Method and system for establishing cryptographic communications between a remote device and a medical device

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:

• 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 of the key request message together with the public key to the medical device;
• generating a pre-master key by the medical device and encryption of the pre-master key with the received public key by the medical device;
• generating a key response message by the medical device and sending of 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;
• and
• deriving a master key as symmetric key from the pre-master key by either using the pre-master key as master key or by using the key request message or the key response message for the derivation of 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/or the key response message contain random data and a time stamp;
• and
• wherein the remote device and the medical device each compute verification data using the master key and each display the computed verification data to a user, and wherein communication of the application data may first start after the user has confirmed that the verification data computed by the remote device and the medical device have the same values.