Help deciphering powershell code

This topic contains 4 replies, has 4 voices, and was last updated by  Poshoholic 4 years, 10 months ago.

  • Author
  • #9658

    Nate Boettcher

    Can you please help me decipher the following code:

    0..0xff | %{ $i=0 } { $i = ($i + $b[$_] + $keySeed[$_]) -band 0xff; $b[$_],$b[$i] = $b[$i],$b[$_] }

    I am trying to convert to C# .net. I understand the code until this: $b[$_],$b[$i] = $b[$i],$b[$_]


  • #9664

    Bob McCoy

    This is how you "swap" two values.
    $b[$_] takes on the value of $b[$i]
    $b[$i] takes on the original value of $b[$_]

  • #9665


    The section you highlighted ($b[$_],$b[$i] = $b[$i],$b[$_]) will swap two values in array $b: the one at index $_ with the one at index $i.

    Also for reference if others are curious, this snippet comes from here: . Just because it's in a function to decrypt some data though doesn't mean it has to be quite so cryptic. 🙂

    Below is another version of the same script, expanded out a little. I haven't tried it but I believe it will do the same thing.

    for ($i = $j = 0; $i -lt 256; $i++) {
        # I didn't figure out what keySeed and b were for, so I can't really comment on this line
        $j += $b[$i] + $keySeed[$i]
        # Make sure $j is less than or equal to 255 (0xff) by stripping off the higher bits so that it continues to be a valid index into our array
        $j = $j -band 0xff
        # Swap $b[$i] with $b[$j]
        $b[$i],$b[$j] = $b[$j],$b[$i]
  • #9666

    Dave Wyatt

    Ah, the old "a cat walked across my keyboard" approach to software development. 😀

    Poshoholic's version is better, though in production code I wouldn't even bother with the comments. It's pretty self-documenting as is, now that you can actually read it. One statement per line, people! (Possible exceptions being very simple conditionals, like if (-not $success) { return } )

  • #9667


    For the record, the comments were added for the forum reader. 🙂

    I wouldn't put those comments in my scripts either, unless it was some particularly obscure piece of logic that I wanted to explain or some note that I wanted others to be aware of when reading the code. I do advocate for using regions in code though, breaking scripts down into business logic and identifying what each chunk does. That makes it easier for someone else to follow later.

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