EasyPG Assistant provides a minor mode
epa-mail-mode to help
user compose inline OpenPGP messages. Inline OpenPGP is a traditional
style of sending signed/encrypted emails by embedding raw OpenPGP
blobs inside a message body, not using modern MIME format.
NOTE: Inline OpenPGP is not recommended and you should consider to use PGP/MIME. See Inline OpenPGP in E-mail is bad, Mm'kay?.
epa-mail-mode is enabled, the following keys are assigned.
You can do it by C-u 1 M-x epa-mail-mode or through the Customize
interface. Try M-x customize-variable epa-global-mail-mode.