Providing security to an electronic device

1. An electronic device, comprising:

a printed circuit board;

a circuit board element;

a microprocessor disposed between the printed circuit board and the circuit element to restrict physical access to the microprocessor, the microprocessor having (i) a bottom which faces the printed circuit board in a first direction, and (ii) a top which faces the circuit element in a second direction which is opposite the first direction;

the microprocessor (i) performing electronic operations in response to power from a power source while the microprocessor is disposed between the printed circuit board and the circuit element, and (ii) being electronically prevented from further performing the electronic operations in response to tampering activity on the circuit element;

wherein the microprocessor is mounted to the printed circuit board;

wherein the circuit element includes a passive electronic component which covers at least a portion of the microprocessor to inhibit electronic probing of the microprocessor;

wherein the tampering activity includes a breaking of electrical continuity through a portion of the passive electronic component; and

wherein the passive electronic component is an electronic display which is (i) mounted to the printed circuit board over the microprocessor and (ii) constructed and arranged to visually output data to a user from the microprocessor while the microprocessor performs the electronic operations.

2. An electronic device as in claim 1 wherein the electronic display includes:

a display portion which is constructed and arranged to output, as the data, a sequence of one-time passcodes to the user while the microprocessor performs the electronic operations; and

a set of pins extending from a periphery of the display portion and connecting with the printed circuit board, the set of pins concurrently (i) conveying signals between the printed circuit board and the display portion, and (ii) surrounding the microprocessor and supporting the display portion in a fixed position over the microprocessor to substantially conceal the microprocessor.

3. An electronic device as in claim 2 wherein the set of pins of the electronic display includes a particular lead; and

wherein the microprocessor is constructed and arranged to (i) perform the electronic operations when the particular lead provides a voltage which exceeds a predetermined voltage threshold, and (ii) no longer perform the electronic operations when the particular lead provides a voltage which is less than the predetermined voltage threshold.

4. An electronic device as in claim 2 wherein the set of pins of the electronic display includes a particular lead; and

wherein the microprocessor is constructed and arranged to (i) perform the electronic operations when the particular lead provides a voltage which is less than a predetermined voltage threshold, and (ii) no longer perform the electronic operations when the particular lead provides a voltage which exceeds the predetermined voltage threshold.

5. An electronic device as in claim 2 wherein the set of pins of the electronic display includes a pair of power signal leads; and

wherein the microprocessor is constructed and arranged to (i) perform the electronic operations when the microprocessor receives power from the power source through the pair of power signal leads, and (ii) no longer perform the electronic operations when the microprocessor no longer receives power from the power source through the pair of power signal leads.

6. An electronic device as in claim 2 wherein the set of pins of the electronic display includes a first lead and a second lead, the first and second leads being coupled together by a signal pathway within the electronic display; and

wherein the microprocessor is constructed and arranged to (i) perform the electronic operations when the microprocessor outputs a microprocessor signal on the first lead and successfully receives the microprocessor signal on the second lead, and (ii) no longer perform the electronic operations when the microprocessor outputs the microprocessor signal on the first lead and fails to receive the microprocessor signal on the second lead.

7. An electronic device as in claim 1 wherein the microprocessor includes an interface section; and

wherein the electronic display substantially conceals the interface section of the microprocessor when the microprocessor is disposed between the printed circuit board and the circuit element.

8. An electronic device as in claim 1 wherein the microprocessor is constructed and arranged to deactivate in response to the tampering activity.

9. An electronic device as in claim 8 wherein the microprocessor includes volatile memory which initially stores cryptographic information;

wherein the microprocessor, when performing the electronic operations, is constructed and arranged to cryptographically generate the data which is visually outputted to the user based on the cryptographic information initially stored in the volatile memory; and

wherein the microprocessor, when being electronically prevented from further performing the electronic operations in response to the tampering activity, is constructed and arranged to switch off the volatile memory to prevent reading of the cryptographic information.

10. An electronic device as in claim 8 wherein the microprocessor includes nonvolatile memory which initially stores cryptographic information;

wherein the microprocessor, when performing the electronic operations, is constructed and arranged to cryptographically generate the data which is visually outputted to the user based on the cryptographic information initially stored in the nonvolatile memory; and

wherein the microprocessor, when being electronically prevented from further performing the electronic operations in response to the tampering activity, is constructed and arranged to erase the cryptographic information which is initially stored in the nonvolatile memory.

11. An electronic device as in claim 8 wherein the electronic device is an authentication token having an external housing; and

wherein at least a portion of the circuit element includes metallic conductive material supported by a portion of the external housing.

12. An electronic device as in claim 1 wherein the microprocessor is constructed and arranged to visually output a series of passcodes exhibiting (i) a first behavior when the microprocessor performs the electronic operations in response to power from the power source while the microprocessor is disposed between the printed circuit board and the circuit element, and (ii) a second behavior when the microprocessor is electronically prevented from further performing the electronic operations in response to the tampering activity.

13. An electronic device as in claim 12 wherein the series of passcodes includes:

a stream of one-time passcodes, a transition between the first behavior and the second behavior which is exhibited by the series of passcodes being visually unidentifiable by the user.

14. An electronic device as in claim 12 wherein the series of passcodes further includes:

a status identifier which is selected from a plurality of status identifiers, each status identifier identifying an operating condition of the electronic device.

15. A method of providing security to an electronic device, the method comprising:

disposing a microprocessor between a printed circuit board and a circuit element to restrict physical access to the microprocessor, the microprocessor having (i) a bottom which faces the printed circuit board in a first direction and (ii) a top which faces the circuit element in a second direction which is opposite the first direction;

delivering power to the microprocessor from a power source while the microprocessor is disposed between the printed circuit board and the circuit element, the microprocessor performing electronic operations in response to the power delivered from the power source; and

in response to tampering activity on the circuit element, electronically preventing the microprocessor from further performing the electronic operations;

wherein the microprocessor is mounted to the printed circuit board;

wherein the circuit element is an electronic display which is mounted to the printed circuit board over the microprocessor;

wherein the method further comprises visually outputting data to a user from the microprocessor through the electronic display while the microprocessor performs the electronic operations; and

wherein the tampering activity includes a breaking of electrical continuity through a portion of the electronic display.

16. A method as in claim 15 wherein visually outputting the data to the user from the microprocessor through the electronic display includes:

visually outputting a series of passcodes exhibiting (i) a first behavior when the microprocessor performs the electronic operations in response to power from the power source while the microprocessor is disposed between the printed circuit board and the circuit element, and (ii) a second behavior when the microprocessor is electronically prevented from further performing the electronic operations in response to the tampering activity.

17. A method as in claim 16 wherein visually outputting the series of passcodes includes:

providing a stream of one-time passcodes, a transition between the first behavior and the second behavior exhibited by the series of passcodes being visually unidentifiable by the user.

18. An electronic device as in claim 1 wherein the microprocessor includes (i) an integrated circuit (IC) package which is solder mounted to the printed circuit board, and (ii) processing circuitry disposed within the IC package to perform the electronic operations; and

wherein the electronic display is external to the IC package of the microprocessor, the electronic display having (i) an underside which faces the IC package of the microprocessor and a display side which faces away from the IC package of the microprocessor to electronically output viewable information generated by the microprocessor to a user of the electronic device.

19. A method as in claim 15 wherein disposing the microprocessor between the printed circuit board and the circuit element to restrict physical access to the microprocessor includes:

solder mounting (i) an integrated circuit (IC) package of the microprocessor to the printed circuit board, and (ii) the circuit board element to the printed circuit board to conceal the IC package processing circuitry disposed within the IC package to perform electronic operations; and

wherein the electronic display is external to the IC package of the microprocessor, the electronic display having (i) an underside which faces the IC package of the microprocessor and a display side which faces away from the IC package of the microprocessor to electronically output viewable information generated by the microprocessor to a user of the electronic device.