Key takeaways
- MPC splits the ability to sign across several parties, so no complete private key sits in one place.
- Custody uses the threshold form, written t-of-n: any t of n share holders can sign, and fewer cannot.
- The blockchain sees one ordinary signature, unlike multisig, where several signatures are checked on-chain.
- NIST published its Threshold Call on 20 January 2026; its work on threshold schemes is reports, not a standard.
- The approval policy in front of the signing step matters as much as the cryptography.
How multi-party computation works
MPC lets a group calculate something together without any member revealing its own input to the others. Applied to a private key, the secret number that authorises a transfer from a blockchain address, the key is never held whole. Each party holds a key share, a piece that reveals nothing on its own.
NIST's Multi-Party Threshold Cryptography project describes threshold schemes as applying MPC principles to achieve a secure distribution of trust in cryptographic operations. The NIST Threshold Call (NIST IR 8214C) adds that the operation is computed in a distributed way while the private key stays secret-shared across the parties.
The usual form is a threshold, written t-of-n. With a 2-of-3 threshold, any two of three share holders can run the signing protocol together; one alone cannot. The result is a single signature that the network accepts like any other.
- Key share A piece of a key that reveals nothing alone. Each MPC party holds one.
- Threshold (t-of-n) The number of parties, t, needed to sign out of the total, n.
- Signing protocol The exchange of messages by which the parties produce a signature without assembling the key.
MPC in digital asset custody
A custodian using MPC places shares with separate parties or systems: for example, the custodian, the client and a backup provider, or several custodian-controlled environments in different places. Compromising one share does not give an attacker the ability to sign.
Before any signing, the steps look alike in every key model: a user proposes a transfer, a policy engine checks it against limits and address lists, and approvers confirm. MPC changes only how the final signature is made. For the wider comparison, read MPC vs HSM vs multisig custody compared.
Two other points distinguish MPC from multisig. First, multisig is a rule on the blockchain, so it is visible there and not every chain supports it; MPC works off-chain and ends in a standard signature. Second, MPC needs its parties online at the same time and exchanging several rounds of messages, which suits frequent, automated transfers. Custodians often combine models, for example keeping each share inside a hardware module.
Key technology is only one layer. How client assets are separated is covered in segregation of client assets, explained, and the decision of who holds keys at all in custody vs self-custody for institutions.
Strengths and limits of MPC
| Topic | Strength | Limit |
|---|---|---|
| Key exposure | No complete key in one place. | The shares and the parties' systems still need protecting. |
| Chain support | Ends in an ordinary signature, so it can reach many chains. | The protocol must support each chain's signature algorithm. |
| Recovery | Shares, not whole keys, are backed up. | The protocol and its implementation are hard to review. |
| Governance | Spreads control across parties. | Approval policies run off-chain in software, so their quality depends on design and audit. |
Prepared for this guide from the sources listed below. Last reviewed .
MPC is a design choice with costs, not a guarantee. If the same operator controls enough shares to reach the threshold, the benefit of splitting is lost, so who holds each share matters as much as how many exist.
Standards and assurance for MPC
An HSM can be validated under FIPS 140-3, the NIST standard for cryptographic modules published on 22 March 2019, and the validation appears on a public list. MPC has no module-level equivalent: NIST is still gathering and studying threshold schemes, and the Threshold Call published on 20 January 2026 asks for public submissions.
Until a standard and a validation programme exist, assurance for an MPC product rests on other evidence: the published protocol and its security proof, independent code audits, penetration tests and the provider's SOC reports. These help most when you know their scope; the security and assurance evidence page lists what Hex Trust publishes.
Regulation is technology-neutral. Part III of VARA's Custody Services Rulebook covers key generation, storage, backups and collusion risk without prescribing HSM or MPC. Where the licence sits and what it covers is set out in crypto custody law in Dubai, Singapore and Hong Kong.
How Hex Trust answers on key storage
Hex Trust states that it keeps private keys in HSMs validated to FIPS 140-3 Level 3, and the live trust centre names the vendor as Securosys Primus (read 6 October 2026).
Gap: the pages read for this guide do not say whether MPC is used for any asset. Ask the contracting entity which key model protects your wallets. Entities and licences are listed on the About page.
What to ask a custodian that uses MPC
- What is the threshold, and who holds each share? Can one operator reach it alone?
- Which protocol and implementation are used, and has it been independently audited? Can you read the report?
- Are shares kept in hardware modules, and if so, which certificate covers them?
- How are shares backed up and recovered, and when was recovery last tested?
- Who sets the approval policy, and can one person change it and then sign?
The wider list is in the crypto custody due diligence checklist, and short answers about Hex Trust are in the Hex Trust FAQ.
FAQ
What does MPC stand for?
MPC stands for multi-party computation, a branch of cryptography in which several parties compute a result together without any of them revealing its private inputs. In custody, the result is a digital signature and the private inputs are the key shares held by each party.
Is MPC the same as multisig?
No. Multisig is enforced by the blockchain, which checks several separate signatures. MPC happens off-chain: the parties run a protocol and the network sees one ordinary signature. Multisig keys are whole keys, whereas MPC holders each have only a share of one key.
Is MPC certified like an HSM?
Not yet in the same way. A hardware security module can be validated under FIPS 140-3 and listed by NIST. NIST's work on threshold schemes, which apply MPC principles, so far consists of reports, and its Threshold Call was published on 20 January 2026. MPC assurance rests on audits, proofs and SOC reports.
Does MPC remove the need for approval controls?
No. MPC decides how a signature is produced, not whether a transfer should happen. Approval policies, address lists, limits and segregation of duties still apply, and a weak policy can authorise a bad transfer as readily as a strong one.
Does Hex Trust use MPC?
Hex Trust states that it keeps private keys in HSMs validated to FIPS 140-3 Level 3. The pages read for this guide do not say that MPC is used for any asset, so ask the contracting entity which key model protects your wallets.
Sources
Standards bodies and regulator rulebooks relied on for this guide, with the date each page was last opened.
- National Institute of Standards and Technology, Multi-Party Threshold Cryptography, opened 12 October 2026.
- National Institute of Standards and Technology, NIST Threshold Call (NIST IR 8214C), opened 12 October 2026.
- National Institute of Standards and Technology, FIPS 140-3, Security Requirements for Cryptographic Modules, published 22 March 2019, opened 12 October 2026.
- Virtual Assets Regulatory Authority, Custody Services Rulebook, version effective from 19 June 2025, Part III, opened 12 October 2026.
Statements about Hex Trust come from its live website trust centre, read on 6 October 2026. The full text of the NIST documents was not re-read for this article beyond the points stated; check them before relying on them.
This guide is for information only and is not investment advice, legal advice or tax advice. It does not recommend any custodian or any digital asset. Digital assets are volatile, and the risk disclosure for digital asset services sets out the main risks.
Ask how your keys would be protected
Ask institutional sales which key model would protect your wallets, the certificates or audit reports behind it and the approval policy for your account.
Risk warning. Not financial advice. Crypto is highly volatile and may drop in value significantly. You may lose the amounts you invest and your investments do not benefit from any form of financial protection.