With the Reader DC release 15.016.20039, we have deprecated use of SHA1 hash while signing. SHA256 has been the default hashing algorithm, but in the prior releases in case the CSP driver doesn’t support SHA256 or higher hashes Reader used to silently fallback to SHA1 hash while creating the signature. In this release, we have removed the silent fallback to SHA1 due to which this error pops up and subsequently signing fails.
Please let me know the driver of the e-token device your are using for signing.
Also, please check with the driver manufacturer for the updated driver that should resolve this error.
We published a KB article related to this issue just a while back.
While we investigate it further, the workaround provided in the article should help.
"Check with your signature device or driver manufacturer for an updated driver that may resolve this error.
If the requested hashing algorithm is not supported by the signature device, then the solution is to set registry key aSignHash to SHA1 as described on this page -http://www.adobe.com/devnet-docs/acrobatetk/tools/PrefRef/Windows/Security.html#Signing:Ha shAlgorithm. However, this is not a recommended approach as this would set SHA1 as the default hashing algorithm for all signatures, which is considered deprecated industry wide. Therefore, Adobe strongly recommends checking with your signature device or driver manufacturer to get a newer device or driver that supports SHA256 or higher hashes."
We have released a patch today that fixes the Digital Certificates issue that was recently introduced. If you are not already updated to the latest patch, simply open Acrobat and visit Help > Check for updates to apply this patch.
More details about this release and bug fixes is available here: https://helpx.adobe.com/acrobat/release-note/acrobat-dc-june-02-2016.html
Please give it a try and let us know.