Method and apparatus for providing secure and private keyboard communications in computer systems

• US 5,748,888 A
• Filed: 05/29/1996
• Issued: 05/05/1998
• Est. Priority Date: 05/29/1996
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Compaq Computer Corporation (HP Inc.)
• Inventors: Angelo, Michael F., Wolford, Jeff W.
• Primary Examiner(s): Beausoliel, Jr., Robert W.
• Assistant Examiner(s): Palys, Joseph E.
• Application Number:
  US08/657,982
• Time in Patent Office: 706 Days
• Field of Search: 395/186, 395/187.01, 395/188.01, 395/490, 395/491, 380/3, 380/4
• US Class Current: 726/26
• CPC Class Codes: G06F 21/83 input devices, e.g. keyboards, mice or controllers thereof

Abstract

A method and apparatus for providing secure and private keyboard communications in a computer system. A request for private keyboard communications causes the computer'"'"'s processor to enter into system management mode by generating an system management interrupt. A secure system management interrupt handler then directs specialized hardware to intercept and divert keyboard interrupts, such that data entered via the keyboard is only communicated to a non-readable black box security device that controls access to protected system resources. Keyboard data is thereby protected from interception by malicious software.

Claims

1. A method for securely communicating data from a keyboard to a non-readable security device in a computer system having a processor incorporating system management mode or similar capabilities, the keyboard and computer system being coupled via a keyboard interface, the method comprising the steps of:

generating a system management interrupt in response to a request for secure communications;

placing the processor in system management mode to execute a system management interrupt handler as a result of said step of generating a system management interrupt;

entering keystroke data via a keyboard, wherein a keyboard interrupt is also generated;

setting a secured keyboard bit or otherwise communicating a command that causes specialized circuitry in the keyboard interface to intercept the keyboard interrupt;

rerouting the keyboard interrupt or a signal generated therefrom to the non-readable security device to indicate the presence of keyboard data; and

diverting the keystroke data to the non-readable security device in response to the step of generating a system management interrupt in response to a request for secure communications.

2. The method of claim 1 further comprising the steps of:

comparing the diverted keystroke data to protected data stored in the non-readable security device, wherein the comparison occurs in the non-readable security device; and

communicating the results of the comparison to other computer system resources through an output of the non-readable security device.

3. The method of claim 1 further comprising the steps of:

prior to said step of generating a system management interrupt, loading appropriate data into processor registers to indicate, to the system management interrupt handler, a request for a secure communications link between the keyboard and the non-readable security device.

4. The method of claim 1, further comprising the step of:

exiting system management mode shortly after the keystroke data has been diverted to the non-readable security device, such that the computer system is in system management mode for a minimal period of time.

5. A method for secure retrieval of data from a keyboard into a computer system, the computer system having a keyboard interface for connecting the keyboard, the computer system further having a non-readable security device containing protected password data or other critical information and a processor incorporating system management mode capabilities, the method comprising the steps of:

loading appropriate data into processor registers to communicate to a system management interrupt handler a request for a secure communications link between the keyboard and the non-readable security device;

generating a system management interrupt in response to a request for secure retrieval of data, whereby the system management interrupt places the computer system in system management mode to execute a system management interrupt handler, wherein execution of the system management interrupt handler comprises the steps of;

retrieving the appropriate data from the processor registers; and

directing the processor to set a secure keyboard bit or otherwise communicate a command to specialized circuitry in the keyboard interface directing the specialized circuitry to intercept the next keyboard interrupt;

entering secure keystroke data via a keyboard, whereby a keyboard interrupt is also generated;

intercepting the keyboard interrupt and communicating a signal from the specialized circuitry to the non-readable security device, the signal from the specialized circuitry indicating the presence of secure keystroke data;

diverting the secure keystroke data to the non-readable security device in response to the signal from the specialized circuitry;

comparing the diverted secure keystroke data to the protected password data or other critical information stored in the non-readable security device; and

repeating the prior steps until entry of an entire password or other critical data has been completed.

6. The method of claim 5, further comprising the step of:

following the step of diverting the secure keystroke data to the non-readable security device, displaying the secure keystroke data on a graphical user interface.

7. The method of claim 5, further comprising the step of:

following the step of diverting the secure keystroke data to the non-readable security device, displaying a character or group of characters on a graphical user interface, the character or group of characters symbolizing the entry of a secure keystroke but not the actual secure keystroke data.

8. A computer system incorporating the capability to securely communicate data between a keyboard and a non-readable security device, the computer system comprising:

a processor including system management mode capabilities;

a keyboard for entering keystroke data;

a keyboard controller electrically coupled to said keyboard for receiving the keystroke data and communicating it to a system bus;

interrupt generating logic responsively coupled to said keyboard controller, said interrupt generating logic producing a keyboard interrupt upon detection of keystroke data;

an interrupt controller for receiving the keyboard interrupt;

a non-readable security device electrically coupled to said system bus;

a system management mode memory for storing a system management interrupt handler routine that executes in response to requests for secure communications;

a gating circuit for selectively intercepting said keyboard interrupt prior to reception by said interrupt controller, said gating circuit being electrically coupled to said interrupt generating logic, said interrupt controller and said non-readable security device, said gating circuit being responsive to the execution of said system management interrupt handler in response to a request for secure communications such that said gating circuit intercepts the keyboard interrupt and communicates a control signal to said non-readable security device directing said non-readable security device to retrieve keystroke data from said system bus.

9. The computer system of claim 8, wherein said gating circuit is a decoder having a control bit responsive to said system management interrupt handler routine.

10. The computer system of claim 9, wherein one output of said decoder is coupled to said interrupt controller in order to communicate a keyboard interrupt to said interrupt controller during normal computer system operation, and wherein a second output of said decoder is coupled to said non-readable security device in order to direct said non-readable security device to retrieve keystroke data from said keyboard controller during periods of secure communication.

11. The computer system of claim 8, wherein said keyboard controller and said interrupt generating logic are integrated into a single circuit.

12. The computer system of claim 8, wherein said keyboard, said keyboard controller and said interrupt generating logic are effectively compliant with the universal serial bus standard.