Multisig Architecture and Practical Setup

What you'll learn

• Why Multisig Exists
• Bitcoin Multisig: P2SH and Taproot
• Ethereum Multisig: Safe
• Choosing the Right Threshold and Signer Distribution
• Consumer Multisig Services: Casa, Unchained, Onramp
• Key Rotation, Time-Locks, and Inheritance
• Practical Signing Workflows
• For Deeper Reading

Key terms

M-of-N multisignature

A wallet configuration requiring M signatures from a set of N total keys to authorize a transaction. Common configurations: 2-of-3 for individuals, 3-of-5 for high-net-worth users, 4-of-7+ for institutions and DAOs.

Safe (formerly Gnosis Safe)

The dominant Ethereum multisig smart contract platform, launched December 14, 2018. Holds approximately $50-58 billion TVL across 9M+ accounts in early 2026. Used by the Ethereum Foundation, most major DAOs, and corporate treasuries.

P2SH (Pay-to-Script-Hash)

Bitcoin script type activated April 2012 (BIP-16) that enables multisig and other complex scripts. Address format starts with "3". Functional but less efficient than SegWit and Taproot variants.

Taproot multisig

Bitcoin multisig using Schnorr signatures (activated November 2021). Combined with MuSig2 or FROST, N signers can produce a single signature indistinguishable from a single-key signature, providing privacy and fee efficiency.

PSBT (Partially Signed Bitcoin Transaction)

Standardized in BIP-174 (2017), the workflow primitive for Bitcoin multisig. Lets signers add signatures to an unsigned transaction asynchronously, supporting airgapped signing via QR code or USB transfer.

Casa

Consumer Bitcoin and Ethereum multisig service founded 2017. Tiers: Standard ($250/yr) is 2-of-3, Premium ($2,100/yr) is 3-of-5 with inheritance, Diamond ($4,500/yr) is bespoke. Casa holds one key in a multisig; never has unilateral access.

Unchained

Bitcoin-only collaborative custody platform founded 2016. Offers 2-of-3 vaults (~$250-500/yr), Bitcoin IRAs, and Bitcoin-collateralized loans. Deep Bitcoin expertise.

Onramp Bitcoin

Multi-Institution Custody service (founded 2021) that distributes the three keys of a 2-of-3 across three independent custodians (BitGo, Coinbase Custody, Onramp). Institutional/HNW only; ~0.50-0.75% AUM/year.

Time-lock (CLTV/CSV)

Bitcoin script primitives (BIP-65, BIP-112) that enforce timing constraints. CLTV requires a transaction wait until a specific block height; CSV requires N blocks after funding. Used to construct dead-man-switch and inheritance scripts.

Sarcophagus

Ethereum-based dead-man-switch protocol. User periodically rewraps a smart contract; if rewrapping fails before deadline, archaeologist nodes release encrypted recovery shards to the beneficiary.

Ledger Recover controversy (2023)

Ledger announced May 2023 a service splitting seed phrases via Shamir across three custodians for fee-based recovery. Community criticized it as undermining self-custody premise. Paused, then released opt-in October 2023. Lesson: be wary of vendor-controlled recovery services.

Key rotation

Periodically replacing one or more keys in a multisig setup (typically annually). Involves generating a new hardware wallet, modifying the multisig owner set via signed transaction, and verifying the new configuration with a test transaction.