This paper describes a holistic approach for establishing content authenticity and maintaining content integrity in a large OAIS repository. The U.S. Government Printing Office (GPO) is developing the Federal Digital System (FDsys), a digital archive to provide permanent public access to United States federal government publications. FDsys is being designed based on the OAIS reference model, which incorporates many archiving best practices and increases the chance for developing a successful archive that will protect and preserve content over time.A cornerstone of any successful preservation system is a solid authentication strategy. GPO disseminates official United States federal government publications across the nation and around the world. Since 1861 users have looked to GPO as a trusted source for federal legal and regulatory information. This historic trust relationship increases the importance for GPO to establish content authenticity and maintain content integrity as it transitions from a publication-based print environment to a content-centric digital environment.Defining, evaluating, and expressing content authenticity is essential for a successful authentication strategy. GPO defines authentic content as content that is verified by GPO to be complete and unaltered when compared to the version approved or published by a content originator such as Congress or a federal agency. Content will flow into FDsys in three distinct streams: deposited in digital format, converted from tangible media, and harvested from digital sources. Each avenue presents a unique challenge to evaluating authenticity and expressing chain of custody information (i.e., custodial history) for that content. Deposited content is submitted by a federal agency. In order to establish content authenticity at the time of submission GPO requires authentication of users including personal identity, corporate identity, and authorization to publish official federal government publications on behalf of their agency. Converted content presents a unique situation in that information must be recorded about the original hard copy publication and associated digitization processes. Establishing content authenticity for harvested content is often challenging because little information is available about the content creation process, and an expression of authenticity information may only indicate that the content was harvested from an official source.Once content has been ingested into FDsys, the system maintains content integrity by providing assurance that content has not been changed in an unauthorized manner. GPO will use a multi-faceted strategy to provide this assurance including deploying a robust content management system, interrogating hashed content on a regular basis in order to detect changes, and applying digital signatures to PDF files that are delivered to public users.