Encryption converts communication content using mathematical algorithms so only recipients with the correct key can restore the original. In telephony, it protects voice calls from eavesdropping, secures SMS messages, and safeguards data in transit.
Mobile call encryption has evolved: 2G (GSM) had weak encryption vulnerable to cheap interception equipment. 3G improved strength, and 4G VoLTE made robust encryption standard. However, content is decrypted within carrier networks, so carriers and legally authorized agencies can access call content.
End-to-end encryption (E2EE) completes encryption between sender and receiver devices, making content unreadable even to carriers and service providers. LINE's "Letter Sealing," WhatsApp, and Signal use E2EE. Standard phone calls lack E2EE, so encrypted messaging apps are recommended for sensitive conversations.
Encryption-related threats include wiretapping, man-in-the-middle attacks, and public Wi-Fi interception. See phone number privacy and call recording legal guide for more.