Foundation's QuantumLink: Post-Quantum Bluetooth for Passport Prime

Foundation Devices wants its Passport Prime hardware wallet to talk over Bluetooth without letting the radio inside it listen. On January 23, 2025, the Boston-based self-custody firm introduced QuantumLink, a secure Bluetooth protocol that its co-founder and CEO, Zach Herbert, has spent recent weeks explaining across X and CoinDesk. The Passport Prime, which shipped with the protocol built in, saw its details emerge on March 26, 2026.

The bet is a sharp turn for a company whose earlier reputation rested on one rule: never let the device talk to anything. Foundation's discontinued Passport Core introduced QR air-gapping to Bitcoin self-custody. One screen displayed a code, another scanned it, and data crossed the gap with no cable or radio involved.

QuantumLink replaces that shuffle with a real-time link to Envoy, Foundation's companion app. The connection handles onboarding, transaction signing, firmware updates and syncing — the full lifecycle, not just signing.

How does a radio stay untrusted?

Foundation's answer is physical separation. Passport Prime uses a dedicated, isolated Bluetooth chip that runs independently from KeyOS, the wallet's primary security processor. The chip carries the traffic but is never allowed to read it. Every message passing through it is end-to-end encrypted before it arrives.

The stack leans on two cryptographic primitives working in sequence. CRYSTALS-Kyber, a NIST-standardized post-quantum algorithm, handles key exchange — the step where wallet and app agree on a shared secret. ChaCha20-Poly1305 then encrypts the actual messages. Kyber sets up the lock; ChaCha20-Poly1305 keeps each conversation behind it.

The pairing process adds another layer. Before any Bluetooth traffic flows, the wallet and app swap public keys out of band using a QR code. Because the initial exchange never touches Bluetooth, the chip never sees plaintext. Even a fully compromised radio would sit on a pile of ciphertext with no way to unlock it.

Foundation also leaves purists an exit. Users can disable Bluetooth entirely and fall back to QR, NFC or USB, so nobody is forced onto the wireless path.

What does this change for self-custody?

The practical question for holders is whether convenience costs isolation. Herbert, a Bitcoin advocate since 2013, frames QuantumLink as delivering live connectivity with air-gap-grade protections and encryption designed against future quantum threats. Blockchain Commons collaborated with Foundation on the design phase.

Skeptics have work to do as well. Community discussions have zeroed in on Bluetooth-related vulnerabilities, and the burden now falls on Foundation to show the hardware separation performs in practice as cleanly as it does on a diagram.

The stakes go beyond one vendor. If a hardware wallet maker can prove that an untrusted radio chip, post-quantum key exchange and out-of-band pairing can coexist with cold-storage guarantees, the industry's long-standing allergy to wireless connectivity weakens. If it cannot, the QR code remains the gold standard. Passport Prime shipments, and the audits they invite, will settle the argument.