Patent ID: 7103911

Claim:
A method for controlling communications in an identity-based encryption (IBE) system in which senders communicate with recipients over a communications network and in which recipients and IBE private key generators are organized in a plurality of districts, each district including a respective one of the IBE private key generators, wherein the IBE private key generator in each district generates IBE private keys for recipients that are associated with that district, wherein each district has IBE public parameter information that is used by senders in encrypting messages for recipients in that district, wherein each district has district policy information that includes IBE encryption protocol information, and wherein the recipients in each district use their IBE private keys in decrypting messages that are encrypted using respective IBE public keys, comprising: when a sender desires to send a message to a recipient in a given district, obtaining the district policy information for the given district for the sender over the communications network, wherein the district policy information that is obtained for the given district includes IBE encryption protocol information for the given district that specifies an IBE public key format that is to be used in creating IBE public keys for the recipients in the given district; at the sender, using the IBE public key format specified by the IBE encryption protocol information to construct an IBE public key for the recipient in the given district; and at the sender, encrypting the message for the recipient using the IBE public parameter information associated with the given district and the IBE public key that has been constructed for the recipient according to the IBE public key format.