IPv6 の ULA を PowerShell で求める

##########################################################
# ULA を生成する(RFC4193)
##########################################################
function GenerateULA(){
    # NTP Time 求める
    $NtpTime =  [long](New-TimeSpan 1900/01/01).TotalSeconds
    $HexNTPTime = $NtpTime.ToString("x")

    # MAC アドレス求める
    $NICs = @(Get-NetAdapter | ?{$_.MediaType -eq "802.3"})
    $MAC = $NICs[0].MacAddress

    # MAC アドレスを EUI-64 にする
    $MAC = $MAC.Replace("-","")
    $HiMAC1 = $MAC.Substring(0,2)
    $hiMAC2 = $MAC.Substring(2,4)
    $LoMAC3 = $MAC.Substring(6,6)
    $numHiMAC1 = [Convert]::ToInt32($HiMAC1,16)
    $XorMask = [Convert]::ToInt32("00000010",2)
    $numHiMAC1 = $numHiMAC1 -bxor $XorMask
    $HiMAC1 = $numHiMAC1.ToString("x")
    $EUI64 = $HiMAC1 + $HiMAC2 + "fffe" + $LoMAC3

    # NTP Time と EUI-64 を連結する
    $BaseString = $HexNTPTime + $EUI64

    # SHA-1 ハッシュを求める
    $ByteDatas = [System.Text.Encoding]::UTF8.GetBytes($BaseString)
    Add-Type -AssemblyName System.Security
    $SHA1 = New-Object System.Security.Cryptography.SHA1CryptoServiceProvider
    $HashBytes = $SHA1.ComputeHash($ByteDatas)
    $SHA1.Dispose()
    $strHash = ""
    foreach( $HashByte in $HashBytes ){
        $strHash += $HashByte.ToString("x2")
    }

    # ラスト10文字を切り取り fd をつける
    $ULA_Bear = "fd" + $strHash.Substring(30,10)

    # IPv6 表記にする
    $ULA1 = $ULA_Bear.Substring(0,4)
    $ULA2 = $ULA_Bear.Substring(4,4)
    $ULA3 = $ULA_Bear.Substring(8,4)
    $ULA = $ULA1 + ":" + $ULA2 + ":" + $ULA3 + "::/48"
    
    return $ULA
}