Your Keeper gave you a word. Speak it, and name yourself. Coming back on another phone? Speak your own word instead and leave the name empty.
This one is yours alone. Speak it on another phone and you come back as yourself, with your sheet and everything you have written.
For the Keeper (DM). Name the campaign; two words will be minted — one to invite players, one that grants the office of Keeper.
Give the player word to your party. Keep the keeper word to yourself — anyone who speaks it holds the office.