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jochenvnltn



Joined: 15 Jul 2011
Posts: 83
jochenvnltn
Hello everyone,

I found an XOR encryption proc, but i can't get it to work..
Can someone please show me what is causing the error ?

Im still learning...

format pe GUI 4.0


include 'win32ax.inc'

section '.data' data readable writeable

Text db 'Unencrypted',0
Size = $ - Text
Key db '1234',0

section '.code' code readable executable

start:
invoke encryptXOR, Text,Size,Key
invoke MessageBoxA,0,Text,'test',0

exit:
invoke ExitProcess,0
.end start

;xor encryption
proc encryptXOR stdcall data_ptr:DWORD, data_size:DWORD, key_ptr:DWORD

local key_counter:DWORD

pushad
mov [key_counter],0
mov edi,[data_ptr]
encxor_loop:
;get key, data and xor it
mov eax,[key_ptr]
add eax,[key_counter]
mov bl,byte [eax]
mov bh,byte [edi]
xor bh,bl
mov [edi],bh
;increase counter variables
mov eax,[key_counter]
inc eax
cmp eax,KEY_SIZE
jne encxor_noreset_keycounter
sub eax,eax
encxor_noreset_keycounter:
mov [key_counter],eax
;increase data ptr
mov eax,[data_size]
dec eax
jz encxor_exit
mov [data_size],eax
inc edi
jmp encxor_loop

encxor_exit:
popad
ret
endp
Post 27 Jul 2012, 01:34
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hopcode



Joined: 04 Mar 2008
Posts: 563
Location: Germany
hopcode
jochenvnltn wrote:
...what is causing the error ?
- invoke macro is generally for API like MessageBoxA.
- KEY_SIZE is not defined. presumably being 4 ?
Code:
  KEY_SIZE = 4
  stdcall encryptXOR, Text,Size,Key   <---- 
  invoke MessageBoxA,0,Text,'test',0
; ...
  cmp eax,KEY_SIZE  <--- 
; ...     
Cheers,

_________________
⠓⠕⠏⠉⠕⠙⠑
Post 27 Jul 2012, 01:56
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jochenvnltn



Joined: 15 Jul 2011
Posts: 83
jochenvnltn
hopcode wrote:
jochenvnltn wrote:
...what is causing the error ?
- invoke macro is generally for API like MessageBoxA.
- KEY_SIZE is not defined. presumably being 4 ?
Code:
  KEY_SIZE = 4
  stdcall encryptXOR, Text,Size,Key   <---- 
  invoke MessageBoxA,0,Text,'test',0
; ...
  cmp eax,KEY_SIZE  <--- 
; ...     
Cheers,


Work's now ! thanks Wink
Post 27 Jul 2012, 03:13
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