Patent ID: 8135952

Claim:
A method for determining position relative to an object, the method comprising: transmitting at least one challenge message using a transmission transducer system to said object; receiving at least one response message using a reception transducer system, wherein said at least one response message comprises a direction of transmission by said transmission transducer system, a time of transmission of said at least one response message, and a time of receipt of said at least one challenge message; determining whether said response message is received from a direction within a predetermined angular bound; accepting the response message if it is within the bound; cryptographically verifying the response message and accepting it if it is cryptographically valid; determining a time difference between the challenge message transmission and the response message receipt and accepting the response message if it is within a predetermined time frame; rejecting the response message if it is not within the angular bound or not within the predetermined time frame or cryptographically invalid; and determining the object position with improved security and accuracy by a narrowed angle of the reception, further comprising transmitting cryptographically authenticated information about the object's position after completing determination of the object's position.