Transparent custody.

CheckSig believes in transparent, publicly verifiable custody. While opacity remains the industry standard, CheckSig stands out for its uncompromising rigor.

First in the world, since 2020 CheckSig provides a public, cryptographic Proof‑of‑Reserves, at least monthly: anyone can verify on-chain the existence, availability, and full control of all funds in custody.

Such a proof might seem obvious; in reality, most crypto companies do not prove their reserves, leaving room for concealed losses that surface only when it’s too late.

The Proof‑of‑Reserves is provided as a transaction, publicly verifiable on the Bitcoin blockchain. The transaction:

• includes (in tech jargon, spends as TxIn) the amount under custody consolidated in the previous Proof‑of‑Reserves;
• collects (spends as TxIn) all deposits received since the last Proof‑of‑Reserves;
• pays transaction fees;
• withdraws (creates a TxOut for) the amount required to satisfy our clients’ withdrawal requests, if any;
• consolidates all remaining Bitcoin as a single amount (creates one change TxOut) at the consolidation address.

The consolidated amount reflects the entirety of Bitcoin in custody at the time of the transaction. Through the use of the previous amount, the locking-script (the pre-image of the P2WSH script) protecting the assets is revealed, making CheckSig’s custody model fully verifiable and transparent.

The Proof‑of‑Reserves performs a simultaneous transfer to the consolidation address, attesting to the effective control of funds at the transaction date. While address reuse is generally discouraged for privacy, in our case it becomes a deliberate and necessary choice to ensure the publicity of the proof.

Any residual potential vulnerability (such as nonce exfiltration) is neutralized by our proprietary protocol. Security relies on a multi-level, multi-signature architecture, based on Hardware Security Modules from diversified manufacturers to eliminate any single point of failure.

Publishing the amount in custody, while fundamental, does not in itself attest to the ability to meet obligations to the entire client base. An authentic proof of solvency requires that the Proof‑of‑Reserves be supplemented by a verification of liabilities (Proof‑of‑Liabilities), i.e., the determination of total deposits. However, cryptographic liability verification models are often partial and difficult to interpret for users and auditors.

Given the need to protect privacy, current approaches do not allow independent and easy verification for non-experts. CheckSig therefore chooses to elevate the standard of transparency by entrusting liability verification to independent external auditors.

Their independent review ensures that publicly demonstrated reserves consistently exceed client liabilities, and constitutes a fundamental pillar of our SOC attestations.

Furthermore, since an on-chain proof could be subject to temporary manipulations, such as taking out loans to conceal shortfalls, only a professional off-chain review guarantees the absence of anomalies. It is this dual level of control, technical and fiduciary, that defines our institutional security.

Verify all Proof‑of‑Reserves transactions performed by CheckSig, with the ability to explore them on-chain.

Altcoins do not support native multi-signature: for this reason, we only provide our addresses whose balances can be verified (Proof‑of‑Addresses, also known as Proof‑of‑Balances). The Proof‑of‑Reserves is only provided implicitly when we spend from these addresses.