> For the complete documentation index, see [llms.txt](https://plabs.gitbook.io/plabs-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://plabs.gitbook.io/plabs-docs/privacy-core/overview.md).

# Overview

**Privacy Core** is the foundation of the pERC20 stack. It has two layers:

1. **Cryptographic layer** — how value exists as **Orchard notes**, how actions are proved and verified, compliance freeze
2. **Asset protocols** — how **private assets** are created (`pERC20` native mint, `Shield ERC20` public → private)

**Applications** (pSWAP, pDEX, pX402) consume private assets built on Privacy Core; they are documented separately and are not part of this book.

## Cryptographic layer

```
Orchard concepts        notes / commitments / nullifiers / encryption
Note state machine      OrchardVerifier on-chain logic
Groth16 action circuit  131,787 constraints, BN254
Signatures              bindingSig + spendAuthSig
Compliance              entry/exit screening (off-chain) + frozenRoot (on-chain)
Compliance freeze       IMT blacklist + pubFields[7] binding
Universal call format   PrivacyCall / BundleAction (shared by all layers)
```

| Component                   | Role                                                     |
| --------------------------- | -------------------------------------------------------- |
| `OrchardVerifier.sol`       | Note state machine: proofs, tree, nullifiers, signatures |
| `ActionGroth16Verifier.sol` | `pubFields[8]` → `pub_hash` → Groth16 pairing            |
| `action.circom`             | Single Orchard action + freeze non-membership            |

## Asset protocols

How privacy assets enter the system:

| Protocol                                                          | Status    | Role                                                                          |
| ----------------------------------------------------------------- | --------- | ----------------------------------------------------------------------------- |
| [pERC20](/plabs-docs/privacy-core/perc20/overview.md)             | ✅ Shipped | Native private fungible token — `mint` / `transfer` / `burn` on `PERC20` pool |
| [Shield ERC20](/plabs-docs/privacy-core/shield-erc20/overview.md) | ✅ Shipped | Deposit public ERC-20 → private notes; `unshield` back                        |

`PERC20.sol` **inherits** `OrchardVerifier` and adds supply + `IPERC20` — see [pERC20 overview](/plabs-docs/privacy-core/perc20/overview.md).

pSWAP / pDEX / pX402 call **`IPERC20.transfer`** (and future app rules) on pools created by these asset protocols.

## Relation to Zcash Orchard

| Inherited                                | EVM adaptation                                                                  |
| ---------------------------------------- | ------------------------------------------------------------------------------- |
| Note format, nullifiers, note encryption | Groth16 instead of Orchard native proofs                                        |
| Action value conservation, binding sig   | On-chain BabyJubJub Schnorr (Solidity)                                          |
| Shielded-pool semantics                  | **Per-asset pool** (not one global shielded pool)                               |
| —                                        | **Compliance** — off-chain screening + in-circuit freeze (`FrozenCmxNonMember`) |

## Trust boundaries

| Component                      | Trust                                                                                                                                                                                                 |
| ------------------------------ | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Groth16 proof                  | Trustless on-chain verify                                                                                                                                                                             |
| Trusted setup                  | Per-circuit ceremony; ≥1 honest participant                                                                                                                                                           |
| binding / spendAuth signatures | On-chain verify                                                                                                                                                                                       |
| Relayer                        | Minimal trust today (cannot tamper ciphertext; can censor). **Planned:** integrate [Kohaku](https://github.com/ethereum/kohaku) ERC-4337 relaying to remove reliance on self-hosted `privacy-relayer` |
| Compliance admin               | Can update freeze root (explicit trade-off)                                                                                                                                                           |

## Next

* [Compliance implementation](/plabs-docs/privacy-core/compliance-implementation.md)
* [Orchard concepts](/plabs-docs/privacy-core/orchard-concepts.md)
* [pERC20 overview](/plabs-docs/privacy-core/perc20/overview.md)


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