What is a relay attack ?

A relay attack uses two radio devices: one near the car owner’s key fob and one by the car. The devices amplify and forward the key’s “I’m nearby” signal, tricking the car into thinking the key is at the door — so the car unlocks and can even be started. It’s fast, cheap, and has been shown to work against many popular models.

How Faraday fabric stops that theft

A Faraday fabric is a conductive textile that blocks or attenuates radiofrequency (RF) waves when fully enclosed. Put your key inside a properly designed pouch or box made with tested Faraday fabric and the fob’s radio can’t reach outside receivers — there’s nothing for the thief to amplify or relay. Multiple reliable sources and consumer-safety guides recommend storing key fobs in signal-blocking containers to reduce relay attack risk.

Chemical composition & how the fabric works

  • Conductive threads: fine wires or metal coatings of silver, copper, nickel, or stainless steel are woven or plated into the textile. Some fabrics use conductive carbon blends or thin metal films laminated to fabric.
  • Structure: woven/knitted conductive mesh or metal-coated fibers embedded in cotton, polyester, or other bases. The conductivity of the network creates a path that redistributes and absorbs incoming RF energy, preventing it from passing through the textile.

Properties & technical specifications

When shopping for real protection, these are the useful technical specs and claims to check:

  • Shielding Effectiveness (SE) — measured in decibels (dB). Higher dB → more attenuation. Typical tested Faraday fabrics for RF shielding report attenuation ranges such as 60–120 dB depending on frequency, layering, and material. Example lab tests have shown fabrics achieving 80–120 dB over wide bands, but performance varies by sample and test setup.
  • Frequency range: the useful range for key fobs is usually hundreds of MHz to a few GHz (different car systems vary). ASTM D4935 test methods typically measure planar material SE over ~30 MHz to 1.5 GHz, which maps well to many keyless systems; other lab setups extend higher.
  • Layering: one layer may reduce signals; two or three layers often improve attenuation significantly.
  • Conductivity & surface resistance: often quoted as ohms/sq for the conductive layer — lower is better.

Durability & washability: some fabrics maintain shielding after laundering; others lose plating or coatings and lose SE. Check manufacturer wash/wear data.

Standards & testing — why certification matters

There are established test methods used in industry labs to measure shielding:

  • ASTM D4935 — Standard Test Method for Measuring the Electromagnetic Shielding Effectiveness of Planar Materials (commonly used for fabrics; valid ~30 MHz–1.5 GHz). If a vendor provides ASTM D4935 test reports, that’s a strong sign of lab verification.
  • IEEE-299 — used for large enclosures and broader frequency ranges (useful if you’re testing boxes or rooms).

Buying tip: ask the seller for the test report PDF with measurement curves and specimen details (layer count, orientation, frequency sweep). Claims without lab data are only marketing.

Shapes available

Key pouches / Faraday bags: Small, zip- or fold-closed pouches lined with conductive fabric to block fob and card signals—pocket-friendly and portable.

Rigid boxes / tins: Sturdy enclosures with an internal conductive lining for reliable sealing and home/office storage.

Fabric rolls / cut pieces: Meter-wide conductive textile sold by the roll for custom sewing, OEM integration, or large panels.

  • Wallet inserts / card sleeves / keyrings: Ultra-thin layered inserts for slim, discreet protection of cards and small fobs.
  • Curtains / blankets / canopies: Large panels or covers of shielding fabric for room-scale or localized RF attenuation.

Applications — where Faraday fabrics are used (expanded)

1.Car-key protection (relay-attack defense)
Blocks a key-fob’s radio signal to stop thieves from relaying it to a vehicle.
Use: keep fobs fully enclosed in a tested pouch or lined tin when not in use.
Tip: verify by trying to lock/unlock the car with the fob enclosed.

2. Personal privacy & device protection
Prevents unauthorized RFID/NFC reads and casual wireless scanning of cards/devices.
Use: wallet sleeves, passport pouches, or phone pouches during travel.
Tip: full-coverage, snug sleeves are essential—partial coverage can leak.

3. Fleet & corporate security (operational use)
Reduces risk from lost or compromised fobs across an organisation.
Use: issue tested pouches to staff, standardise storage procedures (e.g., pouch-in-tin).
Tip: procure tested bulk solutions and archive lab reports for audits.

4. Travel & anti-theft for luggage / gear
Shields small trackers, tags, and fobs inside luggage to prevent unauthorized tracking.
Use: line compartments or keep tags in pouches when privacy is desired.
Tip: clearly mark shielded pockets so you don’t accidentally disable active devices.

5. Infant / health protection (curtains, bassinet covers)
Provides localized reduction of ambient RF in sleeping or resting areas.
Use: canopy panels or partial covers that attenuate nearby signals without sealing.
Tip: ensure breathability and never fully enclose an infant — safety first.

6. Industrial & OEM uses (EMI control)
Used inside enclosures, around cables, or as sensor shields to control EMI/RFI.
Use: cut fabric pieces integrated into device housings or wrapped around sensitive parts.
Tip: match the fabric’s shielding effectiveness (dB) to the device’s frequency range.

7. Clothing & wearable applications
Integrates conductive yarns or liners for mobile, personal shielding in garments.
Use: lab coats, scarves, or removable shielded panels where needed.
Tip: check comfort, washability, and skin-safe materials — tradeoffs exist between shielding and wearability.

Real world effectiveness — cautious optimism

While many labs and vendors demonstrate strong attenuation, independent testing and consumer reports show mixed results: good pouches and boxes backed by lab data can be highly effective, but poorly made items or those with incomplete seals can leak signal and fail. In short: Faraday fabric solutions work — when correctly designed, fully enclosed, and tested. Don’t trust untested claims.

Practical, actionable checklist — how to make your keys hack-proof now

  1. Use a tested Faraday pouch or box that provides a lab report (ASTM D4935 or equivalent).
  2. Fully enclose the key — zips, snaps, or magnetic seals are better than open pockets. Even tiny gaps can leak RF.
  3. Layer up — if you’re unsure about a pouch, use two layers (pouch inside a metal tin) for extra margin.
  4. Test at home simply: close the pouch, try to lock/unlock your car from near the house. If the car responds, the pouch may not be fully blocking. (Note: this is a crude check; lab testing is the only definitive method.)
  5. Complement with other measures: use steering locks, disable passive entry if your car allows it, and park in secure locations. Faraday fabric reduces risk, but layered security is best.

DOMADIA™ recommendation

At DOMADIA™, we design Faraday pouches and fabric rolls engineered for real-world attenuation and durability. Look for our DOMADIA™ KeyShield Series (tested to ASTM D4935 lab reports, multi-layer options, washable variants). If you want help selecting the right pouch for your make/model, we’ll walk you through test reports and fit. (Soft plug — always ask for the lab PDF.)

Environmental & lifecycle note

Good-quality shielding fabrics last longer and maintain protection after washing and regular use. Cheaper, short-lived pouches must be replaced more often — creating unnecessary waste. Investing in proven, durable Faraday fabric is better for both security and the environment over the long run.

Conclusion — can you make your car truly hack-proof?

No single product makes anything 100% hack-proof forever — attackers and defenses evolve. But Faraday fabric for car key protection, when chosen smartly and used properly, significantly reduces the chance of a relay attack and is a highly recommended layer in a broader security strategy. Ask for lab reports (ASTM D4935 or equivalent), seal the pouch completely, and combine physical deterrents for best results.

Contact our experts today!

Need help choosing the right form factor?  Contact our experts today!

Talk to: Kairav Domadia | Aadil Domadia | Er.Pankaj Domadia | Pragati Sanap | Pooja N N 

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