footer.img checksum

[Google Code Exporter]

Hi All, 

I would like to ask how to calcuate the checksum of Zyxel NDMS V2.0 firmware.

I try to unpack and pack the firmware but something wrong by use the web 
interface to upgrade new-firmware.bin.

[root@localhost image_parts]# hexdump -C 
/opt/zyxel/KEENETIC-V2.00[BFW.3]B11.bin |tail

005536e0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00560000  5a 4e 42 47 15 42 00 00  5a 79 58 45 4c 20 63 75  |ZNBG.B..ZyXEL cu|
00560010  73 74 6f 6d 00 00 00 00  00 00 00 00 00 00 00 00  |stom............|
00560020  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00560030  00 00 00 00 00 00 00 00  a1 b3 ea ec              |............|
0056003c


I have download the firmware KEENETIC-V2.00[BFW.3]B11.bin from Zyxel.ru

I guess last 4 bytes are checksum bytes and a1 b3 ea ec is actual checksum 
value. 

I try to use cksum it said that checksum value is not correct. 

Anyone knows how the checksum calculation logic for this kind (Zyxel NDMS V2.0) 
of firmware ?

Many thanks for your help.

Original issue reported on code.google.com by [e-mail] on 25 Jun 2013 at 12:37

[Google Code Exporter]

For now, I've set up a forum here: 
https://bitsum.com/forum/index.php/board,12.0.html .. create a topic if you 
wish, hope for someone to discover it :o. Chances are, you'll be left to this 
duty yourself though. Most of the time they use some common algorithm like 
CRC32, a simple addition checksum, etc... Dump and disassemble the boot loader 
or portions of the vendor firmware if it can't be guessed.

Original comment by [e-mail] on 25 Jun 2013 at 1:28

• Changed state: WontFix
• Added labels: Type-Enhancement
• Removed labels: Type-Defect