Handwritten Signature + Blockchain Solution for Secure Electronic Document Verification

Background – Electronic documents are increasingly used in finance, insurance, and law‑enforcement, but they are vulnerable to undetected modifications; electronic signatures are introduced to address this risk.

Overall Design

Goal: Use electronic signatures to confirm document review (signature equals approval) and blockchain to make the document immutable once on‑chain.

Process: After a law‑enforcement officer reviews a document, they sign it; the signed document is saved and then uploaded to a blockchain server, where it becomes a permanent block.

When a document is reopened, the system queries the blockchain to verify whether the stored hash matches, thereby detecting any tampering. Re‑approval repeats the same flow, creating additional blocks.

Handwritten Electronic Signature Technology

Signature Drawing – Implemented as a custom Android View using self‑drawn graphics because existing system controls lack the required touch‑trajectory capture.

Curve Optimization – Raw touch points are fitted with Bézier curves to produce smooth, natural‑looking strokes.

Background Rendering – The document can be displayed as the background of the signing canvas so the signer can view the content while signing.

Orientation Switching – Supports both portrait and landscape modes for user convenience.

Phone‑as‑Signing‑Board – The mobile app can act as a remote signing pad for a PC browser: the browser sends a signing request, the app receives it via instant messaging, the user signs on the phone, the signature image is uploaded to the server, and the browser refreshes to display the image.

Blockchain Technology for Verification

Structure – Each block contains a header (timestamp, previous hash, current data hash) and a body (the actual document data), forming a decentralized ledger without a central administrator.

Document On‑Chain – After approval, the document content and related metadata are packaged into a new block and linked to the previous block; for first‑time approvals, the block becomes the genesis node.

Verification (Anti‑Forgery) – When a document is read, its stored hash and the latest block hash are recomputed and compared; a mismatch indicates tampering, and the system displays the document’s authentication status.

Multi‑Level Approval – Each approval step creates a new block, preserving a complete audit trail.

Conclusion – The "handwritten signature + blockchain" approach solves both the auditability of electronic documents and the immutability of their content, and can be applied beyond law‑enforcement to finance, insurance, and enterprise management systems.