Tarsnap cache policy

[Gabriel Kerneis <gabriel@kerneis.info>]

Dear all,

how secret and secure should I keep my tarsnap cache?  More specifically:
- Is it okay to keep a backup of it on a non-secure location (without my tarsnap
  keyfile of course), to avoid the cost of --fsck before recovering my data?
  What kind and amount of information does it leak to a potential attacker?
- If someone manages to temper with the backup of my cache (without access to my
  keyfile), can anything worse happen than tarnsnap shouting at me that I should
  run --fsck?

Many thanks,
-- 
Gabriel