#13 CRC64 - hash for file incorrect

[Sergey Petrovich]

Win7_x64
Installed "jacksum-1.7.0-windows-explorer-integration-1.4.0.zip (February 28, 2016)"
I choose "crc64", Jacksum counts it:
"
ae55c63a38c15908 135560 D:\temp\ExperienceIndexOK_x64_p.exe

---

Created with Jacksum 1.7.0, algorithm=crc64
"
However, HashTab shows a different hash sum:
60A132B7AC12C2FA

WHAT'S WRONG? JACKSUM OR HASHtAB?

[Johann N. Löfflmann]

Ticket moved from /p/jacksum/feature-requests/19/

[Johann N. Löfflmann]

Hi Sergey,

thank you for your support request. Let's see ... Jacksum implements the crc64 that is defined in ISO 3309. See also Jacksum's manpage by entering:

jacksum -h crc64
    crc64         algorithm:   CRC-64
...
comment:     this algorithm is described in the
                               ISO 3309 standard.
                               (generator poly is x^64 + x^4 + x^3 + x + 1)

Since Jacksum also supports the Rocksoft Model CRC Algorith model, you can verify it by passing the explicit parameters as defined in ISO 3309 for that model. Example:

jacksum -a crc:64,1B,0,true,true,0 -X 1-9.txt
46A5A9388A5BEFFE        9       1-9.txt

I didn't find any documentation about the crc64 implementation of Hashtab and since it is not open source, and we cannot look into their source code. However, with the help of Jacksum I found out that they don't implement the crc64 as defined in ISO 3309. Actually they implement the crc64 which is known as crc64/WE. See also https://reveng.sourceforge.io/crc-catalogue/all.htm#crc.cat.crc-64-we

With Jacksum you can calculate also the crc64/WE by entering

jacksum -a crc:64,42f0e1eba9ea3693,ffffffffffffffff,false,false,ffffffffffffffff -X 1-9.txt
62EC59E3F1A4F00A        9       1-9.txt

which matches the check value also on reeng's page - who IMHO did a great job to gather his page. he value also matches the one that Hashtab calculates.

So both Hashtab and Jacksum are right, both calculate a crc64, but just with different crc polynomials and different crc parameters. BTW, Jacksum actually supports ALL crc variations, also the CRC64/WE as decribed above.

Kind regards,
Johann