If you don't already use SSH, you'll need to create a public/private key pair to deploy code to Heroku. This keypair is used for the strong cryptography and that uniquely identifies you as a developer when pushing code changes.
To generate a public key:
$ ssh-keygen -t rsa
It will create keys at default location(inside .ssh folder). To add public key to heroku
$ heroku keys:add public-key-path
Ex:
$ heroku keys:add ~/.ssh/id_rsa.pub
Ex:
$ heroku keys:add ~/.ssh/id_rsa.pub
