Why do the first two digits of the hash table not collide within CRC32?

quxinna

10/10/22, 7:29 AM

In this Python CRC32 table look-up method, the polynomial is 0x104c11db7.

I can understand that the generated table does not collide. After all, as long as the start and end of the polynomial binary are 1, then the hash obtained by different raw data is different.

But why do the first two bits of the hash table not collide?

The first four digits of the polynomial are 0x04c1, and the binary end of 04 is not 1. It stands to reason that the first two digits of the hash table should collide.

147

0 + 4

collision-resistance

crc

fgrieu

10/10/22, 9:27 AM

Note that "uses" is not the same as "is": the actual polynomial has degree 32. Independently "the generated table" depends heavily on the method used to compute the CRC, which is unclear in the question. I see no reason to remove the high-order bit. Additionally "the binary end of 04" is not exactly well-defined (for a start, which end?)

quxinna

11/7/22, 1:20 AM

the crc32 poly made from pi so no collide

D.W.

12/10/22, 5:32 PM

What do you mean by "generated table does not collide"? What is the definition of "generated table" in this context, and what is the definition of what it means for to collide or not collide? I suggest clarifying all of these points; and I suggest deleting the copy here and asking on CS.SE (but make sure you clarify all of these points before asking, otherwise I expect it might just be closed as unclear on CS.SE).

quxinna

12/12/22, 4:56 PM

like pi from japanese flag,generated table is no collide.

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: Why do the first two digits of the hash table not collide within CRC32?

TH: เหตุใดตัวเลขสองหลักแรกของตารางแฮชจึงไม่ชนกันภายใน CRC32

RO: De ce primele două cifre ale tabelului hash nu se ciocnesc în CRC32?

RU: Почему первые две цифры хэш-таблицы не сталкиваются в CRC32?

VI: Tại sao hai chữ số đầu tiên của bảng băm không xung đột trong CRC32?

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