A client is intended to be authenticated with a server. The present disclosure relates to a method that includes using an algorithm for the client and server, but independently of one another, to produce a first key. A second key is produced by the client such that its distance from the first key is within a predetermined distance. The second key is sent to the server. The server successfully authenticates the client if the distance between the received second key and the first key is within the predetermined delta. The second key is used as a new start key for further authentication of the client with the server.