The PKIX Working Group was established in the fall of 1995 with the goal of developing Internet standards to support X.509-based Public Key Infrastructures (PKIs). Initially PKIX pursued this goal by profiling X.509 standards developed by the CCITT (later the ITU-T). Later, PKIX initiated the development of standards that are not profiles of ITU-T work, but rather are independent initiatives designed to address X.509-based PKI needs in the Internet. Over time this latter category of work has become the major focus of PKIX work, i.e., most PKIX-generated RFCs are no longer profiles of ITU-T X.509 documents. PKIX has produced a number of standards track and informational RFCs. RFC 3280 (Certificate and CRL Profile), and RCF 3281 (Attribute Certificate Profile) are recent examples of standards track RFCs that profile ITU-T documents. RFC 2560 (Online Certificate Status Profile), RFC 3779 (IP Address and AS Number Extensions), and RFC 3161 (Time Stamp Authority) are examples of standards track RFCs that are IETF-initiated. RFC 4055 (RSA) and RFC 3874 (SHA2) are examples of informational RFCs that describe how to use public key and hash algorithms in PKIs. PKIX Work Plan PKIX will continue to track the evolution of ITU-T X.509 documents, and will maintain compatibility between these documents and IETF PKI standards, since the profiling of X.509 standards for use in the Internet remains an important topic for the working group. PKIX does not endorse the use of specific cryptographic algorithms with its protocols. However, PKIX does publish standards track RFCs that describe how to identify algorithms and represent associated parameters in these protocols, and how to use these algorithms with these protocols. We anticipate efforts in this arena will continue to be required over time. PKIX will pursue new work items in the PKI arena if working group members express sufficient interest, and if approved by the cognizant Security Area director. For example, certificate validation under X. 509 and PKIX standards calls for a relying party to use a trust anchor as the start of a certificate path. Neither X.509 nor extant PKIX standards define protocols for the management of trust anchors. Existing mechanisms for managing trust anchors, e.g., in browsers, are limited in functionality and non-standard. There is considerable interest in the PKI community to define a standard model for trust anchor management, and standard protocols to allow remote management. Thus a future work item for PKIX is the definition of such protocols and associated data models.