Protected Mode

Protected Mode

Protected Mode is a proprietary privacy feature developed by Impinj for their EPC Gen2 RFID tag ICs. When a tag is placed in Protected Mode, it becomes completely invisible to standard RFID readers — it does not respond to inventory commands, does not backscatter, and does not appear in any reader's tag population. Only a reader that first provides the correct Access Password can "wake" the tag and interact with it normally.

How Protected Mode Works

Protected Mode leverages the tag's internal state machine. When activated, the tag enters a deep sleep state where it ignores all standard Query and Select commands. The tag still harvests RF energy and powers up its tag IC, but its protocol engine refuses to participate in singulation.

To interact with a tag in Protected Mode, the reader must:

1. Send a proprietary Impinj command that targets the tag by its TID Memory serial number (the only identifier the reader can know in advance).
2. Provide the correct Access Password.
3. If the password matches, the tag temporarily exits Protected Mode and responds normally for the duration of the RF session.

This approach is more aggressive than the standard Untraceable Command, which merely reduces functionality. Protected Mode renders the tag completely non-existent from the perspective of any reader that does not know the password and TID serial.

Use Cases

Consumer privacy: Retailers using Impinj-based inlays can place tags in Protected Mode at the point of sale. The tagged garment becomes untrackable in public spaces, addressing GDPR privacy concerns. If the customer returns the item, the store reader (which has the Access Password in its database) can re-enable the tag for inventory processing.

Selective visibility: In multi-tenant facilities, each tenant's tags can be placed in Protected Mode with tenant-specific Access Passwords. Only readers authorised by a particular tenant can see that tenant's tags, providing cryptographic isolation without physical separation.

Anti-surveillance: Organisations concerned about competitors scanning their warehouses or shipping containers can protect high-value or sensitive tags. Even a rogue reader operating at maximum EIRP cannot detect a tag in Protected Mode.

Protected Mode vs. Untraceable vs. Kill

Limitations

Protected Mode is a proprietary Impinj feature, not an open standard. Tags from other manufacturers (NXP, Alien, etc.) do not support it. Deployments that require multi-vendor tag compatibility should use the standardised Untraceable Command instead. Additionally, placing a tag in Protected Mode requires knowing its TID serial in advance, which necessitates a database lookup before the mode can be applied — adding complexity to the point-of-sale workflow.