ConvertTo-NTHashMD4

Calculate MD4/NTHash/NTLM Hashes in Powershell based on the work of Larry Song. (https://github.com/LarrysGIT/MD4-powershell)

Fixes

The original can't properly handle UTF16-LE input and strings that result in a message size of more than 55 bytes since there was an error in padding. (Problems started to unfold at 28 characters utf16 and more)

A string in Powershell uses the String Class of .Net, therefore it is encoded as UTF16-LE. https://docs.microsoft.com/en-us/dotnet/standard/base-types/character-encoding-introduction#utf-16-code-units

Due to the little endianness of UTF16-LE, the original way of making an byte array from the input string resulted in it beeing treated as ASCII/UTF8 for ascii chars (lost 8 Bit of zeros) and strange results for non-ascii chars.

Original Method:

    $Array = [byte[]]@()
    if($String)
    {
        $Array = [byte[]]@($String.ToCharArray() | %{[int]$_})
    }

Now the function treats input as UTF16-LE as expected and gives the option for other encodings via parameters (for MD4).

NT HASH/NTLM

This also means that the ouput is a valid NT Hash/NTLM Hash for any given UTF16-LE input as NT Hash = md4(utf16-le(passphrase)).

SecureStrings and Impact on performance:

If you pass a SecureString the script tries to keep it kinda 'secure' by trying to flush the plaintext from memory as soon as possible. https://get-powershellblog.blogspot.com/2017/06/how-safe-are-your-strings.html

This has a quite noticable effect on performance but this is not really important for most use-cases where you specificly choose SecureStrings.

Measure-Command { 1..100 | % {ConvertTo-NTHashMD4 -SecureString $Creds.password} }
Seconds           : 9
Milliseconds      : 384
Ticks             : 93846611
Measure-Command { 1..100 | % {ConvertTo-NTHashMD4 -String 'password1'} }
Seconds           : 0
Milliseconds      : 795
Ticks             : 7950702

Reference

https://tools.ietf.org/html/rfc1320