In our last use case we presented an architecture for securely managing credit card numbers in-house. But in response to a mix of breaches and PCI requirements, some payment processors now offer tokenization as a service. Merchants can subscribe in order to avoid any need to store credit cards in their environment – instead the payment processor provides them with tokens as part of the transaction process. It’s an interesting approach, which can almost completely remove the PAN (Primary Account Number) from your environment.

The trade-off is that this closely ties you to your processor, and requires you to use only their approved (and usually provided) hardware and software. You reduce risk by removing credit card data entirely from your organization, at a cost in flexibility and (probably) higher switching costs.

Many major processors have built end-to-end solutions using tokenization, encryption, or a combination the two. For our example we will focus on tokenization within a fairly standard Point of Sale (PoS) terminal architecture, such as we see in many retail environments.

First a little bit on the merchant architecture, which includes three components:

  1. Point of Sale terminals for swiping credit cards.
  2. A processing application for managing transactions.
  3. A database for storing transaction information.

Traditionally, a customer swipes a credit card at the PoS terminal, which then communicates with an on-premise server, that then connects either to a central processing server (for payment authorization or batch clearing) in the merchant’s environment, or directly to the payment processor. Transaction information, including the PAN, is stored on the on-premise and/or central server. PCI-compliant configurations encrypt the PAN data in the local and central databases, as well as all communications.

When tokenization is implement by the payment processor, the process changes to:

  1. Retail customer swipes the credit card at the PoS.
  2. The PoS encrypts the PAN with the public key of the payment processor’s tokenization server.
  3. The transaction information (including the PAN, other magnetic stripe data, the transaction amount, and the merchant ID) are transmitted to the payment processor (encrypted).
  4. The payment processor’s tokenization server decrypts the PAN and generates a token. If this PAN is already in the token database, they can either reuse the existing token (multi-use), or generate a new token specific to this transaction (single-use). Multi-use tokens may be shared amongst different vendors.
  5. The token, PAN data, and possibly merchant ID are stored in the tokenization database.
  6. The PAN is used by the payment processor’s transaction systems for authorization and charge submission to the issuing bank.
  7. The token is returned to the merchant’s local and/or central payment systems, as is the transaction approval/denial, which hands it off to the PoS terminal.
  8. The merchant stores the token with the transaction information in their systems/databases. For the subscribing merchant, future requests for settlement and reconciliation to the payment processor reference the token.
  9. The key here is that the PAN is encrypted at the point of collection, and in a properly-implemented system is never again in the merchant’s environment. The merchant never again has the PAN – they simply use the token in any case where the PAN would have been used previously, such as processing refunds.This is a fairly new approach and different providers use different options, but the fundamental architecture is fairly consistent.In our next example we’ll move beyond credit cards and show how to use tokenization to protect other private data within your environment.