Convert to and from Base64, since there's no built-in Windows command for this

Base64.ps1

function ConvertTo-Base64 {
    Param(
        $Text
    )
    $Bytes = [System.Text.Encoding]::Unicode.GetBytes($Text)
    [System.Convert]::ToBase64String($Bytes)
}

function ConvertFrom-Base64 {
    Param(
        $EncodedText
    )
    $DecodedBytes = [System.Convert]::FromBase64String($EncodedText)
    [System.Text.Encoding]::Unicode.GetString($DecodedBytes)
}

Technique from Sean Metcalf: https://adsecurity.org/?p=478