Ecryptfs directory on USB Drive

I have an encrypted directory on my USB drive that I encrypted using ecryptfs on an old computer. I know the passphrase I used at the time to encrypt this directory but I cant seem to decrypt it on a new machine with the same passphrase. Is is possible to do this on a new machine? Or the old machine contains some key unique to the passphrase that cannot be recreated on my new machine? Thanks for any input. Tony