Tamper-Proof Examination System

Encrypted artifacts and verifiable lifecycle

The examination system separates confidential question/answer content, lifecycle commitments and constrained proof verification. React/TypeScript and Node/Express orchestration connect AES-GCM encryption, IPFS/Kubo storage, Solidity contracts on Sepolia and Circom/SnarkJS Groth16 workflows.

Large artifacts remain off-chain. Content references and exam events provide an integrity/lifecycle path without publishing plaintext files.

Content and verification

1. Encrypted artifact
2. IPFS content ID
3. Proof generation
4. Solidity verification
5. Indexed events / UI

The application, storage and verification layers have separate responsibilities.

Examination workflow

• Role-oriented application screens organize administrator, examiner and student actions.
• Question papers and submissions are encrypted before their storage references enter the exam workflow.
• Lifecycle contracts record exam creation, submission and result-publication events.
• Circom/snarkjs tooling supports proofs for bounded conditions such as valid marks and submission timing.

Engineering decisions

AES-GCM protects artifacts before content-addressed storage. CIDs identify encrypted files; encryption keys remain part of the authorized application access path. Contract events represent creation, submission and result transitions separately from the file contents.

Score-range constraints establish a value within permitted marks; timing constraints bound submission time to the configured interval. Private witnesses carry circuit inputs, while public signals and proof verification expose the encoded predicate. Storage, encryption and verification serve different purposes: a reference identifies content, encryption protects it and a proof establishes specified constraints. A valid range proof verifies that predicate rather than the entire grading procedure.