If your are looking to re-create (re-generate) your SharePoint Root Authority "local" certificate, here are the commands to do so...
I accidentally deleted mine, so I exported from other farm members
To Export:
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$rootCert = (Get-SPCertificateAuthority).RootCertificate
$rootCert.Export("Cert") | Set-Content C:\Temp\FarmRoot.cer -Encoding byte
To Import:
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$rootCert = Get-PfxCertificate C:\Temp\FarmRoot.cer
New-SPTrustedRootAuthority -Certificate $rootCert
I accidentally deleted mine, so I exported from other farm members
To Export:
-------------
$rootCert = (Get-SPCertificateAuthority).RootCertificate
$rootCert.Export("Cert") | Set-Content C:\Temp\FarmRoot.cer -Encoding byte
To Import:
-------------
$rootCert = Get-PfxCertificate C:\Temp\FarmRoot.cer
New-SPTrustedRootAuthority -Certificate $rootCert