Wireshark mailing list archives
Re: Calculating CRC5 of 11-bit data
From: Tomasz Moń <desowin () gmail com>
Date: Sun, 21 Jul 2019 07:37:48 +0200
On Sat, Jul 20, 2019 at 8:42 PM John Sullivan <jsethdev () kanargh org uk> wrote:
One of the properties of LFSRs is that a 1 bit in the input toggles a completely predictable set of register bits *at any point in the future*. This isn't often useful for most CRC caculations on variable sized input, as the cost of working out which those bits are vastly outweighs most other methods.
This is very interesting property! Thanks John!
But here we have a fixed 11 bit input
I am sorry, but I have completely missed out there there are two places where CRC5 is calculated: * In SETUP, OUT, IN, PING and SOF the CRC5 is calculated on 11 bits * In SPLIT the CRC5 is calculated on 19 bits
static const char ival = 0x08;
This looks like swapped bit order to me. The CRC5 value for 11-bits of 0 is 0x02. ___________________________________________________________________________ Sent via: Wireshark-dev mailing list <wireshark-dev () wireshark org> Archives: https://www.wireshark.org/lists/wireshark-dev Unsubscribe: https://www.wireshark.org/mailman/options/wireshark-dev mailto:wireshark-dev-request () wireshark org?subject=unsubscribe
Current thread:
- Calculating CRC5 of 11-bit data Tomasz Moń (Jul 19)
- Re: Calculating CRC5 of 11-bit data Ross Jacobs (Jul 19)
- Re: Calculating CRC5 of 11-bit data Tomasz Moń (Jul 19)
- Re: Calculating CRC5 of 11-bit data Guy Harris (Jul 19)
- Re: Calculating CRC5 of 11-bit data Tomasz Moń (Jul 19)
- Re: Calculating CRC5 of 11-bit data Tomasz Moń (Jul 20)
- Re: Calculating CRC5 of 11-bit data John Sullivan (Jul 20)
- Re: Calculating CRC5 of 11-bit data Tomasz Moń (Jul 20)
- Re: Calculating CRC5 of 11-bit data John Sullivan (Jul 21)
- Re: Calculating CRC5 of 11-bit data Tomasz Moń (Jul 25)
- Re: Calculating CRC5 of 11-bit data Tomasz Moń (Jul 19)
- Re: Calculating CRC5 of 11-bit data Ross Jacobs (Jul 19)