Rekey index generation method and rekey index generation apparatus

A rekey index generation method, the method comprising:

• inserting leave information into a first field of a rekey index when members leave a group;
• inserting node numbers of the highest nodes of all ancestor nodes in the group, whose descendant leaf nodes all leave, to a second field of the rekey index to perform a first node change;
• inserting node numbers of ancestor nodes of leaf nodes, corresponding to the first node change, to a third field of the rekey index to perform a second node change in which nodes connected with only one member are removed and replaced by the ancestor node, and to select a necessary key among encoded keys in a receiver;
• and
• transmitting, to one or more receivers corresponding to one or more update target nodes, encoded keys for each respective update target node and the rekey index comprising the leave information in the first field, the node numbers of the highest nodes of ancestor nodes in the group whose descendant leaf nodes all leave in the second field, and the node numbers of all nodes connected with only one member in the third field.

A non transitory computer-readable recording medium storing a program for implementing a rekey index generation method, the method comprising:

• inserting join information to a first field of a rekey index when new members join a group;
• splitting one or more existing nodes corresponding to one or more existing members to generate new nodes corresponding to the new members and the one or more existing members;
• inserting node numbers, corresponding to each of the new members, into a second field of the rekey index in an order that enables a receiver to select a necessary key from among transmitted encoded keys based on the order of the new node numbers included in the second field;
• and
• transmitting, to one or more receivers corresponding to one or more update target nodes, encoded keys for each respective update target node and the rekey index comprising leave information in the first field, the node numbers of the highest nodes of ancestor nodes in the group whose descendant leaf nodes all leave in the second field, and the node numbers of all nodes connected with only one member in the third field.

A rekey index generation apparatus, the apparatus comprising:

• a first field generation module for inserting join information to a first field of a rekey index when new members join a group;
• a second field generation module for inserting node numbers, corresponding to each of the new members, to a second field of the rekey index in an order that enables a receiver to select a necessary key from among transmitted encoded keys based on the order of the new node numbers included in the second field;
• a memory for storing the rekey index;
• and
• a transmitter for transmitting, to one or more receivers corresponding to one or more update target nodes, encoded keys for each respective update target node and the rekey index comprising leave information in the first field, the node numbers of the highest nodes of ancestor nodes in the group whose descendant leaf nodes all leave in the second field, and the node numbers of all nodes connected with only one member in the third field,
• wherein when the new members join the group, one or more existing nodes corresponding to existing members are split to generate new nodes corresponding to the new members and the one or more existing members.

A rekey index generation apparatus, the apparatus comprising:

• a first field generation module inserting leave information to a first field of a rekey index when members leave a group;
• a second field generation module inserting node numbers of highest nodes of all ancestor nodes in the group, whose descendant leaf nodes all leave, into a second field of the rekey index to perform a first node change;
• a third field generation module inserting node numbers of ancestor nodes of leaf nodes, corresponding to the first node change, into a third field of the rekey index to perform a second node change in which nodes connected with only member are removed and replaced by the ancestor node, and to select a necessary key among encoded keys in a receiver;
• a memory for storing the rekey index;
• and
• a transmitter for transmitting, to one or more receivers corresponding to one or more update target nodes, encoded keys for each respective update target node and the rekey index comprising the leave information in the first field, the node numbers of the highest nodes of ancestor nodes in the group whose descendant leaf nodes all leave in the second field, and the node numbers of all nodes connected with only one member in the third field.