Encryption

CRC
Cyclical redundancy checks are numeric checksums used to validate the contents of a firmware file. They are not cryptographically secure, but are used to detect errors in transfer and storage.

Encryption
Symmetrical Key Encryption is used to protect the firmware from people like us.

D7000 Family
TODO: Extract info from source pages, eg. http://simeonpilgrim.com/blog/2011/11/07/how-to-decode-the-nikon-dslr-firmware/