Getting GPG error

Hi, Everytime update my ubuntu I get GPG error. Please help me. Below I am providing the error. Thanks

W: GPG error: http://sfo1.mirrors.digitalocean.com/mariadb/repo/10.1/ubuntu xenial InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY F1656F24C74CD1D8
W: The repository 'http://sfo1.mirrors.digitalocean.com/mariadb/repo/10.1/ubuntu xenial InRelease' is not signed.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: GPG error: http://download.opensuse.org/repositories/home:/rtCamp:/EasyEngine/xUbuntu_16.04  Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 3050AC3CD2AE6F03
W: The repository 'http://download.opensuse.org/repositories/home:/rtCamp:/EasyEngine/xUbuntu_16.04  Release' is not signed.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
1 Like

Please, look at the forum history. Two days ago several people asked for the same thing. Why would the answers they got be different from the ones you expect to get?