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#1 2015-11-04 04:37:54

hkplus
Contributor
Registered: 2015-01-07
Posts: 127

HID 36 Bit Napco/Alarm Lock format Parity Calculation

Hi Guys,

I have two cards, that are for Alarm lock, HID compatible 36 bit.  Trying to figure out the parity calculation.  Bit structure looking like the following:

Card ID = 1127069 (26 bits), FC = 19 (8 bits), 2 party bits, one upper and one lower
P IIIIIIIIIIIIIIIIIIIIIIII FFFFFFFF P
0 00000100010011001010011101 00010011 1

Card ID = 546084, FC 19
1 00000010000101010100100100 00010011 0

Does not make much sense to me...usually you split the Weigand data down the middle and compute either an odd or even parity on the upper and lower end.  I can't see to do that consistently with these two cards and I wonder if anyone has an idea.

Thanks in advance,

HKPLUS

Last edited by hkplus (2015-11-04 04:40:09)

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#2 2015-11-04 04:42:54

marshmellow
Contributor
From: US
Registered: 2013-06-10
Posts: 2,302

Re: HID 36 Bit Napco/Alarm Lock format Parity Calculation

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#3 2015-11-04 04:48:45

hkplus
Contributor
Registered: 2015-01-07
Posts: 127

Re: HID 36 Bit Napco/Alarm Lock format Parity Calculation

Thanks marshmellow.  I saw that already and unfortunately it does not provide the parity calculation info...

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#4 2015-11-04 04:50:39

marshmellow
Contributor
From: US
Registered: 2013-06-10
Posts: 2,302

Re: HID 36 Bit Napco/Alarm Lock format Parity Calculation

it does - in the image file

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#5 2015-11-04 04:51:01

hkplus
Contributor
Registered: 2015-01-07
Posts: 127

Re: HID 36 Bit Napco/Alarm Lock format Parity Calculation

Maybe it does actually and I don't understand it as of yet...sinking in...

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#6 2015-11-04 04:56:00

hkplus
Contributor
Registered: 2015-01-07
Posts: 127

Re: HID 36 Bit Napco/Alarm Lock format Parity Calculation

Do you understand what they are talking about...offset and 35 bits?  Looks like 1 parity is the opposite of the other...all bits are computed for both even and odd parities?

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#7 2015-11-04 04:57:42

marshmellow
Contributor
From: US
Registered: 2013-06-10
Posts: 2,302

Re: HID 36 Bit Napco/Alarm Lock format Parity Calculation

it works doesn't it?

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#8 2015-11-04 04:58:23

hkplus
Contributor
Registered: 2015-01-07
Posts: 127

Re: HID 36 Bit Napco/Alarm Lock format Parity Calculation

Only with these two samples, the only two that I have...

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#9 2015-11-04 04:59:15

marshmellow
Contributor
From: US
Registered: 2013-06-10
Posts: 2,302

Re: HID 36 Bit Napco/Alarm Lock format Parity Calculation

the image file is from the security company itself.  i see no reason to doubt it.

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#10 2015-11-04 05:01:59

marshmellow
Contributor
From: US
Registered: 2013-06-10
Posts: 2,302

Re: HID 36 Bit Napco/Alarm Lock format Parity Calculation

to check yourself in your understanding of the image file they have an image file for standard 26 bit to compare to.

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#11 2015-11-04 05:02:38

hkplus
Contributor
Registered: 2015-01-07
Posts: 127

Re: HID 36 Bit Napco/Alarm Lock format Parity Calculation

Don't doubt it, just didn't understand it.  The offset stuff was throwing me off, but that just means that you just look at the data portion to compute the lower even parity.

Do you have any knowledge on the Keri K card format?  Looks like an Indala type and really scrambled...?

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#12 2015-11-04 05:04:53

hkplus
Contributor
Registered: 2015-01-07
Posts: 127

Re: HID 36 Bit Napco/Alarm Lock format Parity Calculation

Also looking at the Keyscan 36 bit format for kicks...got it figured out but I think my parity calculation is wrong...

Last edited by hkplus (2015-11-04 05:05:01)

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#13 2015-11-04 05:14:18

marshmellow
Contributor
From: US
Registered: 2013-06-10
Posts: 2,302

Re: HID 36 Bit Napco/Alarm Lock format Parity Calculation

as for keri, i think i only had the 26W format started.   i believe it is an old format though. but it is very much like indala.

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#14 2015-11-04 05:20:11

marshmellow
Contributor
From: US
Registered: 2013-06-10
Posts: 2,302

Re: HID 36 Bit Napco/Alarm Lock format Parity Calculation

hmmm what keyscan?  i don't see one on their site..  what am i missing now?

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#15 2015-11-04 05:26:21

marshmellow
Contributor
From: US
Registered: 2013-06-10
Posts: 2,302

Re: HID 36 Bit Napco/Alarm Lock format Parity Calculation

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#16 2015-11-05 05:55:50

hkplus
Contributor
Registered: 2015-01-07
Posts: 127

Re: HID 36 Bit Napco/Alarm Lock format Parity Calculation

Thanks for the help.  Let me see if I can get back to you, in order to fill in unknowns in the Keri format.

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