> 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/compliance-freeze.md).

# Compliance freeze design

Compliance freeze is the **on-chain half** of Privacy Core compliance (Layer 2 — post-hoc note freeze). For entry/exit address screening (Layer 1, off-chain TRM + Chainalysis) and the full operational model, see [Compliance implementation](/plabs-docs/privacy-core/compliance-implementation.md).

Compliance freeze is Privacy Core’s **explicit extension** over Zcash Orchard: the circuit proves spent notes are **not** on an admin-maintained blacklist.

## Goals

| Goal                  | Mechanism                                                  |
| --------------------- | ---------------------------------------------------------- |
| Sanctions / blacklist | Off-chain set, on-chain root updates                       |
| Hide list contents    | Only Merkle root public                                    |
| No bypass             | Prove **input** `cm_old` non-membership (not output `cmx`) |

## Indexed Merkle Tree (IMT)

| Parameter   | Value                                    |
| ----------- | ---------------------------------------- |
| Depth       | 20                                       |
| Leaf format | Ordered `(val, next_val)` low-leaf chain |
| Empty root  | `0`                                      |
| On-chain    | `cmxFrozenRoot()`                        |

Admin rebuilds IMT off-chain, then `setFrozenRoot(newRoot)`.

## Circuit: `FrozenCmxNonMember`

Witness includes low-leaf bracket + IMT path proving `cm_old` falls in a gap → not in frozen sorted set.

### Why bind cm\_old not cmx (audit H-01)

Binding only output `cmx` lets attacker spend frozen note with fresh output randomness. **Input commitment** must be constrained.

## On-chain: pubFields\[7]

```
pubFields[7] == cmxFrozenRoot()   // else BadFrozenRoot
```

Each action’s Groth16 public input commits to this root via `pub_hash`.

## Trust trade-off

Admin can freeze identified notes. Should use multisig / timelock in production.

## Shared by applications

* **pERC20**: per-pool `cmxFrozenRoot`
* **pSWAP**: each leg must pass non-membership in its pool

## Admin workflow

1. Identify `cmx` to freeze off-chain
2. Rebuild IMT → new root
3. `setFrozenRoot(newRoot)`
4. Wallets/provers use new root in witness

## Next

* [Compliance implementation](/plabs-docs/privacy-core/compliance-implementation.md) — entry/exit screening + freeze overview
* [Universal call format](/plabs-docs/privacy-core/universal-call-format.md)
* [pERC20 overview](/plabs-docs/privacy-core/perc20/overview.md)


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