# Glossary and References

**BLE GATT.** Bluetooth Low Energy Generic Attribute Profile — the application layer over which TaτsuOS receipts are written to a device.

**ECDSA.** Elliptic Curve Digital Signature Algorithm — the signature scheme TaτsuOS uses, instantiated over the secp256k1 curve.

**Feature ID.** A `bytes32` value, typically `keccak256` of a human-readable name (e.g. `keccak256("GPS_TRACKING")`).

**Device ID.** A `bytes32` value computed from the device's hardware-unique identifier, used to bind a receipt to a specific physical device.

**Receipt.** A 130-byte signed payload that authorizes a single feature unlock on a single device.

**TATSU.** The Taτsu Ecosystem's utility token.

**TimescaleDB.** A time-series-optimized extension of PostgreSQL, used as the cloud's primary store.

**Zephyr.** A Linux Foundation project — a small, permissively licensed real-time operating system targeting resource-constrained devices.

### References

* Taτsu Ecosystem — <https://tatsuecosystem.io/>
* Zephyr Project — <https://zephyrproject.org/>
* EIP-191 / EIP-712 signed-message standards — <https://eips.ethereum.org/EIPS/eip-712>
* OpenZeppelin Contracts v5 — <https://docs.openzeppelin.com/contracts/5.x/>
* OWASP IoT Top 10 — <https://owasp.org/www-project-internet-of-things/>
* Bluetooth Core Specification 5.x — Bluetooth SIG


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