Continuous authentication in a security environment

An authentication system comprising:

• a stylus that operates to:
• generate a stylus token using a key stored in a memory in the stylus and a current timestamp, wherein the stylus token is valid for a first selected period of time;
• transmit the stylus token to a computer system;
• repeat generating, by the stylus, the stylus token using the key stored in the memory in the stylus and the current timestamp and transmitting, by the stylus, the stylus token to the computer system in response to the stylus token expiring after the first selected period of time;
• generate a stylus capacitance of the stylus using the key stored in the stylus and the current timestamp, wherein the stylus capacitance is valid for a second selected period of time that is a longer period of time than the first selected period of time corresponding to how long the stylus token is valid;
• transmit the stylus capacitance of the stylus to the computer system in response to the stylus touching a capacitive sensing device that is separate from and in communication with the computer system;
• and
• repeat generating, by the stylus, the stylus capacitance of the stylus using the key stored in the stylus and the current timestamp and transmitting, by the stylus, the stylus capacitance of the stylus to the computer system in response to an expiration of the second selected period of time that is the longer period of time than the first selected period of time corresponding to how long the stylus token is valid.

A stylus comprising:

• an elongate body;
• a memory in the elongate body, wherein a key is stored in the memory;
• a near field communications transmitter in the elongate body, wherein the near field communications transmitter transmits radio frequency signals;
• a variable capacitance unit in the elongate body, wherein the variable capacitance unit transmits a stylus capacitance of the stylus to a computer system in response to the stylus touching a capacitive sensing device that is separate from and in communication with the computer system;
• and
• a controller in the elongate body, wherein the controller operates to:
• generate a stylus token using the key stored in the memory in the elongate body and a current timestamp, wherein the stylus token is valid for a first selected period of time;
• control the near field communications transmitter to transmit the stylus token to the computer system using the radio frequency signals;
• generate the stylus capacitance of the stylus using the key stored in the memory in the elongate body and the current timestamp;
• control the variable capacitance unit to transmit the stylus capacitance of the stylus to the computer system in response to the stylus touching the capacitive sensing device that is separate from and in communication with the computer system, wherein the stylus capacitance is valid for a second selected period of time that is a longer period of time than the first selected period of time corresponding to how long the stylus token is valid;
• repeat generating the stylus token using the key stored in the memory in the elongate body and the current timestamp and controlling the near field communications transmitter to transmit the stylus token to the computer system using the radio frequency signals in response to the stylus token expiring after the first selected period of time;
• and
• repeat generating the stylus capacitance of the stylus using the key stored in the memory in the elongate body and the current timestamp and controlling the variable capacitance unit to transmit the stylus capacitance of the stylus to the computer system in response to an expiration of second selected period of time that is the longer period of time than the first selected period of time corresponding to how long the stylus token is valid.