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Question

Here is a tiny Perl script that takes a MAC Address (xx-xx-xx-xx-xx-xx) as its only parameter and returns a hash.

I have converted it to a console VB NET app with some difficulty and I'd like to see some other approaches to the conversion.

Bear in mind that my skills in Perl are very very low. I had to look up most of the operators.

#!/usr/bin/perl
if (! defined $ARGV[0]) {
print "+========================================== \n";
print "+ MAC Address Hash Generator \n";
print "+ April 23 2012 \n";
print "+ Usage:\n$0 macaddress \n";
print "+========================================== \n";
exit; }
$a = $ARGV[0];
$a =~  s/[^A-F0-9]+//simg;
@b = reverse split /(\S{2})/,$a;
$c = join "", @b;
$c .= "0000";
$d = hex($c) % 999999929;
print "$d\n";

Examples:

Input = 00-0A-DC-00-00-00
Hash = 60644375
Input = FE-0A-BF-00-9D-57
Hash = 403925255

Option Strict On please....

If there is any significant response, I'll post my code in a few days / a week

Answer 1

    Function GetHash(ByVal input As String) As ULong
        Dim tokens As String() = (("00-00-" & input).Split(New Char() {"-"c})).Reverse().ToArray()
        Dim number As ULong = ULong.Parse(String.Join("", tokens), Globalization.NumberStyles.HexNumber)
        Return (number Mod 999999929)
    End Function

Sub Main()
  Console.WriteLine(GetHash("00-0A-DC-00-00-00")) 
  Console.WriteLine(GetHash("FE-0A-BF-00-9D-57"))
  Console.ReadLine()
End Sub

' Ouput:
60644375
403925255

Another one:

Function GetHash2(ByVal input As String) As ULong
  Return (BitConverter.ToUInt64((
       From token As String In (("00-00-" & input).Split(New Char() {"-"c}))
       Select Byte.Parse(token, Globalization.NumberStyles.HexNumber)).ToArray(), 0)) _
          Mod 999999929
End Function

Answer 2

With a MAC Address like "03-41-BF-35-49-9F" where the last byte is > 0x80, the hash is negative.

Answer 3

You can change the returned datatype to ULong (modified my post)

Answer 4

Thanks for replying, too bad nobody else could - oh well........

        Dim StrRevMAC As String = String.Join("", (args(1).Split("-"c).Reverse().ToArray())) & "0000"
        Dim PW As ULong = 0
        Dim ModVal As ULong = 999999929
        If ULong.TryParse(StrRevMAC, NumberStyles.AllowHexSpecifier, Nothing, PW) = True Then
            Console.WriteLine("Password is: " & (PW Mod ModVal).ToString)
        Else
            Console.WriteLine("Password could not be derived from specified MAC Address")
        End If
        Console.WriteLine("Press any key to exit the application")
        Console.ReadKey()

Thats the code I used.......

Cheers - Devon

Answer 5

Devon,

I not sure what you were expecting from the community.

If you are just interested in seeing alternate ways to accomplish this task, here is my entry for the "let's confuse them category" ;)

Private Function MACandCheeseHash(ByVal MAC As String) As UInt64
   'Validate MAC format
      MAC = MAC.ToUpperInvariant.Trim 'Prep it
      Dim validchars() As Char = New Char() {"0"c, "1"c, "2"c, "3"c, "4"c, "5"c, "6"c, "7"c, "8"c, "9"c, "A"c, "B"c, "C"c, "D"c, "E"c, "F"c}

      Dim Invalid As Boolean = MAC.Length <> 17 _
                               OrElse MAC.Replace("-", "").AsEnumerable.Union(validchars).ToArray.Count <> validchars.Count _
                               OrElse (MAC(2) & MAC(5) & MAC(8) & MAC(11) & MAC(14) <> "-----")
      If Invalid Then
         Throw New ArgumentException("Invalid MAC")
      End If

   'Value to get remainder from
   Dim sum As UInt64 = (Convert.ToUInt64(MAC.Substring(15, 2), 16) << 56) + _
                       (Convert.ToUInt64(MAC.Substring(12, 2), 16) << 48) + _
                       (Convert.ToUInt64(MAC.Substring(9, 2), 16) << 40) + _
                       (Convert.ToUInt64(MAC.Substring(6, 2), 16) << 32) + _
                       (Convert.ToUInt64(MAC.Substring(3, 2), 16) << 24) + _
                       (Convert.ToUInt64(MAC.Substring(0, 2), 16) << 16)

   Const Divisor As Decimal = 999999929D
   Return CType(Decimal.Remainder(CType(sum, Decimal), Divisor), UInt64)

End Function

Answer 6

Hi Devon_Nullman,

You could use your code in a Function and even make it an extension method like this.>>

Option Strict On
Option Explicit On
Option Infer Off

Public Class Form1

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

        Dim hashValue As ULong
        hashValue = "00-0A-DC-00-00-00".GetHash
        MessageBox.Show(hashValue.ToString)

        hashValue = "FE-0A-BF-00-9D-57".GetHash
        MessageBox.Show(hashValue.ToString)

    End Sub

End Class

Public Module MyExtensions

    <System.Runtime.CompilerServices.Extension()> _
    Public Function GetHash(ByVal input As String) As ULong
        Dim strRevMAC As String = String.Join("", (input.Split("-"c).Reverse().ToArray())) & "0000"
        Dim pW As ULong = 0
        If ULong.TryParse(strRevMAC, System.Globalization.NumberStyles.AllowHexSpecifier, Nothing, pW) = True Then
            Return Convert.ToUInt64(pW Mod 999999929)
        Else
            Throw New Exception("Password could not be derived from specified MAC Address.")
        End If
    End Function

End Module

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Regards,

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Answer 7

What I was hoping for is exactly what I see here - several different ways to solve the same problem.

Your approach is certainly unique.

Answer 8

That's a new concept to me - thanks

Answer 9

very smooth John