SmartBhoomi: Design, Implementation, and Empirical Evaluation of a Sovereign Blockchain Architecture for Government Land Registration with Dual-Layer Cryptographic Security, AI Fraud Detection, Geodesic Spatial Verification, and Biometric Audit Trails

Government land registration in India suffers from two structurally distinct fraud vectors: submission-stage fraud — where falsified documents, duplicate GPS coordinates, and impersonated identities enter the system unchallenged — and post-commitment integrity fraud, where insider access to centralised databases enables silent record alteration. Blockchain immutability resolves the second but is blind to the first; every prior blockchain land registry in the literature addresses at most one of these dimensions. This paper presents SmartBhoomi, a production-grade platform engineered to defeat both simultaneously through seven tightly integrated technical subsystems. Post-commitment tamper-resistance is delivered by Bharat Land Chain, a purpose-built sovereign permissioned blockchain with three-node PBFT consensus achieving 100,410 peak TPS (single-node loopback), deterministic sub-millisecond finality, and verified zero hash, Merkle, or timestamp violations across all committed blocks. Pre-commitment fraud interception is delivered by: (i) a Random Forest classifier across eight engineered features — achieving 97.5% accuracy, precision = 1.000, F1-score = 0.957, and ROC-AUC = 1.000 on a synthetic held-out test set with zero false positives; (ii) a Haversine geodesic spatial engine resolving parcel conflicts to ±0.08 m accuracy at 100 m separation in 0.087 µs per computation across India's full 8.5°N–37°N latitude range; and (iii) FIDO2/WebAuthn device-bound biometric authentication with six-action liveness detection requiring independent consent from both transacting parties. A dual-layer AES-256-GCM cryptographic architecture provides: document-level encryption with HKDF-SHA256 per-document key derivation (4.34 µs/key; 55.5% avalanche effect; 100% byte-value entropy coverage) before IPFS upload; and field-level PII encryption for all eight sensitive database field types including Hindi Unicode. A 25-test empirical evaluation suite — the most comprehensive published for any blockchain land registry — validates all seven subsystems through throughput benchmarks, Byzantine fault injection, cryptographic entropy analysis, latitude-dependent error quantification, IPFS tamper detection across four attack classes, ML decision matrix validation, dual JWT channel isolation, admin security model verification, and 15-step audit hash-chain integrity. SmartBhoomi is, to our knowledge, the first system in the land administration literature to unify all seven security dimensions within a single deployable platform evaluated by a rigorous multi-dimensional test battery.