As part of the holiday giving tradition, the PCI SSC has given us an updated FAQ (#1091) on the subject of PAN truncation and it will likely go down as the most confusing FAQ ever.
The FAQ starts out simple enough with the statement:
“A maximum of the first 6 and last 4 digits of the PAN is the starting baseline for entities to retain after truncation, considering the business needs and purposes for which the PAN is used.”
But it is the table that follows that gets messy.
It seems that each of the card brands has their own take on PAN truncation based on PAN length and other factors. Only American Express has stayed the course.
Based on the guidance for UnionPay, Visa, Mastercard, JCB and Discover, the idea of first six/eight and ANY OTHER four is a bit bizarre not to mention risky.
Never mind the obvious warning note at the end of the FAQ that states:
“Access to different truncation formats of the same PAN greatly increases the ability to reconstruct full PAN, and the security value provided by an individual truncated PAN is significantly reduced. If the same PAN is truncated using more than one truncation format (for example, different truncation formats are used on different systems), additional controls should be in place to ensure that the truncated versions cannot be correlated to reconstruct additional digits of the original PAN.”
Personally, I would stick with the good old first six, last four and avoid any of these other formats as you are likely setting yourself up for problems and PCI non-compliance.
Happy holidays to all!
PCI Guru 