If you want to contact me, use the channel that succeeded last time. If this does not help and you do not know my email address, you can contact me through LinkedIn.
If the information is more sensitive, use one of public keys (below), depending on whether you want to grant me access to something (file, server) on your end, or send me some message securely (eg. in the email).
If you want to give me secure access to your server, use my public SSH key.
If you want to send me a message no one else will be able to read (even when having access to my email account), use my public PGP key.