> ## Documentation Index
> Fetch the complete documentation index at: https://docs.phala.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Request Signature

> Fetch a cryptographic signature for a Confidential AI response.

## Endpoint

```bash theme={"system"}
GET https://api.redpill.ai/v1/signature/{request_id}?model={model}&signing_algo={algo}
```

Use this endpoint after a chat completion request. The signature proves a specific response was signed by a TEE key. Bind that key to fresh attestation evidence before treating the response as fully verified.

## Parameters

<ParamField path="request_id" type="string" required>
  The `id` returned by `POST /v1/chat/completions`.
</ParamField>

<ParamField query="model" type="string" required>
  The model ID used for the original request.
</ParamField>

<ParamField query="signing_algo" type="string">
  Signature algorithm. Common values include `ecdsa`, `ecdsa-p256`, and `rsa`; use the algorithm supported by the model response.
</ParamField>

## Examples

<CodeGroup>
  ```bash cURL theme={"system"}
  RESPONSE=$(curl -s https://api.redpill.ai/v1/chat/completions \
    -H "Content-Type: application/json" \
    -H "Authorization: Bearer <API_KEY>" \
    -d '{"model":"phala/qwen3.5-27b","messages":[{"role":"user","content":"hello"}]}')

  REQUEST_ID=$(echo "$RESPONSE" | jq -r '.id')

  curl "https://api.redpill.ai/v1/signature/$REQUEST_ID?model=phala/qwen3.5-27b" \
    -H "Authorization: Bearer <API_KEY>"
  ```

  ```python Python theme={"system"}
  import requests

  chat_response = requests.post(
      "https://api.redpill.ai/v1/chat/completions",
      headers={
          "Authorization": "Bearer <API_KEY>",
          "Content-Type": "application/json",
      },
      json={
          "model": "phala/qwen3.5-27b",
          "messages": [{"role": "user", "content": "hello"}],
      },
  )

  request_id = chat_response.json()["id"]

  signature_response = requests.get(
      f"https://api.redpill.ai/v1/signature/{request_id}",
      params={"model": "phala/qwen3.5-27b"},
      headers={"Authorization": "Bearer <API_KEY>"},
  )

  signature_data = signature_response.json()
  ```
</CodeGroup>

## Response

```json theme={"system"}
{
  "text": "phala/qwen3.5-27b:116478638341bd2b...:3d0b2a2df73dc93a...",
  "signature": "0xee817b30e13ec3c320997ec37076a600e194dc64...",
  "signing_address": "0x56d070df1c6be444b007839ef9cf67cec7c12b8b",
  "signing_algo": "ecdsa"
}
```

## Response Fields

| Field             | Description                                                                                      |
| ----------------- | ------------------------------------------------------------------------------------------------ |
| `text`            | Signed text. Format is either `request_hash:response_hash` or `model:request_hash:response_hash` |
| `signature`       | Signature over `text`                                                                            |
| `signing_address` | TEE signing address or public key                                                                |
| `signing_algo`    | Signature algorithm used                                                                         |

<Note>
  When `text` has three colon-separated parts, the first part is the model name used inside the signing path. It may differ from the alias you sent if the gateway rewrote the model ID internally.
</Note>

## Bind to Attestation

For production verification, use the returned `signing_address` to fetch fresh attestation evidence:

```bash theme={"system"}
NONCE=$(openssl rand -hex 32)

curl "https://api.redpill.ai/v1/attestation/report?model=phala/qwen3.5-27b&nonce=$NONCE&signing_address=$SIGNING_ADDRESS" \
  -H "Authorization: Bearer <API_KEY>"
```

The response is verified only when:

1. The request and response hashes in `text` match the bytes you sent and received.
2. The signature is valid for `text`.
3. The attestation report binds the same `signing_address` to genuine TEE evidence and your fresh nonce.