# Device Layer

The **Device Layer** forms the foundation of the DecentraFit ecosystem.\
It represents the physical interface between human activity and cryptographic verification.\
Both the **DecentraFit Watch** and **DecentraFit Health Ring** operate as trusted hardware oracles, responsible for capturing authentic biometric data and generating zero-knowledge proofs directly on-device.

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### **Our Watch**

The DecentraFit Watch is an advanced wearable designed for secure, real-time biometric authentication. It transforms raw health signals into encrypted proof statements while maintaining user privacy through local computation.

**Key Specifications:**

* Secure enclave implementing elliptic-curve cryptography (Ed25519) for local signing and encryption.
* Multi-sensor array including heart rate (HR), heart-rate variability (HRV), blood oxygen (SpO₂), body temperature, accelerometer, and GPS.
* Embedded SNARK chip running a zk-WASM runtime for efficient, low-latency proof generation directly on the device.
* Adaptive AI algorithms that detect genuine physiological patterns while filtering synthetic or replayed data.
* Validate spatial data for performance-based metrics and travel-related activity verification. Sensor calibration occurs locally, with noise-reduction filters powered by embedded AI models to ensure signal integrity.
* Machine-learning models embedded within the watch continuously analyze biometric data to distinguish authentic human behavior from artificial or manipulated inputs.
* When reconnected, it performs a mutual-authentication handshake with the DecentraFit App before securely transmitting encrypted ZK-PoA packages via Bluetooth LE or NFC.\
  This guarantees that user data remains protected even in environments with limited connectivity.

The device is capable of fully **offline proof generation**, storing encrypted proofs locally until a trusted connection is established.

**Functional Role:**\
The watch operates as a real-time proof generator.\
It compiles activity statements such as:

> “Heart rate increased by more than 40% and motion entropy exceeded threshold for over 20 minutes.”

This statement is then verified locally using a SNARK circuit, producing a proof that confirms the claim without exposing the underlying biometric data.

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### **Our Ring**

The DecentraFit Health Ring complements the watch by providing **continuous passive biometric monitoring** and **seamless connectivity** for proof synchronization.

**Key Specifications:**

* Continuous tracking of sleep quality, stress response, blood circulation, and temperature variation.
* Connectivity via NFC and Bluetooth Low Energy (BLE) for efficient data transfer and device pairing.
* Lightweight ZK proof circuits optimized for low-power consumption, enabling 24/7 operation.
* Hardware-accelerated encryption for secure local storage and proof signing.

**Functional Role:**\
The ring is optimized for background proof generation, particularly during rest and recovery cycles. It computes and verifies activity statements like:

> “Average resting heart rate decreased by 10% over 72 hours with consistent sleep intervals.”

Each verified statement is encoded as a **Zero-Knowledge Proof (ZKP)** and passed to the DecentraFit App for aggregation and submission to the Layer-2 verifier.

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By processing these proofs locally, the Device Layer upholds **DecentraFit’s core principle**: privacy by design, verification at the edge, and trust without exposure.