Is it possible to encrypt gpg with a public key instead of the recipient?

Gpg encrypt with public key is a common method, however GnuPG does not support encrypting to a recipient specified by a key file. The key must be imported in advance, and the recipient defined with either his mail address or key ID. I'd recommend using a cleaner approach as expected by GnuPG and hard-code either the key's fingerprint, or a user ID given by that key and import it as usual. If you really do not want to import the key, you could do following as workaround (which actually imports the key, but to a temporary GnuPG home directory): Import the key to a temporary folder, for example using gpg --homedir /tmp/gnupg --import my.pub

Determine the key ID of the key stored in the file:

  KEYID=`gpg --list-public-keys --batch --with-colons --homedir /tmp/gnupg | head -n1 | cut -d: -f5`

Encrypt a message to the recipient

  gpg --homedir /tmp/gnupg --recipient ${KEYID} --encrypt

Clean up temporary GnuPG home directory

rm -f /tmp/gnupg You could of course save this as a script to make using it more convenient.