Are Electronic Signatures Legally Binding? A Developer's Engineering & Legal Guide

import fs from "fs";
import crypto from "crypto";

export function verifySignedDocumentIntegrity(pdfFilePath: string, expectedHash: string): boolean {
  // Read raw PDF bytes
  const fileBuffer = fs.readFileSync(pdfFilePath);

  // Compute SHA-256 digest
  const computedHash = crypto
    .createHash("sha256")
    .update(fileBuffer)
    .digest("hex");

  console.log("Computed Document Hash:", computedHash);
  console.log("Expected Certificate Hash:", expectedHash);

  const isUntampered = computedHash.toLowerCase() === expectedHash.toLowerCase();
  if (isUntampered) {
    console.log("✅ Cryptographic Seal Verified: Document is 100% untampered.");
  } else {
    console.error("❌ Tampering Detected: Document bytes do not match certificate hash!");
  }

  return isUntampered;
}

// Example Execution:
// verifySignedDocumentIntegrity("./signed_contract.pdf", "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855");

import hashlib
import sys

def verify_document_integrity(pdf_path: str, expected_sha256: str) -> bool:
    """Verifies that a signed PDF matches its cryptographic audit certificate."""
    sha256 = hashlib.sha256()
    with open(pdf_path, "rb") as f:
        while chunk := f.read(65536):
            sha256.update(chunk)

    computed_digest = sha256.hexdigest()
    matches = computed_digest.lower() == expected_sha256.lower()

    if matches:
        print(f"✅ Verified: {computed_digest} matches audit certificate.")
    else:
        print(f"❌ TAMPER DETECTED: {computed_digest} != {expected_sha256}")
    return matches

if __name__ == "__main__":
    verify_document_integrity("contract.pdf", sys.argv[1] if len(sys.argv) > 1 else "")