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.

Filter by
Sorted by
Tagged with
10
votes
0answers
1k 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 ...
7
votes
2answers
473 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 ...
6
votes
2answers
511 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 ...
6
votes
1answer
411 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, ...
5
votes
3answers
1k 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 ...
5
votes
1answer
673 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
1k 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 ...
4
votes
1answer
1k 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 ...
4
votes
2answers
348 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 ...
4
votes
0answers
318 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 ...
3
votes
2answers
145 views

Reverse engineering the IBM BSC (Bisync) protocol

I am trying to connect to an old piece of communication controller which use the IBM BSC synchronous protocol but I have problems to get the CRC right. Background The protocol itself is described ...
3
votes
1answer
247 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 ...
3
votes
1answer
679 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 ...
3
votes
1answer
786 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
0answers
365 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 ...
3
votes
0answers
2k 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
1answer
162 views

Identification of RF hash algorithm

I have an unbranded LED lamp with a remote control. I would like to reverse the protocol of the remote but unfortunately I can't create my own packages. The frequency of the remote transceiver is 2....
2
votes
1answer
196 views

Reverse engineering CRC and rolling code

Using an SDR I read out the transmitted message of a key fob for my old car. The car is a 98 Mercury Grand Marquis. It's quite old so I dought it's very sophisticated. 55549d1748c2aa11d2044f ...
2
votes
1answer
58 views

Behringer CRC8 algorithm

The Behringer DEQ2496 audio device can have commands sent to it via MIDI, however they require a valid CRC code in order for the device to accept them. I have thus far been unable to work out how the ...
2
votes
2answers
319 views

Reverse engineering a checksum algorithm

I am attempting to implement an editor for a discontinued hardware drum synthesizer which uses undocumented system exclusive MIDI messages for communication. I've figured out the patch format, but I ...
2
votes
2answers
5k 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 ...
2
votes
1answer
234 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
votes
1answer
73 views

crc - reverse engineering GAL16V8 checksum method

While working with the GAL16V8 (an old programmable logic device), I found out that the Programmers Electronic Signature (PES) of each GAL has a checksum byte I've read the PES of some GALs but was ...
2
votes
2answers
544 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 ...
2
votes
0answers
76 views

Which value is used for verifiying Zip password?

I am studying the way that can be used to check if a given password for an encrypted zip file is correct or not. I see this link: How does a zip file detect a correct password? In the answer of this ...
2
votes
0answers
552 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 "...
2
votes
0answers
271 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
votes
0answers
559 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
vote
2answers
2k 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 ...
1
vote
1answer
366 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 ...
1
vote
1answer
316 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 ...
1
vote
1answer
717 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 ...
1
vote
1answer
89 views

Finding the CRC / Checksum in a control unit message

I have a list of messages from a control unit that i'm trying to replicate. I have the body of the message correct, however, i can't seem to work out what CRC or checksum is being utilised. 00 FE 0F ...
1
vote
1answer
94 views

Checksum field within IR protocol

I am trying to reverse engineer the IR protocol for my air conditioner (GREE - remote control YAP1FF) and with the data I found online and a lot of testing with a IR receiver there is only one field I ...
1
vote
1answer
413 views

CRC8 reverse engineering

I am creating a CAN Bus on-bench testing solution which replicates the entire vehicle to test a single module. I have a number of messages that require a CRC byte in order to be valid. The messages ...
1
vote
1answer
283 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 ...
1
vote
1answer
595 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 ...
1
vote
0answers
55 views

CRC16 Reverse in C166 Arch

Before that I asked about piece of code that used in this algorithm (here). Now I have a bit problem with the rest of algorithm. So I have to describe this with detail. Sorry if i vast your time for ...
1
vote
0answers
57 views

Bin patching Arm7tdmi CRC32?

Ok so I am total noob here. I wanted to play with the bin from an instrument cluster I work on a lot. I was able to pull the bin off the MCU with a J-link. If I erase the chip and flash it with a bin ...
1
vote
0answers
47 views

CRC Checksum? (Used in can open system)

We want to put our own messages on a can-open system. (So we can program our own functions to the system). We can put our message on the system, but when we do this, the safety relay stops the system. ...
1
vote
0answers
175 views

Checksum Calculation

Can anyone manage to work out how the checksum is calculated in the following data? Have tried reverse engineering crc and xor and anything else I can think of. There is a definite pattern there, but ...
1
vote
0answers
244 views

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 + ...
1
vote
0answers
204 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 ...
1
vote
0answers
431 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 ...
1
vote
0answers
160 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 ...
1
vote
0answers
225 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 ...
1
vote
0answers
141 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 ...
0
votes
1answer
1k 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 ...
0
votes
2answers
246 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
votes
1answer
317 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/...