Subtractive Metacryptography: Communication by Thermodynamics of Carrier Modulation

This paper introduces Subtractive Metacryptography, a communication paradigm encoding information through structured modulation of pre-existing carrier streams rather than signal generation. Drawing on the analogy of stone carving—where ancient messages persist through material removal rather than construction—we establish four critical advantages: (1) superior energy efficiency (factors of $10^7$--$10^{20}$) through one-time modulation versus continuous generation, (2) extreme temporal stability ($10^6$--$10^9$ years) limited only by carrier longevity, (3) inherent stealth through mimicry of natural variation, and (4) universal detectability via shared physics knowledge. We develop a rigorous information-theoretic framework quantifying metacryptographic information as structured entropy reduction: $I_{\text{meta}} = H(C_{\text{nat}}) - H(C_{\text{enc}}) - H(\eta)$, where detection relies on Kolmogorov complexity analysis. Central to our framework is the \textit{embedded key}—self-revealing artificiality through statistical anomalies, physical impossibilities, mathematical encodings, or meta-referential structures. We demonstrate universality across scales from stellar photometry to isotopic ratios, necessitating a paradigm shift in SETI methodology toward detecting impossibly structured absences rather than anomalous presences.