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\chapter{Conclusions}\label{ch:conclusions}
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\glsresetall % Resets all acronyms to not used

% build a framework for esim security analysis
% LPA in python

% Found bug in esim on sim cards

% reverse engineered the estk.me update mechanism


This thesis presented a systematic security analysis of commercial eSIM-on-SIM card implementations through the application of differential testing.\marginpar{Thesis introduces a differential testing framework to analyze commercial eSIM-on-SIM card implementations.} Given the opaque and proprietary nature of most \gls{euicc} firmware, black-box testing approaches remain one of the few viable options for assessing correctness and security in deployed systems. With the design and implementation of a custom framework, this work introduces a reproducible method for identifying behavioral inconsistencies across vendor-specific \gls{esim} implementations.

The developed framework integrates trace recording, scenario-driven testing, and property-based structured fuzzing, allowing the systematic mutation and replay of \gls{apdu} traces. The combination of syntactically valid \gls{asn1}-based input generation with deterministic mutation provides a strong fuzzing implementation.\marginpar{It reveals security flaws and highlights the need for independent implementation validation across vendor implementations.} Through this approach, several notable implementation differences were identified, including a critical certificate validation bypass in one vendor’s \gls{euicc} side provisioning logic. 

These findings highlight the importance of independent verification and validation of \gls{esim} implementations. The observed deviations from \gls{gsma} specifications suggest that even well-established standards do not guarantee uniform security guarantees across vendors. Differential testing, as demonstrated, offers a scalable and automation-friendly approach to detect such inconsistencies without requiring access to proprietary source code.
