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Questions tagged [crc]

Cyclic redundancy check (CRC) is an error-detecting code commonly used in digital networks and storage devices to detect accidental changes to raw data.

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Reverse engineering key fob checksum

I am trying to reverse engineer the key fob of my Ford Fiesta 2014 but I am stuck at finding the used checksum algorithm. I've successfully demodulates the key fob signal (using on-off keying + ...
4
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1answer
94 views

Reverse-engineering a weird 24-bit possibly not CRC checksum

Yes, it's one of these! I have a 199mumble Brother integrated word processor, with a very weird non-PC floppy format. I've built a floppy controller and have successfully read the flux off the disk, ...
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68 views

EEPROM data bytes verification

I'm investigating a tool. I have an section of an eeprom memory dump that this tool uses, shown in the figure below. By my inquiries, the two bytes highlighted in red are based on the bytes ...
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1answer
74 views

How to calculate checksum from known data? [closed]

I'm trying to create the algoritm to produce the actual checksum byte (D0) in a vehicle 11-bit CAN bus message, where all values are known by scanning the current bus (which I'm trying to replicate ...
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70 views

Reverse engineer CRC16

I have not had success with reveng on figuring out how to calculate these CRCs. I successfully figured out another similar CRC from the same author so I'm pretty sure that the first four bytes as ...
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0answers
71 views

How determine correct checksum algorithm for this NFC Data?

I maae a dump of a Mifare Classic, NXP, tag. I can read some information without a problem, but if I write data in a block, I need to terminate the block with a checksum (CRC?, one byte). I tried ...
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2answers
150 views

Backtracing where a register gets initialized

I am currently trying to bypass a CRC check, that exists inline on many places in an application to check if memory pages in the .text section have been modified. Short explanation of the crc32 ...
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1answer
117 views

What Checksum/CRC algorithm in RF packet?

I am banging my head to figure out the checksum of a RF device, it seems to be a simple one but no luck so far... The first 3 bytes is the SyncWord then 9 bytes is the payload and the last byte ...
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1answer
277 views

CRC32 reverse engineer without knowing parameters, but knowing the input value

Dear members, I am trying to figure out the parameters of some hexadecimal CRC32 values I have. The values are: Value - input (before hashing) 55D3028A - J 73AF2D02 - O 6742BE71 - T I hope I can ...
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1answer
125 views

Reverse engineer CAN-Bus checksum

I am trying to figure out a checksum algorithm. D1 to D6 is data, D7 is a counter obviously and byte 8 must be a CRC, but I didnt have any idea on how to build it. Tried to check if it fits any ...
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68 views

Reverse engineer 6 bit checksum algorithm

I'm trying to understand the algorithm behind a 6 bit checksum calculated from a single byte value. I have collected several samples to study: 00 => 000000 01 => 110010 05 => 011110 0b => ...
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0answers
75 views

Reverse engineer checksum in AC Sharp IR packet

i use microcontroller and received ir frame of air conditioner SHARP. This Ir frame have 13 byte data (in decimal number, not hex) like below: 85 90 243 8 131 140 66 0 176 1 32 7 133 85 90 243 8 142 ...
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241 views

Trouble finding the right Checksum algorithm

After reading a lot of posts here and their solutions, Punching lines in CRC calculators for several days now. I can't seem to find on which Checksum this code is based. Background This is a data ...
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1answer
108 views

Checksum in CAN message

I'm trying to fake a CAN message, but I'm not able to understand how the 8-bit checksum is calculated. The checksum follows a pattern along with a 4-bit rolling counter. As long as the data of the ...
0
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1answer
141 views

Find out the checksum/crc/whatever is used in this file

There is a game called The Hunter, call of the Wild, in which you can spend skill points in skills. Whenever you spend 1 skill point there is an statistics file in which 2 changes are done: the crc/...
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123 views

Determining checksum parameters

I have some data from a game which appears to possibly contain a checksum or CRC implementation. The game has different arenas with a "share" link for each team in the arena (and there are 4 teams). ...
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0answers
77 views

Figuring out what CRC is being used

I'm trying to figure out how a CRC is being calculated for packets sent via USB. Supposedly they are CRC-32 and using the "Freescale Hardware 32bit CRC", but I haven't been able to reproduce the same ...
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93 views

Need help for an unknown 7-bit checksum

i am struggling since a long time to determine the checksum of the following sequences. I have two examples. Ex1: Have the same checksum and one have a payload incrementation by 0x0A at the same ...
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0answers
44 views

Unknown radio message checksum

I'm trying to reverse engineer the checksum of short radio messages for my thesis, but did not have any success. I tried to use reveng to find a CRC but it found no model. 4bc9 0009 33a25301 9c59 ...
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1answer
1k views

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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1answer
61 views

Do I have sufficient information to determine a checksum algorithm?

What I would like to know is whether or not I have sufficient information to determine a particular checksum algorithm being used. In my case I have a very large stream of data with many frames of ...
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1answer
234 views

De-ciphering help needed

As a total noob in this territory, I am trying to decipher a serial protocol between two devices A and B. It looks like the frames that are sent from B to A are somehow protected with a CRC or ...
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1answer
409 views

Daikin A/C 4bit CRC/Checksum

I am reverse engineering IR protocol of Daikin A/C. AC sends the whole current state of remote on each key press. Data sent is 8 byte long, last 4 bits seem to be the some kind of error checking. ...
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318 views

Finding out crc16 algorithm

Here are some example of data: 7B 5A C9 1F 1B 14 2B 28 39 D0 73 80 00 00 34 82 7B 5A CB 1F 1B 14 2B 28 39 D0 73 80 00 00 F6 CD 00 00 00 00 00 80 00 00 30 00 00 00 00 00 0E 59 00 00 00 00 00 C7 ...
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1answer
464 views

Reverse engineering serial communication CRC algorithm

I'm working on reverse engineering the serial communication protocol of an obsolete electronic control system, but I'm having trouble figuring out the CRC algorithm and polynomial. I have reverse ...
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0answers
278 views

Reverse Engineering a 16-bit CRC algortihm

I have a set of data bytes and their CRC values available to me. I want to know the CRC algorithm used by it. CRC is 16 bit long. firstly I tried to find out using CRC RevEng but that is showing "no ...
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0answers
576 views

Reverse Engineering 2 byte checksum on RFID card

I am currently researching my studentcard. Money is stored on this card. But the vending machine also checks a checksum on the card. I already did a lot of effort to find it but didn't succeed. The ...
3
votes
1answer
555 views

Reverse engineer checksum algorithm

I am trying to reverse-engineer the protocol used between my Air-conditioner and the wired control unit on my wall. (In order to have my home automation be able to monitor and control the A/C.) The ...
3
votes
2answers
3k views

how to bypass CRC checksum in firmware header

I have this Ubiquiti firmware and I successfully extract the firmware and rebuild it, I modify Squashfs filesystem and rebuild it using build-firmware.sh script from firmware-mod-kit, but the problem ...
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2answers
351 views

Backblaze 16-bit checksum (“bzsanity”)

I use Backblaze to back up my computer. You restore files from your backups by selecting files to restore, which are then packed into large zip files. Of course, it's fairly rare to be able to ...
1
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1answer
436 views

Figuring out the CRC part of a packet

Currently, I am trying to figure out the packet structure (for encryption) of an old MMO in order to create an emulator. Its official servers shut down 3 years ago and this version is over 11 years ...
7
votes
2answers
448 views

I really struggled to figure it out, now can anyone help me reverse engineer this checksum?

I have a device at work with no documentation about it's checksum calculation. I know that the last byte in each message is the checksum, and most of the messages to the device requires a correct ...
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0answers
104 views

figure out the CRC bytes [closed]

I am trying to write some code to figure out a CRC on the following byte sequence for an AI algorithm class project, and would like to seek some suggestions from this forum. For example, the ...
2
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1answer
124 views

Trying to figure out the CRC or checksum for a Fluke 233 wireless display multimeter

Downloaded and compiled CRC_reveng, but it's not finding any solutions. Maybe I'm over-thinking this? Not knowing too many other tricks that might be performed on the data or CRC before or after it's ...
2
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0answers
224 views

Puzzling 16bit checksum/CRC reverse engineering problem

We're having a hard time figuring out how the checksum/CRC is calculated for this serial communication protocol we're required to reverse engineer. This is a communication protocol used back in the ...
2
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0answers
442 views

find CRC algorithm, having some input and output data pairs

I'm trying to discover the algorithm of a lost software, there is an equipment that requiest some data, and validates the data using the "KEY", if you change any parameter of the data then you need a ...
1
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1answer
163 views

Reversing checksum calculation of embedded communication

I need to find relations last byte with others. Tried these solutions, but it didn't work. My tries: * When I write all datas as binary, 1's count not equal but last byte same for some datas. * When ...
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1answer
586 views

Reverse engineering of some checksum algorithm

I am trying to reverse some communication protocol between transmitter (controlled by PCF7952 chip) and receiver on 433 Mhz frequency I know how to prepare the "right" package which would be received ...
4
votes
1answer
897 views

Finding out checksum algorithm

I have old serial communication protocol and having some trouble finding out about checksum algorithm that has been used. I've tried several CRC16 algorithms and none of them seem to work. Tx message ...
3
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1answer
899 views

Reverse engineer 4-bit CRC in LG IR packet

I am reverse engineering IR protocol of LG air conditioner. AC generally send the whole current state of remote on each key press. Data sent is 28 bits long, last 4 bits seem to be the checksum. I ...
1
vote
2answers
1k views

Bypassing CRC check

I am trying to reverse a software which loads its own dll-file filled with protection stuff. I was able to successfuly locate the functions of interest. Then I patched the first function and test the ...
5
votes
3answers
949 views

Hash algorithm written in C decompiled with IDA

I have been working on rewriting a program, although it uses a hash to fingerprint the file, I have used IDA to find the function doing the hash and what it is doing to the file before it sends it to ...
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1answer
467 views

Reversing checksum algorithm

I am writing a program to control an old camera over serial. I have no access to the protocol or source code of the demonstration program that i have, but i can generate some correct checksums by ...
3
votes
0answers
1k views

Reverse Engineering a 8 bit CRC checksum

I am trying to create a communication interface using C Language to an Air conditioning system, after analyzing the data packets I have identified that the data packet is consist of an 8 bit CRC (I am ...
2
votes
2answers
405 views

Single step exception at the beginning of an unrelated function

I'm reversing an application and I know for a fact it employs CRC checks, so if I modify the code, for instance hooking something, it'll be detected. The application uses a DLL which I replaced with ...