Let's say that you created more then one key pair. From now on, you would like to use the key with the id 10X01Y07 as your new default or primary key.

1. Open up Terminal (Application»Utilities»Terminal)
2. TextEdit comes preinstalled on your machine and offeres you a gui but feel free to open following document with a different text editor

   open -a TextEdit ~/.gnupg/gpg.conf

3. Search for the text snippet “default-key”.
4. Remove the comments character (#) if needed. Now add your key id. e.g. “default-key 10X01Y07” after default-key
5. Save and close the file
6. Come back to the Terminal and test your new default key e.g.

   gpg --clearsign  /Users/fiona/Documents/helloworld.txt

7. The following output should confirm your new settings.

Find out more: GnuPG manual

Go back to the party