unable to sign a PDF document with national certification authority key In Acrobat XI Pro

[Omar272341907l9z]

I'm attempting to use Acrobat 11 Pro XI to digitally sign a PDF document with ''national certification authority key'' from our internal certificate authority, and I'm receiving the following error:
"Creation of this signature could not be completed.
Size limit error
Unsupported public key algorithm".

key size  is 1 875 bytes

https://pki.gov.kz/en/

Thanks in advance

Omar

[Meenakshi Negi]

Hi Omar272341907l9z,

Thank you for reaching out, an sorry about the delay in response.

As you are using Acrobat XI, we would like to inform you that it is an old and unsupported version.

You may or may not experience issues while using this application on the latest OS versions. 

Refer to the steps suggested in the following help document on a similar discussion: https://helpx.adobe.com/acrobat/kb/error-creation-signature-could-completed.html. Check if that helps.

Please try to install Acrobat Reader's latest version and then try to add a Digital signature via Reader.

Check if you still get the error message.

Let us know how it goes.

Thanks,

Meenakshi