How to encrypt a file, using GPG, which is shared between two users? [closed]

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http://stackoverflow.com – For user1 I make the keys by calling gpg --gen-key and I do the same with user2. Once both keys are made, I export the public key for user1 by calling gpg --export -a "user1@example.com" > pub_user1.key and I export the public key for user2 as well, gpg --export -a "user2@example.com" > pub_user2.key. Then I give user2 the public key of user1 and import it by calling, gpg --import pub_user1.key. I do this for user1 as well and import user2 public key, gpg --import pub_user2.key. Then user1 encrypts a file, gpg -ae -r 'user2@example.com' test.txt and I give user2 the encrypted file, t (HowTos)