The Cyclic Redundancy Check is a non-cryptographic error-detecting code. While CRCs occasionally appear as parts of a cryptosystem, questions purely about CRCs and other non-cryptographic checksums are off-topic here, and should be asked on Stack Overflow instead.

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Why is CRC said to be linear?

It is commonly understood that CRC satisfies the linear identity with respect to the $\oplus$ (XOR) operation: $\operatorname{CRC}(a) \oplus \operatorname{CRC}(b) = \operatorname{CRC}(a \oplus b)$ ...
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4answers
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What alphanumeric string length can be used to guarantee no hash collisions from CRC-64? [closed]

If I'm hashing alphanumeric strings (chars in the set 0-9, a-...
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2answers
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Brute forcing CRC-32

I'm working on a cryptosystem which uses IDEA. The designer made the mistake of including a CRC-32B hash of the password unencrypted in the header, so that the system can quickly reject bad passwords....
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3answers
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Understanding CRC [closed]

There are zillions of articles describing CRC. What can I read to (more deeply) understand what's really going on? Both from an algebraic perspective and a bit-manipulation perspective, I'd like to ...
5
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1answer
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How do I calculate CRC32 mathematically? [closed]

I want to calcuate the CRC32 algorithm using polynomials directly but I don't know how. I found the generating polynomial listed here https://en.wikipedia.org/wiki/Cyclic_redundancy_check. This ...
4
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4answers
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Increased CRC collision probability when adding bits to input message [closed]

The Scenario I have a message string I need to transport over a wireless network that may be unreliable. This message string is about 100 bits long, and is packaged with an 8-bit CRC. When the ...
4
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1answer
708 views

Is there a generic attack on encrypted CRC32 when used as a MAC?

I am examining a protocol that uses CRC32 as a MAC (see note 1) the weaknesses of this method but I would nevertheless like to see if it is just weak or actually relatively easily to break. The ...
3
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1answer
451 views

Can i modify data “protected” by a CRC16?

There are 100 bytes with a CRC16. However I only know the first 50. I want to change byte 5 from a known value X to another value Y, and fix up the CRC16 to be valid - without knowing bytes 50-100. ...
3
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2answers
375 views

Achieving 32-bit verification code with 16-bit CRC? [closed]

I am programming an embedded chip that has a hardware 16-bit CRC module. I have to protect some data bytes $d_0,d_1,...,d_{n-1}$ against corruption caused by sudden loss of power; a 32-bit CRC would ...
2
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1answer
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Finding CRC collisions for specific divisor [closed]

My current textbook (Information Security: Principles and Practice by Mark Stamp) discusses how to determine the CRC of data via long-division, using XOR instead of subtraction to determine the ...
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2answers
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Is Dropbox's hashing method cryptographically secure?

Dropbox uses CRC32 and md5 to create a checksum of each 4 mb "block" as part of the their compression/file system. I suspect that Dropbox uses an additional cryptographic hash to check if there's a ...
2
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2answers
186 views

Reversing N CRC steps [closed]

Starting from a known CRC result(let's call it CRC1), could I undo the CRC operations for last N bits, so I could obtain the CRC (let's call it CRC2) of the message sequence without the last N bits. $...
1
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2answers
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CRC32 vs. low 32 bits of cryptographic hash

I was having a discussion with a colleague yesterday whose education and experience exceeded mine. He said something yesterday that sounded incorrect to me intuitively, but I don't have the knowledge ...
1
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1answer
553 views

Suggestion : CRC vs SHA1

I need some suggestions about the use of the CRC in my application. I need to be sure about the BIOS run by the CPU. I have a FPGA between the BIOS flash and the CPU that sniff every read performed by ...
0
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2answers
1k views

Modifying a [CRC32] checksum protected file [closed]

I dont want to ask for help without showing how far I came by myself, so this is what I have so far: The file of interest is an encrypted/obfuscated .bin script, which cotains information on certain ...
0
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1answer
78 views

Authenticating small packets

I intend to authenticate small packets of data, between 16 and 256 bytes each. For some of them encryption will also be required. This will be used on small micro controllers, with RAM sizes ranging ...