Authentication

Introduction

Security lies at our heart, so we have taken steps to help you to process transactions more safely. To reduce the risk that someone other than you can use your integration, our platform uses security codes linked to your PSPID.

The so-called API Key and API Secret provide a unique signature to the traffic between your system and our platform. You can define these for each of your PSPIDs in the Merchant Portal. Any server-to-server request from your system to our platform (via your PSPID) needs to contain both the API Key and API Secret. Our platform tries to match the codes we receive from you with the ones configured in the Merchant Portal.

Our Server SDKs offer a simple solution for this mechanism, requiring only few lines of coding. If you wish to use your own software, manual implementation is also possible.

API key/secret configuration

To configure the API Key / Secret pair in the Merchant Portal, follow these steps:

1. Login to the Merchant Portal. Go to Developer > Payment API
2. If you have not configured anything yet, the screen shows "No keys generated". To create both a API Key / Secret pair, click on “Add API Key”. The screen now shows both codes in the table in the “API Key ID” / “Secret API Key” line respectively
   
   

You can look up the API Key and the following information about the API Key / Secret pair anytime via Developer > Payment API:

If you wish to use a new API Key / Secret pair to replace an existing one, follow these steps

1. Click on "Add API Key". Click on "Confirm" in the dialogue box to proceed with the creation of a new API Key / Secret pair
   
   

1. The screen now shows the new API Key / Secret pair at the bottom of the table in status "Active". The former active one now is in status "Expiring in xh yym"

Authentication with SDK

Once you have set up your API Key/Secret in the Merchant Portal, you can use them for requests you send to our platform. Our Server SDKs make it really easy to do so.

Have a look at this code sample that demonstrates how to add them in a standard Hosted Checkout Page request:

Authentication without SDK

You can use our API without the SDKs by sending requests to our endpoints directly. This requires you to follow a different authentication mechanism.

Essentially, you need

• To hash with your API Secret over several HTTP headers (the signature contents or signed-data) you send along with your request
• Send this hash (the signature) together with your API Key to verify the authentication

Have a look at the following chapters to understand how this works and our GET, POST and DELETE examples.

Understand authentication process

A GET/POST/DELETE request following this approach includes the following steps:

1. Create a string-to-hash, consisting of several HTTP headers
2. Calculate the hash using the algorithm HMAC-SHA256 with your API Secret
3. Send the actual request to our platform, including the headers, the hash and your API Key

1. Create string-to-hash

Compose the string-to-hash (the signature contents or signed-data) by following these rules:

Order of the headers

The string-to-hash consists of the following headers, listed in a specific order: 

<HTTP method>
<Content-Type>
<Date>
<CanonicalizedHeaders>
<CanonicalizedResource>

Header Content Conventions

Each header is constructed as follows: 

<lowercased header name>:<header value>;

Apply the following conventions for the content of the headers:

Unwrap Header Values

If a header value is wrapped over multiple lines, unwrap each line as described here. Unwrap by replacing a new line or multiple spaces by a single white space.

Have a look at this example:

A very long line<CR><LF>
<SPACE><SPACE><SPACE><SPACE>that does not fit on a single line 

becomes


A very long line that does not fit on a single line

Trim White Spaces

Trim all whitespaces which exist at the start and end of the value.

Have a look at this example:

<space><space><space>Some text<space><space><space>

becomes

Some text

Have a look at this code sample for a CreateHostedCheckout request:

2. Calculate hash

Once you have created the string-to-hash (the signature contents or signed-data), you need to hash it via the MAC algorithm HMAC-SHA256 with your API Secret.
The result of the hashing is the signature you need to provide in the authorisation header of your request.

Have a look at this code sample:

3. Send request

Finally, you can send your request, including

• The headers you used for creating the string-to-hash (the signature contents or signed-data)
• The base64-encoded hash result (the “signature”) and your API Key (which our platform uses to identify your PSPID on our account) in the HTTP header 'Authorization' according to this formula:
  
  

  Authorization = "GCS v1HMAC:" + API Key + ":" + signature

• The JSON-encoded request body for POST requests (GET/DELETE do not require a request body)
  Have a look at this code sample:

Understand string-to-hash examples

As the general requirements for a GET/POST/DELETE request differ, the construction of the string-to-hash does as well.
Have a look at the following examples to learn how to implement them in your system:

1. POST request

The string-to-hash (the signature contents or signed-data) for a CreateHostedCheckout request:

POST
application/json; charset=utf-8
Wed, 02 Mar 2022 11:15:51 GMT
/v2/yourPSPID/hostedcheckouts

2. GET request

The string-to-hash (the signature contents or signed-data) for a GetHostedCheckout request:

GET

Wed, 02 Mar 2022 11:15:51 GMT
/v2/yourPSPID/hostedcheckouts/yourHostedCheckoutID

3. DELETE request

The string-to-hash (the signature contents or signed-data) for a DeleteToken request:

DELETE

Wed, 02 Mar 2022 11:15:51 GMT
/v2/yourPSPID/tokens/yourTokenID