Patent ID: 8457307

Claim:
In a communication system comprising at least a certification authority computer of a certification authority, a sender computer of a sender and a recipient computer of a recipient, the certification authority computer, the sender computer and the recipient computer communicating with each other over communication network, a computer-implemented method of transmitting messages encrypted with identity-based public keys derived from information provided by the certification authority, said certification authority having a pair of public and private keys, said method comprising: the recipient computer providing a recipient's registration request to the certification authority computer over the communication network, said registration request correlating to a first secret value selected by the recipient computer; upon receiving a request from the sender computer, said request from the sender computer including an identity information of the recipient selected by the sender, the certification authority computer generating a public key reconstruction data from said registration request, said identity information selected by the sender, a second secret value selected by the certification authority computer and a certificate information selected by the certification authority computer; the certification authority computer transmitting an implicit certificate to the sender computer over the communication network, said implicit certificate including said public key reconstruction data and said certificate information; the sender computer reconstructing a public key of the recipient from said implicit certificate, said certificate information and the certification authority's public key; the sender computer transmitting to the recipient computer over the communication network a message encrypted with said public key of the recipient together with an indication that said public key is reconstructed from said implicit certificate, said indication including said sender selected identity information.