_RC4Crypt UDF

[a6m1n0]

What is posted I ported from ASP VBScript to AutoIt3 as the syntax was the most similar. Tested with ASP VBScript, PHP with mcrypt, and Flash AsCrypt Library.

Please note that I use the _StringToHex and _HexToString UDF's to handle the case of non-printable characters. Also note that the same function is used to decrypt as well as encrypt.

expandcollapse popup

Func _RC4Crypt($plaintxt, $psw)
    Local $sbox[256]
    Local $key[256]
    Local $temp, $a, $k, $cipherby, $cipher, $tempSwap, $aa, $bb, $intLength
    Local $i = 0
    Local $j = 0
    $intLength = StringLen($psw)
    For $aa = 0 To 255
        $key[$aa] = Asc(StringMid($psw, Mod($aa,$intLength)+1, 1))
        $sbox[$aa] = $aa
    Next
    $bb = 0
    For $aa = 0 To 255
        $bb = Mod(($bb + $sbox[$aa] + $key[$aa]),  256)
        $tempSwap = $sbox[$aa]
        $sbox[$aa] = $sbox[$bb]
        $sbox[$bb] = $tempSwap
    Next
    For $a = 1 To StringLen($plaintxt)
        $i = Mod(($i + 1), 256)
        $j = Mod(($j + $sbox[$i]), 256)
        $temp = $sbox[$i]
        $sbox[$i] = $sbox[$j]
        $sbox[$j] = $temp
        $k = $sbox[Mod(($sbox[$i] + $sbox[$j]), 256)]
        $cipherby = BitXOR(Asc(StringMid($plaintxt, $a, 1)), $k)
        $cipher &= Chr($cipherby)
    Next
    Return $cipher
EndFunc; _RC4CryptoÝ÷ ØLZ^RÆ y«­¢+Ø¥¹±Õ±ÐíÍÑÉ¥¹¹ÔÌÐì(¥¹±Õ±ÐíIйÔÌÐì)¥´ÀÌØíµåÁÍÌ°ÀÌØíµåÑáаÀÌØíµå¹ÑáаÀÌØíµå¡á¹ÑáаÀÌØíµåÑáаÀÌØíµ½áÑáÐ(ÀÌØíµåÁÍÌôÅÕ½ÐìÄÈÌÐÔØÅÕ½Ðì(ÀÌØíµåÑáÐôÅÕ½ÐíQ¡¥Ì¥ÌͽµÑáÐѼ¹ÉåÁСɸÅÕ½Ðì(ÀÌØíµå¹ÑáÐô}MÑÉ¥¹Q½!à¡}IÑ
ÉåÁÐ ÀÌØíµåÑáаÀÌØíµåÁÍ̤¤(ÀÌØíµåÑáÐô}IÑ
ÉåÁС}!áQ½MÑÉ¥¹ ÀÌØíµå¹ÑáФ°ÀÌØíµåÁÍ̤(ÀÌØíµ½áÑáÐôÅÕ½ÐìÅÕ½Ðì(ÀÌØíµ½áÑáеÀìôÅÕ½ÐíAÍÍݽÉèÅÕ½ÐìµÀí
I1µÀìÀÌØíµåÁÍ̵Àí
I1µÀí
I1(ÀÌØíµ½áÑáеÀìôÅÕ½ÐíQáÐMÑÉ¥¹èÅÕ½ÐìµÀí
I1µÀìÀÌØíµåÑáеÀí
I1µÀí
I1(ÀÌØíµ½áÑáеÀìôÅÕ½Ðí!`ÌäíIйÉåÁÑèÅÕ½ÐìµÀí
I1µÀìÀÌØíµå¹ÑáеÀí
I1µÀí
I1(ÀÌØíµ½áÑáеÀìôÅÕ½Ðí!`ÌäíIÐÉåÁÑÅÕ½ÐìµÀí
I1µÀìÀÌØíµåÑáеÀí
I1µÀí
I1)5Í  ½à À°ÅÕ½ÐìÅÕ½Ðì°ÀÌØíµ½áÑáаÈÀ¤

I hope someone finds this useful.

Edited September 24, 2006 by a6m1n0

[Valik]

As far as I know, the version I posted for you the other day is correct. I don't see any appreciable difference in your version which would make it any more "right" than what I've posted. Some of the others were broken, yes, but nobody has ever shown mine to be broken.

In short, before you say all the others are wrong, please prove they are wrong, mine in particular.

[a6m1n0]

My apologies if I gave you the impression your code was wrong or broken, but I never stated that the your RC4 UDF or the others available here were 'wrong' or 'broken'. I stated they were incompatible with the implementations that I use in other programming languages.

I am no expert in cryptography just a user of the methods. However, the scope of my current project require using AutoIt to interface with my existing code base, some of which was acquired from the links in my first post.

Otherwise your RC4 implementation as well as the others offered here seem to work fine within AutoIt3 itself.

EDIT: I planned to post a 'thank you' directly after posting this with a thorough explanation but was called away from my computer before I had a chance. So, Thank you for digging up your old code and posting it -- if I weren't in need of interfacing with RC4 implementations I already have then it would have been fine I am certain.

Edited September 24, 2006 by a6m1n0

[Valik]

My code produces the same output as your code does with your example.

[RazerM]

I also have an RC4 Encryption UDF, check my signature. It works perfectly as far as i know.

[a6m1n0]

Well I'll be damned. When you're wrong you are just wrong, and wrong I was, lol. I ran a test (attached) and it seems that I didn't do enough testing.

But I have a good excuse. My first attempt using RC4 in AutoIt was _StingEncrypt. My second attempt was using RazerM's _StringEncryptRC4/_StringDecryptRC4 BUT I did not realize that the HEX conversion was called from within that UDF, and I was using it like _StringToHexEx(_StringEncryptRC4($mytext,$mypass)) and hence the assumed incompatibility. My third attempt was using Valik's script, and to be honest I can't remember what I was doing with it, but whatever it was it was not producing compatible results -- by this time it was early morning and I was to tired to worry about it deciding that I just needed to port it from something I knew worked.

So, I stand corrected and apologies all around -- your script Valik, as well as your script RazerM, both work fine. I can at least say I learned a great deal about porting ASP VBScript to AutoIt3. The only bonus my UDF seems to have is that it is defined as one function instead of two, otherwise it produces the same results.

RC4Test.au3

Edited September 24, 2006 by a6m1n0