The present teaching relates to exchanging a key with a device. In one example, a secret value is generated. A message is transmitted to the device. The message includes information related to the secret value based on which the device is to create a cryptographic key. A visual code displayed on the device is captured. The visual code includes a first piece of information and a second piece of information. A key value is generated based on the first piece of information and the secret value. A test value is calculated based on the key value. It is determined whether the device is securely connected based on the test value.