GPG allows you to send files securely without having to send a passphrase.

If the destination has their own GPG key, you can encrypt the files so that only they can open it. 

For example, gpg -e -r E8888BDN thefile.zip will allow only i88ca to open thefile.zip with its GPG key without communicating a passphrase. Alternatively gpg-zip -e -r E8888BDN *.crt will zip and encrypt all *.crt files in one command.

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