One major update for Kindle 2.5 firmware is (although not stated in Amazon's release notes) the support for Kindle Programs - called Kindlets.
The main support jar file is a bootlet called 'Kindlet-1.0.jar', which is in every 2.5 bin file.
After spent some little time with JD and the file, it seems:
1. Kindlet files are actually jar files ended with '.azw2'
2. Reside in each jar file, there're
META-INF/Kindlet.data - signature (stores developer's license, security... etc.)
META-INF/MANIFEST.MF - Java ordinary info file.
Something like xxxxxxxxxxx-DIGEST-MANIFEST
Base64-Decode(xxxxxxxxxxx) = MD5(Device-id)
RSA key is in /opt/amazon/security. There's an access permission file, too.
Everything seems pretty straightforward and it shouldn't take much time to get KDK working.
The KDK document could be found at:
http://kdk-javadocs.s3.amazonaws.com...w-summary.html