Comment gpg (Score 4, Informative) 210
gpg, when you can.
To encrypt, but have the encrypted output be encoded as text (so can be put copy/paste into an email)
gpg --symmetric --cipher-algo AES256 --armor example.txt
(gpg will then ask for a passphrase, make it long, as random as possible, upper and lower case, a punctuation, and a number)
TO DECRYPT
gpg example.txt.gpg
Steve Gibson has a very cool Internet resource for helping people learn about password strength: https://www.grc.com/haystack.h...
Per the haystack page:
Example passphrase = search space size
64characters of hex = 4.13 x 10^99
63characters of hex, plus adding a punctuation symbol = 4.93 x 10^117
62characters of hex, plus adding a punctuation symbol, plus adding an upper case letter = 3.79 x 10^126