GPO Authenticates Online Content
Beginning with the 110th Congress, the Public and Private Laws on GPO Access have been digitally signed and certified. GPO has signed and certified the PDF files to assure users that the online documents are official and authentic.
"To help meet the challenge of the digital age, GPO has begun implementing digital signatures to certain electronic documents on GPO Access that not only establish GPO as the trusted information disseminator, but also provide the assurance that an electronic document has not been altered since GPO disseminated it." Read more at GPO Access' authentication efforts.
Source: FDLP-listserv via my colleague, Bill Ebbott