MPC vs. Multisig vs. Single-Key Custody: Which Should a Fintech Use?

How you hold private keys is one of the most consequential decisions a fintech makes. Lose a key and you lose the funds; expose a key and someone else can move them. Three approaches dominate. Here’s how they differ.

Single-key custody

One private key controls the wallet. It’s simple and cheap, but it’s a single point of failure: whoever holds that key — or steals it — has full control. For anything beyond small balances, single-key custody is hard to justify.

Multisig

Multisig requires several independent keys to approve a transaction (say, 2 of 3). It removes the single point of failure: compromising one key isn’t enough. The trade-offs are that multisig is chain-specific (implementations differ across networks), on-chain, and can be operationally heavy to manage at scale.

MPC (multi-party computation)

MPC custody splits a single key into mathematical shares held by different parties. No party ever holds the full key, and a threshold of shares is required to sign — but to the blockchain, it still looks like one ordinary signature. You get the no-single-point-of-failure property of multisig, with chain-agnostic flexibility and lower on-chain overhead.

Which to choose

For most fintechs, MPC has become the default: it protects against key compromise, works the same across networks, and integrates cleanly into an API-driven product. Pairing it with hardware-backed key management (KMS) and device-bound approval for high-value moves raises the bar further.

That’s the model Hamirach uses: 2-of-3 MPC custody with KMS-secured tiers and a device-bound mobile approval app. No single point of failure, and an auditable trail of every signature.

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