Disclosure: As an Amazon Associate, CardWise earns from qualifying purchases at no additional cost to you. This does not affect our recommendations.

Apple Watch Ultra 3 vs Galaxy Watch 8 — NFC Payment, Secure Enclave & Knox

Smartwatches have quietly become the most intimate security device most people own. They sit on your wrist with a biometric sensor, an NFC chip for tap-to-pay, an eSIM for cellular connectivity, and increasingly, a UWB chip that can unlock your car. The Apple Watch Ultra 3 and the Samsung Galaxy Watch 8 represent the pinnacle of each platform's wearable security stack. But their approaches diverge sharply when you look under the hood: Apple's S10 SiP pairs with a dedicated Secure Enclave coprocessor, while Samsung's 3nm Exynos chip relies on the Knox security platform baked into the watch's firmware. This comparison focuses exclusively on the security and connectivity technology: NFC payment tokenization, secure element architecture, UWB digital car keys, eSIM cellular, and what happens when the battery dies.

Secure Element & Chip Architecture

The fundamental difference between these two watches is where the security lives. Apple uses a physically separate coprocessor; Samsung integrates security into the main SoC with a dedicated secure area managed by Knox.

Apple Watch Ultra 3: S10 SiP + Secure Enclave

The Ultra 3 runs on the S10 System in Package (SiP), a 64-bit dual-core processor with a 4-core Neural Engine. Buried inside is Apple's Secure Enclave — a coprocessor with its own secure boot chain, encrypted memory, and hardware UID that is fused during manufacturing. The Secure Enclave handles all cryptographic operations: payment tokenization for Apple Pay, biometric data (the watch has no fingerprint sensor but uses wrist detection + skin contact), and key management for files and messages. The critical property is that the Secure Enclave's UID is device-bound and不可extractable — even Apple cannot read it after manufacturing.

Galaxy Watch 8: 3nm Exynos + Knox

The Galaxy Watch 8 uses a 3nm Exynos processor (Samsung's most advanced wearable chip to date). Security is handled by Samsung Knox — a defense-in-depth platform that spans from hardware roots of trust through the bootloader, kernel, and application layer. Knox uses a Trusted Execution Environment (TEE) within the main SoC: a secure partition that isolates sensitive operations like Samsung Pay tokenization and biometric data. Unlike Apple's physically separate Secure Enclave chip, Knox's TEE is a software-isolated region within the main processor die. This is a legitimate design choice but a different threat model: a main SoC compromise could theoretically affect the TEE, whereas Apple's Secure Enclave would remain isolated.

NFC Payment: Apple Pay vs Samsung Pay on the Wrist

Both watches support NFC contactless payments, but the tokenization and ecosystem integration differ significantly.

Apple Pay on Apple Watch Ultra 3

Apple Pay on the Ultra 3 works by holding a Device Account Number (DAN) in the Secure Enclave. When you tap your watch to a terminal, the watch sends the DAN and a transaction-specific dynamic security code — never your actual card number. The DAN is generated during card provisioning and is bound to that specific watch's Secure Enclave UID. If someone steals your watch, they cannot extract payment data even with physical access to the chip. Key advantages on the Ultra 3:

• Double-click side button to activate payment before reaching the terminal (no accidental triggers)
• Wrist detection requires skin contact before Apple Pay is accessible — if the watch leaves your wrist, payment locks within seconds
• Offline payments: Apple Pay tokens are pre-provisioned, so payments work without phone or cellular connection

Samsung Pay / Samsung Wallet on Galaxy Watch 8

The Galaxy Watch 8 uses Samsung Wallet (which absorbed Samsung Pay) for NFC payments. Samsung Pay uses a similar tokenization scheme: the watch holds a token in the Knox TEE, and a dynamic security code is generated per transaction. Samsung explicitly states that all transactions are processed within Knox's secure domain, and customer information is not stored on the device in plaintext. Key features:

• Long-press side button to open Samsung Wallet before tapping
• MST discontinued: Unlike older Samsung phones, the Watch 8 relies purely on NFC (no Magnetic Secure Transmission for older terminals)
• Transit cards: Samsung Wallet supports transit cards on the watch (tap through subway gates directly from the wrist)
• Smart Octopus (Hong Kong): Integrated transit + payment for HK users

UWB: Digital Car Key & Spatial Awareness

Both watches include Ultra-Wideband (UWB) chips, but they serve different ecosystems and have different security implications.

Apple Watch Ultra 3: Second-Generation UWB

The Ultra 3 features Apple's second-generation UWB chip (an upgrade from the U2 in the Series 9). This chip enables:

• Digital Car Key (CCC Release 3): Approach your BMW, Hyundai, or Genesis with the watch on your wrist — the car unlocks automatically via UWB passive entry. The UWB chip uses Time of Flight (ToF) and Angle of Arrival (AoA) to precisely locate the watch and prevent relay attacks via scrambled timestamp sequence (STS).
• Precision Finding: Spatial awareness for locating other Apple devices (Find My directional arrows)
• HomePod handoff: Transfer audio sessions based on proximity

Galaxy Watch 8: UWB for Samsung Wallet Digital Key

The Galaxy Watch 8's UWB chip works with Samsung Wallet's digital car key feature. Samsung supports two types of digital car keys:

• NFC type: Touch the watch to the car door to lock/unlock, then place it on the wireless charging pad to authenticate and start the car
• UWB type: The car unlocks automatically as you approach, and you can start the car with the start button after authentication

Samsung's digital car key is compatible with select BMW, Audi, and Hyundai models that support the Digital Key Alliance standard.

eSIM & Cellular Connectivity

Both watches offer cellular variants with eSIM, but the ecosystems differ.

Apple Watch Ultra 3: 5G RedCap + LTE eSIM

The Ultra 3 supports 5G RedCap (Reduced Capability) — a low-power 5G variant designed for wearables and IoT. This allows the watch to connect to 5G networks for data and calls without needing your phone. Key features:

• Apple Watch for Family Members: Set up an Ultra 3 for a child or elderly family member using your iPhone, with their own phone number via eSIM. Includes parental controls (Schooltime, Activity tracking, location sharing)
• Dual eSIM: Not supported on watch, but you can have one eSIM active
• International roaming: Limited carrier support for watch eSIM roaming

Galaxy Watch 8: LTE eSIM

The Watch 8 LTE variant supports standard LTE eSIM connectivity. Samsung's One UI 8 Watch includes Samsung Wallet transit cards on the watch, allowing you to tap through subway gates directly from the wrist — useful in cities like Seoul, Hong Kong, and London where Samsung Wallet transit is supported.

Physical Security & Durability

While not directly a "security chip" feature, the physical build affects how secure the device is in harsh environments.

Software Ecosystem Lock-In

The biggest practical security difference isn't the chip — it's the ecosystem requirements.

Quick Comparison Table

Which Watch Is More Secure?

Related Reading

• iPhone 17 Pro vs Pixel 10: NFC, Secure Enclave & eSIM — phone-level security comparison
• iPhone 17 Pro vs Galaxy S25: NFC, Knox Vault & Samsung Pay — phone-level Knox vs Secure Enclave
• AirTag vs SmartTag2 vs Chipolo — NFC & UWB tracker comparison
• Best NFC Phones 2026 — NFC payment phone guide

Want to test NFC tag interactions? Try our NFC Forum Tag Type Detector or NDEF Writer Simulator.