A method for securing an off-the-shelf smartphone, a secure communication system, and a security insert is provided. The method comprises removing the battery from the off-the-shelf smartphone and inserting the security insert to the battery compartment. The security insert comprises cryptographic module. The method further comprises modifying off-the-shelf smartphone and providing a power and data connection between the security insert and the smartphone. The secure communication system wirelessly transmits outgoing cellular encrypted black data, which is encrypted by the cryptographic module, from the modified off-the-shelf smartphone to a cellular network, and decrypts, by the cryptographic module, incoming cellular black data receives from the cellular network to the modified off-the-shelf smartphone. The security insert enclosure configured to be deployed in a battery compartment.