Which of the following may be used to render PAN unreadable in order to meet requirement 3.4?

To meet requirement 3.4 of the PCI DSS, which aims to protect the Primary Account Number (PAN) by rendering it unreadable, hashing the entire PAN using strong cryptography is highly effective. Hashing transforms the PAN into a fixed-size string of characters, which is practically impossible to reverse without the original data. This process ensures that even if the hashed data is exposed, it cannot be easily converted back to the original PAN, thereby protecting sensitive information from unauthorized access.

Strong cryptographic methods used for hashing include algorithms like SHA-256, which are designed to be secure and resistant to collision attacks. When utilized correctly, hashing complies with the PCI DSS requirement to protect stored cardholder data and mitigates the risk of data breaches.

The other methods, while they address data security, do not effectively render the PAN unreadable in the context set forth by PCI DSS. For example, encryption of the PIN only would not protect the PAN; storing the PAN in plain text with limited access does not provide any security against unauthorized access; and removing all digits from the PAN may lead to loss of necessary information without providing an effective solution for protection.