When trying to add a digital signature to a DWG file, AutoCAD reports "No valid digital ID is available on your system", so it cannot find any installed certificate of a digital ID. This error appears also on PCs with proven personal certificate installed, issued by a qualified certificate authority, in the .p12 format (PKCS#12), compliant with the X.509 standard. The certifikate is stored in the OS certificate store and other Windows applications can "see" it.
The certifikate structure (digital ID) allows various content types (by different PKI standards) and AutoCAD does not support all the combinations. If the specific certificate does not match AutoCAD's expectations, it can be refused when trying to sign the drawing or the signature process hangs (hourglass). There are some points from the tip author's personal experience:
- to sign AutoCAD drawings you can use both qualified and "unqualified" certificates issued by non-accredited certificate authorities (CA) - e.g. private or company CAs
- you cannot use an expired (no longer valid) certificate
- you cannot use a self-signed certificate despite the X.509 standard allows it
- each certificate in the OS Windows certificate store (the Personal folder!) must have stored (in the "Intermediate Certification Authorities" folder) the CA-certificate of the authority which has issued (signed) his/her personal certificate
- the CA-certificate (see above) may be stored (just to be sure) also to the the "Trusted Root Certification Authorities" folder
- the certificate should have a valid CN (common name)
When you do not comply with the above rules, signing a DWG may end up with the error message "A Digital ID is required". In any case the AutoCAD requirements for the certificates are higher than those of other Windows applications.
The tip author: P.Sonenberk
More information - see Wikipedia - X.509