mc-insert-public-key will extract a key from your
public keyring and insert it into the current buffer.
mc-write-mode binds this function to C-c / x by default.
This function is useful for sending your public key to someone else or
for uploading it to the key servers (see Key Servers). The inserted
key will be the first one on your public key ring which matches the
mc-pgp-user-id (see Encrypting).
You may want to insert a different public key instead; for example, you
may have signed someone's key and want to send it back to them. To do
so, pass a prefix argument to
mc-insert-public-key. (That is,
type C-u C-c / x.) You will be prompted for a string; the first key
on your public key ring which matches that string will be inserted.