Converting Modern PKCS#12 Files for Windows Server 2016

This page describes how to convert a modern PKCS#12 (.p12) certificate bundle into a format compatible with Windows Server 2016.

Contemporary certificate authorities and tooling often generate .p12 files using updated encryption algorithms, key derivation functions, or MAC settings that are not fully supported by Windows Server 2016. As a result, importing these files may fail or produce errors when using Windows Certificate Services, MMC, or legacy tooling.

Conversion Steps

Extract Certificate and Private Key

Extract the certificate and private key from the modern .p12 file into an intermediate PEM format:

openssl pkcs12 -in clm.p12 -out temp.pem -nodes

The -nodes flag exports the private key unencrypted.

Repackage with Windows-Compatible Algorithms

Create a new .p12 file using encryption and MAC algorithms supported by Windows Server 2016:

openssl pkcs12 -export -in temp.pem -out clm_win16.p12 \
  -certpbe PBE-SHA1-3DES \
  -keypbe PBE-SHA1-3DES \
  -macalg sha1

Parameter explanation:

-certpbe PBE-SHA1-3DES: Certificate encryption algorithm
-keypbe PBE-SHA1-3DES: Private key encryption algorithm
-macalg sha1: Message authentication code algorithm

Clean Up Temporary Files

Remove the intermediate PEM file and original .p12 file:

rm temp.pem
rm clm.p12

Only delete clm.p12 after verifying the converted file works correctly.

Verify Conversion

Confirm the new .p12 file uses Windows Server 2016-compatible algorithms:

openssl pkcs12 -info -nodes -in clm_win16.p12

Expected output:

MAC: sha1, Iteration 2048
MAC length: 20, salt length: 8
PKCS7 Encrypted data: pbeWithSHA1And3-KeyTripleDES-CBC, Iteration 2048

If the output matches, the file is ready for import on Windows Server 2016.