5G • Security
Anti-Replay Protection
NAS and AS Anti-Replay Mechanism
Security mechanism using 32-bit COUNT values to detect and reject intercepted and retransmitted signaling packets.
Technical Explanation
Every NAS and PDCP packet increments a 32-bit COUNT value. The receiver maintains a sliding reception window. If an attacker intercepts a valid ciphered packet and re-transmits it over the air, the receiver detects that the COUNT is stale or duplicate and immediately discards the packet, neutralizing replay attacks.
Key Functions
- Utilizes monotonically increasing 32-bit COUNT values per security context
- Maintains sliding verification window at PDCP and NAS receivers
- Discards duplicate or delayed replayed packets automatically
Specifications
3GPP TS 33.501, TS 38.323
Interfaces
UuN1
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