At the end of 2023, NIST disallows the use of three-key TDEA for use in protecting security sensitive data within US Federal information systems. However, as per NIST SP800-57 part 1, TDEA using three keys can still provide an effective strength of 112 bits when applied using appropriate key management and modes of operation.

The definition of ‘strong cryptography’ was updated in PCI DSS v4.0 to reference only the effective key size of the algorithm/key combination - specifically to a minimum of 112 bits of effective strength, with a recommendation to use systems that provide 128 bits of effective strength.

For other PCI SSC standards, refer to the subject standard for whether and how use of three-key TDEA is allowed.