I recently installed Ubuntu 13.10 on an SSD drive using the "encrypt the new Ubuntu installation for security" option. I wanted to enable TRIM, so was following the guide provided here.
One step says to add the discard
option to /etc/crypttab
. However, the crypttab man page somewhat vaguely states:
WARNING: Assess the specific security risks carefully before enabling
this option. For example, allowing discards on encrypted devices may
lead to the leak of information about the ciphertext device
(filesystem type, used space etc.) if the discarded blocks can be
located easily on the device later.
What exactly are the security risks of enabling TRIM on an encrypted SSD partion/drive?