A Presence-sensing drive for Securely Storing Secrets

When we hear about flash drives in the context of cybersecurity, we tend to think of them more as threats than as targets. When youâre using flash drives to store encryption keys, however, it makes sense to pay more attention to their security. [Juergen] designed the PECKUS (Presence Enforcing Crypto-Key USB-Storage) with this specifically in mind: a few-kilobyte storage device that only unlocks if the ownerâs Bluetooth device is in the vicinity.
[Juergen] needed to store an infrequently-used keyfile on an air-gapped system, and commercial encrypted flash drives were rather expensive and left much to be desired in terms of usability. Instead, he designed a CircuitPython custom firmware for MakerDiaryâs nRF52840 micro development kit, which provided a BLE-capable system in the form of a USB dongle.
After flashing the firmware to the board, the user sets it up with a particular Bluetooth device and a file to be stored; after writing the file during setup, it cannot be rewritten. Before reading from the device, the user must pair the previously-set device with the board and press a button on the board, and only then does the device appear to the computer.
The limited amount of storage space means that this device will probably only serve its intended purpose, but in those cases, itâll be handy to have an open-source and inexpensive protected storage device. [Juergen] notes that attackers could theoretically defeat this system by desoldering the microcontroller from the board and extracting the memory contents from the its storage, but if you have enemies that resourceful, you probably wonât be relying on a $20 board anyways.
Weâve previously seen a few flashdrives cross these pages, including one meant to self-destruct, and one made from a rejected microSD card.
from Blog â Hackaday https://ift.tt/A75yclY
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