An Equal Opportunity Provider and Employer

CENTER FOR VETERINARY BIOLOGICS NOTICE 18-11

TO: Biologics Licensees, Permittees, and Applicants

Directors, Center for Veterinary Biologics

Veterinary Services Leadership Team

FROM: Bryon Rippke

Director

SUBJECT: Policy for Long-Term Recognition of CVB Digital Signatures in 

Microsoft Word documents.

I. PURPOSE

This Notice informs licensees, permittees, and applicants of procedures to 

compensate for an inability to prevent a “Revoked Signature” message from 

appearing on Microsoft (MS) Word Documents previously signed by CVB 

employees. This message appears when documents are opened after the original 

signing credentials are out of date, even though a valid signature was applied at the 

time of signing. This Notice is a follow-up to CVB Notice 18-07.

II. BACKGROUND

The CVB recently discovered issues with ensuring the long-term validity of digital 

signatures applied to MS Word documents, which are currently used for electronic 

outlines and labels. With many digital signature formats, the validity of the 

signature must be verified by an external Certificate Authority whenever it is 

opened. Once the credential used at the time of signing is inactivated or is replaced, 

external confirmation is no longer possible and the signature no longer is 

characterized as valid. The USDA “revokes” signing credentials when they reach 

expiration or an employee leaves Federal service. Hence, a “Revoked certificate” 

message eventually appears on CVB signatures, once the credential is obsolete.

Animal and Plant

Health Inspection

Service

Veterinary Services

Center for Veterinary 

Biologics

1920 Dayton Avenue

PO Box 844

Ames, IA 50010

(515) 337-6100
CENTER FOR VETERINARY BIOLOGICS NOTICE 18-11

Page 2

 An Equal Opportunity Provider and Employer

It was hoped that converting to the XAdES-X-L standard, wherein a third-party time 

stamp and the signatory’s signing credentials are embedded in the document, would 

allow the signature to be validated without an external Certificate Authority check upon 

opening. APHIS recently held discussions with Microsoft, however, and MS Word does 

not currently have a mechanism to suppress the external check for revoked certificates, 

regardless of the signature standard used. 

The CVB is taking the following action to compensate for this inability to prevent a 

“Revoked certificate” message from appearing on MS Word documents signed by the 

CVB.

III. ACTION 

As described in CVB Notice 18-07, the CVB will continue to recognize documents 

with a Revoked Certificate message for APHIS regulatory purposes, provided that the 

Signature Details confirm that the document was signed while the signing certificate 

was valid. Stepwise instructions to drill into Signature Details are available at 

https://support.office.com/en-us/article/view-digital-signature-and-certificate-details76ba00cb-1e58-42aa-8717-0caee76bb3cf.
CENTER FOR VETERINARY BIOLOGICS NOTICE 18-11

Page 3

 An Equal Opportunity Provider and Employer

If an outline or label processed by the CVB is required for international registration 

purposes, two options are available:

• If the international authority will accept a “copy” of the outline or label

(analogous to a photocopied paper document), create an archival PDF version 

of the signed document immediately upon receipt, while the CVB signature 

still shows as valid. Instructions for creating a PDF version while retaining a 

photographic image of the signature are found in NCAH Portal User 

Guide 12. This produces a copy of the document where the signature is a 

static photographic image, and the signature appearance will never change.

• Certain international authorities may require a “verifiable” digital signature, in 

which the link to the certificate server is still functional (i.e., not a

photographic image of a signature). If this need arises after the CVB 

signature is revoked, submit a “revision” of the document for an updated 

signature. Indicate in the Brief Description “No content changes; updated 

signature requested”. The document will then be signed by a CVB reviewer

having a lengthy valid period left on his/her current signing credential to 

provide the maximum possible use period.

IV. IMPLEMENTATION/ APPLICABILITY

This action is effective immediately. It applies to all submissions of electronic outlines

and labels. Paper submissions are not affected.