> ## Documentation Index
> Fetch the complete documentation index at: https://kraken-sandbox.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# FIX Authentication

> SenderCompID assignment, Logon message structure, password encoding, and session-level authentication for the Kraken Unified FIX API

## SenderCompID

Every FIX message — including the initial [Logon](/exchange/api-reference/unified-fix/logon) — requires a `SenderCompID` (tag 49). This identifier is assigned to you by Kraken during onboarding.

* **Spot** sessions use your standard SenderCompID
* **Derivatives** sessions use a SenderCompID with a `DRV` suffix
* Trading and Market Data sessions use the same SenderCompID but connect to different ports

<Info>
  Contact your Account Manager to request your SenderCompID and connection details.
</Info>

## API Key Setup

Private trading sessions require an API Key with **FIX** permissions. Create one in [Kraken Pro settings](https://pro.kraken.com/app/settings/api).

| Session             | API Key type needed                            |
| ------------------- | ---------------------------------------------- |
| Spot trading        | FIX key created under your Spot account        |
| Derivatives trading | FIX key created under your Derivatives account |

We recommend using separate API Keys for Spot and Derivatives, even though the authentication mechanism is identical.

## Authentication Flow

Market Data sessions authenticate with the SenderCompID alone. Trading sessions require an additional HMAC signature:

1. Generate a `Nonce` — current time in milliseconds since Unix epoch
2. Build the `MessageInput` string from fixed FIX fields
3. Compute `SHA256(MessageInput + Nonce)`
4. Sign it with `HMAC-SHA512` using your base64-decoded API Secret
5. base64-encode the result → this is your `Password` (tag 554)
6. Send the Logon with `UserName` (tag 553), `Password` (tag 554), and `Nonce` (tag 5025)

See the [Logon](/exchange/api-reference/unified-fix/logon) page for the full field reference and code examples in Python, Node.js, Java, Go, and C#.