crc | 易学教程

CRC32 Collision

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问题 I am trying to find a collision between two messages that will lead to the same CRC hash. Considering I am using CRC32, is there any way I can shorten the list of possible messages I have to try when doing a brute force attack? Any links to websites with hints on this will be helpful. I already have a brute force algorithm that will do this but it simply increment integers and sees if it will match other hashes. 回答1: It depends entirely on what you mean by "message". If you can append four

24-ESP8266 SDK开发基础入门篇--Android TCP客户端.控制 Wi-Fi输出PWM的占空比,调节LED亮度

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https://www.cnblogs.com/yangfengwu/p/11204436.html 刚才有人说需要点鸡汤.... 我想想哈;我还没问关于哪方面的鸡汤呢!!! 增加一个SeekBar 一个 Switch 协议: 00 01 70 C0 控制LED点亮 70 C0 为CRC高位和低位 00 00 B0 01 控制LED熄灭 B0 01 为CRC高位和低位 PWM数据 01固定后四位为PWM数据(高位在前低位在后,按照IEEE754规约) 最后两位为CRC16校验位,高位在前,低位在后列如:举几个例子,PWM数据是0-1000 01 03 E8 00 00 B0 99 注:03 E8 00 00 为1000 B0 99 为CRC检验数据高位在前,低位在后 01 01 F4 00 00 CE 59 500 01 64 00 00 00 F0 06 100 01 00 00 00 00 C0 19 0 大家可以用此工具生成CRC,用于验证咱写的CRC程序. 注:01 03 E8 00 00 B0 99 其实可以省掉两个0 01 03 E8 B0 99 但是我所用过的大部分的仪器仪表都是4位的所以咱就还是用四位现在看Android 端怎么写现在呢给大家计算CRC的程序,判断数据CRC是不是正确的程序 /** * CRC检验值 * @param modbusdata *

Reversing CRC32

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问题 I\'m looking for a way to reverse a CRC32 checksum. There are solutions around, but they are either badly written, extremely technical and/or in Assembly. Assembly is (currently) beyond my ken, so I\'m hoping someone can piece together an implementation in a higher level language. Ruby is ideal, but I can parse PHP, Python, C, Java, etc. Any takers? 回答1: A CRC32 is only reversible if the original string is 4 bytes or less. 回答2: Read the document called "Reversing CRC Theory and Practice".

Probability of collision when using a 32 bit hash

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问题 I have a 10 character string key field in a database. I\'ve used CRC32 to hash this field but I\'m worry about duplicates. Could somebody show me the probability of collision in this situation? p.s. my string field is unique in the database. If the number of string fields is 1 million, what is probability of collision ? 回答1: Duplicate of Expected collisions for perfect 32bit crc The answer referenced this article: http://arstechnica.com/civis/viewtopic.php?f=20&t=149670 Found the image below

When is CRC more appropriate to use than MD5/SHA1?

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问题 When is it appropriate to use CRC for error detection versus more modern hashing functions such as MD5 or SHA1? Is the former easier to implement on embedded hardware? 回答1: CRC works fine for detecting random errors in data that might occur, for example, from network interference, line noise, distortion, etc. CRC is computationally much less complex than MD5 or SHA1. Using a hash function like MD5 is probably overkill for random error detection. However, using CRC for any kind of security