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Relay.md

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Relay Mode

Relay mode enables the user to relay NFC traffic over the network. All traffic on the ISO 14443 layer can be relayed, along with initial tag information. Please see clone mode for more information.

Requirements

Devices

  • Two Android devices that will perform the relaying (called relay devices). A device cannot be used as both the reader and the tag (HCE) when participating in relaying.
  • Reader and tag whose traffic should be relayed (called relayed devices). These devices can be Android devices.
  • Any device running the NFCGate server application. This can also be one of the Android devices running Termux.

Configuration

Relay devices:

  • Android 4.4+ (API level 19+)
  • EdXposed or Xposed
  • Architecture: ARMv8-A, ARMv7
  • The device acting as tag (in "tag mode") requires HCE support.
  • Networking connectivity with the server application, more specifically a TCP connection is required.

Relayed devices:

  • No special configuration required.

Usage

On both relay devices:

  1. Switch to Settings in the navigation drawer.
  2. Specify Hostname and Port and Session.
  3. Make sure the server application is running and accessible over the network.
  4. Switch to Relay Mode in the navigation drawer.
  5. Click Reader or Tag depending on device: For a relay, one device in "reader mode" and one device in "tag mode" is required.
  6. When the connection has been successfully established, the app will show a green status indicator.

Relaying traffic:

  1. Place the relay device in "reader mode" to read the tag that you want to relay.
  2. Place the second relay device in "tag mode" on the relayed reader.

The NFC traffic is captured and available in Logging for later use.

Technical Information

See clone mode documentation.

Architecture

Relay mode architecture

Caveats

Timing

If the relayed reader and/or tag have constrained requirements for communication time, timeouts can occur. In addition to that, poor network connectivity might also negatively affect performance and reliability.