International Association
for Cryptologic Research

The fundamental incompatibility between confidentiality, reliability, and le gal opposability, formalized as the CRO trilemma, imposes an entropic bound Γ_CRO on cryptographic security in contextual adversarial settings. This pa per introduces Q2CSI (Quantum Composable Contextual Security Infras tructure), a layered framework resolving this trilemma through dialectical separation. Q2CSI decomposes security guarantees into three isolated yet composable layers: Iron (reliability: temporal/logging integrity), Gold (con f identiality: semantic entropy preservation), and Clay (opposability: insti tutional interpretability). By embedding entropic constraints into an ex tended Universal Composability (UC) model, Q2CSI achieves Γ_CRO < 0.4, surpassing monolithic designs, while maintaining post-quantum resilience. The architecture is abstractly instantiated with minimal primitives (IND CCA2 encryption, EUF-CMA signatures) and validated via a symbolic UC framework. Proofs demonstrate strict dialectical isolation, bounded contex tual leakage, and compatibility with quantum adversaries. Q2CSI establishes a foundation for legally verifiable post-quantum protocols, with applications in zero-knowledge attestations and regulatory-compliant signatures.