obscuresec

# define and encode test data
$TestString = 'This is a test. A short test for encoding and padding.'
$Encoded = [Convert]::ToBase64String([Text.Encoding]::UTF8.GetBytes($TestString))

# insert random '='
$Length = $Encoded.Length
$RandomChar = 1..($Length - 3) | Get-Random
$Encoded = $Encoded.Insert($RandomChar,'=')

# strip out '='