Fitbit Sense 2 (GB513FL)

Fitbit Sense 2 (GB513FL)
Security Grade C Calculator v	Fitbit Sense 2 (GB513FL) Brand: Fitbit (Parent: Google LLC) Category: Smartwatch / Health & Fitness Wearable • Model / Gen: Sense 2 (2nd gen Sense) GB513FL Release Date: 2022-09-02 • Status: In sale Classification Date: • Official Website

Security Evaluation

1. Device Security

Criterion	Value	Proof	Comment
Known hardware tampering	Rare	🔗 Proof	Sealed wearable; no user-serviceable parts; standard consumer build
Known vulnerabilities	Rare	🔗 Proof	No widely-reported critical hardware flaws; embedded RTOS
Prior attacks	None	🔗 Proof	Consumer wearable; no major public compromise
Updatability	Very common	🔗 Proof	Fitbit/Google provides firmware updates; at least 2 years of security updates guaranteed
Category Score	Score: 2 / 3

2. System Security

Criterion	Value	Proof	Comment
Authentication with other systems	Partial	🔗 Proof	Requires Google/Fitbit account; syncs via phone Bluetooth; no enterprise SSO
Communications	Encrypted with up-to-date encryption	🔗 Proof	Bluetooth LE with encryption; cloud sync over HTTPS/TLS
Storage	Encrypted with up-to-date encryption	🔗 Proof	On-watch data protected; health data synced encrypted to Google cloud
Category Score	Score: 2 / 3

3. User Authentication

Criterion	Value	Proof	Comment
Account management	Basic	🔗 Proof	Google/Fitbit account required for sync and cloud features
Authentication	Basic	🔗 Proof	Swipe-to-wake + optional 4-digit PIN; no biometric unlock on watch
Brute-force protection	Basic	🔗 Proof	PIN-based unlock; limited lockout; relies on phone pairing security
Event logging	Partial logging	🔗 Proof	Limited on-device logging; cloud activity visible in Fitbit app
Passwords	Default/Common/Easy to guess	🔗 Proof	No default watch password; user sets optional 4-digit PIN; no complexity requirement
Category Score	Score: 3 / 3

Technical Specifications

Property	Details
Operating System & App	Fitbit OS (proprietary RTOS) (Companion App: Fitbit app (iOS / Android))
Hardware (CPU / GPU)	CPU: Proprietary ARM Cortex-M class MCU • GPU: None (no discrete GPU)
Memory & Storage	Memory: 512 MB • Storage: 4 GB internal
Power, Battery & Charging	Battery: ~260 mAh Li-Po, up to 6+ days • Power: proprietary magnetic charger • Charging: fast charge (12 min = 24 hrs)
Display & Camera	Display: 1.58" AMOLED, 336×336, always-on, Gorilla Glass 3 • Camera: None
Sound & Connectivity	Sound: Vibration motor, built-in microphone & speaker (Bluetooth calls) • Connectivity: Bluetooth 5.0, NFC (Google Pay), GPS+GLONASS, WiFi (disabled in firmware)
Physical (Dimensions & Mass)	Dimensions: 0.5 × 40.5 × 11.2 mm • Mass: 37.64 g

GB513FL is the model number for the Fitbit Sense 2, released in September 2022 as Fitbit's premium health-focused smartwatch, now owned by Google (acquired in 2021). It succeeded the original Fitbit Sense (2020).

Key hardware: 40.5 mm square AMOLED touchscreen (336 x 336, always-on display), Gorilla Glass 3, aluminum case. Sensors include ECG, cEDA (continuous electrodermal activity), skin temperature, SpO2 (red/infrared), altimeter, 3-axis accelerometer, ambient light, and gyroscope. Built-in GPS + GLONASS for standalone workout tracking. NFC supports Google Pay. Bluetooth 5.0 for phone connection and hands-free calling via built-in mic/speaker. WiFi hardware is present but disabled in firmware.

Battery is ~260 mAh Li-Po rated for 6+ days, with fast charging (12 minutes gives 24 hours). Water resistance is 5 ATM. Weight is only 37.64 g (without band).

Security model: the watch pairs with a phone running the Fitbit app (iOS 11+ / Android 10+). A Google/Fitbit account is required for cloud sync, health data backup, and features like Alexa. On-device security is minimal: no biometric unlock, no TPM, no secure element. The watch can be protected with an optional 4-digit PIN. Health data (ECG, EDA, SpO2, sleep, heart rate) syncs encrypted to Google's cloud. Fitbit/Google guarantees at least 2 years of security updates after the device is last sold. No enterprise MDM support.