Which method is recommended to meet the requirement of rendering PAN unreadable?

The method of hashing the entire PAN (Primary Account Number) using strong cryptography is the recommended approach to make the PAN unreadable. Hashing algorithms are designed to convert the input data (in this case, the PAN) into a fixed-length string of characters, which is typically very difficult to reverse engineer. When done correctly with a strong cryptographic hash function, this process ensures that the original PAN cannot be reconstructed from the hash. This adds a layer of security by protecting sensitive information against unauthorized access or data breaches.

Additionally, using strong cryptography when hashing provides an additional layer of protection by making it significantly more challenging for attackers to crack the code and gain access to the original PAN, thus maintaining the confidentiality of cardholder data as required by PCI DSS guidelines.