Patent ID: 8656156

Claim:
A method of authentication between mobile devices, the method comprising: transmitting, by a first mobile device, an authentication request message including a first authentication information to a second mobile device; receiving, by the first mobile device, an authentication response message including a second authentication information from the second mobile device after verifying whether the first authentication information is valid by the second mobile device; verifying, by the first mobile device, whether the second authentication information is valid, wherein the first mobile device receives from a management server, rights information on permissions or constraints for using content, and transmitting, by the first mobile device, the rights information to the second mobile device, wherein the first authentication information comprises a first certification message having certificate revocation information related to the first mobile device, the first certification message being obtained from the management server when the first mobile device registers to the management server before transmitting the rights information to the second mobile device and provided from a certification server, and wherein the second authentication information comprises a second certification message having certificate revocation information related to the second mobile device, the second certification message being obtained from the management server when the second mobile device registers to the management server before receiving the rights information from the first mobile device and provided from the certification server, wherein each of the first certification message and the second certification message includes first time information indicating when the certification message is issued and second time information indicating when the certification message expires, and wherein the verifying performed by the first mobile device is based on the first time information and the second time information included in the second certification message, and the verifying performed by the second mobile device is based on the first time information and the second time information included in the first certification message.