> 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/quickstart.md).

# Overview

#### User Docs

BlackCoin Money is a privacy protocol on Solana that enables private transfers and swaps without linking your wallet addresses or transaction history. Built with zero-knowledge proofs, an append-only Merkle tree, and a relayer system, BlackCoin Money breaks the on-chain link between shields and unshields.\
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BlackCoin Money has privately transferred and swapped $1M+ in volume. The on-chain program and zero-knowledge circuits are fully open-sourced, verified on-chain, audited 10 times.

#### Private transfers

BlackCoin Money lets you transfer funds to a clean wallet without linking past addresses or transaction history.\
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To make a private transfer, you first shield your tokens into Shielded Pool. Later, you can unshield those tokens to a recipient address.\
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BlackCoin Money breaks the link between shields and unshields using zero-knowledge proofs, an append-only Merkle tree, and a relayer system. Your signed shield transaction is sent to a relayer, which screens your wallet address. If your address is flagged as malicious, the shield is rejected.\
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The unshield process is similar, except the transaction is signed by the relayer. Your unshield in the onchain transaction (e.g. on SolScan or Orb) contains no information about the original shielder, breaking the link between shields and unshielders. A zero-knowledge proof generated on the client ensures that the relayer cannot modify the recipient address, amount, or other parameters. Any tampering will cause the on-chain transaction to fail.\
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Each shield and unshield creates a UTXO that is encrypted and submitted to the Solana program on-chain. These encrypted UTXOs are indexed off-chain. Only the user who holds the encryption key can decrypt their UTXOs and spend the balance. The encryption key per user is deterministically derived on the client by the user signing a fixed message and is accessible only to the user, unless it is intentionally or unintentionally leaked (for example, through phishing). Don’t blindly sign messages on phishing sites!

#### Platform Fees

**Shield Fee:**\
Free — you don’t pay anything to shield.

**Unshield Fee:**\
When you unshield, there are two parts to the fee:

* **BLACKCOIN holders:**\
  0.5% of the unshield amount + 0.006 SOL
* **Non-holders:**\
  1.5% of the unshield amount + 0.006 SOL

The extra **0.006 SOL** covers the Solana token account rent (network storage cost).