HNDL (Harvest-Now-Decrypt-Later)

Also known as: Store-Now-Decrypt-Later, SNDL

HNDL is the threat model where an adversary passively collects encrypted traffic today with the expectation of decrypting it later once a cryptanalytically-relevant quantum computer (CRQC) is available. It drives PQC/hybrid migration priorities: long-lived secrets (LI content, subscriber identifiers, PKI roots) and roaming/interconnect traffic with 10+ year confidentiality requirements are prioritized first.

Categories: SignalingRoaming and InterconnectThreats and Attacks

HNDL in context

Signaling protocols carry the control-plane messages that set up calls, register subscribers and route SMS. SS7, Diameter, GTP-C and SIP are the four dominant families, and interconnect exposure of any of them is treated by GSMA as top-tier telecom risk.

Roaming and interconnect are where two operators exchange signaling and user-plane traffic. Trust boundaries here are the primary attack surface for location tracking, SMS interception and fraud, which is why GSMA now mandates SEPP with PRINS on 5G interconnect.

To place HNDL in the wider telecom-security picture, review ISUP, NetFlow / IPFIX / sFlow, BGP Hijack, Anomaly Detection, Attack Surface Mapping and Behavioral Signaling Detection — 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.