4.2.1 Strong cryptography safeguards PAN over public networks

Wherever PAN crosses open, public networks (such as the Internet, Wi-Fi, Bluetooth, cellular and satellite links), PAN must be protected with strong cryptography and security protocols, arranged so that: only keys and certificates that are trusted are accepted; certificates guarding PAN in transit are confirmed as valid and neither revoked nor expired; the protocol permits only secure versions or configurations and cannot use or fall back to any insecure version, algorithm, key size or implementation; and encryption strength suits the encryption method chosen. Protection may be at the data level, the session level, or both. Applicability: a self-signed certificate can be acceptable when an internal CA of the organisation issued it, its author is confirmed, it is verified (for instance by hash or signature) and it has not expired. The bullet on confirming certificates are valid and neither revoked nor expired was advisory only up to 31 March 2025; the remaining bullets were already mandatory. Objective under the customized approach: nobody can read or capture cleartext PAN from traffic over open, public networks. Future-dated: treated as a best practice up to 31 March 2025 and mandatory since then.

Source: PCI DSS v4.0.1, 4.2.1. The statement above is our statement of the clause, read from the published text and cited so you can check it against the official text, not the instrument verbatim. Open PCI DSS v4.0.1 in the compliance library.

Version 4.0.1 is the active version; 4.0 has been retired. Appendix A1 applies only to multi-tenant service providers, A2 only to card-present POS POI terminals that still use SSL or early TLS, and A3 only when a payment brand or acquirer requires it. Which requirements apply to you follows your validation type.