# Signature Algorithm

## Signature Payload

The signature payload consists of **5 lines**, separated by `\n`:

```
METHOD
URI
TIMESTAMP
NONCE
RAW_BODY
```

Field descriptions:

| Field       | Description                                                               |
| ----------- | ------------------------------------------------------------------------- |
| `METHOD`    | HTTP method in uppercase, e.g., `GET`, `POST`, `DELETE`.                  |
| `URI`       | Request path with sorted query string, excluding domain and context path. |
| `TIMESTAMP` | Identical to `x-api-ts`, in milliseconds.                                 |
| `NONCE`     | Identical to `x-api-nonce`.                                               |
| `RAW_BODY`  | Raw request body string. Empty string when no body.                       |

## Query String Sorting

Query strings are sorted by parameter name in **ascending order** for signature calculation. For example, if the actual request is:

```
GET /api/v1/orders?page=1&limit=10
```

The `URI` used for signing will be reordered to:

```
/api/v1/orders?limit=10&page=1
```

{% hint style="warning" %}
When the same parameter appears multiple times, the server sorts by parameter name and preserves the value order of same-name parameters. Avoid using duplicate query parameters in signing.
{% endhint %}

## Body Signing Rules

JSON requests must use `Content-Type: application/json`. The `RAW_BODY` used in signing must be **exactly identical** to the actual body string sent, including spaces, line breaks, and field order.

For `GET` requests and `POST` requests without a body, use an empty string for `RAW_BODY`.

## HMAC-SHA256 Algorithm

```
x-api-sign = hex(HMAC_SHA256(payload, apiSecret))
```

Where `payload` is the 5-line signature payload, and `apiSecret` is the API Key's secret. The server computes HMAC using UTF-8 encoding and outputs a hex string.

<details>

<summary>Python Signature Implementation</summary>

```python
import hmac
import hashlib
import json
from urllib.parse import urlencode

def canonical_uri(path: str, query: dict = None) -> str:
    if not query:
        return path
    sorted_pairs = sorted(query.items(), key=lambda x: x[0])
    return f"{path}?{urlencode(sorted_pairs)}"

def sign_trading_api(
    method: str,
    path: str,
    query: dict = None,
    timestamp: int = None,
    nonce: str = None,
    raw_body: str = "",
    api_secret: str = "",
) -> str:
    import time
    import uuid
    timestamp = timestamp or int(time.time() * 1000)
    nonce = nonce or str(uuid.uuid4())

    uri = canonical_uri(path, query)
    payload = f"{method.upper()}\n{uri}\n{timestamp}\n{nonce}\n{raw_body}"

    return hmac.new(
        api_secret.encode("utf-8"),
        payload.encode("utf-8"),
        hashlib.sha256,
    ).hexdigest()
```

</details>

<details>

<summary>cURL Signature Example</summary>

```bash
# 1. Construct signature payload
METHOD="GET"
URI="/api/v1/symbols"
TIMESTAMP=$(date +%s%3N)
NONCE=$(uuidgen)
RAW_BODY=""

# 2. Build payload
PAYLOAD="${METHOD}\n${URI}\n${TIMESTAMP}\n${NONCE}\n${RAW_BODY}"

# 3. Compute HMAC-SHA256
SIGNATURE=$(printf '%s' "$PAYLOAD" | openssl dgst -sha256 -hmac "$API_SECRET" -hex | awk '{print $NF}')

# 4. Send request
curl -X GET "https://rwa-api.anchored.finance/rwa/trading/api/v1/symbols" \
  -H "x-api-key: ${API_KEY}" \
  -H "x-api-ts: ${TIMESTAMP}" \
  -H "x-api-nonce: ${NONCE}" \
  -H "x-api-sign: ${SIGNATURE}" \
  -H "x-api-chain-id: 10143" \
  -H "x-api-p: Anchored"
```

</details>


---

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