Another caveat:
Try not to put your cron scripts in a user's home directory.
I just had a problem where everything seemed good, but just after a while - probably a few hours after I log out, the cron jobs stops working, and these messages appear in the log:
Signature not found in user keyringPerhaps try the interactive 'ecryptfs-mount-private'My home directory, at least as far as I know, is not encrypted. But still, moving those scripts outside of the home dir solved the problem.