A Dynamically Zero Trust and Risk Aware Cryptographic Orchestration Framework of Secure Multi Cloud Electronic Health Records

The adoption of multi-cloud infrastructures for Electronic Health Records (EHRs) improves scalability and accessibility but introduces security challenges such as fragmented trust management, high cryptographic overhead, and inefficient integrity verification. Existing frameworks rely on static authorization and uniform encryption mechanisms, which fail to dynamically evaluate behavioural risks associated with user access requests. Consequently, Distributed Trust Inconsistency, Cryptographic Scalability Saturation, and Distributed Integrity Verification challenges emerge in large-scale healthcare cloud environments. To address these limitations, this study proposes the Adaptive Intelligent Cryptographic Zero-Trust Multi-Cloud Electronic Health Records (AIC-ZTMC-EHR) framework, which integrates behavioural risk evaluation, adaptive encryption orchestration, and lightweight integrity verification. Initially, the Distributed Trust Inconsistency Problem is resolved through the Risk-Adaptive Behavioural Access Control-Extended (RABAC-E) technique, which evaluates behavioural patterns, device trust, access frequency, and location anomalies to generate a risk-based trust score for adaptive authorization. Subsequently, the Cryptographic Scalability Saturation Issue is mitigated through Tri-Partition Adaptive Encryption Orchestration (TAEO), employing AES-256, ChaCha20, and AES-128 encryption algorithms to generate encrypted EHR partitions. Furthermore, the Integrity-Confirmed Virtual Ledger Chain (ICVLC) enables lightweight SHA-256 hash-chain verification to provide tamper-resistant validation of distributed healthcare data. Experimental evaluation using the MIMIC-IV Electronic Health Records dataset within a simulated multi-cloud environment achieves 94.6% access control accuracy, 29 s encryption time, 235 ms integrity verification, 99% tamper detection, and 74 MB/s encryption throughput. The results indicate improved access security, enhanced cryptographic scalability, and efficient integrity validation for large-scale multi-cloud Electronic Health Record systems.