A Public Key Proves a Signature, Not a Settlement

A public key verifies a digital signature by checking that a private key signed a particular message without revealing that private key. For a fund, the practical puzzle is narrower: if its custodian accepts a signed $20 million collateral transfer, why can the trading desk still be unable to use the collateral? Verification proves control of a key and the integrity of transaction data; it does not complete policy approval, blockchain settlement or venue credit.

How does a public key check a signature?

The verifier tests a mathematical relationship among the public key, the message and the signature. First, the fund builds the transaction: destination address, amount, fee, network identifier and a nonce that prevents replay. A signing device hashes those exact bytes, then uses the private key to produce a signature. The private key stays inside the custodian’s hardware module or distributed signing system.

A node or custodian then:

• recreates the hash from the received transaction;
• checks the signature against that hash and the public key;
• rejects the request if even one transaction field changed; and
• separately checks balance, nonce and policy before broadcast.

The public key does not decrypt the signature, and successful verification does not expose the private key. It confirms that the signature and message fit the key pair’s rules.

The transaction still has a queue

Once the signature passes, the custodian may require an allowlisted address, a second approver or a withdrawal limit check. The network must accept the transaction, validators must include it, and the venue receiving the collateral may wait for finality before extending buying power. Only then can a market maker or other counterparty take the opposite side with confidence that margin is available.

That gap between authorization and availability also appears in bridge operations; the Manta Bridge analysis shows why a completed inbound step need not make the reverse path equally light on capital.

What does verification actually prove?

It proves two narrow claims: the signature was made with the private key corresponding to the supplied public key, and the signed message has not been altered. It does not prove that the key holder is the legal owner, that an employee had authority to trade, or that a transfer is economically sensible.

The closest familiar arrangement is a bank checking an authorized signature on a payment instruction. The analogy breaks because a bank can rely on customer records, reverse some errors and exercise discretion. A blockchain verifier applies a mathematical rule. Identity, mandate and recovery sit in custody controls around that rule.

The liquidity consequence outweighs the cryptography

Consider a clearly labeled hypothetical. A fund wants to post $20 million to a derivatives venue that requires 20% initial margin and grants no provisional credit. Its existing $5 million supports only $25 million of notional exposure; after the transfer becomes usable, $25 million of total collateral supports $125 million, before haircuts. A valid signature produced at noon does not create that extra $100 million of capacity if compliance releases the transfer at 12:10 and the venue credits it at 12:20.

The fund gains capacity only at the final credit step. Until then, it absorbs missed execution, funding or liquidation risk, while the custodian and venue reduce fraud and reversal exposure. That allocation deserves more weight than the headline claim that public-key verification is “instant.” The cryptography can settle the authenticity question quickly; operational liquidity follows the slowest control after it.