PIN Block
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The encrypted block that carries a personal identification number between a PIN entry device and the system that verifies it. A PIN is never transmitted or stored in the clear: it is combined with account data, formatted into a block and encrypted, typically inside a hardware security module or a PTS-approved device. PIN blocks are Sensitive Authentication Data and must not be retained after authorization.
Applies to. 3.3.1.3 applies to any entity whose systems see a PIN in transit: merchants with PIN entry devices, acquirers, processors, and the switches that translate PIN blocks between encryption zones. The requirement is that neither the PIN nor the PIN block is stored after the authorisation process completes, and the testing procedure has the assessor examine data sources rather than accept the design on trust.
Example. A regional acquirer's switch logs the full inbound message from each terminal for troubleshooting. The message includes the encrypted PIN block. Because the block is ciphertext the logging looked harmless, but keeping it after authorisation breaks 3.3.1.3, and the acquirer has to mask that field before the message reaches the log.
Limits. Encryption does not make a PIN block storable: 3.3.1.3 has no exception for encrypted data. A PIN block is not a PIN, and 3.3.1.3 says nothing about how the block is encrypted in transit; the keys that protect PIN blocks between devices are managed under the Council's separate PIN security standard rather than under PCI DSS. The term is sometimes confused with the card verification code. The code comes from the card, the PIN from the cardholder, and both are Sensitive Authentication Data.
In PCI DSS v4.0.1. 3.3.1.3