Abstract: A method of and system for secure data transmission between a client and a third party computer arrangement. The method includes authenticating a user of the client by a security server via a communication session; making available a key pair by the security server, the key pair including a public key and a private key; and performing the secure data transmission between the client and the third party computer arrangement while using the key pair. The key pair having a limited life time defined by: a predetermined duration in time, a predetermined number of communication sessions, or a predetermined number of actions.