One-way transfer device with secure reverse channel

1. A data diode, comprising:

a first processing element;

a second processing element;

a main channel coupled between the first processing element and the second processing element, providing hardware-enforced one-way communication from the first processing element to the second processing element;

a secure reverse channel coupled between the first processing element and the second processing element providing hardware-enforced one-way reverse communication from the second processing element to the first processing element; and

a cellular interface coupled to the second processing element and configured to transmit to a destination data received from a source via the main channel,

where the reverse communication consists of a request to execute one of a predetermined set of commands.

2. The data diode of claim 1 ,

wherein the main channel comprises a first optocoupler configured to pass data from the first processing element to the second processing element, and

wherein the secure reverse channel comprises a second optocoupler configured to pass the reverse communication from the second processing element to the first processing element.

3. The data diode of claim 2 , wherein the second optocoupler is an analog optocoupler.

4. The data diode of claim 2 , wherein the secure reverse channel further comprises:

a first controller configured to receive the request as a first digital data; and

a digital to analog converter coupled to the first controller configured to convert the first digital data into an analog signal.

5. The data diode of claim 4 , wherein the secure reverse channel further comprises:

a second controller; and

an analog to digital converter coupled to and controlled by the second controller and configured to:

receive analog signals from an analog optocoupler, and

convert the analog signals into a second digital data,

wherein the second controller converts the second digital data into the request.

6. The data diode of claim 1 , further comprising a cellular input interface coupled to the first processing element and configured to receive data from a source for transmission to a destination via the main channel.

7. The data diode of claim 1 , wherein the secure reverse channel comprises a digital optocoupler.

8. The data diode of claim 7 , further comprising:

a first converter unit; and

a second converter unit, coupled to the first converter unit,

wherein the digital optocoupler passes the request received from the second processing element to the first converter unit,

wherein the first converter unit converts the request into an analog signal, and

wherein the second converter unit converts the analog signal, upon receipt from the first converter unit, into the request.

9. The data diode of claim 1 , wherein the request comprises a command of the predetermined set of commands.

10. The data diode of claim 1 ,

wherein the request comprises a representation that corresponds to a command of the predetermined set of commands, and

wherein the first processing element interprets the representation to determine the command.

11. The data diode of claim 1 , wherein the first processing element comprises:

a secure memory circuitry that is only rewritable with physical access to the data diode, in which the set of predetermined commands is stored,

wherein the first processing element compares the request with the set of predetermined commands to determine whether to accept the request.

12. The data diode of claim 11 , wherein the request is an identifier corresponding to one of the set of predetermined commands stored in the secure memory circuitry.

13. The data diode of claim 11 , where the request is a location in the secure memory circuitry.

14. The data diode of claim 11 , wherein a hash value corresponding to a command associated with the request is returned by the first processing element in response to the request.

15. The data diode of claim 14 , wherein a change to the secure memory circuitry is detectable by comparing the hash value returned by the first processing element in response to the request with a known acceptable value.

16. The data diode of claim 11 ,

wherein the request comprises a hash value corresponding to a command of the set of predetermined commands stored in the secure memory circuitry, and

wherein the first processing element detects a change in the secure memory circuitry by using the hash value.

17. A method of sending a command via a data diode, comprising:

sending a request to execute the command via a secure reverse channel of the data diode that provides hardware-enforced one-way communication from a second processing element of the data diode to a first processing element of the data diode;

executing the command responsive to a determination by the first processing element that the command is a member of a set of predetermined commands;

responding to the command with data transmitted via a main channel that provides hardware-enforced one-way communication from the first processing element to the second processing element; and

transmitting the data to a destination via a cellular interface coupled to the second processing element.

18. The method of claim 17 , wherein sending the request comprises converting the request from a first digital data to an analog signal then converting the analog signal to a second digital data.

19. The method of claim 17 , further comprising:

storing the set of predetermined commands is stored in a secure memory circuitry of the first processing element; and

detecting a change to the set of predetermined commands.