Patent ID: 8225084
Filing Date: 2012-07-17
Classification: H04L

Abstract:
1. A content transmitting device comprising: an authenticator performing an authentication with a content receiving device by transmission of authentication information and reception of acknowledgment for the authentication information, and producing and sharing an exchange key with the content receiving device; an encryptor generating an encryption key based on the exchange key produced by the authenticator as a result of execution of an authentication process in the authenticator, and encrypting a content to be transmitted to the content receiving device, by using the encryption key; and a timer measuring a time interval between transmission of authentication information to the content receiving device and reception of acknowledgement of authentication information, wherein the authenticator measures the time interval between the transmission of the authentication information and the reception of the acknowledgement by using the timer, and if a measurement value of the time interval exceeds a predetermined value, the authenticator does not share the exchange key with the content receiving device to restrict transmission and/or copy of content; and wherein the authenticator transmits the authentication information with information that indicates a number of devices the authentication information can pass through, and limits the number of devices the authentication information passes through and a range of transmission of the authentication information.