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

# Architecture

A high-level view of how Black Sheep protects funds.

```
┌──────────────┐         ┌────────────────────────┐         ┌────────────────┐
│  Your app    │ HTTPS   │  Black Sheep API       │ RPC     │  Solana        │
│  (LLM/bot)   │ ──────▶ │  ┌──────────────────┐  │ ──────▶ │  mainnet/devnet│
│              │ Bearer  │  │ Policy engine    │  │         │                │
└──────────────┘ key     │  └──────────────────┘  │         └────────────────┘
                         │  ┌──────────────────┐  │
                         │  │ Signer (in-mem)  │  │
                         │  └──────────────────┘  │
                         │  ┌──────────────────┐  │
                         │  │ Encrypted secret │◀─┼── Vault key (HSM-backed)
                         │  │ store (DB)       │  │
                         │  └──────────────────┘  │
                         └────────────────────────┘
```

## Layers

### 1. Authentication

* API keys are random 256-bit tokens hashed at rest.
* Dashboard auth uses Supabase Auth (httpOnly cookies, refresh rotation).
* SIWS supported for wallet-native sign-in.

### 2. Authorization

* All API routes are user-scoped via Postgres Row Level Security.
* A given API key only ever sees its own account's data — enforced at the database, not just the application layer.

### 3. Policy engine

* Runs server-side inside a transaction.
* Evaluates daily caps, per-tx caps, allowlists, and approval thresholds before any signing happens.
* The LLM can't influence the rules — they live in the database, not in the request.

### 4. Key custody

* Agent secret keys are generated server-side with `tweetnacl`.
* Encrypted with `xchacha20-poly1305` using a per-environment vault key.
* Decrypted only in-memory at signing time. Never logged. Never returned via API.

### 5. Transport

* TLS 1.2+ enforced.
* HSTS on the public domain.

### 6. Audit

* Every policy decision, approval, and signature is logged with user, IP, timestamp, and metadata.
* Audit log is append-only at the database level.

## What we do **not** do

* We don't auto-sweep wallets to a treasury.
* We don't take fees or skim transactions.
* We don't expose secret keys via any API surface.
* We don't allow API keys to read other accounts' data.


---

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