With the 0.5.0 version just released, crytto now allows file sharing (e.g., via email) by sharing public keys:

encrypt_send -o /tmp/my-secret.enc \
   -p /home/marco/.ssh/my-key.pub \
   ./my-secret.doc

This generates an encrypted file (in the location specified with the -o option) and an equally encrypted “passphrase” which can then be sent (ideally via a separate sharing mechanism; although, as it is securely encrypted, it could be sent alongside the encrypted file).

Upon receiving both, the owner of the my-key.pem secret file, using the crytto tools, can simply decrypt it with:

decrypt -s /tmp/pass-key-145207.enc \
    -o ~/Documents/my-secret.doc \
    ~/Downloads/my-secret.enc

Sensible defaults are applied if any of the non-mandatory options (like the -o) are omitted.

To install, simply execute:

pip install -U crytto

and make sure that release 0.5.0 is applied.

The README has more information.