Replace ARC4 with SHA2-512.
Change lock-structure encoding to use random ordering rather for obscurity.
Encrypt lock-structure with AES/256 instead of AES/128.
Change kkey derivation to be MD5 hash based.
Watch for malloc(M_NOWAIT) failures and ditch our cache when they happen.
Remove clause 3 of the license with NAI Labs consent.
Many thanks to "Lucky Green" <shamrock@cypherpunks.to> and "David
Wagner" <daw@cs.berkeley.edu>, for code reading, inputs and
suggestions.
This code has still not been stared at for 10 years by a gang of
hard-core cryptographers. Discretion advised.
NB: These changes result in the on-disk format changing: dump/restore needed.
Sponsored by: DARPA & NAI Labs.
