There are two sets of credentials and you may use either authentication method for API usage.
Password: Use for Basic Authentication.
ConsumerSecret: Use for Basic and OAuth 1.0a Authentication.
You also need a MerchantId from the merchant account that you have access to.
merchantId: Use this merchant account for making API calls such as POST a payment.
Priority Payment Systems Checkout API v3 supports both Basic Authentication and OAuth 1.0a Authentication to help developers integrate with our APIs for accepting payments. Basic Authentication is the simplest way to make calls to APIs without managing Access Tokens manually from client side over SSL. Basic authentication calls also reduce implementation overhead time. OAuth Authentication is a more complex process but is more secure. It involves first obtaining a RequestToken then an AccessToken and finally you can make API calls using the AccessToken. The instructions below will walk you through step-by-step on how to use both types of authentication.
Need an API Key?
To learn how to generate an API Key and Secret, click here