Posts tagged "Adobe Acrobat"

What is a Certified Document and when should you use it?

A Certified Document provides PDF document and forms recipients with added assurances of its authenticity and integrity.  Here are two frequent uses cases for Certified Documents that illustrate these capabilities:

  1. You publish files and want the recipients to know that the files really did originate from you and they have not been accidentally or maliciously modified since you published them.
  2. You distribute electronic forms with pre-populated information, and want to make sure recipients are not accidentally or maliciously modifying your form data when returning them to you.

To certify a document,you can use Acrobat on the desktop or LiveCycle Digital Signatures as part of an automated process on a server.  To verify the certification on a document, desktop users simply open PDFs with the free Adobe Reader or Adobe Acrobat.  If you would like an automated process to verify certified documents on a server, LiveCycle Digital Signatures can also verify certified document status.

When a document has valid certification, a blue ribbon in a blue bar will show above the document in the viewer, like this:

In this case, the document originated from the United States Government Printing Office.  It was published as part of an automated Adobe LiveCycle process, and the source document is publicly available here (http://www.gpo.gov/fdsys/pkg/BILLS-106s761enr/pdf/BILLS-106s761enr.pdf) as part of their Federal Digital System which has very specific requirements on authentication when publishing official US Government documents to the public.  In 2008, the Executive Office of the President, Office of Management and Budget (OMB) stated the White House was no longer ordering hard copy paper versions of the US Federal budget, and instead has posted certified PDF documents online.

Certified documents are also implemented at Antwerp Port Authority for electronic invoices and at a number of higher education institutions for delivering student transcripts electronically, including Penn State, Northwestern, Stanford, and more.

In addition to static documents, certifying a document increases the level of security in electronic forms workflows.  Here is an example:
a) Organization generates a form for recipient to complete and return
b) Form contains some specific transactional information, like an interest rate (3%) and term (15yrs).
c) Recipient decides they will change the rate and term to be more favorable, and then digitally signs it and returns it.

Typically, the form publisher would have to manually review every completed form to look for such errors, and they can often be overlooked.  The better solution is to certify the form as it is published to the recipient.  The added assurances here are that the recipient knows it’s an official form that hasn’t been tampered with, and when the publishing organization receives a completed and signed form back – they know that what was sent out has not been changed along the way.  The certification also allows the form author/publisher to specify which fields and form elements are locked, and which can be filled in by the recipient.

Here is an example of a certified form:

The source PDF file is available here as a Sample.

In either of these cases, if an unauthorized change is made to a certified document, the blue ribbon will turn to a red X – indicator.

More information on automating digital signatures for documents and forms is available in this previous post (LiveCycle Digital Signatures: Three Common Use Cases)

Certified documents utilize PKI and digital signatures to provide the assurances of authenticity and integrity.  These are capabilities built into the ISO 32000 standard PDF specification as well as Adobe Acrobat, Reader, and LiveCycle.  Adobe products utilize FIPS certified encryption implementations of RSA and SHA hashing algorithms (up to RSA4096 and SHA512).  The publisher/signer utilizes their private key certificate to sign documents on the desktop (Acrobat) or server (LiveCycle) and recipients simply use Acrobat or Reader to view them.

Recommendations and best practices:

A. Make sure your signing certificate is trusted by your recipient community.  This can be accomplished in several ways:

1) Utilize the Adobe CDS/AATL program, where certificates are automatically trusted and the recipients have zero configuration to validate digital signatures.  You can either obtain a certificate from a registered Adobe provider, or if you meet the strict program requirements – have your certificate authority automatically trusted.  NOTE: If you are publishing documents to the general public, CDS/AATL is the only recommended option.

2) Utilize enterprise install and management capabilities to push out trust anchors in pre-configured installations as well as maintained on an internal server

3) Utilize an enterprise desktop configuration setting to trust the existing certificate store in the operating system (e.g. Windows CAPI)

B) When certifying a document, make sure that all certificates from the trust chain are available on the signing system (desktop or server).  This includes not only the end-entity signing certificate, but also any intermediate certificates up to the trust anchor.  That way, the recipient only needs to have the trust anchor, as described in the previous section.

C) When publishing a certified document with a digital signature, make sure you are online and able to reach the revocation information published by the certificate authorities.  That way, long term validation (LTV) information is stored in the document.  If this information is not included, the certified document will no longer validate after a signing certificate expires.

D) By default certified documents utilize the system clock as a date/time indicator.  If you have higher assurance needs for time, utilize an RFC3161 based timestamp authority as part of the digital signature process