# Data diode

A data diode is a hardware device that physically permits data to flow in one direction only. Unlike firewalls, which enforce policy in software, a diode makes reverse communication physically impossible, which is why cross-domain solutions built on diodes are trusted in defense, critical infrastructure, and air-gapped custody.

## From defense networks to custody

In a technical air gap, the diode sits between the connected domain and the signing domain: transaction requests pass one way through deep content filtering, and no path exists for an attacker to reach the HSMs or exfiltrate key material.

Taurus uses hardware data diodes with real-time content filtering in its technical air gap cold storage, deployed in production for regulated institutions.

FAQ:

- Why is a diode stronger than a firewall? A firewall is software rules on a bidirectional link, and rules can be misconfigured or exploited. A diode has no return channel to attack: the reverse direction does not exist physically.

Related: https://www.taurushq.com/glossary/technical-air-gap/ https://www.taurushq.com/security/air-gapped-custody/

Learn more: https://www.taurushq.com/glossary/data-diode/