iTechNote

PayPal and Google Checkout are few of the many online payment services that offer web service payment integration.

PayPal

PayPal is the most popular P2P (Person-to-Person) payment service online. PayPal web service payment is only available in Website Payment Pro. A site owner can leverage the Direct Payment API to accept credit card payments without any redirection to PayPal web site. PayPal remains invisible throughout the customer experience.

When a customer clicks on the “Pay” button on your website, the web server sends the DoDirectPaymentRequest to the PayPal Web Services API service. The parameters include amount of transaction, buyer’s credit card number, expiration date, browser IP address, a flag that marks final sale or an authorization for a final amount captured later.

The DoDirectPaymentResponse will then return a TransactionID. It also returns the total amount, U.S. banking industry standard Address Verification System (AVS) code and Credit Card Verification (CVV2). The TransactionID is the key to the transaction processed with PayPal or as an authorization key to capture deferred final sale.

PayPal Website Payment Pro supports integration using Java, ASP.NET and PHP and is available in US only. There are four levels of security:

• A required API username and password
• A third required authentication mechanism, which is either one of the following:
  - Client-side request signing via a PayPal-issues API Certificate
  - Request authentication via an API Signature included in the request
• An optional third-party authorization to make the API call on some other account’s behalf
• Secure Sockets Layer (SSL) data transport

Google Checkout

Google Checkout on the other hand is a relative new comer that is tightly integrated to AdWords. Shoppers who see the Google Checkout badges on AdWords ads can easily get Google Checkout to streamline checkout process when they buy things from the advertising merchants.

Google Checkout is friendly to all level of merchants - from the absolute beginner with only working knowledge on HTML, to integrating with e-commerce providers such as Infopia to the ultimate flexibility of using the Google Checkout API.

While PayPal focus on the ease of payment online, Google Checkout differentiates by adding values to AdWords customers by managing the full cycles of an order - post cart, place order, charge order and ship order. It offers features similar to PayPal’s Website Payment Standard or Express Checkout on the checkout process but goes beyond managing just online payment.

To manage the full cycles of an order, you can opt for Level 1 or Level 2 integration. With Level 1 integration, you use Google Merchant Center to manage orders after the initial checkout process. Level 2 integration represents the ultimate flexibility. Google provides a few sets of Web Services API for merchants to manage orders. The APIs include Checkout API, Order Processing API, Notification API and Merchants Calculations API.

To make sure security of a transaction, Google requires a merchant to transport SOAP messages using a 128-bit SSL v3 or TLS connection together with Merchant ID and Merchant Key to do HTTP Basic Authentication. There is no tool but only samples available for using Google Checkout. Sample codes are available for ASP, ASP.NET, PHP and Java.