@startuml General Invitation Steps
InitiatingUser -> InitiatingUser : STEP_1 = Create InivitedUser_Id generate a public key, invitation uid & message for InvitedUser optionnally password protected
InitiatingUser -> InvitedUser: STEP_1_SEND= transmit step 1 data (QR Code, Bluetooth, messaging, mail, ...) optional password being tranmitted through another channel

InvitedUser -> InvitedUser :Create InitatingUser_Id & InvitedUser ContactCard
InvitedUser -> InitiatingUser: STEP_2_SEND=transmit InvitedUser ContactCard (QR Codes, Bluetooth, messaging, mail, ...) encrypted with initiating user pub key

InitiatingUser -> InitiatingUser : STEP_3=InitiatingUser_Id Accept Invitation and create answer (Generate InitiatingUser ContactCard and create finalized InvitedUser contact)
InitiatingUser -> InvitedUser: STEP_3_SEND=Send answer through invited user's message servers from contact card

InvitedUser -> InvitedUser : Finalize InitiatingUser from its ContactCard
InvitedUser -> InitiatingUser: STEP_4= Send confirmation to InitiatingUser that communication is possible  through initiating user's message servers from contact card
@enduml