; standard and basic xor encryption
BASE = 2525h

_xor:
mov edx,BASE
xor edx,25h ; just any number to encrypt
; result is 2500h
; now to retrieve the encrypted number back
; xor base by result
xor edx,BASE ; remember edx have 2500h from last xor operation
; now edx have the original number which is 25h    

; another use of xor i dont know what to call it but it can be useful to store qword values and write them later to memory location
LOW_QWORD = 0ABCDEF10h
HIGH_QWORD = 23456789h
; FULL_QWORD = 23456789ABCDEF10h

_label:
mov edx,LOW_QWORD ; store the low 32bit value
xor edx,HIGH_QWORD ; we need the result
; result is 88888899h ; the KEY
mov eax,88888899h ; store it in eax for later use

; now to get the HIGH_QWORD, xor KEY by LOW_QWORD
xor edx,LOW_QWORD ; remember edx have 88888899h and being xored by ABCDEF10 which is low qword
; the result is 23456789h = high qword

; to get the LOW_QWORD xor KEY by the HIGH_QWORD
xor edx,eax ; = eax is our key 88888899h, edx = high qword
; result is 0ABCDEF10 = low qword    

xor al,1 ; Flips the first bit    

It can be used to flip bits...

mov eax,1011b
; eax now is 1011b
xor eax,1000b
; eax now is 0011b
xor eax,1000b
; eax now is 1011b
xor eax,0001b
; eax now is 1010b
ret
    

Can we get another unique xor usage/trick by the next person? We want this thread to grow larger

It can be used to flip bits
Can we get another unique xor usage/trick by the next person?

; Swap two registers

xor eax, ebx     
xor ebx, eax     
xor eax, ebx  
    

; Equality comparison

mov eax, [value1]
mov ebx, [value2]
xor eax, ebx
jz equal_label  
    

; Encrypt / Decrypt (XOR cipher)

mov al, 'A'          ; character to be encrypted
mov bl, 0x5A         ; encryption key
xor al, bl           ; encryption step (AL now holds encrypted value)
; ...
; ...
xor al, bl           ; decryption step (AL returns to original 'A')
    

; ASCII character case manipulation

and al, 0DFh     ; convert to uppercase
or  al, 20h      ; convert to lowercase 
xor al, 20h      ; toggle case 
    

; XOR Bitwise NOT trick

not eax     ; same as xor eax, -1
    

MacroZ wrote:

It can be used to flip bits
Can we get another unique xor usage/trick by the next person?

Some vintage XOR wizardry found in the legendary FASM forum over the years. 😎

Code:

; Swap two registers

xor eax, ebx     
xor ebx, eax     
xor eax, ebx  
    

Code:

; Equality comparison

mov eax, [value1]
mov ebx, [value2]
xor eax, ebx
jz equal_label  
    

Code:

; Encrypt / Decrypt (XOR cipher)

mov al, 'A'          ; character to be encrypted
mov bl, 0x5A         ; encryption key
xor al, bl           ; encryption step (AL now holds encrypted value)
; ...
; ...
xor al, bl           ; decryption step (AL returns to original 'A')
    

Code:

; ASCII character case manipulation

and al, 0DFh     ; convert to uppercase
or  al, 20h      ; convert to lowercase 
xor al, 20h      ; toggle case 
    

Code:

; XOR Bitwise NOT trick

not eax     ; same as xor eax, -1
    

Performs a bitwise exclusive OR (XOR) operation on the destination (first) and source (second) operands and stores the result in the destination operand location.

; we have 2 values a and b, simple example
mov eax, [a]
xor eax, [b]
mov [var], eax    

mov eax, [var]
xor eax, [a]
; eax = b

mov eax, [var]
xor eax, [b]
; eax = a    

But it will be a superior single linked list, since you can go either forward or backward while using the same amount of memory per node (only 1 pointer).

And if the list elements are aligned and of even (or other power-of-two) length then the lower bits can also be elided since they are always zero.

; rax - previous element pointer
; rbx - current element pointer
    xor ax, [rbx] ; compute next element pointer
    xchg rax, rbx ; walk

;-----------------------------------------------------

; rax - previous element pointer
; rbx - current element pointer
    movzx rdx, word [rbx] ; get pointer
    imul rdx, rdx, alignment ; ...
    xor rax, rdx ; compute next element pointer
    xchg rax, rbx ; walk    

These cases are wonderful from the artistic point of view.
But, in real code --- would you just not use XCHG or CMP?

; if a <> 0 then a = b else a = c

cmp eax, 1
sbb eax, eax
xor ecx, ebx
and eax, ecx
xor eax, ebx
    

Just found another one buried in my notes.

Code:

; if a <> 0 then a = b else a = c

cmp eax, 1
sbb eax, eax
xor ecx, ebx
and eax, ecx
xor eax, ebx    

cmp eax, 1
cmovnz eax, ebx
cmovz eax, ecx    

1) Ruins the value of C

cmp eax, 1
cmovnz eax, ebx
cmovz eax, ecx

; if a <> 0 then a = b else a = c

cmp eax, 1
sbb eax, eax
xor ecx, ebx
and eax, ecx
xor eax, ebx
xor ecx, ebx ; just not the full code    

Code:

; if a <> 0 then a = b else a = c

cmp eax, 1
sbb eax, eax
xor ecx, ebx
and eax, ecx
xor eax, ebx
xor ecx, ebx ; just not the full code