Keystone

Keystone is a 100% air-gapped, open-source hardware wallet built around a single principle: private keys should never touch an internet-connected device — not at setup, not at signing, and not during firmware updates. Its flagship product, the Keystone 3 Pro, achieves this by communicating exclusively through QR codes, eliminating the USB data paths, Bluetooth channels, WiFi interfaces, and NFC connections that have historically served as attack surfaces in competing devices.

Core Mechanism

The signing flow is entirely offline. A paired software wallet — MetaMask, Solflare, Rabby, and dozens of others — generates a QR code representing an unsigned transaction. The Keystone device scans that code through its camera, decodes the raw transaction data into a human-readable summary on its 4-inch touchscreen, and waits for the user to review and confirm. After biometric fingerprint verification, the device signs the transaction internally and generates a new QR code containing only the signed output, which the software wallet then scans to broadcast to the network. At no point does any private key material cross the air gap.

This architecture eliminates the entire category of remote software attacks. There is no driver to exploit, no wireless handshake to intercept, and no firmware-over-USB vector to abuse.

The Keystone 3 Pro

The Keystone 3 Pro is Keystone's current flagship hardware wallet, priced at $149. Its standout hardware features include:

• Triple secure element chips rated CC EAL6+, the highest certification level used in consumer-grade security hardware. Three chips in parallel rather than one adds redundancy and makes physical extraction of key material substantially harder.
• Physically Unclonable Function (PUF)-based key derivation on the secure elements, meaning key material is intrinsically tied to the specific physical chip and cannot be cloned.
• Biometric fingerprint sensor for transaction authorization, with an anti-peeping display designed to prevent shoulder-surfing.
• PCI-grade tamper resistance with active self-destruct circuitry that wipes sensitive data if physical tampering is detected.
• 4-inch 480×800 color LCD touchscreen for full display of transaction details before signing.
• Multi-seed support: up to three independent recovery phrases can be stored on a single device, enabling portfolio segmentation without carrying multiple hardware units.

Keystone also offers a Bitcoin-only firmware variant for users who want the smallest possible attack surface, reducing the device's code footprint to Bitcoin-specific signing logic only.

Key Products and Accessories

Beyond the device itself, Keystone offers the Keystone Tablet and Keystone Tablet Plus — steel plates for physically stamping or punching seed phrases, designed to survive fire and corrosion. The Keystone Nexus serves as an optional companion software wallet for users who prefer a Keystone-native interface rather than a third-party integration.

Keystone also supports Shamir Backup (SLIP39), a cryptographic seed-splitting scheme that divides a recovery phrase into multiple shares, each of which is individually useless but collectively sufficient to recover a wallet. This lets users distribute shares across physical locations with no single location holding a complete backup.

Software Wallet Integrations

Keystone integrates with more than 45 software wallets and interfaces. These include MetaMask, OKX Wallet, Rabby, BlueWallet, Sparrow, Safe (formerly Gnosis Safe), Keplr, and — for Solana users — Solflare and Backpack. Co-branded Keystone devices have been released in partnership with Solflare, OKX, and Safe.

Solana Support

Keystone's Solana integration is delivered primarily through Solflare and covers the full range of common on-chain operations in an air-gapped context:

• Native SOL staking: users can delegate stake through Solflare and sign staking transactions on the Keystone device.
• Token swaps: in-wallet swaps within Solflare are signable on-device.
• DApp connections: Keystone can sign transactions initiated by Solana DApps through the Solflare interface.
• Message signing: arbitrary message signing for authentication flows is supported.
• Clear-signing: rather than presenting a raw hash for blind approval, Keystone decodes the Solana transaction and displays full details — from address, to address, amount, and program interactions — on the device screen before the user confirms. This eliminates blind signing, where users historically approved transactions without visibility into their contents.

Security Audits and Open Source

Keystone's codebase and hardware design are fully open-source. Notably, Keystone claims to be the first hardware wallet company to publish Secure Element firmware for public review. Hardware design documents, including circuit diagrams and bill of materials, are also publicly available. The firmware is hosted at github.com/KeystoneHQ/keystone3-firmware.

The device has been audited by multiple independent security firms: Keylabs, PeckShield, Offside Labs, BlockSec, and SlowMist. The Keylabs audit, completed in November 2023, was the first formal security review of a hardware wallet with three secure elements and an effective tamper circuit. It identified one high-severity issue and five lower-severity findings across hardware and firmware; Keystone's published blog post states all reported issues were resolved prior to publication.

Fit Within the Solana Ecosystem

Hardware wallet support has historically been a gap in the Solana user experience. The ecosystem's transaction model and instruction formats required custom integration work that most hardware wallet vendors deprioritized for years. Keystone addressed this directly with its Solflare partnership, making it one of the few hardware wallets offering genuine Solana clear-signing rather than hash-only blind approval. For Solana users managing significant on-chain positions — in liquid staking, DeFi protocols, or long-term SOL holdings — Keystone's air-gap model provides cold-storage security without requiring users to abandon the software wallet ecosystems they already use.

Keystone was founded in 2018 and remains an active, commercially available product line, with regular firmware updates, expanding software wallet integrations, and ongoing security content published through its blog and social channels.