Patent Application
20080010242
The above and other objects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:
Throughout the drawings, the same reference numerals will be understood to refer to the same elements, features, and structures.
The matters defined in the description such as a detailed construction and elements are provided to assist in a comprehensive understanding of the exemplary embodiments of the invention. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the exemplary embodiments described herein can be made without departing from the scope and spirit of the invention. Also, descriptions of well-known functions and constructions are omitted for clarity and conciseness.
Hereinafter, certain exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawing figures.
A device A and a device B transmit a version contained in their stored group key information (hereafter, referred to as a group key version) to each other for mutual authentication (S110). Herein, the group key version differs every time a revoked device and an authorized device change.
Next, the device A determines the latest version in the two group key versions by comparing its stored group key version information A with the group key version B received from the device B (S120). Likewise, the device B determines the latest version by comparing its group key version B with the group key version A received from the device A. The latest version is determined using date and time when the group key information is generated, index, and the like.
The devices A and B share the group key information of the latest version determined (S130).
Accordingly, when the group key version B is determined to have the latest version in step S120, the device A sends a group key information request message to the device B. Upon receiving the group key information request message, the device B sends its stored group key information B to the device A. Thus, the devices A and B share the group key information B of the latest version.
When the group key version A is determined to have the latest version, the devices A and B share the group key information A of the latest version in the same way.
Next, the device A and the device B calculate a group key using the sharing group key information (S140). The group key is calculated according to the broadcast encryption (BE). Since the BE is a well-known technique, its detailed explanation will be omitted for clarity and conciseness.
Based on the calculated group key, the devices A and B carry out mutual authentication (S150).
In more detail, referring now to
The device B also generates a random number RB, encrypts the generated random number RB with the group key, and then sends the encrypted RB (E(group key, RB)) to the device A. The devices A and B decrypt the encrypted RB and RA, respectively, encrypt values RC=RB⊕RA and RD=RA⊕RB, which are acquired by applying the exclusive OR on the decrypted RB and RA and their generated random numbers RA and RB, with the group key, and then send E(group key, RC=RB⊕RA) and E(group key, RD=RA⊕RB) to each other. The device A executes the mutual authentication with the device B by decrypting the RD and verifying whether the decrypted RD is the same as its calculated RC. Likewise, the device B executes the mutual authentication with the device A by decrypting the RC and verifying whether the decrypted RC is the same as its calculated RD.
The device authentication method has been illustrated in case where the group key information is stored to both the device A and the device B. Note that the device authentication method is applicable to a case where the group key information is stored to either the device A or the device B.
Even if the group key information is stored to neither the device A nor the device B, the mutual authentication of the device A and the device B is feasible by receiving the group key information from authentication servers respectively connected to the device A and the device B. In this case, when the group key information is stored to either authentication server connected to the device A or the device B, the mutual device authentication of an exemplary embodiment of the present invention is feasible.
For example, referring to
Descriptions have been provided above on how to share the group key based on the group key version contained in the group key information according to the BE and to mutually authenticate the devices using the secret key. The following descriptions illustrate the integrity verification of the group key version when the devices are mutually authenticated using the group key version in reference to
Since the authentication server is capable of generating the signature to the group key information, the device receiving the group key information with the signature of the authentication server for the group key information can verify the integrity of the group key version.
Referring to
The device, which receives the group key information as shown in
Referring to
The authentication server generates a version and a hash value relating to the group key information every time the group key information is generated. For instance, when there are n-ary group key versions, hash values corresponding to the n-ary versions are generated respectively. The hash values are acquired by substituting an arbitrary random number ran into the hash function.
In doing so, the authentication server acquires the hash values by substituting the random number ran into the hash function to correspond to the increasing group key version. For instance, when the group key version is n−1, the authentication server sets the value h(ran) acquired by hashing the random number ran one time, to the hash value. When the group key version is n−2, the value h2(ran) acquired by hashing the random number two times is set to the hash value.
The one-way hash function transforms an input value of an arbitrary length to a fixed-length output value. The one-way hash function has the following properties. The one-way hash function is impossible to calculate an original input value with a given output value and is impossible to find another input value that produces the same output value with a given input value. In addition, the one-way hash function is impossible to find and calculate two different input values that result in the same output value.
The hash function characterized by the above features is one of important functions applied for data integrity, authentication, repudiation prevention, and the like. In an exemplary embodiment of the present invention, the one-way hash function can be a Secure Hash Algorithm version 1.0 (SHA-1).
Accordingly, to verify the integrity of the group key version using the group key information including the encrypted hash value, the device receiving the group key information from the device to be authenticated can compare the hash value of its stored group key information with the value which is hashed from the encrypted hash value in the group key information for several times, as shown in
By way of example, the device B has a more recent version than the device A such that the group key version of the device B is 3 and the group key version of the device is 2. The device A compares the value hn-2(ran) acquired by hashing the hash value hn-3(ran) of the group key information received from the device B once (1=3−2), with the hash value hn-2(ran) of its stored group key information, and confirms that the received group key information is of the latest version when the two values equal.
In the integrity verification method of the group version using the group key information containing the encrypted hash value in an exemplary embodiment of the present invention, when the group key version equals to a preset value, the authentication server resets and issues the group key version. Accordingly, the hash value corresponding to the group key version is re-issued.
In the authentication method and the integrity verification method according to an exemplary embodiment of the present invention, the group key information used to authenticate the device and verify the integrity of the group key version may comprise the BE group key information, but not limited to this group key version.
As set forth above, the authenticating devices carry out the mutual authentication by use of the group key version comprised in the group key information. Thus, the computations required for the authentication can be reduced and the exclusion of the revoked device from the object devices can be facilitated.
Furthermore, the secure data communications between privileged devices can be achieved by providing the integrity of the group key information using the group key version.
While the invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-62813 | Jul 2006 | KR | national |
