I was looking for PowerShell solutions for generating a random password (in order to set the Administrator password on a Windows instance provisioned in OpenStack), and found several solutions using the GeneratePassword method of System.Web.Security.Membership (documentation here), along the lines of this:

Function New-RandomComplexPassword ($length=8)
    $Assembly = Add-Type -AssemblyName System.Web
    $password = [System.Web.Security.Membership]::GeneratePassword($length,2)
    return $password

While this works, I was unhappy with the generated passwords: they were difficult to type or transcribe because they make heavy use of punctuation. For example:

  • (O;RK_wx(IcD;<V
  • +3N)lkU5r)nHiL#

These looks more like line noise (remember that? No? Get off my lawn...) than anything else and feel very unnatural to type.

I was looking for longer strings consisting primarily of letters and digits. Thanks to Hey, Scripting Guy I learned about the Get-Random and ForEach-Object methods (and the % alias for the latter), and ended up with the following:

# Generate a random password
# Usage: random-password <length>
Function random-password ($length = 15)
    $punc = 46..46
    $digits = 48..57
    $letters = 65..90 + 97..122

    # Thanks to
    # https://blogs.technet.com/b/heyscriptingguy/archive/2012/01/07/use-pow
    $password = get-random -count $length `
        -input ($punc + $digits + $letters) |
            % -begin { $aa = $null } `
            -process {$aa += [char]$_} `
            -end {$aa}

    return $password

This generates strings of letters and digits (and ".") that look something like:

  • 2JQ0bW7VMqcm4UB
  • V4DObnQl0vJX1wC

I'm a lot happier with this.