> For the complete documentation index, see [llms.txt](https://blackcoin.gitbook.io/blackcoin-money/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://blackcoin.gitbook.io/blackcoin-money/getting-started/publish-your-docs-1.md).

# Core Concepts

#### Shielded Pool

The Shielded Pool is an on-chain program that holds encrypted UTXOs rather than public balances.

* Shields create **encrypted UTXOs**
* Unshields consume existing UTXOs and create new ones
* All UTXOs are committed to an **append-only Merkle tree**

Only the user who controls the encryption key can decrypt and spend their UTXOs.

#### Zero-Knowledge Proofs

All unshields are authorized using **zero-knowledge proofs (ZKPs)** generated client-side.

#### Relayer System

BlackCoin Money uses a relayer to execute on-chain transactions.