Resilience in practice

Red Hook WiFi after Hurricane Sandy

Hurricane Sandy struck New York on 29 October 2012. The Red Hook Initiative (RHI), a community organisation in Brooklyn, had built a mesh network with the Open Technology Institute before the storm. RHI's building kept power, so the network stayed up. According to the New America case study, up to about 300 people a day used it to contact family, get news and seek aid.

This is the strongest documented example of a community mesh in a disaster, and its limits are part of the lesson:

• Power was luck as much as design. The network worked because the building kept power. The New America case study says that at one site, the Visitation Church Rectory, which was also without power, the team installed a UPS that could run the routers for 12 hours at a time.
• The uplink was borrowed. The network depended on donated bandwidth. A FEMA satellite link was offered "for only 30 days and provided modest bandwidth".
• It was prepared in advance. The mesh existed before the storm. Building one afterwards is a different and much harder project.

Hurricane Helene, 2024: what we could verify

Hurricane Helene hit western North Carolina in September 2024. The Benton Institute reports that more than 1,700 miles of fibre were destroyed (per the state's Statewide Interoperability Coordinator), 200,000 customers lost connection, and about $100 million of communications infrastructure was damaged. The article says no comprehensive public report yet explains why the region stayed dark for so long.

The Iberian blackout, 2025

The Iberian blackout began at 12:33 CEST on 28 April 2025 and lasted about ten hours in most areas. About 31 GW of generation disconnected (around 25.2 GW in Spain and 5.9 GW in Portugal). Netblocks reported traffic fell to 17 per cent of normal, and mobile voice and data were severely limited, especially in Portugal.

We found no documented use of Meshtastic, other LoRa meshes or Guifi.net during the blackout. Some commentary says the event raised interest in Meshtastic; interest is not use, so we make no claim about use.

Offline messaging apps: Bridgefy and security

Bridgefy is a phone-to-phone mesh messaging app. Its developers reported increased uptake around protests, including in Hong Kong, India, Iran, Lebanon, Zimbabwe and the US. In August 2020, Royal Holloway researchers reported that users could be tracked and deanonymised, messages intercepted, mesh networks disabled, and that messages had no authenticity. The original analysis is published as IACR ePrint 2021/214 and describes tracking, no authenticity, weak confidentiality and fragility to crafted messages. Bridgefy then moved to the Signal protocol. A follow-up by researchers at ETH Zurich and Royal Holloway, reported by Royal Holloway on 17 August 2021, showed those fixes were insufficient: users could still be tracked, broadcast messages remained unauthenticated, and an attacker in the middle could break the confidentiality of messages.

The lesson is general. "Works without internet" says nothing about whether messages are confidential, authentic or untraceable. See privacy and encryption. We did not find a source covering FireChat, so we say nothing about it.

Power is the first constraint

Every node needs power, and a power cut that takes out the internet often takes out the node's mains supply too.

• Battery and solar. LoRa nodes can run from batteries and panels; RAK sells solar repeaters (listed in Meshtastic's hardware docs). We have no sourced panel or battery sizing, so we give none; the power guide covers the principles.
• Power banks can cut out. Zak Kemble measured three banks that switched off when the draw fell below thresholds of 100 mA (after 10 seconds), 30 mA (16 s) and 10 mA (18 s). A very low-power node on such a bank may be switched off by the bank itself.
• Mains-powered Wi-Fi nodes (rooftop radios, routers) fail with the grid unless fitted with batteries, as the Red Hook UPS figure shows.
• Placement. Nodes on tall buildings or hills do the most work, and also tend to be the hardest to reach during an emergency. See antenna placement.

What local-only messaging buys you, and what it does not

Coverage is the catch. A mesh is only useful if enough nodes exist in the places people are. In an unprepared area, one node is a private network of one. See find a local mesh and the ISP as a single point of failure.

Summary

Documented: Red Hook WiFi worked because it was prepared, powered and had donated bandwidth, and it faced real limits. Documented the other way: offline apps can be insecure. Undocumented, so not claimed: Meshtastic in Helene, any mesh use in the Iberian blackout. The realistic claim for mesh resilience is local communication, set up in advance, with power planned.