Cipher

A cipher is the cryptographic algorithm that transforms plaintext into ciphertext (and back) under control of a key. Modern symmetric ciphers in telecom include AES (used in IPsec, TLS, EEA2/EIA2 for LTE, NEA2/NIA2 for 5G), ChaCha20, and the SNOW family used in 3G/4G/5G air-interface encryption. Asymmetric ciphers (RSA, ECDSA, ECDH, EdDSA) are used in PKI and key exchange. Cipher choice and key length must follow current NIST/ENISA guidance to avoid downgrade and quantum-readiness gaps.

Categories: Radio Access NetworkCore NetworkSecurity Controls

Cipher in context

The radio access network is where mobile devices attach to the operator's infrastructure. Attacks in this layer include IMSI catching, rogue base stations and downgrade attacks; defenses rest on mutual authentication, integrity-protected signaling and Open RAN supply-chain hygiene.

The mobile core carries subscriber sessions, mobility and policy. In 4G it is the EPC (MME, HSS, S/PGW); in 5G it is the Service-Based Architecture with AMF, SMF, UPF, AUSF, UDM and the NRF.

To place Cipher in the wider telecom-security picture, review HTTP, Inter-Network Function Authentication, OAuth2 in 5G Core, SMPP, NRF Poisoning and 1G — each entry cross-references back to this page so you can walk the topic in either direction.

Related terms

More from the TelcoSec Glossary

Browse the full TelcoSec Glossary, the Ultimate Guide to Mobile Network Security, or the P1 Arsenal of telecom-security tools.