A method for establishing cryptographic communications between a remote device and a medical device with the medical device having less processing power than the remote device, comprising the steps of: - establishing unencrypted communication between the remote device and the medical device, - generating an asymmetric key pair by the remote device, the asymmetric key pair comprising a public key and a private key, - generating a key request message by the remote device and sending the key request message together with the public key to the medical device, - generating a pre-master key by the medical device and encrypting the pre-master key with the received public key by the medical device, - generating a key response message by the medical device and sending the key response message together with the encrypted pre-master key from the medical device to the remote device, - decrypting the encrypted pre-master key with the private key by the remote device, - deriving a master key as symmetric key from the pre-master key by using the key request message and the key response message for deriving the master key from the pre-master key by each of the medical device and the remote device, the master key to be used for both decryption and encryption of application data to be communicated, wherein the key request message and the key response message contain random data and a time stamp, wherein the key request message and/or the key response message contain a session identifier, - completing pairing of the medical device and the remote device and terminating communication between the medical device and the remote device, wherein after termination of the communication, the remote device sends a connection request to the medical device, the connection request containing the session identifier contained in the key request message and/or in the key response message. - establishing unencrypted communication between the remote device and the medical device, - generating an asymmetric key pair by the remote device, the asymmetric key pair comprising a public key and a private key, - generating a key request message by the remote device and sending the key request message together with the public key to the medical device, - generating a pre-master key by the medical device and encrypting the pre-master key with the received public key by the medical device, - generating a key response message by the medical device and sending the key response message together with the encrypted pre-master key from the medical device to the remote device, - decrypting the encrypted pre-master key with the private key by the remote device, - deriving a master key as symmetric key from the pre-master key by using the key request message and the key response message for deriving the master key from the pre-master key by each of the medical device and the remote device, the master key to be used for both decryption and encryption of application data to be communicated, wherein the key request message and the key response message contain random data and a time stamp, wherein the key request message and/or the key response message contain a session identifier, - completing pairing of the medical device and the remote device and terminating communication between the medical device and the remote device, wherein after termination of the communication, the remote device sends a connection request to the medical device, the connection request containing the session identifier contained in the key request message and/or in the key response message.