X923

X9.23 is a formal standard in the ANSI X9 family that specifies methods for generating and using message authentication codes (MACs) in financial services. Developed by the American National Standards Institute’s X9 committee, it has been widely used to provide data integrity and authentication in electronic funds transfer environments, including interbank communications, card processing, and point-of-sale networks.

The standard defines a DES-based MAC algorithm suitable for environments that require symmetric-key authentication. It describes how data blocks are processed in a cipher mode akin to CBC and how a final encryption step yields the MAC value. The typical output is an eight-byte (64-bit) MAC. X9.23 also addresses key management considerations, such as using separate keys for encryption and for MAC computation, and it outlines testing and conformance requirements.

X9.23 exists alongside other MAC-related standards in the X9 family, notably X9.9 and X9.19, which cover related approaches to retail and triple-DES-based MAC generation. Over time, revisions have updated terminology and guidance to align with evolving cryptographic practices.

Current status and usage context vary by organization. DES-based MACs defined by X9.23 have historical significance and remain documented in legacy systems, though many modern deployments have shifted toward stronger cryptographic algorithms, such as AES-based MAC schemes. Nevertheless, X9.23 remains part of the historical and regulatory framework governing financial cryptography and interoperability.