Cryptocurrency support on online casino platforms

Introduction

The integration of cryptocurrencies gives online casinos advantages: instant P2P transactions without intermediaries, reduced commissions, and an influx of new audiences. At the same time, developers have to take into account the features of the blockchain infrastructure: network confirmations, gas commissions, exchange rate volatility and AML/KYC requirements.

1. Choice of supported cryptocurrencies

Bitcoin (Bitcoin, BTC): the most common, high liquidity, confirmation delay (~ 10 minutes), commissions depend on the network load.
Ethereum (Ethereum, ETH) and ERC-20 tokens: smart contracts allow you to implement bonus and loyalty programs on the chain; confirmation delay ~ 15 s, commissions (gas) change dynamically.
Stable coins (USDT, USDC, BUSD): reduced volatility, fast calculation, work with different blockchains (Ethereum, Tron, BSC) is necessary.
Altcoins with fast blocks (Litecoin, Dogecoin, Solana): confirmations <1 min, low fees, but liquidity and support risks on exchanges.
Own tokens (casino-token): release based on Ethereum or BSC for internal incentives, requires smart contracts and emission management.

2. Integration architecture

```mermaid
flowchart LR

User [Player] -->	Send payment	Frontend
Frontend -->	REST API	Backend
Backend -->	RPC/WebSocket	NodeProvider [Blockchain Node]
Backend -->	Webhooks	BlockchainListener
BlockchainListener -->	Confirmation Event	TransactionService [(Accounting Microservice)]
TransactionService -->	Update Balance	Database [(DB)]
Database -->	Response	Frontend
```

Backend ↔ NodeProvider: via JSON-RPC or WebSocket to a public or native node.
BlockchainListener: subscribing to new blocks and filtering transactions by platform addresses.
TransactionService: txid validation, number of confirmations, net-amount calculation taking into account network commission, database entry.

3. Working with crypto wallets

1. Hot wallets:

• Keep small balances for operational payments.
• Connect to HSM (Hardware Security Module) services to protect private keys.
2. Cold wallets:
• Storage of reserves of most of the funds offline.
• Automatic rotation of funds: periodic transfer from hot wallets to pay a large amount.
3. HD wallets (Hierarchical Deterministic):
• Generation of addresses by BIP-32/BIP-44, a unique address for each player or transaction.
• Simplify the accounting of incoming payments and automatic reconciliation.

4. Processing Incoming Transactions

Event subscription: JSON-RPC method 'eth _ subscribe' or WebSocket filters for Ethereum; ZMQ/WebSocket для Bitcoin.
Confirmation threshold:
• BTC: ≥ 3 confirmations (~ 30 min)
• ETH/USDT/ERC-20: ≥ 12 confirmations (~ 3 min)
• Altcoins - Configured based on network security.
• Calculation of the net amount: the amount was received − the block commission (if the platform does not subsidize it).
• Player identification: by deposit address or tag (Memo/Tag) for Ripple, Stellar.

5. Initiation of payments

1. The player requests output → Backend generates a payment transaction with UTXO sampling (for UTXO coins) or calling 'transfer' (for ERC-20).
2. Calculation of the commission: analysis of mempool, setting a competitive gasPrice/gasLimit or choosing UTXO taking into account dust.
3. Transaction signing: offline via HSM or locally with private key.
4. Shearcasting to network - sending via RPC 'sendRawTransaction'.
5. Tracking confirmations: similar to incoming, updating the payment status in the database.

6. Volatility Management

Instant conversion: integration with exchange aggregators (Changelly, 1inch, OpenOcean) for instant swap into a stable coin.
Liquidity pool: create your own pool on DEX (Uniswap, PancakeSwap) to reduce slippage.
Reserves in fiat currency: keeping part of the funds in banks or stablecoins to compensate for sharp fluctuations in the exchange rate.

7. Security

TLS and encryption: HTTPS/WSS for all external and internal calls.
HSM and security modules: storing private keys and signing transactions without leaving the key from a secure container.
Rate limiting and WAF: protection against attacks on RPC/WebSocket interfaces.
Monitoring suspicious activity: a sharp increase in the amount of deposits/withdrawals, multiple small-tx to bypass limits.

8. Compliance

KYC/AML procedures: player identification prior to first withdrawal; integration with ID providers (Onfido, Sumsub).
Reporting: storing records of transactions ≥ 5 years, exporting data in CSV/XML formats for regulators.
Checking the source of funds: analysis of receipts to hot wallets through Chainalysis or Elliptic services.

9. Monitoring and analytics

Metrics (Prometheus/Grafana):
• number of incoming/outgoing tx, average confirmation time, commissions.
• share of failed tx due to low fee or noncescip.
• Logging (ELK/EFK): tracing raw-tx, signing errors, reorg in the blockchain.
• Alerting: alerts when the threshold of unknown incoming addresses is exceeded or when confirmations fall.

10. Practical recommendations

Separate hot- and cold-storage, do not keep large reserves online.
Automate private-key rotation through HSM and Vault.
Configure dozens of nodes on different providers (Infura, Alchemy, own) so as not to depend on a single point of failure.
Conduct regular audits of smart contracts when working with ERC-20 and native tokens.

Conclusion

Supporting cryptocurrencies requires deep integration with blockchain infrastructure, proper key management, protection against volatility, and compliance with AML/KYC. With the architectural division into signing, network listening and transaction accounting services, the platform gains flexibility, security and the ability to quickly add new coins and tokens.