Abstract: A method of managing a key of a user for a broadcast encryption. The method includes forming a tree comprising m hierarchies by repeating a process of setting a ith level comprising groups into which at least one node is grouped in a unit of ni, and setting a i+1th level comprising the groups of the ith level that are re-grouped in a unit of ni+l until i is from “1” to “m”. The method further includes mapping users on at least one node of the tree and message providers on the mth hierarchy, going down from the mth hierarchy to the first hierarchy to map key encryption keys with respect to the i+1 th level connected to the ith level, and transmitting the message using the key encryption keys.

Abstract: A broadcast encryption (BE) for acquiring an encryption key which is used to decrypt a session key by a node receiving services, with less computation overhead. A plurality of subgroups, each consisting of at least one of a plurality of nodes, are generated, and layers are formed according to a number of nodes which form the subgroup. Prime numbers are assigned to the subgroups not to overlap one another, and a subgroup at an upper layer is connected with a subgroup, which includes nodes forming the subgroup of the upper layer, at a lower layer. A prime number assigned to a subgroup at an upper layer, a prime number assigned to an unconnected subgroup at the same layer, and a prime number assigned to a subgroup at a lower layer, are re-assigned to each subgroup, and an encryption key which is generated from the re-assigned prime numbers is assigned to the each group.

Abstract: A seed value making method and device for a PRNG (Pseudo Random Number Generator) are provided. The seed value making method includes the steps of: accumulating in memory units of a First Data Pool data from various external sources, analyzing the data to determine a source type, computing entropy estimations for each of the external sources basing on the source type as determined, and generating a seed value by using the entropy estimations and the data accumulated in the memory units of the First Data Pool. Accordingly, in generating a seed value, dynamic estimation of random sources rate, and classification of sources on slow and fast ones, and reliable and unreliable ones, can be provided, and also, seed values can be made with taking in account rate and reliability of the sources.

Abstract: This scheme proposes a method for reducing the number of security keys allocated to each node of a wireless network, and number of security keys required by the wireless network. N nodes are grouped into a first and a second groups, each group comprising N/2 nodes without nodes being shared. The first group is grouped such that at least two nodes are included and at least one node is different, and first security keys are allocated to the first group nodes without any security keys being shared among the groups. (N/2) groups are grouped to include a security key arrangement of (B/2) number of security keys of B number of second security keys, and the second security keys of each group are allocated to each node of the first group. Here, the security key arrangement of each group differs from that of the others.