crc

CRC Reverse Engineer (Checksum from Machine / PC)

由 喜欢而已 提交于 2020-01-14 05:29:07
问题 I'm currently looking for on how to determine the CRC produced from the machine to PC (and vice-versa). The devices are communicating using serial communication or RS232 cable. I do only have data to be able for us to create a program to be used for both devices. The data given was from my boss and the program was corrupted. So we are trying for it to work out. I hope everyone can help. Thanks :) 回答1: The sequence to use for the CRC calculation in your protocol is the ASCII string starting

Find used CRC-16 algorithm

由 会有一股神秘感。 提交于 2020-01-06 05:21:44
问题 I'm struggling to reverse engineer a section of data associated with a CRC-16 checksum. I know the polynom used to calculate the original checksums is 0x8408 but nothing else, I don't know initial value (if any), final XOR value (if any), if the input or the result is reflected... It seems like there is a known CRC-16 generator using thing polynom, CRC-16-CCITT but despite everything I've tried I just can't understand how the original checksum is being calculated. Here is the data I've got

Binary division issue: bad examples on internet or what am I missing?

由 寵の児 提交于 2020-01-04 01:57:16
问题 I would like to create a 16 bit CRC. Actually I am entirely ready whit that, so a couple of hours ago I tested it, but did not work properly. But what I discovered is that the examples on the internet might be wrong when its about binary division. I link just two of them (from a lot!): http://www.ross.net/crc/download/crc_v3.txt , http://en.wikipedia.org/wiki/Cyclic_redundancy_check So what I am doing with the binary division is that I use BigIntegers. Just like this: BigInteger divisor = new

How do you compute the XOR Remainder used in CRC?

由 半世苍凉 提交于 2020-01-04 01:15:29
问题 I'm trying to remember how the math is worked out to compute the remainder of an XOR algorithm in Cyclical Redundancy Checks to verify the remainder bits of a network message. I shouldn't have tossed that text book. This is easily done in code, but how is it worked out by hand? I know it looks something like a standard division algorithm, but I can't remember where to go from there to get the remainder. ___________ 1010 | 101101000 Note: I did google it, but wasn't able to find a place where

How do you compute the XOR Remainder used in CRC?

由 青春壹個敷衍的年華 提交于 2020-01-04 01:15:07
问题 I'm trying to remember how the math is worked out to compute the remainder of an XOR algorithm in Cyclical Redundancy Checks to verify the remainder bits of a network message. I shouldn't have tossed that text book. This is easily done in code, but how is it worked out by hand? I know it looks something like a standard division algorithm, but I can't remember where to go from there to get the remainder. ___________ 1010 | 101101000 Note: I did google it, but wasn't able to find a place where

Java CRC32: not the same as CRC from C#

由 余生长醉 提交于 2020-01-02 10:21:06
问题 I have to compare files with java with a CRC32 code provided by a C# script. When I calculate the CRC32 with java.util.zip.CRC32 the result is completely different ... My guess is that the polynom = 0x2033 of the C# script is not the same as used in zip.CRC32. Is it possible to set the polynom ? Or any ideas of a java-class for calculating a CRC32 where you can define your own polynom? UPDATE: problem is not the polymnom. This is the same between C# and Java This is my code, maybe something

Java CRC32: not the same as CRC from C#

由 别说谁变了你拦得住时间么 提交于 2020-01-02 10:17:10
问题 I have to compare files with java with a CRC32 code provided by a C# script. When I calculate the CRC32 with java.util.zip.CRC32 the result is completely different ... My guess is that the polynom = 0x2033 of the C# script is not the same as used in zip.CRC32. Is it possible to set the polynom ? Or any ideas of a java-class for calculating a CRC32 where you can define your own polynom? UPDATE: problem is not the polymnom. This is the same between C# and Java This is my code, maybe something

Find out CRC or CHECKSUM of RS232 data

由 六眼飞鱼酱① 提交于 2020-01-01 11:46:10
问题 I need to communicate with a RS232 device, I have no specs or information available. I send a 16 byte command and get a 16 byte result back. The last byte looks like some kind of crc or checksum, I have tried using this http://miscel.dk/MiscEl/miscelCRCandChecksum.html with no luck. Anyone can reverse engineer the crc/checksum algorithm? here is some data captured with an RS-232 monitor program: 01 80 42 00 00 00 00 00 00 00 00 00 00 00 01 B3 01 80 42 00 00 00 00 00 00 00 00 00 00 00 02 51 01

CCITT CRC 16 Bit Start Value 0xffff

由 纵然是瞬间 提交于 2020-01-01 05:38:07
问题 I need to calculate a CCITT 16 bit checksum value for data passed as a parameter together with the length. If I fill my array TempStr with the test data "123456789", use the polynomial 0x8408 with the length excluding the null termination character, I get the result string 6E90(Hex). Together with the null termination char I get 907A. When I swap out the polynomial to 0x1201 then I get results 29E2(Hex) and EFE8(Hex) with and without termination character. My questions are: Do I need to

单片机 压缩 CRC

由 孤街浪徒 提交于 2020-01-01 05:07:51
常用的2个压缩，rar zip，但是MCU好像都支持的不好，打开WINRAR.EXE文件，还可以看到原文件CRC32值， 以后验证文件的CRC校验的话，用RAR来看，还真是个简单的办法。 但是单片机要怎么压缩呢，quicklz fastlz minilzo, 感觉都不是很知名，想找个在PC上运行的客户端都找不到， RTT下这个打包器，支持quicklz \ fastlz\ gzip三种压缩算法，RTT是在单片机上运行的，所以它选择的这3种算法前2种都比较容易实现，RTT的软件仓库中也月相关的源源代码。 但GZIP没有找到源代码，百度了一下，发现GZIP可能有些难度，RTT仓库里没有这种压缩的源程序，据说GZIP实现要耗费的资源多些，尤其是RAM，，这个我没研究过，我的目的不是要实现多么高的压缩率，所以暂时挑过。 我要实现的是bin文件的完整性，及合适的压缩率，及容易实现的方法。 https://mp.weixin.qq.com/s?__biz=MzA3MTk0OTk2NQ==&mid=2653844594&idx=1&sn=9e1fddc92055c27a1e8956d39e470052&chksm=84ff1f90b388968606d08373ef394d454e702a1eb84aa1e5adef2c64dbc541eedf6e6d6d72b5&scene=0&xtrack
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