Len() Function Returning 0 on a 32 length string?

Greywacke · October 28th, 2003, 02:13 PM

hi all, usually i dont get stuck while developing, but this time i am and i have no idea which way... why would Len(string) return 0 here even tho it is of length 32?

ok... this has been bugging me all day, let me paste the code i am using for a 128-bit encryption string generator, as well as the functions to encrypt and decrypt using one pass (1-bit encryption), as well as the master function which calls the individual functions and saves to db when encrypting, and deletes from db when decrypting.

Code:

'*******************************************************************
'**************** DECLARE: Generate 128-bit Key Function ***********
'*******************************************************************
Function GenKey()
    Dim i, cypher
    cypher = ""
    For i = 1 To 32 Step 1
        Randomize()
        cypher = cypher & Chr(Round(Rnd() * 254) + 1)
    Next
End Function

'*******************************************************************
'**************** DECLARE: Encryption Function *********************
'*******************************************************************
Function EnCrypt(strCryptThis, g_Key)
    Dim strChar, iKeyChar, iStringChar, i, n, iCryptChar, strEncrypted
    For i = 1 To Len(strCryptThis)
        If n > Len(g_Key) Then ' problem is here, Len(g_Key) keeps returning 0 even tho GenKey creates a 32 length key...
            n = 1
        Else
            n = n + 1
        End If
        iKeyChar = Asc(mid(g_Key,n,1))
        iStringChar = Asc(mid(strCryptThis,i,1))
        iCryptChar = iKeyChar Xor iStringChar
        strEncrypted =  strEncrypted & Chr(iCryptChar)
    Next
    EnCrypt = strEncrypted
End Function

'*******************************************************************
'**************** DECLARE: Decryption Function *********************
'*******************************************************************
Function DeCrypt(strEncrypted, g_Key)
    Dim strChar, iKeyChar, iStringChar, i, n, iDeCryptChar, strDecrypted
    For i = 1 To Len(strEncrypted)
        If n > Len(g_Key) Then ' I guess the problem would be here too
            n = 1
        Else
            n = n + 1
        End If
        iKeyChar = (Asc(mid(g_Key,n,1)))
        iStringChar = Asc(mid(strEncrypted,i,1))
        iDeCryptChar = iKeyChar Xor iStringChar
        strDecrypted =  strDecrypted & Chr(iDeCryptChar)
    Next
    DeCrypt = strDecrypted
End Function

'*******************************************************************
'**************** DECLARE: Cryptography Master Function ************
'*******************************************************************
Function Crypto(Input, Key)
    Dim i, n, cypher, gwConn, gwRS, crypt_id, encrypted, char, parsed, return
    return = "; "
    return = Split(return, "; ")
    Set gwConn = Application("gwConn")
    Set gwRS = Server.CreateObject("ADODB.Recordset")
    gwRS.Open "Cryptography",gwConn,adOpenDynamic,adLockOptimistic,adCmdTable
        If Key = "" Then    ' Encrypt
            cypher = GenKey()
            return(0) = EnCrypt(Input, cypher) & ""
            Do While InStr(return(0),"; ") > 0
                cypher = GenKey()
                return(0) = Encrypt(Input, cypher)
            Loop
            gwRS.AddNew
                gwRS("crypt_key") = cypher
            gwRS.Update
            crypt_id = gwRS("crypt_id")
            return(1) = crypt_id & ""
        Else                ' Decrypt
            gwRS.Find("crypt_id = " & Key)
            If Not gwRS.EOF Then
                gwRS.MoveFirst
                cypher = gwRS("crypt_key")
                return(0) = DeCrypt(Input, cypher)
                return(1) = (gwRS.Delete(adAffectCurrent))
            Else
                return(0) = Input & ""
                return(1) = "0"
            End If
        End If
        Crypto = join(return, "; ")
End Function

now, when callinng Crypto("test","") then the key is generated and saved to database successfully. After which Encrypt(Input, cypher) is called, where the n if statement is buggered due to Len(g_Key) returning 0... now why would this be anyone?

A swift response would be greatly appreciated and thanks in advance,
Pierre du Toit

Sincerely,
Pierre du Toit.

Imar · October 28th, 2003, 04:00 PM

I had just a quick look, but it looks like there's a problem in GenKey(). It creates the string cypher, but it never returns it.

Code:

Function GenKey()
    Dim i, cypher
    cypher = ""
    For i = 1 To 32 Step 1
        Randomize()
        cypher = cypher & Chr(Round(Rnd() * 254) + 1)
    Next
    GenKey = cypher
End Function

Could that be causing the problem?

HtH,

Imar

---------------------------------------
Imar Spaanjaars
Everyone is unique, except for me.

Greywacke · October 28th, 2003, 05:20 PM

oh thanks you are so sharp, or perhaps i am overworked o_O
wierd thing is, it writes the key to database successfully, and reads it successfully, just that when i pass it through g_Var when calling the Encrypt function it reads the length wrong... now i know why it might be...

thanks,
Pierre du Toit

Sincerely,
Pierre du Toit.

Imar · October 28th, 2003, 05:25 PM

Yeah, you may be overworked. Simple test: look in the mirror. Do you see square eyes?? ;)

Cheers,

Imar

---------------------------------------
Imar Spaanjaars
Everyone is unique, except for me.