Encryption interface cable

• US 20030167391A1
• Filed: 02/28/2003
• Published: 09/04/2003
• Est. Priority Date: 03/01/2002
• Status: Active Grant

• Current Assignee: Masimo Corporation
• Original Assignee: Masimo Corporation
• Inventors: Al-Ali, Ammar
• Granted Patent: US 7,509,494 B2
• Time in Patent Office: Days
• US Class Current: 713/153
• CPC Class Codes: A61B 2560/045 with a separable interface unit, e.g. for communication
• CPC Class Codes: A61B 2562/08 Sensors provided with means for identification, e.g. barcodes or memory chips
• CPC Class Codes: A61B 2562/222 Electrical cables or leads therefor, e.g. coaxial cables or ribbon cables
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/6826 Finger
• CPC Class Codes: A61B 5/6838 Clamps or clips

Abstract

An interface cable is configured to connect a host instrument to a physiological sensor. The interface cable has an ID signal input from the sensor and a LED drive signal input from the host instrument sensor port. The interface cable also has a data signal output to the host instrument sensor port. The LED drive signal and the data signal provide an encrypted handshake to and from the host instrument. The handshake is responsive to the ID signal so as to enable normal operation of the host instrument and the sensor.

Claims

1. An interface cable configured to connect a host instrument to a physiological sensor, said interface cable comprising:

an ID signal input from said sensor;

a LED drive signal input from a sensor port of said host instrument; and

a data signal output to said sensor port,

said LED drive signal and said data signal providing a handshake to and from said host instrument, said handshake responsive to said ID signal so as to enable a normal operation state of said host instrument.

2. The interface cable according to claim 1 further comprising:

an ID reader that inputs said ID signal and outputs an ID measurement; and

a processor responsive to said ID measurement so as to generate a sensor ID.

3. The interface cable according to claim 2 further comprising:

a current sense circuit that inputs said LED drive signal and outputs a current measurement,

said processor responsive to said current measurement so as to determine a seed generated by said host instrument, said processor configured to generate an encryption key based upon said seed.

4. The interface cable according to claim 3 further comprising:

a conditioning circuit that inputs transmit data from said processor and outputs said data signal,

said processor generating a cipher text responsive to said sensor ID and said key, said transmit data responsive to said cipher text.

5. The interface cable according to claim 4 further comprising:

a switch having an closed state connecting said LED drive signal to said sensor and an open state disconnecting said LED drive signal from said sensor;

a control input to said switch determining said open state and said closed state,

said processor generating said control in response to said normal operation state.

6. The interface cable according to claim 1 wherein:

said LED drive signal has a plurality of current levels,

at least a portion of said current levels each representing a unique combination of bits so that data is transmitted on said LED drive signal by varying said current levels.

7. The interface cable according to claim 1 wherein:

said data signal has a plurality of voltage levels,

a first portion of said voltage levels each representing a unique combination of bits so that data is transmitted on said data signal by varying said voltage levels, and

a second portion of said voltage levels indicating sensor status.

8. An interface method of interconnecting a host instrument and a sensor comprising the steps of:

detecting if said sensor is valid;

performing an encryption handshake with said host instrument upon valid sensor detection; and

enabling normal physiological measurements with said host instrument only after completion of said encryption handshake.

9. The interface method of claim 8 wherein said detecting step comprises the substeps of:

reading an ID element of said sensor;

outputting an ID measurement corresponding to said ID element; and

comparing said ID measurement to a plurality of predetermined values for known sensor types.

10. The interface method of claim 8 wherein said performing step comprises the substeps of:

indicating sensor status to said host instrument;

receiving a seed from said host instrument;

generating a cipher text based upon said seed; and

transmitting said cipher text to said host instrument.

11. The interface method of claim 10 wherein said indicating substep comprises the substeps of:

outputting a data signal to a sensor port of said host instrument; and

varying voltage levels on said data signal corresponding to said sensor status.

12. The interface method of claim 10 wherein said receiving substep comprises the substeps of:

inputting a LED drive signal from said host instrument; and

varying current levels on said drive signal corresponding to at least one data bit.

13. The interface method of claim 10 wherein said generating substep comprises the substeps of:

generating a key from said seed;

deriving a sensor ID corresponding to a type of said sensor based upon said ID measurement; and

combining said sensor ID and said key.

14. The interface method of claim 13 wherein said combining substep comprises the substeps of:

storing a predetermined password;

incorporating said sensor ID into a data word; and

performing an “

exclusive or”

of said data word, said password and said key.

15. The interface method of claim 10 wherein said transmitting substep comprises the substeps of:

outputting a data signal to a sensor port of said host instrument; and

varying voltage levels on said data signal corresponding to at least one data bit.

16. The interface method of claim 8 wherein said enabling step comprises the substeps of:

receiving an indication of a successful handshake from said host instrument; and

closing a switch so as to connect LED drivers of said host instrument to LEDs of said sensor.

17. An interface cable for connecting a host instrument to a sensor comprising:

a measurement means for reading a sensor ID element;

a verification means for determining from said measurement means that said sensor is valid and for determining a corresponding sensor ID;

a handshake means for establishing a communications link to said host instrument and for transmitting said sensor ID; and

an adapter means for connecting said host instrument and said sensor upon establishing said link.

18. The interface cable according to claim 17 wherein said handshake means comprises:

an encryption means for securing said communications link; and

a signal level means for transmitting data to and from a sensor port of said host instrument.

19. The interface cable according to claim 18 wherein said encryption means comprises:

a key means for encrypting said data; and

a seed means for generating said key means.

20. The interface cable according to claim 19 wherein said encryption means further comprises a password means for further encrypting said data.