group. Hereinafter, for convenience of explanation, it is assumed that the server is a group key management device . At this time, the server and the group key management apparatus may be the same apparatus, and the group key management apparatus may be a module existing as a part of the server.

2 is a diagram illustrating a group key management apparatus according to an embodiment of the present invention.

3 is a flowchart illustrating a group key management method of a group key management apparatus according to an exemplary embodiment of the present invention.

2 and 3, the group key management apparatus 100 includes a group key generation unit 110, a transmission unit 120, and a group key update unit 130, (S310), a transmitting step (S320), and a group key updating step (S330).

First, in step S310, the group key generation unit 110 uses the hash calculation result values of n symmetric keys and random values shared by n (two or more natural number) terminal apparatuses belonging to a predetermined group Create a group key.

According to an embodiment of the present invention, the group key may be generated by XORing n hash operation results for n symmetric keys and random values.

The random value according to an exemplary embodiment of the present invention may be an integer variable and is set to an arbitrary value for each group.

 As described below, the random value is a value that is modified when the group key is updated, and is utilized as a means for ensuring forward and backward security of the group key together with the hash function.

For example, when one of n terminal apparatuses belonging to a predetermined group leaves a group, the random value is incremented by 1 and used for hash calculation and group key renewal. As another example, when another terminal device subscribes to a predetermined group, the random value can be similarly increased by 1 and used for hash calculation and group key renewal.

This random value is generated by the group key management apparatus 100 and is hashed to be used for generating a group key. In this case, each terminal apparatus can know only the information on the group key, Can not.

Next, in step S320, the transmitting unit 120 encrypts the group key generated in step S310 with n symmetric keys, respectively, and transmits them to the corresponding terminal device.

FIG. 4 is a diagram schematically illustrating a message exchanged between a group key management apparatus and each terminal apparatus in a step of generating and transmitting a group key according to an embodiment of the present invention.

4, the group key generation unit 110 first shares with the first terminal apparatus 200A, the second terminal apparatus 200B, and the third terminal apparatus 200C belonging to the group A (H (count)) of the three symmetric keys K _{S -A} , K _{S -B} and K _{S -C} and the random value count to obtain a group key K _G ).

At this time, the initial value of the random value may be set to an arbitrary value for each group, but it is modified every time the group key is updated due to joining or leaving of the terminal device as described below. , It is indicated by a count (count).

The transmitting unit 120 encrypts the generated group key K _G with the first symmetric key K _{S- A} shared with the first terminal apparatus 200A and transmits the encrypted first group key K _G to the first terminal apparatus 200A number and _{(K S -A {K G}} ), generate a group key (K _G) to the second terminal device (200B) and the second symmetric key that is shared by encrypting a (K _SB) the second terminal device (200B (K _{S -B} {K _G }), and encrypts the generated group key (K _G ) with a third symmetric key (K _{S -C} ) shared by the third terminal device (200C) 3 terminal apparatus 200C (K _{S -C} {K _G }).

As described above, the group key is generated from the symmetric key shared with all the terminal devices belonging to the group, and can be generated and distributed only by the group key management device 100, that is, the server.

Next, in step S330, when the number of members of the group is changed, the group key renewing unit 130 corrects the random value and stores m (n is an integer of 1 or more) The group key is updated using the result of the hash operation on the symmetric key and the modified random value.

In this case, the transmitting unit 120 encrypts the updated group key with m symmetric keys, respectively, and transmits them to the corresponding terminal apparatuses.

According to an embodiment of the present invention, when k (one or more natural number) terminal apparatuses join a group, the group key renewing unit 130 increments the random value by 1, and transmits n symmetric keys, A new group key is generated by using k shared symmetric keys and a hash operation result value of the increased random value, and the group key generated in step S310 is updated with a new group key.

Hereinafter, with reference to FIG. 5, it will be described that, when a new terminal device joins a group, a result of a hash operation on a modified random value can guarantee the backward security of the group key.

5 is a diagram schematically showing a message exchanged between a group key management apparatus and each terminal apparatus in a step of updating a group key when a subscription of a terminal apparatus is made to a group according to an embodiment of the present invention; to be.

As shown in FIG. 5, the fourth terminal device 200D, which intends to join the group A, shares information of the corresponding group, for example, a group name with the group key management device 100 And transmits it to the group key management apparatus 100 (K _{S -D} {Group Name}).

Therefore, the group key update unit 130, so, if necessary, the updating of the key group, to increase the value of 1 and random, the old first symmetric key (K _{S -A),} a second symmetric key (K _{S -B),} the third symmetric key (K _SC) a fourth symmetric key that is shared with the fourth terminal device to join the newly with (K _{S -D),} and increases by one the randomized value hash result value to the (count ++) (H (count ++)) to generate a group key K _G , update an existing group key, and provide the group key K _G to the transfer unit 120.

Then, the transmitting unit 120 encrypts the updated group key with the symmetric key shared with each terminal device, and the group key (K _{S -A} {K _G }) encrypted with the first symmetric key is transmitted to the first terminal device (K _{S -A),} the second group key encrypted with a symmetric key (K _{S G -B} {K}) of the second terminal device (K _{S -B),} the third symmetric key encrypted group key (K _{S -C} {K _G}) is the third terminal device (K _{S -C)} to, and the fourth encrypted symmetric key group keys (K _{G S -D} {K}) is the fourth terminal device (K _{S -D} Respectively.

At this time, the fourth terminal device (200D) is passed received group key (K _G) {K in other than their symmetric key of the fourth symmetric key (K _{SD) S -A -B} XOR XOR K _S K _S to join the new Though it is possible to figure out _{-C XOR H (count ++)}} , a new group key is a state increased by a random value 1, since becoming out different hash result value for this (H (count) ≠ H ( count ++)), sign up It is impossible for the fourth terminal device 200D to know the group key used before joining.

Accordingly, the terminal device newly joining the group does not know the group key used before joining, so that the backward security of the group key can be assured.

According to an embodiment of the present invention, when k (at least one natural number) terminal apparatuses withdraws from the group of the group key update unit 130, the random value is incremented by 1, At least one remaining symmetric key except for the k symmetric keys shared by the first group key and the second group key, and a result value of the hash operation for the increased random value is used to generate a new group key, Update the key.

Hereinafter, with reference to FIG. 6, it will be explained that when the terminal device leaves the group, the hash operation result value of the modified random value can guarantee the forward security of the group key.

6 is a diagram schematically showing a message exchanged between a group key management apparatus and each terminal apparatus in the step of renewing a group key when a terminal apparatus is withdrawn from a group according to an embodiment of the present invention; to be.

6, the fourth terminal device 200D desiring to leave the group A transmits the group information and its own information, for example, the name of the group and its own name to the group key management device 100 And transmits it to the group key management apparatus 100 (K _{S -D} {Group Name, User Name}).

Therefore, the group key update unit 130, so, if necessary, the updating of the key group, to increase the random value one and, in the existing symmetric key, except for the fourth symmetric key (K _SD), rest of the symmetric key (K _{S -A,} K _{S -B,} K _{S -C)} and increased, a random value (the hash result value (H (count ++ to count ++))) to the XOR operation generate group keys (K _G), and updates the old group key do.

Then, the transmitting unit 120 encrypts the updated group key with the symmetric key shared with each terminal device, and the group key (K _{S -A} {K _G }) encrypted with the first symmetric key is transmitted to the first terminal device (K _{S -A} ), the group key (K _{S -B} {K _G }) encrypted with the second symmetric key is transmitted to the second terminal device (K _{S -B} ) K _{S -C} {K _G }) to the third terminal device (K _{S -C} ).

At this time, the fourth terminal device 200D, which has left the group, can not decrypt the new group key even if the group key is received because the updated group key is not received.

(K _G = {K _{S -A} XOR K _SB XOR K _{S -C} XOR K _{S -D} XOR H (count ++)} that the fourth terminal device 200D leaving the group has used before the withdrawal Even if it is possible to calculate {K _{S -A} XOR K _{S -B} XOR K _{S -C} XOR H (count ++)} except for the fourth symmetric key (K _{S -D} ) as a key, 1, and the result of the hash calculation is also different. Therefore, it is impossible to deduce a new group key after the withdrawal using the group key used before the withdrawal.

Therefore, the terminal device leaving the group does not know the updated group key, so the forward security of the group key can be assured.

As described above, the group key is generated and distributed from the symmetric key for all the terminal devices in the group and the result value of the hash operation for the random value, and is updated as necessary, so that the group key according to the embodiment of the present invention It can be generated by the group key management apparatus 100, i.e., the server, and the forward and backward security of the group key is ensured.

Also, since the group key is encrypted and decrypted with each symmetric key shared between each terminal device in the group and the server, message exchange can be performed more quickly.

Hereinafter, an operation of verifying whether or not a group key is normally acquired by each terminal apparatus after the transmission of the updated group key is performed will be described.

As described above, the transmitting unit 120 encrypts the group key updated by the group key renewing unit 130 with m symmetric keys, respectively, and transmits them to the corresponding terminal apparatuses. Each of the terminal apparatuses receiving the encrypted group key transmits its own The updated group key is obtained by decrypting the group key encrypted with the symmetric key.

The group key management apparatus 100 according to an embodiment of the present invention further includes a receiving unit 140 and a verifying unit 150 as shown in FIG. .

The receiving unit 140 receives the hash value of the result of the OR operation of the symmetric key and the group key from each terminal device.

The verification unit 150 determines whether or not the hash value of the result obtained by ORing the self-operated symmetric key with each terminal device and the updated group key is the same as the hash value received by the reception unit 140 Thereby verifying the updated group key acquisition of the terminal apparatus.

5 and 6, the first terminal device calculates a hash value (H (K _SA OR K) for the result of OR operation of the first symmetric key, which is the symmetric key of the first terminal, with the obtained group key _G ) to the group key management apparatus 100, and the receiving unit 140 receives the same.

Similarly, receiver 140 is a second terminal apparatus from the H (K K _G OR _{S -B),} the third from the terminal H (K K _{G S -C} OR), the fourth from the terminal H (K _{S -D} OR K _G ).

The verification unit 150 verifies whether or not the hash value H '(K _SA OR K _G ) of the result of the OR operation between the first symmetric key shared with the first terminal device and the updated group key (K _{S -A} OR K _G )) received from the first terminal device, and confirms that the first terminal device correctly received the updated group key if it is the same.

In the same manner, the verification unit 150 determines whether or not the hash value H '(K _SB OR K _G ) of the result of the OR operation between the second symmetric key and the updated group key is the hash value H (K _SB OR K _G )), it is checked whether the second terminal device correctly received the updated group key, and the same verification process can be performed for the third terminal device.

As described above, according to the present invention, it is possible to reduce the group key generation and update cost by minimizing the operations required to generate the group key.

In addition, all the messages and group keys exchanged between the group key management apparatus, i.e., the server and the terminal apparatus are encrypted and decrypted through the symmetric key, which is advantageous in speed.

Further, according to the present invention, it is possible to solve the problem of restriction on the number of group key renewal times by using a random value that increases each time a group key update is made. According to one embodiment of the present invention, when a random value that is incremented by 1 in update is stored as a 4-byte integer variable, the number range is -2,147,483,648 to 2,147,483,647, There is no need to look at it.

Embodiments of the present invention may be implemented in the form of program instructions that can be executed on various computer means and recorded on a computer readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions recorded on the medium may be those specially designed and constructed for the present invention or may be available to those skilled in the art of computer software. Examples of computer-readable media include magnetic media such as hard disks, floppy disks, and magnetic tape; optical media such as CD-ROMs and DVDs; magnetic media such as floppy disks; Examples of program instructions, such as magneto-optical and ROM, RAM, flash memory and the like, can be executed by a computer using an interpreter or the like, as well as machine code, Includes a high-level language code. The hardware devices described above may be configured to operate as at least one software module to perform operations of one embodiment of the present invention, and vice versa.

As described above, the present invention has been described with reference to particular embodiments, such as specific elements, and specific embodiments and drawings. However, it should be understood that the present invention is not limited to the above- And various modifications and changes may be made thereto by those skilled in the art to which the present invention pertains. Accordingly, the spirit of the present invention should not be construed as being limited to the embodiments described, and all of the equivalents or equivalents of the claims, as well as the following claims, belong to the scope of the present invention .

100: server, group key management apparatus 110: group key generation unit
120: Transmitting unit 130: Group key renewing unit
140: Receiver 150: Verifier
200: terminal device

Claims (13)

A group key management apparatus for group communication, comprising:
A group key generation unit for generating a group key by using symmetric keys and random values of n (two or more natural number) terminals belonging to the group; And
Encrypting the group key with the corresponding symmetric key, and transmitting the group key to the terminal devices,
Wherein the group key is updated when the group membership is changed, and the symmetric key is used for decrypting the transmitted group key in the terminal devices. The method according to claim 1,
Wherein the group key generation unit generates the group key by XORing all the symmetric keys in the group and the result of the hash operation on the random value. 3. The method of claim 2, wherein the random value is changed when the group membership is changed, and the updated group key is generated from a result of a hash operation on all the symmetric keys in the group and the changed random value A group key management apparatus for group communication. The apparatus as claimed in claim 1, wherein each of the terminal devices has only its own symmetric key and information on the group key, and does not have information on the random value. delete The method according to claim 1,
A receiver for receiving a hash value of an OR operation result of a group key obtained by decoding a first symmetric key and the transmitted encrypted group key from a first terminal device among the terminal devices; And
A verification unit for verifying the obtained group key of the first terminal device based on whether or not the received hash value is the same as the received hash value by calculating a hash value of an OR operation between the first symmetric key and the updated group key, The group key management apparatus according to claim 1, further comprising: The method of claim 3,
When k (one or more natural number) terminal apparatuses in the group withdraw, the random value is incremented by one, and the updated group key includes the remaining symmetric keys excluding the k symmetric keys in the n symmetric keys, 1 < / RTI > and the hash operation result for the incremented random value. ≪ RTI ID = 0.0 > 31. < / RTI > The method of claim 3,
If the group joins the group k (one or more natural number) terminals, the random value is incremented by one, and the updated group key includes the n symmetric keys, the k symmetric keys, and the 1 incremented random value Is generated from the hash calculation result value for the group key. A group key management method of a group key management device for intra-group communication,
Generating a group key using symmetric keys and random values of n (n is a natural number of 2 or more) terminals belonging to the group; And
Encrypting the group key with the corresponding symmetric key, and transmitting the encrypted group key to the terminal devices,
Wherein the group key is updated when a member of the group is changed, and the symmetric key is used for decrypting the transmitted group key in the terminal devices. 10. The method of claim 9,
Wherein the generating step generates the group key by performing an XOR operation on all the symmetric keys in the group and a result of the hash operation on the random value. 11. The method of claim 10, wherein the random value is changed when the group membership is changed, and the updated group key is generated from a result of a hash operation on all the symmetric keys in the group and the changed random value How to manage group keys. 10. The group key management method according to claim 9, wherein each of the terminal devices has only its own symmetric key and information on the group key, and does not have information on the random value. A computer-readable recording medium on which a program for performing the group key management method according to any one of claims 9 to 12 is recorded.

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