Zero-Knowledge Proofs in iGaming: A Privacy Guide
Blockchain-based gambling creates a privacy problem. Public blockchains expose wallet balances, transactions and betting patterns. Regulated gambling also requires identity checks, which can expose personal and financial data. Players may also need to prove their identity or available funds without sharing more information than necessary.
Zero-knowledge proofs (ZKPs) let someone prove a claim without revealing the underlying data. In iGaming, they could support private identity checks, balance verification and verifiable game outcomes. Some blockchain projects already use ZKPs, but many casino applications remain theoretical. ZKPs do not guarantee anonymity or remove KYC requirements. The challenge is to reduce data exposure while meeting security and regulatory obligations.
Why Privacy Matters in Blockchain-Based iGaming
Public blockchains record every transaction. Anyone can read the ledger. Wallet addresses look anonymous, but they are only pseudonyms. Researchers showed this by grouping Bitcoin addresses by shared ownership and tying the clusters to real services. Once an address links to a person, its full history follows. That history includes deposits, balances and betting patterns.
For casino players, that trail grows with every deposit, wager and withdrawal made on-chain. Operators publish licensing details, bonus terms and wagering rules so users can compare their services. A page such as https://automatenspielex.com/en/casino-bonus/ shows how casino bonus information is presented to users. Personal and financial data raise a different issue. Users often disclose more than a platform needs for a specific check.
Centralized operators face the opposite problem. UK-licensed operators must verify a customer's name, address, and date of birth before that person can gamble. They then store ID scans, proof of address and source-of-funds records. One breach exposes all of it. ZKPs offer a narrower route. A player proves one fact, such as age, and keeps the rest private. This does not replace KYC. It limits what each check collects. In this article, privacy covers three things: wallet and balance privacy, identity minimization and transaction confidentiality. Fairness is a fourth issue, covered later.
How Zero-Knowledge Proofs Work
A zero-knowledge proof (ZKP) lets one party prove a statement is true without revealing the data behind it. Two roles, three core properties and two main proof families explain how it works.
Provers, Verifiers, and Cryptographic Proofs
A prover creates a proof. A verifier checks it. A classic illustration is Ali Baba's cave, a ring-shaped cave with a locked door at the back. The prover walks in by one side. The verifier then calls out which side the prover must come out of. A prover who knows the door's secret word can always comply, while one who does not will be caught within a few rounds. The verifier becomes convinced without ever hearing the word.
The formal idea comes from a 1985 paper by Goldwasser, Micali and Rackoff. It describes a method where one party proves something is true and reveals nothing else. Ethereum.org lists three properties every valid ZKP must meet:
● Completeness: If the statement is true and both sides act honestly, the verifier accepts.
● Soundness: If the statement is false, a cheating prover cannot convince the verifier, except with a tiny chance.
● Zero-knowledge: The verifier learns that the statement is true and nothing more.
A proof follows these steps:
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Write the statement as a circuit. A circuit is the claim expressed as math constraints.
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The prover holds the private witness, such as a date of birth.
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The prover generates a proof from the witness and the public inputs.
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The verifier checks the proof against the same public inputs.
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The verifier accepts or rejects. It never sees the witness.
zk-SNARKs and zk-STARKs
Two common proof systems are zk-SNARKs and zk-STARKs.
A zk-SNARK is a zero-knowledge succinct non-interactive argument of knowledge. “Succinct” means the proof is small and quick to check. “Non-interactive” means the prover sends one message, with no back-and-forth. An argument of knowledge means nobody can build a valid proof without the witness.
A zk-STARK is a zero-knowledge scalable transparent argument of knowledge. “Scalable” means proving time grows slowly as the computation grows. “Transparent” means it needs no trusted setup. Ben-Sasson and colleagues introduced zk-STARKs in 2018.
The first trade-off is trust. Many SNARKs need a trusted setup. A group generates shared public parameters, and a leak of the secret randomness would let someone forge proofs. STARKs use public randomness instead.
The second is cost. STARK proofs are larger and generally cost more to verify. The third is quantum risk. STARKs rely on hash functions, so they are considered resistant to quantum attacks. SNARKs built on elliptic curves could be exposed if large quantum computers arrive, according to Ethereum.org.
Both families run in production. Zcash launched with a trusted setup. Its Halo 2 system later removed that requirement, so SNARKs don't always need one. Starknet uses STARKs, and L2BEAT lists its scheme as transparent with no trusted setup. Starknet proves batches of transactions for scale, not privacy.
Practical Applications of ZKPs in iGaming
Zero-knowledge proofs could help iGaming platforms verify balances, age, and game actions without exposing the underlying data. Some related uses already exist in blockchain products, but casino adoption remains limited. Each section below says which is which.
Private Wallet and Balance Verification
A player could prove "I hold at least X" without showing the address or full balance. An operator could use that to check a deposit threshold or a stake limit. The same logic could prove funds do not come from a flagged source. For casinos, this is a design idea, not a standard practice.
Adjacent products show the pieces exist. Binance added zk-SNARKs to its proof-of-reserves system. Users check that their balance sits in the total. The proof shows the total was built correctly. That proves an exchange's solvency, not a player's balance. Transaction confidentiality is a related but separate use. Zcash shields transaction details with ZKPs, so a payment can be verified as valid without exposing the sender, recipient or amount on the public ledger. A casino that accepted shielded deposits could receive payment without learning the player's wallet history. It would still need to meet its AML screening duties, and the regulatory section below explains why that is difficult.
Selective Identity and Age Verification
A player could verify that they are over 18 without sharing their full ID. This approach is already being used in digital identity systems.
Bhutan's National Digital ID, built on Ethereum, uses ZKPs to prove facts such as "I am over 18 without exposing the rest of the ID. In July 2025, Google open-sourced its ZKP libraries for age assurance. It noted that EU rules encourage ZKPs in the European Digital Identity Wallet.
Gambling rules go further than age. UK licensees must verify name, address and date of birth before play. An age-only proof alone would not meet that rule. A selective check works like this:
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A trusted issuer verifies the player's identity and age, then issues a suitable credential.
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The player stores the credential in a digital wallet.
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The casino requests proof that the player is at least 18.
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The wallet generates a proof from the credential without revealing the full birth date.
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The operator verifies the proof and the issuer's authenticity.
Verifiable Game Outcomes and Fairness
"Provably fair" in crypto casinos is not zero-knowledge. It uses hash commitments. The casino publishes a hash of its server seed before the bet. The player adds a client seed. After the round, the casino reveals the seed, and the player recomputes the result with HMAC-SHA256. The aim is to stop the operator from changing the outcome after the bet, not to hide data, so no ZKP is needed.
ZKPs fit games with hidden information. Dark Forest, an on-chain strategy game, uses zk-SNARKs to build a fog of war. Players prove their moves follow the rules without revealing hidden positions. The same idea could prove a card shuffle followed the rules without revealing the deck order for casinos; that use is experimental.
There is a limit to this. A proof can show that a computation followed specified rules. It cannot prove that the rules are fair or that the random inputs were unbiased. Developers must design and verify the randomness source separately.
Traditional iGaming vs ZKP-Based Systems
Traditional iGaming and ZKP-based systems handle the same jobs in different ways. The table compares six areas and shows the maturity of each ZKP approach today.
| Area | Traditional iGaming | ZKP-based approach | Maturity |
| Wallet and balance checks | Operator sees account and transaction records | Prove a threshold without revealing the balance | Early, mostly adjacent products |
| Age and identity | Document upload; operator stores the data | Credential-based proof of one attribute | Pilots and emerging standards |
| Game fairness | Audits, RNG certification or hash-based checks | Proof that a shuffle or draw followed the rules | Experimental to limited |
| Transaction privacy | Operator and payment processor receive transaction data; public chains expose on-chain activity | Shielded transfers or proofs that hide selected details | Live on some blockchains; regulatory challenges |
| Regulatory reporting | Operator retains records and reports required information | Use proofs with selective disclosure where accepted | Largely theoretical for routine casino reporting |
| Cost and latency | Low overhead | Proof generation and verification costs | Improving, but still a constraint |
Adoption will depend on proof costs, implementation quality and whether regulators accept the resulting evidence.
Technical and Regulatory Challenges
ZKPs can reduce the personal and financial data that platforms expose. They also create technical and legal questions, especially for licensed operators that must verify customers and monitor activity.
KYC, AML, and Compliance Requirements
Licensed operators must verify identity, monitor transactions and report suspicious activity. UK guidance covers customer due diligence, record-keeping and suspicious activity reporting. In Malta, the FIAU and MGA publish procedures for remote gaming that cover identity verification, ongoing monitoring and politically exposed persons. US state regulators set their own rules. ZKPs can limit what a check collects. They cannot replace these duties.
Record retention adds friction. UK guidance says identification and verification records must be kept for five years after the customer relationship ends. A proof leaves little to store. A regulator may still expect the record itself. Operators would need to confirm what a proof satisfies.
Tornado Cash shows the wider tension with this system. It used ZKPs to obscure transaction details. The US sanctioned it in August 2022. A federal appeals court overturned the sanctions in November 2024, and Treasury removed them in March 2025. The court ruled on whether immutable smart contracts count as property, not on privacy itself.
Privacy Pools is a compliance-focused design. Buterin and co-authors propose that users publish a ZKP showing their funds do or do not come from known sources, without revealing their full transaction history. It is a research proposal, not a licensed casino tool.
Scalability, Costs, and Security Risks
Proofs cost compute and money. Generating one takes heavy computation, and verifying it costs fees. Ethereum.org puts one SNARK verification at about 500,000 gas on Ethereum, with STARKs costing more. Phones add a limit. Zcash needed its Sapling upgrade to make shielded transactions work on mobile devices. A casino app that asks phones to generate proofs faces the same limit.
Security risks sit in the setup and the code. Trusted setups depend on honest participants. Circuits can also hold bugs. A proof shows that a statement was met. If the circuit encodes the wrong statement, a valid proof still proves the wrong thing. Zcash's Orchard pool carried such a flaw from May 2022 until a researcher found it in May 2026. BlockSec reports it could have allowed undetectable counterfeiting. It found no confirmed exploitation.
Metadata also leaks. A proof hides the data inside it. It does not hide timing, fees or network details. Researchers linked Tornado Cash withdrawals to deposits using gas use, timing and relayer behavior. Another study found that five combined heuristics raised the chance of linking a withdrawer to a depositor by about 52% on average on Ethereum. IP addresses sit outside the proof, too.
The Future of Privacy-Preserving iGaming
The nearest changes come from digital identity and finance, not casinos. Gambling may borrow what those sectors build.
The European Commission declared its ZKP-based age verification app technically ready in April 2026 and moved it into pilots. The app is built for online child protection, not gambling. It is designed to work with EU digital identity wallets, which could one day carry credentials that operators accept. ZK-based proof-of-reserves is already live. Binance runs one.
However, their road isn’t clear just yet. Regulators decide what counts as evidence. UK operators must verify name, address and date of birth, which an age-only proof doesn’t cover. Proof costs and phone limits add friction. Standards lag, too. National age-check schemes in the EU vary in approach and age thresholds, and the Commission plans a coordination mechanism.
Two uses are worth monitoring. One is eligibility proofs stored in ID wallets that operators accept. The other is verifiable card shuffles. Hidden-information games such as Dark Forest already use ZKPs for similar tasks. Both are early.
The signal to watch is whether a gambling regulator accepts a ZK proof as evidence for a licensed check.
