I tested ecryptfs-setup-swap in Debian sid and, guess what: it worked!
When running that command, swapon gave an error but, after reboot, the encrypted swap was working.
So, the bug is in Ubuntu!
In Debian, /etc/crypttab contains /dev/sdxX instead of the UUID.
And funny thing: ecryptfs-utils version in Debian sid is 103-3, while in Ubuntu Trusty it's 104-0ubuntu1 (the package is not being imported from Debian?).
I tested ecryptfs-setup-swap in Debian sid and, guess what: it worked!
When running that command, swapon gave an error but, after reboot, the encrypted swap was working.
So, the bug is in Ubuntu!
In Debian, /etc/crypttab contains /dev/sdxX instead of the UUID.
And funny thing: ecryptfs-utils version in Debian sid is 103-3, while in Ubuntu Trusty it's 104-0ubuntu1 (the package is not being imported from Debian?).