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Questions tagged [xor]

Exclusive or (xor) is a logical operation that outputs true only when both inputs differ (one is true, the other is false).

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Attempting to auto reverse XOR

Does anyone know of any helpful tools or a way to automate decryption of XOR in IDA? I know that they have a built in function to do some bare XOR encryption but this one seems a bit more ...
2 votes
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61 views

Figuring out the algorithm for an NFC reader, which displays values increased by 1.52 times

I have two NFC readers, reader A reads card ID numbers according to the ISO standard and the algorithm is publicly available. Reader B is from a Canon printer. The card numbers read by reader B are 1....
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Trying to reverse encypter to decrytper in C. Can't figure out what I'm missing

Goal: Trying to reverse encrypter to decrypter that successfully decrypts. This is the pseudo-code of the disassembled encrypting program. There are no function calls, and I've been able to somewhat ...
3 votes
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318 views

How would I crack a software that has Xor encryption

So, before you shout at me to go on google I would just like to say I am new to reverse Engineering. Like I have been doing it for a hour. So, I was doing a bunch of crackmes.one using the search all ...
1 vote
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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 ...
2 votes
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How would I decode this XOR Cipher

I have been given a XOR Cipher which is a bunch of hexidecimal looking charcters. This cipher is: fa ce fd d3 fa df ed d3 fa ce d3 d3 fa de df d3 fa de df d3 fa de f9 d3 fa ce f9 d3 fa de f1 d3 ...
3 votes
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592 views

How to decrypt cocos2d luac type?

I am new with IDA and cocos2d. Since I have learned how to decrypt cocos2d Lua file, I found xxtea tool with Sign and Key and how to find Sign header in some game in Lua file. But that method does not ...
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2 answers
2k views

Decode xor data in IDA

I have code that looks like this: byte_100031BA4 = v41; byte_100031BA5 ^= 0x3Eu; byte_100031BA6 ^= 0x47u; LOBYTE(a1) = -9; byte_100031BA7 ^= 0xF7u; byte_100031BA8 ^= 0xA9u; byte_100031BA9 ^= 0xE8u; ...
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RE on firmware images that seem to use weak encryption/obfuscation. Robot vacuum

I have been playing with some robot vacuums that utilize very basic navigation, and I am wanting to play around with my own provisioning along with adding a Rpi to augment features. These vacuums are ...
2 votes
1 answer
534 views

Help regarding XOR game decryption algorithm

I'm currently trying to reverse engineer the decryption algorithm for an old online game, using a chat message packet, as it contains text which is easily recognizable. I used a packet sniffer to get ...
5 votes
1 answer
1k views

Stuck on XOR decryption of firmware

TL;DR I have an encrypted image and the cleartext version, and I'm almost certain it's an XOR cipher, but I can't figure out how to decrypt it. I have a few clues listed below. Ciphertext excerpt (...
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236 views

xor eax,3 why does the input change the way it does?

I am new to reverse engineering and I am trying to figure out exactly what xor is doing in this little program. I know if I put any number other than 0 I get a xor eax,3 so if I put in 1 I get 2 if I ...
4 votes
1 answer
352 views

Tektronix firmware XOR puzzle

As a means of learning about packing firmware and for fun I am trying to unpack the latest firmware for an entry level Tektronix Function generator firmware attached I have read the forum and ...
1 vote
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115 views

File Decryption Problems

over the past year, I provided an English patch to a community of thousands of players of a game I love and which is not available in English (just Chinese and Korean). Sadly, besides me, other ...
0 votes
1 answer
268 views

Does someone recognize this "lookup table"? (used for xor encryption)

This table is part of the packet encryption of an old game for which I am developing a server. The crypto algorithm doesn't just xor the password with the message. It uses a multiple of the ascii ...
4 votes
2 answers
2k views

Identify password generation algorithm

I'm a newbie who just started own way through reverse engineering so I apologize if my question is not appropriate. Currently I'm going through different Crackme puzzles and now I'm stuck. I've spend ...
2 votes
1 answer
2k views

Help me understand how to actually break an XOR/Vigenère cipher

My friend's server was recently hacked and I'm trying to decipher the malicious files I found in hopes of understanding the hack better. I can tell that they're using an XOR/Vigenère cipher and I've ...
4 votes
2 answers
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Inverse And operation

I'm trying to write a keygen to a crack me that I'm learning from and I got stuck. What happens there is pretty simple: Let's say that I entered the password: "12121212" XOR DWORD PTR DS:[ECX+EAX],...
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Simple 8bit checksum

I'm trying to find out, how the checksumming in an RS485 communication works. The data is packetized and seems to be using 8bit checksums. One packet per line, the last byte that isn't 0x00 seems to ...
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2 answers
2k views

How XOR works in my code?

I have this assembly code: XOR DWORD PTR DS:[ECX+EAX],1234567 And what it does is just xoring the first 4 bytes of EAX with 1234567. So if the first 4 bytes are : 31 32 31 32 After xor they become:...
2 votes
1 answer
3k views

Help me reverse this

It's been 4 nights I'm struggling decompiling this one. It's an Android native library that I ran through IDA to get C code. Java signature : byte[] resultArray = new byte[-2 + dataArray.length]; ...
2 votes
1 answer
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XOR Encryption (XPost from Crypto)

Dear ReverseEngineering@SE, Background information: I have reason to believe that an old game I've played is still using their XOR encryption for nearly all in/out-going packets. I also believe that ...
2 votes
1 answer
1k views

What kind of compression/obfuscation algorithm is this?

I have a couple of streams that look pretty odd within a DICOM file. In a few words, DICOM is very close to what binary XML would look like. Almost all of the information from those DICOM files are ...
0 votes
1 answer
11k views

How to decrypt data in binary file by XOR operator using a given key at specific offset? [closed]

I've a binary data files which are encrypted by a simple XOR cipher using a given key at offset +0x88 (which is 0x80 long), then the data (+0x108) is compressed by lzo1x. What would be the most ...
3 votes
1 answer
12k views

How does scanf interact with my code in assembly

I have recently started getting into assembly for the purpose of reverse engineering. I started small with understanding basic datatypes, but I want to move on to more complex datatypes and functions. ...
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How to find out what encryption/encoding has been used

So my uni just had some on break into the email server and send out a load of emails with a suspicious looking executable. I'm on Linux so I downloaded the file and ran the Strings command and saw a ...
1 vote
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411 views

Getting Encryption Method When I Know Encrypted File Name & Original File Name

I'm busy trying to decrypt some game data. All the encrypted filenames are hexadecimal strings with the same length e.g. 1790C6E445C7E38EFCD5B3042F9B4443. I've figured out that a few of the files ...
1 vote
1 answer
981 views

How to efficiently debug Loops with OllyDbg/Immunity?

I'm currently reversing a function which looks like the following .text:0040383F 8D 04 BF lea eax, [edi+edi*4] .text:00403842 6A 14 push 20 .text:00403844 C1 E0 03 ...
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XORing command-line for encryption?

I have the following lines push [ebp+dwBytes] push 8 ; dwFlags call ds:GetProcessHeap push eax ; hHeap call ds:HeapAlloc push [ebp:lpCmdLine] ; char * mov ...