About C:Amie · Technical Articles · Analog C:Amie Edition Tuesday, 17 July 2018

PowerShell - Convert DER Encoded Certificate file into a Base64 .cer

System Requirements:

  • Windows PowerShell

The Problem:

If you have a binary encoded .cer (certificate) file that you need to get into a Base64 format, you can either follow the advice and use OpenSSL to convert it or you can import it into the Windows Certificate Store and re-export it.

If you want to do it automatically, without having to download and install anything else, neither option is particularly appealing.

The Fix

You can use the following function to convert the binary encoded file into a Base64 ASCII encoded file

function Convert-CertificateBinaryToBase64 {
  param( [string]$SourceFile, [string]$DestinationFile )
  $cert = get-content "$SourceFile" -Encoding Byte
  $content = @(
    '-----BEGIN CERTIFICATE-----'
    [System.Convert]::ToBase64String($cert, 'InsertLineBreaks')
    '-----END CERTIFICATE-----'

  $content | Out-File -FilePath "$DestinationFile" -Encoding ASCII

Example usage

Convert the file, retaining the source file

Convert-CertificateBinaryToBase64 -Sourcefile 'C:\myBinary.cer' -DestinationFile 'C:\myBase64.cer'

Convert the binary file, overwriting it with the Base64 file

Convert-CertificateBinaryToBase64 -Sourcefile 'C:\myCertificate.cer' -DestinationFile 'C:\myCertificate.cer'



Article Published: Monday, 9 April, 2018
Article Revision Date: Monday, 9 April, 2018

This site is not associated with the Microsoft Corporation. The information on this page is provided as is and is free for those who visit to use. Microsoft Operating Systems, Internet Browsers and applications are the property of the Microsoft Corporation. Windows software patches and updates are the property of the Microsoft Corporation and are provided through the hard work and dedication of the Microsoft Security, Operating System, and Application development teams.

© C:Amie
1996 - 2018. All Rights Reserved (551)
All trademarks mentioned are the property of their respective owners.