> For the complete documentation index, see [llms.txt](https://docs.fairway.global/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.fairway.global/developers/build-on-cardano/merkle-compliance-utxo/architecture-overview.md).

# Architecture Overview

#### Core Components

* **Compliance UTXO**
  * Holds root, timestamp, epoch, signature, midnight reference.
  * Updated when sanctions/risk lists change, or when new users are onboarded.
* **Merkle Proofs**
  * Submitted by users in transactions.
  * Leaf = `{ address, claims, kyc_verified_at }`.
* **Policy Engine (Aiken)**
  * Verifies membership, signature, timestamp vs. max-age, and sanctions epoch freshness.
* **Trust Registry (future)**
  * Will manage Fairway issuer keys + versioning.

***

#### Mermaid (high level)

```mermaid
flowchart LR
  A[User completes KYC once] --> B[Vault stores PII + kyc_verified_at]
  B --> M[Midnight proof UTXO posted]
  M --> C[Compliance UTXO root, kyc_verified_at, sanctions_epoch, sig]
  C --> D[dApp Validator]
  D -->|Proof verified, timestamp ok, epoch fresh| E[YES → allow]
  D -->|fail| F[NO → deny]

```

<figure><img src="/files/Owvd6P7UKGzTNGMTroAy" alt=""><figcaption></figcaption></figure>