Keys in Flux: A Forensic Perspective on Implementation Diversity in Cryptographic Protocols

Cryptographic key extraction from memory is central to modern digital forensics. However, most research evaluates extraction techniques against a single implementation - often treating widely used libraries like OpenSSL as representative of entire protocol families.This paper challenges that assumption by analyzing how implementation behaviors (memory allocation, control flow, removal timing) impact the in-memory lifespan of cryptographic key material.We introduce a systematic state-aligned measurement methodology that anchors key lifespans to protocol state transitions rather than absolute timestamps, enabling implementation-independent comparison and forensically actionable findings. We implement this methodology in an experimental framework and apply it to 19 implementations of TLS, IPsec, and SSH.Our measurements reveal substantial differences in key lifespans across implementations of the same protocol. We show that protocol state boundaries systematically reveal key management differences: while specifications mandate key roles at protocol states, implementations differ in when and how they materialize, copy, and remove keys at those transitions. For forensic practitioners, these findings indicate that memory acquisition timing must account for both the specific implementation and its protocol state to optimize key recovery. Our results highlight the risks of generalizing from single-implementation studies and call for a shift toward more comprehensive, implementation-diverse evaluation methods in forensic research.