Collaborative Custody

Unchained operates as a U.S.-regulated bitcoin financial services company founded in 2016 and based in Austin, Texas. The platform has secured billions of dollars in bitcoin and originated over $500 million in bitcoin-backed loans, establishing a multi-year track record in the industry. Their collaborative custody model uses standard bitcoin multisignature technology where clients typically hold 2 of 3 keys, meaning Unchained cannot unilaterally move funds—a verifiable security property that eliminates the counterparty risk that led to failures at centralized exchanges.

The security architecture allows clients to independently verify their holdings using external wallet software and open-source tools, avoiding the opaque off-chain accounting that has plagued custodial services. For those wanting additional institutional backing, Unchained offers multi-institution custody arrangements where keys are distributed among the client, Unchained, and independent third-party key agents like Bakkt. This design prevents any single entity from accessing funds while maintaining professional recovery options if a client loses access to their keys.

Bitkey is developed and operated by Block, Inc. (NYSE: SQ), a publicly traded financial technology company with a market cap in the tens of billions and regulatory compliance across multiple jurisdictions through its Square and Cash App products. This corporate backing means Bitkey benefits from institutional-grade security practices, ongoing development resources, and accountability to shareholders and regulators. The hardware and software are designed with transparency in mind, and Block has published details about the 2-of-3 multisig architecture where the company holds only one server key that cannot move funds without user participation.

The security model distributes trust across three keys: one on your phone, one on the hardware device, and one held by Block's servers. Any two keys are required to move funds, meaning Block alone cannot access your Bitcoin, while you retain ultimate control through your two keys. The hardware device stores its key offline with fingerprint authentication and NFC tap-to-sign, and the mobile key can be backed up to your cloud account. Privacy protections ensure Bitkey cannot see transaction details when you use your own keys, and the system is designed so that even if Block's servers went offline, users with both their phone and hardware device could still access funds.

Lloyd's of London Coverholder (AM Best A+ rated). Launched December 2024. Uses Miniscript-powered Trident Vaults.

Casa operates as a non-custodial service where users maintain control of their funds through distributed key management. In their standard 2-of-3 multisig setup, you hold a mobile key and hardware wallet key while Casa holds only a single Recovery Key that cannot move funds without your authorization. This architecture means Casa cannot unilaterally access or transfer your bitcoin, and vaults use open multisig standards compatible with external wallet software, ensuring fund recovery remains possible even if Casa ceases operations.

The platform has operated since 2018, building a track record serving high-net-worth individuals, family offices, and institutional clients. Their security model emphasizes geographic key distribution, built-in key rotation for compromised devices, and optional seedless configurations that reduce the attack surface of traditional seed phrase storage. Higher-tier memberships include dedicated security advisors who assist with threat modeling and incident response, providing human oversight alongside the technical architecture.

First multi-user multisig wallet. Zero KYC. Famously refused Canadian court order during Freedom Convoy.

2-of-3 multisig vault with keys held by 3 separate institutions (Onramp, BitGo, Coincover). No single entity can move funds. On-chain auditable. Full-reserve model.

The Bitcoin Adviser operates as a non-custodial advisory service, meaning they never hold your Bitcoin or control your keys. Their collaborative custody model uses 2-of-3 multi-signature setups with hardware isolation, on-chain recording, audit trails, and optional video attestation for geographically distributed security. They recommend established hardware wallets like Trezor Safe 3 or Safe 5 for client self-custody implementations.

The firm has been serving Bitcoin clients since 2016 and reports managing advisory relationships covering over $1 billion in Bitcoin assets. They are recognized by Bitcoin Magazine as one of the top Bitcoin consultants for secure self-custody in 2025, alongside other leading specialist firms.

Client testimonials show 24+ verified reviews averaging 4.8/5 rating, with a separate listing rated 4.9/5 (25 reviews). Their approach emphasizes reducing single points of failure and ensuring heirs can access Bitcoin safely through structured inheritance planning without exposing keys to unnecessary risk.

Bitcoin Keeper is a fully non-custodial, open-source wallet where users maintain complete control of their private keys. The company never has access to user funds and cannot sign or authorize transactions on behalf of users.

The application code is publicly available on GitHub (bithyve/bitcoin-keeper), allowing independent security review by the community. Bitcoin Keeper provides signed checksums and detached GPG signatures for APK verification, enabling users to confirm they are running authentic, unmodified software. WalletScrutiny has included Bitcoin Keeper in their build verification efforts, indicating attention to transparency.

The wallet supports connecting to your own Bitcoin node, eliminating reliance on third-party servers for transaction verification. Multi-key vault configurations distribute signing authority across multiple devices and locations, removing single points of failure. The app is Bitcoin-only, avoiding the complexity and attack surface of multi-asset wallets.