How Crypto Custody Actually Works

Custody determines who can move an asset and what happens to it if the entity holding it fails. It is a legal question as much as a technical one, and the two are frequently confused.

The spectrum

“Not your keys, not your coins” describes the endpoints and skips the middle, which is where most institutional exposure actually sits.

Self-custody. You hold the private key. You bear the operational risk entirely — key loss is unrecoverable, and there is no counterparty to make you whole.

Exchange custody. The exchange holds keys and owes you a balance. What you own is a claim against that entity, not an asset. This distinction is invisible until the entity fails, at which point it becomes the only thing that matters.

Third-party custody. A specialist firm holds keys under a custody agreement, typically with the assets held for your benefit rather than on the custodian’s balance sheet. This is the arrangement most regulated institutions use.

Shared control. Multisig or multi-party computation splits authority so no single party can move assets alone. Common for treasuries and funds.

Omnibus versus segregated

The most consequential distinction and the least visible from the outside.

In an omnibus structure, client assets are pooled in shared addresses and individual entitlements are tracked in the custodian’s internal ledger. It is operationally efficient and it means your on-chain position is not individually identifiable.

In a segregated structure, your assets sit in addresses attributable to you.

Under normal conditions the difference is invisible. In an insolvency it is decisive. Segregated assets held for your benefit are more readily identified as yours rather than as part of the estate. Pooled assets, particularly with poor internal record-keeping, become a reconciliation exercise conducted by an administrator over a period measured in years.

The technical arrangement matters less here than the legal one: whether the custody agreement establishes a trust or bailment relationship, or merely a debt. Two custodians using identical cryptography can offer entirely different outcomes on this axis.

Cold, warm and hot

A operational spectrum rather than a security guarantee. Cold storage keeps keys entirely offline; withdrawals require a manual process measured in hours. Hot wallets are connected and automated, holding the working balance needed for operations.

Every custodian runs a mix, because a fully cold operation cannot service withdrawals at usable speed. The informative questions are what proportion sits hot, what the withdrawal process requires, and how many people must act to move a large balance.

Multisig and MPC

Both remove single points of failure; they do it differently.

Multisig is enforced on chain — the protocol itself requires several signatures. It is transparent, auditable by anyone, and visible as a multisig on chain, which is occasionally undesirable.

Multi-party computation splits a single key into shares held by different parties who jointly produce a signature without ever reconstructing the key. On chain it looks like an ordinary single-signature address. It works across chains that lack native multisig support, and the trade-off is that the security guarantee is a property of the implementation rather than of the blockchain — it cannot be verified externally.

What “qualified custodian” means

A regulatory designation, not a technical one, and it varies by jurisdiction. It generally implies capital requirements, audit obligations, segregation rules and supervision.

It says relatively little about cryptographic practice. A qualified custodian is one an institution is permitted to use, which is a different property from being the most secure available. Both matter; conflating them is a common error.

The questions that matter

Who can move the assets, and how many people must act? Are assets segregated or omnibus, and what does the agreement say about ownership? What happens in insolvency — are assets part of the estate? Is there insurance, what does it actually cover, and what is the per-client limit? Has the custodian ever published a reconciliation performed by someone independent?

Nothing here is advice about any provider. It is the structure that determines what your claim is worth on the day it is tested.