Objective

When digitally signing a PDF in Acrobat DC or Acrobat Reader DC, the following warning message appears:
Your signature device does not support the SHA256 algorithm. Do you want to continue with the outdated SHA1 algorithm or do you want to cancel?  

Even after trying the following settings:-
aSignFormat=adbe.pkcs7.detached
aSignHash=SHA
you still get the above-mentioned message.

Environment

  • Acrobat Reader DC
  • Acrobat DC PRO, STD
  • Windows

Steps

  1. Make sure that Acrobat/Reader is closed.
  2. Launch Registry Editor with administrator rights.
  3. To permanently suppress SHA1 warning message you can set the below registrykey:
    [HKEY_CURRENT_USER\SOFTWARE\Adobe\<Adobe Acrobat/Reader>\<Track/version>\AVAlert\ cCheckbox]
    Create a new REG_DWORD iDontShowSHA1Dep and set its value to 1.

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