Systems and methods to instruct a mobile device to switch from a first protocol to a second protocol after registering the device on a network associated with the first protocol. This may be done to obtain a cryptographic key used by the device. For example, for some communication protocols, such as 3G and 4G communication protocols, obtaining the cryptographic key is difficult. However, the 2G communication protocol uses a cryptographic key that is easier to obtain. Only after obtaining the key, the phone instructed to again switch to the first communication protocol. During the exchange of communication, the user is likely to be holding the phone at his ear, such that he is unlikely to notice that the phone is using the first communication protocol. Hence, the exchange of communication may be decrypted and monitored, without the user noticing anything amiss.