If you do X, then Y is secure unless there are other dimensions to the problem, e.g., an airgapped network in a Faraday cage is secure from data exfiltration vi

If you do X, then Y is secure unless there are other dimensions to the problem, e.g., an airgapped network in a Faraday cage is secure from data exfiltration via radio emissions, but not necessarily via optical or acoustic emissions. That said, the NSA recommends multiple encryption, for instance using "inner" and "outer" VPN gateways: https://www.nsa.gov/resources/everyone/csfc/capability-packages/assets/files/vpn-cp.pdf https://www.nsa.gov/resources/everyone/csfc/capability-packa... This sort of thing should be standard protocol for critical infrastructure, such as water supply, power grid and healthcare systems.