"Signature verification failed" when trying to install non-official Cyanogenmod 10 ROM for Sanei N10 Android tablet
Well, at last I could finally solve the problem thanks to chris5s from the xda-developers.com forum.
These are the steps that worked for me:

Download the latest ClockWorkMod for Allwinner A10 tablets from here:
http://forum.xda-developers.com/showthread.php?t=1802268

Put all three files in the ZIP inside the root of a MicroSD card and insert it in the tablet

Check from the Terminal app inside the tablet to see if the MicroSD card is mounted in /sdcard (just type &quot;ls /sdcard&quot;).

If the &quot;ls&quot; command doesn't show anything (that's what happened in my case), then you must modify the &quot;install-recovery.sh&quot; file and replace all instances of &quot;/sdcard&quot; with &quot;/mnt/extsd&quot;.

With the proper &quot;install-recovery.sh&quot; file, run the commands specified in the above xda link (in my case the card is in &quot;/mnt/extsd&quot; instead of &quot;/mnt/sdcard&quot; as the original example shows):



su
cd /mnt/extsd
sh install-recovery.sh
sh reboot-recovery.sh

The tablet will then reboot to CWM recovery. Then follow the regular steps to install Cyanogenmod (wipe plus install ROM + GApps + Compatibility). This time the Recovery menu won't care about the files being unsigned and will install them right away!
I hope this helps somebody else!