Encryption the old-fashioned way: ccrypt
For encrypting small text files, I use ccrypt, a nifty utility which uses Rijndael-256 (aka AES-256) and just does it work as it is supposed to do.
$ ccrypt -e my_file
Asks you for a password twice, encrypts my_file (naming the new encrypted file my_file.cpt) and overwrites the old my_file (however, notice that journaling filesystems like ext3 or non-block filesystems might keep some or all the data elsewhere).
$ ccrypt -d my_file.cpt
Asks for the password and, if correct, decrypts my_file.cpt as my_file (and deletes my_file.cpt).
A more useful option for small text files is:
$ ccrypt -c my_file.cpt
which, after asking for the password, sends the ...