command line I use to extract the hash, note that everything is done as root,
you need an iPod with (only) OF installed, in DFU mode:

root@gloria:~/Rockbox/extract_sha# python ./ipoddfu.py ./s5l8702-sramloader.dfu
Connected to S5L8702 Bootrom DFU mode, USB version 00.01
Upload: .................................................................. done

root@gloria:~/Rockbox/extract_sha# python ./ibugger.py upload 22008000 ./spireader.classics.bin
Connected to iBugger Loader v0.1.1 on iPod Classic, USB version 00.01
Uploading ./spireader.classics.bin to 0x22008000.... done

root@gloria:~/Rockbox/extract_sha# python ./ibugger.py execute 22008000 22010000
Connected to iBugger Loader v0.1.1 on iPod Classic, USB version 00.01
Passing control to code at 0x22008000... done

root@gloria:~/Rockbox/extract_sha# python ./ibugger.py download 22020000 20000 NOR.decrypted.bin
Connected to iBugger Loader v0.1.1 on iPod Classic, USB version 00.01
Downloading 0x20000 bytes from 0x22020000 to NOR.decrypted.bin..... done

root@gloria:~/Rockbox/extract_sha# hexdump NOR.decrypted.bin -s 16 -n 16 -e '"\\\x" /1 "%02X"'; echo
\x06\x85\xDF\x28\xE4\xD7\xF4\x82\xC0\x73\xB0\x53\x26\xFC\xB0\xFE