Arch AUR Unknown Public Key

While trying to install an update for network-manager strongswan from AUR I got the following error:

==> Verifying source file signatures with gpg...
    NetworkManager-strongswan-1.4.1.tar.bz2 ... FAILED (unknown public key 765FE26C6B467584)
==> ERROR: One or more PGP signatures could not be verified!
:: failed to verify networkmanager-strongswan integrity

The public key needs to be downloaded using the following command:

user@Raspberry ~ % gpg --recv-keys 765FE26C6B467584                                                                                                                      :(
gpg: key 765FE26C6B467584: public key "Tobias Brunner <tobias@strongswan.org>" imported
gpg: no ultimately trusted keys found
gpg: Total number processed: 1
gpg:               imported: 1

Reference:

Michal Zuber