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Questions tagged [assembly]

A family of very low-level programming languages, just above machine code, where each statement corresponds to a single machine code instruction.

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Reverse engineering with IDA

I'm trying to reverse engineer a program (with IDA Freeware) which receives serial data packet and manipulates it. I need to decode the received message but I can't find the function that does the ...
Jdx's user avatar
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struggle with Decrypt Byte Array with a key of unity game using il2cpp

So i'm trying to reverse an unity game using il2cpp to get the assets of it. After some reverse stuff i found that the asset's (especially here the png image) byte array get encrypted with a key and i ...
NoName's user avatar
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Offset addressing

I’m writing a C-SKY (CK803S) processor module for IDA Pro, and a question arose about offsets in transitions, small ones are fine, but long ones lead to nowhere, from the documentation: in code I ...
Andynvkz's user avatar
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X64DBG Conditional Breakpoint on Specific Opcode?

Is there any way to break on specific opcode in X64DBG? For example i want to break on start of a function which is 55 | push ebp 8BEC | mov ebp,esp can i set a breakpoint like opcode == 0x00EC8B55? ...
Behrooz Sohrabloo's user avatar
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Searching for a byte pattern and then hooking all instances of it using frida on iOS

I'm using a frida script to scan for a certain byte pattern when I launch an iOS app. I can log each offset and confirm these are correct by also printing out the instructions at those locations and ...
Jon's user avatar
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how to diassemble an .obj file

I'm new to programming and recently studying an ancient DOS assembly program written for 80186 and assembled with MASM. There are some .obj files that I want to open and take a look. I tried obj2asm....
skyforest's user avatar
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how to set a BP on button in SunAwtCanvas in x96dbg

I'm trying to debug a program in x96dbg that I think this is written in Matlab. There is no string related to buttons or something interesting. Then I go to Handles tab to find buttons and set break ...
owl's user avatar
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Address arithmetic in Ida Pro

Can someone tell more about address arithmetic in Ida? I were looking for assembly instructions and saw this LDR R0, =(byte_255914C - 0xC63D50) I understood right that in r0 will be an address which ...
switch_case's user avatar
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1 answer
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Mnemonic suffixes for x86-64 assembly for AT&T syntax

I'm trying to understand suffixes used for the AT&T syntax for the x64 assembly used for instruction mnemonics. For regular cases: 'b', // 8_bit 'w', // 16_bit 'l', // 32_bit 'q', /...
c00000fd's user avatar
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11 votes
2 answers
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Why did Intel chose 90h machine code for their NOP instruction instead of a 0?

Probably just a historical question, if anyone knows.
c00000fd's user avatar
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Is DOS Assembly Hexadecimal Different To Modern Hex Editor Hexadecimal?

I am trying to find the correct Data Segment, corresponding to a certain File in a 16bit DOS Game. The Assembly Instructions for the Decompiled .exe File in IDA Pro Version 5, I am looking at. I was ...
Edward Winch's user avatar
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DOS .exe File Decompiled in Cutter Program Showing Different Than In IDA Pro

I am having an issue when using the Cutter Reverse Engineering Program, Here is a Segment of Decompiled Assembly, in Cutter :- at 0000:4ed5 in the picture I posted the .string line of text is there, ...
Edward Winch's user avatar
2 votes
2 answers
116 views

Keystone rust bindings error when assembling "syscall; ret" shellcode

I'm working on a project related to Process Injection for learning Rust. I have to inject shellcode at some points and use the Keystone engine for assembling shellcode from source. I detected that the ...
MAD KHAJIIT's user avatar
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What guidelines and/or tools exist that facilitate the analysis of a program in assembly language for PIC-Microchip?

What tools exist that facilitate the interpretation of a program written in assembly language of a PIC-Microchip, appealing to the construction, for example, of a flowchart and then recoding it in ...
Dany's user avatar
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Cracking cryptographic function with radare2

I want to reverse engineer an android game, found a method public static byte[] MNNOPKMJMFP(byte[] AFFEPNLBIIC, byte[] OENOGNMAMPO, byte[] GLLEHJKGIBK) { } Names are obfuscated, i know that this is a ...
Gold Moon's user avatar
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Convert hex chars string to int

For example we have chars buffer with hex value: char * buff = {"e000"}; //this is our hex value in eax - input for Get_Val(). Then there is function Get_Val() - converts hex (string) to ...
black4's user avatar
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How to run exe program loaded into IDA Pro or Ghidra

I'm new to reverse engineering, just learning. After the exe program is loaded into IDA or Ghidra, how do I run the exe program that loaded into IDA/Ghidra? so I can interact with the exe program? and ...
valaGQ237's user avatar
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Assembler OR operation

Is this asm code: or unknown_byte_0004AAA7, 1 dseg05:000C7FDC unknown_byte_0004AAA7 db 0 equivalent to this C++ code below? bool unknown_byte_0004AAA7 = 0; unknown_byte_0004AAA7 = ...
black4's user avatar
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2 answers
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MS DOS development - Interrupt controller

cseg01:0005229A mov dx, 21h ; '!' cseg01:0005229E in al, dx ; Interrupt controller, 8259A. cseg01:0005229F or al, 1 cseg01:...
black4's user avatar
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1 answer
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What means this code?

cseg01:00020DB8 mov eax, offset screen_with_height cseg01:00045704 mov dword ptr [eax+0Ah], 0 cseg01:0004570B call sub_466F8 ; call some proc ...
black4's user avatar
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Reverse engineering JCALG/LZ?? compression

I think this is related to this this question, but the consts in the example code don't exist in mine, so maybe it's a different level of compression, but I am unsure. Can anyone provide me the right ...
Johnathon's user avatar
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138 views

from executable to assembly source code?

let's say i have an ".exe program" and i want to disassemble it and get "disassembled code" . my question is => can i maintain and organize that "disassembled code" ...
0x00001F's user avatar
2 votes
0 answers
141 views

Trying To Understand DOS Game Assembly Instructions

I am trying to understand assembly language instructions, for a DOS Game. I have looked at the following Link :- https://atrevida.comprenica.com/atrtut07.html reading about how VGA Graphics work in ...
Edward Winch's user avatar
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1 answer
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Assembly for malware analysis

I know we have some architectures for assembly language. But I wanna know this: I need learn x86 assembly ? , or arm assembly ? , or both ? , or others ?.. Please help me , what should I learn?
MHD's user avatar
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3 votes
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Is it legal in the US to reverse engineer a product and then share the CAD for free to whoever needs it?

First some background. I have this 3D printer that sucks, is pretty expensive, and unreliable. Whenever you need a spare part, the manufacturer sells you the entire kit! I needed a thermistor and they ...
Andres Cobos's user avatar
2 votes
0 answers
292 views

Help Needed With Finding Image Data In DOS Game File

I have been analysing, an File called FW190AS.PAC from a 16 Bit Game called Secret Weapons Of The Luftwaffe, in a Hex Editor, the Bytes are displayed in Little Endian format. My aim with this game, is ...
Edward Winch's user avatar
1 vote
1 answer
170 views

How can i remove dead code and opaque predicates?

I have the following problem on my agenda: There is an obfuscated .exe (this is a virus that I am investigating) in addition to having an MBA, etc. bullshit, he has Opaque predicates and dead code, I ...
Swoke's user avatar
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1 vote
0 answers
140 views

Reversing Assembly to C

I've read the open letter addressing students asking for help with their homework and I agree with it, therefore I will try to be less of a pain in the *** ;) I need to reverse the x86-64 (AT&T) ...
mikealexx's user avatar
2 votes
1 answer
100 views

other than x32dbg, is there a more friendly way to check functions, their args and their return values on runtime?

atm I'm using ida and x32dbg, when I find a function that interests me, I set a breakpoint on x32dbg, however, I'm not good enough at assembly to know everything from a function just from looking at ...
felipebubu's user avatar
3 votes
1 answer
260 views

How can you tell where an assembly function ends?

Finding the start of a function is sometimes obvious - for example if some part of the code has a call foo then foo must be a function. But what about finding the end of a function? I realize tools ...
Alex Shroyer's user avatar
1 vote
1 answer
236 views

Where is the XOR operation?

I am doing TryHackMe REloaded room, level 3. When I got stuck I followed this tutorial which mentions an XOR by 7 operation being performed on a string, however I cannot see it anywhere. Where is it ...
securityauditor's user avatar
4 votes
1 answer
944 views

Change string value when string is in a RAM address x64 c++ program

I'm new to reverse engineering. I'm simply trying to change the value of a string in x64dbg, of a program I make myself in VS (It's a c++ program, and is VERY simple; it just prints a string, and two ...
clouded.'s user avatar
4 votes
2 answers
1k views

How to bypass anti debugger? IDA Pro

Im new to reverse engineering and doing a crackme that requires me to make a keygen, yes i know making a keygen isn't a beginner task however im stuborn, i am trying to debug the program to understand ...
alias's user avatar
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3 votes
1 answer
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Reverse engineer a blackbox function operating on single or double precision floats for emulation

I own and run a NEC VectorEngine 10C which is a PCIe accelerator running a proprietary ISA which has many fun instructions among them is VRSQRT which computes an approximation of the inverse ...
worldsmithhelper's user avatar
2 votes
1 answer
70 views

why some functions push data before the prologue

i am a newbie in the world of RE , i start to explorer a main entry of a classic game from 90's and i start to see something confuse me as a newbie this main entry function start with pushing stuff to ...
0x00001F's user avatar
2 votes
1 answer
249 views

What are the prerequisite knowledge needed to start solving crackmes?

I started by reading a book on C language and then moved on to "Programming From Ground Up," which teaches basic programming in x86. School just ended, I'm working on cracking a game called ...
buffednerdkid's user avatar
2 votes
1 answer
156 views

Ghidra Shows Structure Strange

I am new to assembly. When I was disassembling some code, I encounter some strange instruction here. The instruction shows that (RBP + -0x40) is equal to local_48, however at the beginning of the code,...
Pytai's user avatar
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2 votes
1 answer
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Why did I have gotten only null bytes argv variable from angr?

I have made simple program to test the angr. My python code is here. import angr import claripy p=angr.Project('./test2') buf=claripy.BVS('buf', 8*10) initial_state=p.factory.entry_state(args=[&...
doldom's user avatar
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3 votes
4 answers
559 views

Reverse Engineering CTF help

I am having trouble figuring out this microcorruption challenge in the link below: https://microcorruption.com/debugger/Halifax Basically, the 0x7f interrupt has been disabled so I must reenable it ...
PurpleHacker's user avatar
2 votes
2 answers
276 views

Reverse engineer a calculation rule from a video game

I have recently bought an economic simulation video game, but neither the docs not the game UI describe how to estimate some costs; the user needs to actually invest and spend their money, then ...
devio's user avatar
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1 vote
1 answer
84 views

What was the original math operation after optimizing compiler?

I'm pretty sure that original code was much simpler: (((x + 16) >> 31) ^ abs(x + 16) & 3) + 4 * ((y + 16) % 4) - ((x + 16) >> 31) Looks like division with remainder... Any ideas what ...
mastermind's user avatar
3 votes
1 answer
199 views

What tricks can I use to manually decompile a set of instructions

ELF Binary takes user input and stores it in loc.buffer address 0x4020e8. Further, the registers going into the instruction set are eax ebx ecx edx esi length of user input (min length is 3) 0 ...
Mr. Kelsey's user avatar
2 votes
0 answers
285 views

ghidra assigns local variable to register

im reversing a android native library and im trying to understand how a token is generated the toke n is passed to a callback java method and i traced where the method is getting called from this is ...
ahmed mani's user avatar
3 votes
1 answer
371 views

Reading memory values in IDA

Want to get 32 bits from 0x8000 adress as 8 bytes MEM_EXT:00008000 db 54h MEM_EXT:00008001 db 53h, 57h, 20h MEM_EXT:00008004 dd 322E3256h, 31332030h, ...
dev's user avatar
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2 votes
1 answer
104 views

Overclock CPU in BIOS - ARM/C/C++/Py

new guy here. Working on Bi0S script, adding as many features as possible. It is possible to change fan speeds, advanced security, manipulate voltages, etc. How do you overclock the microprocessor ...
Calculus Lui YaleTessy's user avatar
2 votes
0 answers
196 views

How to decrypt data during runtime before executing and then encrypting it back

I was doing some research and came across the term protectors. From my understanding is they encrypt a file to be protected but run it without an issue. During its execution it is able to decrypt the ...
soqq's user avatar
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3 votes
1 answer
257 views

How to call Windows console in ASM and printf some values there?

Is there a working way to embed the windows console in disasm code? I tried AllocConsole with GetStdHandle or AttachConsole with PID of an existing console but it didn't work. I have tried printf ...
EvilCracker's user avatar
3 votes
0 answers
127 views

debug stripped file

I've system embedded mips big endian with gdb-server and I want debug stripped file of the target, I can run in target gdb server with stripped file (--attach PID), but when I try to connect with gdb-...
timb55's user avatar
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1 vote
1 answer
144 views

Unable to understand x86 instruction(s)

Recently I have been given a set of assembly instructions which I must learn to understand. I know an extremely basic level of x86 assembly but I'm starting to come across more nuances that are very ...
guest1's user avatar
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3 votes
0 answers
45 views

Data placement in memory

I am playing with buffer overflow attacks in C. I have the following code: int foo(void*, void*); // Calculates the distance (in bytes) between two addresses in memory int main(int argc, char**...
Stone Paul's user avatar

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