@startuml
actor User
autoactivate on

User -> Backup : Create Repository
Backup -> Backup : generate P-256 key pair
return keypair
Backup -> Yubikey : Read the public key of the YubiKey
return public key
Backup -> Backup : Calculate ECDHE shared secret
return shared secret
Backup -> Backup : Generate Curve 25519 key pair
return keypair
Backup -> Backup : Generate encyption key from the shared secret
return encryption key
Backup -> Backup : Encrypt the private key with the encryption key
return encrypted private key
Backup -> Backend : Store the encrypted private key and public key
return success
return success
@enduml