> For the complete documentation index, see [llms.txt](https://docs.onta.network/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.onta.network/basics/interactive-blocks/cardhash.md).

# CardHash

CardHash uses an innovative algorithm that generates unique blockchain wallet addresses directly from payment card numbers. This creates seamless integration between traditional financial instruments and cryptocurrency. The process uses a one-way hashing function that preserves privacy while linking a user's payment card to their on-chain identity.

When consumers make purchases with their cards at participating merchants, the system instantly identifies their associated wallet address without requiring any wallet connection or authentication. This enables automatic crypto rewards, loyalty programs, and membership benefits that arrive directly in users' wallets without any additional steps. The system includes security measures to prevent reverse-engineering card details from wallet addresses, maintaining payment card industry compliance.

For merchants and brands, CardHash provides a direct channel to deliver targeted incentives to existing customers based on purchasing history without collecting personal data. This transforms everyday payment cards into Web3 participation tools, allowing mainstream users to accumulate digital assets through normal spending.

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