TTL Data Diode (breadboard)
The hardware data diode is a device that physically blocks covert return channels in compromised firmware of serial interfaces. This document is based on USB-TTL-USB Data Diode (version 16.10.a) by pseudonym Sancho_P, and material is used under GNU FDL v1.3.
| PCS | Item |
|---|---|
| 3 | USB-to-TTL adapter |
| 2 | HCPL-7723 optocoupler |
| 4 | 0.01-0.1μF capacitor |
| 1 | Perfboard |
| jump wiring |
As optocoupler is an integrated circuit the internal functionality of which is hard to audit, to avoid interdiction by nation states, users should avoid buying components online.
The circuit diagram for single direction data diode is as follows
Start by pressing the TTL board against bread board with pins and solder then to board.
Solder the switch to 5V setting. Be careful not to bridge the 3.3V side with center
Assemble the components on data diode as follows. Note that the optocouplers' orientation marks point to opposite directions.
Ensure that the capacitors only touch the pins 1 and 4 or 5 and 8 of the optocoupler.
Connect the lower right TTL-adapter to TxM, upper right to RxM and the one on the left to NH.
