Upload your default SSH key:
curl -s ssh.keychain.io/<email>/upload | bash
Install your key into authorized_keys:
curl -s ssh.keychain.io/<email>/install | bash
ssh.keychain.io/<email>
ssh.keychain.io/<email>/upload
ssh.keychain.io/<email>/install
ssh.keychain.io/<email>/fingerprint
ssh.keychain.io/<email>/confirm/<token>
ssh.keychain.io/<email>/all
ssh.keychain.io/<email>/all/install
ssh.keychain.io/<email>/<namedkey>
ssh.keychain.io/<email>/<namedkey>/fingerprint
ssh.keychain.io/<email>/<namedkey>/install
ssh.keychain.io/<email>/<namedkey>/upload