I wanted to make a keyfile for added security in TrueCrypt. You may use any filetype you’d like, but to create a new layer of security, I made a pass-phrase and encrypted this into a file using bcrypt. The same approach may be used to encrypt any file you want, to share with a friend or send by e-mail. Just as long as the decrypter knows the password, you are good to go.
Bcrypt uses the Blowfish algorithm, and is available in the official Debian repo.
$ echo “pass-phrase” > keyfile
$ bcrypt keyfile
You will be asked to provide a password, and the encrypted file is created.
$ bcrypt keyfile.bfe
Provide the password used for encryption, and the file is converted back to the original ‘keyfile’.