By Arch Lending·
Proof of Reserves Explained
Introduction
When a crypto platform tells you your funds are safe, what does that actually mean? Proof of reserves is the way many firms prove it. It’s a procedure that lets a custodian publicly demonstrate it holds enough on-chain assets to cover all customer balances at a specific point in time, and it lets any individual user verify their own balance is included.
The mechanism exists given the 2022 collapses of FTX, Celsius, Voyager, and BlockFi, which exposed the gap between what platforms claimed to hold and what they actually controlled. FTX alone reported around $9 billion in liabilities it could not cover. Proof of reserves, or PoR, emerged as the industry’s first serious attempt to replace press releases with math.
This guide covers how proof of reserves works, what it does and doesn’t prove, how it differs from a full financial audit, and what to look for in a credible report.
What Is Proof of Reserves?
Proof of reserves is a verification process that confirms a crypto custodian, exchange, lender, or stablecoin issuer holds the assets it claims on behalf of users. An independent third party takes a snapshot of customer balances, organizes them into a cryptographic structure, and verifies that the platform’s on-chain holdings match or exceed what is owed.
You can think of it as the crypto version of a bank statement, except that anyone with the right tools can verify the underlying math without needing a regulator to vouch for it.
Reserves, liabilities, and solvency
Three terms get used interchangeably in casual conversation. They are not the same.
- Proof of reserves: The assets side. Confirms the platform controls a specific amount of crypto.
- Proof of liabilities: The customer-deposits side. Confirms what is owed.
- Proof of solvency: Reserves greater than or equal to liabilities. The full equation.
Many platforms publish only the assets half. That is part of why PoR has its critics, and part of why methodology matters.
Why Proof of Reserves Emerged
The 2022 collapses that forced the issue
FTX’s bankruptcy in Nov 2022 was the catalyst. As court filings revealed customer funds had been used for purposes other than custody, the second order effects affected others who operated similarly.
Celsius, Voyager, and BlockFi had already collapsed earlier that year, each tracing back to risky lending, rehypothecation, or balance-sheet mismatches. These were not isolated bookkeeping errors. They were structural transparency failures.
Earlier precedent
Mt. Gox in 2014 was the original wake-up call. Kraken pioneered PoR audits that same year and has continued the practice ever since. Vitalik Buterin published an essay shortly after FTX’s filing arguing for cryptographic proof of solvency as the path to a “safe CEX,” and his framing shaped much of the subsequent industry adoption.
From voluntary to expected
Most major exchanges published some version of a PoR within months of FTX. Regulators are catching up. The EU’s Markets in Crypto-Assets framework codifies reserve transparency for stablecoin issuers, and US frameworks are evolving in the same direction. What started as a marketing differentiator is becoming a baseline requirement.
How Proof of Reserves Works
The three-step mechanism
- Snapshot liabilities. An auditor captures an anonymized record of every customer balance at a specific moment.
- Aggregate via Merkle tree. Balances are hashed and combined into a single cryptographic fingerprint called the Merkle root.
- Verify reserves. The auditor confirms the platform controls enough on-chain assets, typically by collecting signed messages from the platform’s wallet addresses, to match or exceed the total liabilities encoded in the tree.
What is a Merkle tree?
A Merkle tree is a binary hash structure that compresses thousands of individual balances into one root hash. Each pair of balances is hashed together, those hashes are paired and hashed again, and the process repeats until a single hash remains.
The useful property is that any individual user can be given a “Merkle path,” a small set of sibling hashes, which lets them confirm their own balance was included in the tree without revealing anyone else’s data.
How users verify their own balance
The process is more accessible than it sounds. After a PoR snapshot is published, a user logs into their account, navigates to the transparency portal, and retrieves a record ID and Merkle path. Using the published hashing methodology (typically SHA-256), they reconstruct the path from their leaf node up to the root and compare against the published Merkle root.
If the values match, their balance was included. If anything in the tree was altered, even a single number, the recomputed root will not match the published one.
The auditor’s role
The third party has two jobs. First, confirm the platform actually controls the wallets it claims to control, usually through cryptographically signed messages or test transactions. Second, confirm the Merkle tree is constructed honestly, with no excluded accounts and no inflated balances.
Types of Proof of Reserves
Exchange and custodian PoR
Kraken publishes quarterly reports that include client liabilities and user-level Merkle verification. Binance, Bitget, Bybit, and BTCC publish monthly reports of varying depth. Reserve ratios above 100% are common, indicating an over-collateralization buffer.
Stablecoin reserve attestations
Off-chain reserves backing on-chain tokens. USDC publishes monthly attestations of its cash and Treasury holdings; USDT publishes quarterly. These are different from Merkle-based exchange PoRs because the reserves sit in bank accounts and money market funds, not on-chain wallets, so verification depends entirely on the attesting accountant.
Real-time, oracle-based PoR
Chainlink Proof of Reserve uses decentralized oracle networks to push reserve data on-chain continuously. Instead of waiting for a quarterly PDF, smart contracts can read live collateral data and act on it. Issuers including TUSD, Ethena’s USDe, Backed, and Matrixdock use Chainlink PoR for tokenized assets ranging from stablecoins to short-term Treasury bills.
Wrapped assets and tokenized RWAs
Wrapped Bitcoin, tokenized Treasuries, and tokenized commodities use PoR to prove 1:1 backing of their underlying collateral, whether that collateral lives on another chain or in a custodian’s vault.
What a Credible Proof of Reserves Looks Like
A useful PoR generally includes:
- An independent third-party auditor with reputation outside the issuer’s influence
- Both sides of the balance sheet, assets and liabilities
- User-level verification tools that let any individual confirm their own balance
- A regular cadence, quarterly at minimum, monthly or real-time when feasible
- Clear scope, including which assets are covered and whether margin, staking, and futures balances are included
- A published reserve ratio showing reserves as a percentage of liabilities, where 100% indicates full backing and figures above 100% indicate a buffer
Limitations and Common Criticisms
It’s a snapshot
A PoR conducted on December 31 says nothing about January 1. Funds can move the moment after the audit closes. Real-time, oracle-based PoR addresses this for some asset classes, but most exchange PoRs remain periodic.
Reserves without liabilities are misleading
An exchange could show $10 billion in assets while owing $15 billion. Without a verified liabilities side, the report does not prove solvency. This was a central critique of the early reports issued in late 2022, when several major exchanges published wallet balances without disclosing what they owed.
The borrowed funds problem
A platform could borrow assets immediately before a snapshot to pass the audit and return them after. Without unannounced reviews, continuous monitoring, or proof of asset origin, this is difficult to detect.
Scope gaps
Most PoRs cover only on-chain assets. They do not account for off-chain holdings, internal lending books, hidden encumbrances, or the possibility that private keys have been duplicated or compromised.
No standardized framework
There are no professional audit standards governing PoR. Methodology, disclosure depth, and rigor differ across providers, which makes cross-platform comparison harder than it should be. PwC and other major audit firms have publicly argued that PoR is not a substitute for a full financial-statement audit.
The auditor problem
FTX itself was audited. The strength of any PoR depends on the firm conducting it and the rigor of the methodology, not the existence of a report.
Proof of Reserves vs. Traditional Financial Audits
| Attribute | Proof of Reserves | Full Financial Audit |
|---|---|---|
| Scope | On-chain assets, sometimes liabilities | Entire balance sheet, including off-chain |
| Cadence | Periodic or real-time | Annual |
| Standard | None standardized | GAAP, IFRS, PCAOB |
| Forward-looking | No | Includes going-concern review |
| User-verifiable | Yes (via Merkle proof) | No |
| Covers operational risk | No | Partially |
PoR is a transparency tool, not a replacement for audited financials. The strongest platforms publish both.
Proof of Reserves Across the Crypto Ecosystem
Centralized exchanges
The most visible adopters. Coverage and methodology vary, with Kraken generally cited for the highest rigor based on its inclusion of liabilities and quarterly cadence.
Stablecoin issuers
Critical because stablecoin de-pegging events tend to trace back to opaque or insufficient reserves. Real-time PoR is most advanced in this segment.
Crypto-backed lenders and custodians
A growing application area. Lenders that hold customer collateral, particularly bitcoin and other crypto used to secure loans, face many of the same trust questions as exchanges: does the platform actually hold the collateral, and is it being rehypothecated to generate yield elsewhere?
For borrowers evaluating any lender in this category, the relevant questions extend beyond whether a PoR report exists. Custody structure, segregation of client assets, key control, and the lender’s policy on rehypothecation often matter more in practice. Some crypto-backed lenders, including Arch, publish information on how client collateral is custodied and segregated, which gives borrowers a basis for comparison even where formal PoR reporting is still maturing.
Tokenized real-world assets and DeFi
On-chain PoR enables programmatic enforcement. Smart contracts can pause minting, halt redemptions, or trigger circuit breakers when reserves fall below predefined thresholds, turning transparency into automatic risk management.
Frequently Asked Questions
What does proof of reserves mean in crypto?
It is a verification method showing that a custodian holds enough assets to cover what it owes customers, typically using cryptographic structures like Merkle trees and an independent third-party auditor.
How often should an exchange publish proof of reserves?
Quarterly is the emerging baseline. Monthly is stronger. Real-time on-chain reporting is the most rigorous, currently most common in stablecoins and tokenized assets.
Is proof of reserves the same as proof of solvency?
No. Proof of reserves shows assets. Proof of solvency requires both assets and liabilities, demonstrating that reserves cover obligations.
Can a proof of reserves be faked?
Methodology gaps create room for manipulation, including borrowed funds for the snapshot window, omitted user accounts, or weak auditors. User-level Merkle verification and the inclusion of liabilities reduce, but do not eliminate, this risk.
Conclusion
Proof of reserves is a verification mechanism. It proves something specific at a specific moment, and it does so cryptographically rather than rhetorically.
A credible PoR includes assets, liabilities, an independent auditor, user-level verification, and a regular cadence. The strongest transparency stack combines PoR with traditional financial audits, clear custody disclosures, and explicit policies on rehypothecation. Each addresses a different question, and together they get closer to the kind of accountability the industry has lacked for most of its history.
About Arch
Arch is building a next-gen wealth management platform for individuals holding alternative assets. Our flagship product is the crypto-backed loan, which allows you to securely and affordably borrow against your crypto. We also offer access to bank-grade custody, trading and staking services.
Disclaimer: This article is for informational purposes only and does not constitute investment, legal, or tax advice. Cryptocurrency investments are volatile and risky. Always conduct your own research before making investment decisions.