A de-identification technique that hides original data with modified content (characters or other data). In many cases, masking will keep the data value valid by not fully masking all the data.

This technique is commonly applied to credit card data in production systems. For instance, an operator at a call centre might bill an item to a customer’s credit card. They then quote a billing reference to the card with the last 4 digits of XXXX XXXX xxxx 6789. As an operator they can only see the last 4 digits of the card number, but once the billing system passes the customer’s details for charging, the full number is revealed to the payment gateway systems.

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