posted August 23, 2000 04:44 AM            

For example, a byte's bits could be shifted, this takes to long for complete strings.
Shifting complete strings seems to be impossible.

Every text length can occur, from 1 byte to let's say 100bytes.

"ABCDEFGHIJKLMNO" should be made unreadable.
It's not important that it's simply to discover what 'encryption' was used.

How to shift a complete string in one command (and back)?

Thanks,

posted August 23, 2000 05:30 AM            

Use as: CALL asmROT13(txt)

'¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤
' asmROT13 encryption/decryption - no extended ANSI here (a-z, A-Z only).
' Repeat action to encrypt/decrypt
'¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤
SUB asmROT13(a$)
  LOCAL ln AS LONG
  ln = LEN(a$)             ' get string's len into ln
 
  ! cmp ln, 0              ; does the string have a length?
  ! je Exit13Loop          ; exit if zero
 
  ! mov eax, a$            ; eax = pointer to string handle
  ! mov eax, [eax]         ; eax = pointer to string data
 
  Bgn13Loop:
     ! mov edx, [eax]      ; move current char into edx
     ! cmp ln, 0           ; exit when ln = zero
     ! jne Continue13Loop
        ! jmp Exit13Loop   ; jump out on end of string
 
  Continue13Loop:
     ! cmp dl, 65          ; CASE 65 TO 90
     ! jb NoRot            ;    if dl < 65  then get next character
     ! cmp dl, 90
     ! jbe Rot13Upper      ;    if dl <= 90
     ! cmp dl, 97          ; CASE 97 TO 122
     ! jb NoRot            ;    if dl < 97  then next character
     ! cmp dl, 122
     ! jbe Rot13Lower      ;    if dl <= 122
     ! jmp NoRot           ; CASE ELSE - get next character
 
  Rot13Lower:
     ! add dl, 13          ; Rotate 13 steps forward
     ! cmp dl, 122
     ! ja AdjChar          ; if dl became > 122
     ! mov [eax], dl       ; else write changed char back into a$
     ! jmp NoRot
 
  Rot13Upper:
     ! add dl, 13          ; Rotate 13 steps forward
     ! cmp dl, 90
     ! ja AdjChar          ; if dl became > 90
     ! mov [eax], dl       ; else write changed char back into a$
     ! jmp NoRot
 
  AdjChar:
     ! sub dl, 26
     ! mov [eax], dl       ; else write changed char back into a$
     ! jmp NoRot
 
  NoRot:
     ! inc eax
     ! dec ln              ; decrease the ln (length) counter
     ! jmp bgn13Loop
 
  Exit13Loop:
 
END SUB

posted August 23, 2000 07:17 AM            

'==============================================================================
'Scramble  -  Very simple and fast scrambling of a string
'             For descrambling : call sub again
'             The MOD is added to prevent adjacent chars to be scrambled equal.
'------------------------------------------------------------------------------
Sub Scramble (pStr As String)
  Local lStrPtr As Byte Ptr, lCnt As Long
  lStrPtr = StrPtr (pStr)
  For lCnt = 0 To Len(pStr) -1
    @lStrPtr[lCnt] = @lStrPtr[lCnt] Xor (lCnt Mod 4) + 1
  Next
End Sub
Function PbMain() As Long
  Local pStr As String
  pStr = Command$
  Print "Before    :" ;pStr
  Scramble pStr
  Print "Scrambled :" ;pStr
  Scramble pStr
  Print "After     :" ;pStr
End Function

------------------
Peter.
peterL@pabx-group.com

posted August 23, 2000 11:57 AM            

I think the ASM procedure will do very well here..

    T! = Timer
    AA = repeat$( 100, "ABCDEFABCDEFABCDEFABCDEFABCDEF" )
    For a = 1 to 10000
        ASMROT13 AA
    Next a

Took about ~2.5 seconds on my P333.

My strings will allways around 10 to 20 char's.

Repeat (1) took : 4.84374999941792E-2 seconds

--------------------

The for next and XOR is known to me, i assumed it would be very slow.

posted August 23, 2000 12:42 PM            

Sub Scramble (pStr As String)  
  Local lStrPtr As Byte Ptr, lCnt As Long  
  lStrPtr = StrPtr (pStr)  
  For lCnt = 0 To Len(pStr) -1    
    @lStrPtr[lCnt] = @lStrPtr[lCnt] Xor (lCnt And 6) + 1  
  Next
End Sub

posted August 24, 2000 01:40 PM            

Used;
AA = repeat$( 100, "ABCDEFABCDEFABCDEFABCDEFABCDEF" )

Results;
ROT13 2.69968750000407
SCRAMBLE1 @C@G@CFEBEFEDGDCDGBAFABA@C@G@CFEBEFEDGDCDGBAFABA@C@G@CFEBEFE
SCRAMBLE2 ABCDEFABCDEFABCDEFABCDEFABCDEFABCDEFABCDEFABCDEFABCDEFABCDEF
SCRAMBLE 1.74656250000407

Thank you both, both procedures are preserved.

posted August 25, 2000 01:06 AM            

#compile exe
#dim all
#register none
  
declare function GetFile(byval File as string, Buffer as string) as long
declare function PutFile(byval File as string, Buffer as string) as long
  
function Scrample(File as string, NewFile as string) as long
  
	local pl as long pointer
	local Buffer as string
	local n as long, i as long
 
	if ucase$(File) = ucase$(NewFile) then exit function  ' security
	if GetFile(File, Buffer) = 0 then exit function	
 
	pl = strptr(Buffer)
	n = len(Buffer)/4
 
	for i = 1 to n
	    @pl = - @pl				
	    incr pl
	next i
  
	PutFile NewFile, Buffer
  
	function = 1
  
end function
   
'===============================
  
function pbmain
  
	local t as double
  
	t = timer
  
	Scrample "c:\pbdll60\winapi\win32api.inc", "c:\pbdll60\winapi\win32api.scp"
  
	msgbox format$(timer-t,"#.###"),,"Time consumed..."
  
end function
  
'===============================
  
function GetFile(byval File as string, Buffer as string) as long
  
    local hFile as long
  
    err = 0 : hFile = freefile
  
    open file for binary as hFile
    if err then exit function
    get$ hFile, lof(hFile), Buffer
    close hFile
  
    function = 1
  
end function
  
'===============================
  
function PutFile(byval File as string, Buffer as string) as long
  
    local hFile as long
  
    err = 0 : hFile = freefile
  
    open File for binary as hFile
    if err then exit function
    put$ hFile, Buffer
    close hFile
  
    function = 1
  
end function

------------------

posted August 25, 2000 09:51 AM            

SUB asmScramble (a$)
  LOCAL ln AS LONG
  ln = LEN(a$)             ' get string's len into ln
 
  ! cmp ln, 0              ; does the string have a length?
  ! je ExitScLoop          ; exit if zero
 
  ! mov eax, a$            ; eax = pointer to string handle
  ! mov eax, [eax]         ; eax = pointer to string data
 
  BgnScLoop:
     ! mov edx, [eax]      ; move current char into edx
     ! cmp ln, 0           ; exit when ln = zero
     ! jne ContinueScLoop
        ! jmp ExitScLoop   ; jump out on end of string
 
  ContinueScLoop:
     ! xor dl, 2           ; xor dl with 2 (or 1, 3, whatever..)
     ! mov [eax], dl       ; write changed char back into a$
     ! inc eax             ; get next character
     ! dec ln              ; decrease the ln (length) counter
     ! jmp bgnScLoop
 
  ExitScLoop:
END SUB

posted August 26, 2000 12:49 AM            

Note that it's indeed not a meant to encrypt data but simply make it unreadable.
A (dynamic) string up to 2mb must be converted but only at fileread and filewrite.
The filewrite/update could happen often in this app.
Therefore speed is important.

Thanks!

posted August 26, 2000 12:54 AM            

??