Implementing Qualified Electronic Signature (QES) on Your Website

Clients often complain: "Our EDI system doesn't work with QES in the browser." The problem is typical — an outdated approach via ActiveX or NPAPI plugins that are unsupported by modern browsers. We've solved it dozens of times. How to integrate QES according to Federal Law 63-FZ without headache — we break it down practically.

QES is the only type of electronic signature equivalent to a handwritten signature. According to the Ministry of Digital Development, over 70% of Russian companies already use QES in corporate document flow, tax reporting, or real estate transactions. Certified cryptographic tools (CSP) like CryptoPro CSP or VipNet CSP and a qualified certificate from an accredited certification authority are mandatory components of a legally valid signature. Without QES, it is impossible to submit reports to Rosreestr or sign a contract with a counterparty. Typical implementation time is 14 days, and transaction cost savings reach 40%. This article is a practical integration experience, from choosing an architecture to deployment.

How to Choose a QES Integration Method: Plugin or Cloud?

Two main approaches: installing CryptoPro Browser Plugin on each computer or cloud QES via DSS. Let's compare them.

What to Do If the Browser Doesn't Support ActiveX?

Modern browsers (Chrome, Edge, Yandex) block NPAPI plugins. The only reliable solution is cloud QES via DSS or CryptoPro CSP Web (Chromium support via Chrome Extension). In practice, we recommend cloud QES as a future-proof option. It does not require CSP installation on the user's PC and works on any device.

Why Cloud QES Is Replacing Plugins?

According to our data, over the last period more than 80% of new projects choose cloud QES. The reasons are obvious: no need to maintain outdated technologies, users sign documents from any device. We have implemented CryptoPro DSS on 6 projects — no failures in half a year. Moreover, cloud QES is implemented 2 times faster than plugin-based and reduces support costs by 40% due to the absence of CSP installation on each computer.

Technical Stack

CryptoPro CSP is the most common CSP in Russia. It is installed on the user's computer. For browser operation, CryptoPro EDS Browser Plugin (NPAPI/COM component) or CryptoPro CSP Web is used.

Alternatives:

• Rutoken EDS — token with built-in GOST cryptography, Rutoken Web plugin
• VipNet CSP — alternative CSP
• CryptoARM GOST — desktop application with API

For SaaS without CSP installation requirement — cloud QES via DSS (Directory Services of Signing): the user receives SMS confirmation, the signature is created on the server in a trusted environment. Providers: CryptoPro DSS, Kontur.Crypto, Trusted Environment.

Architecture of Signing via CryptoPro Browser Plugin

// Check for plugin availability
async function checkCryptoProPlugin() {
  try {
    const plugin = await cadesplugin;
    return true;
  } catch (e) {
    return false;
  }
}

// Get list of user certificates
async function getUserCertificates() {
  const plugin = await cadesplugin;
  const store = await plugin.CreateObjectAsync('CAdESCOM.Store');
  await store.Open(
    plugin.CADESCOM_CONTAINER_STORE,
    plugin.CAPICOM_MY_STORE,
    plugin.CAPICOM_STORE_OPEN_MAXIMUM_ALLOWED
  );

  const certs = await store.Certificates;
  const validCerts = await certs.Find(plugin.CAPICOM_CERTIFICATE_FIND_TIME_VALID);
  const result = [];

  for (let i = 1; i <= await validCerts.Count; i++) {
    const cert = await validCerts.Item(i);
    const subjectName = await cert.SubjectName;
    const validTo = await cert.ValidToDate;
    result.push({ index: i, subjectName, validTo, cert });
  }

  await store.Close();
  return result;
}

// Create CAdES-BES signature (attached)
async function signDocumentCAdES(documentBase64, certificateItem) {
  const plugin = await cadesplugin;
  const signer = await plugin.CreateObjectAsync('CAdESCOM.CPSigner');
  await signer.propset_Certificate(certificateItem.cert);
  await signer.propset_CheckCertificate(true);

  const signedData = await plugin.CreateObjectAsync('CAdESCOM.CadesSignedData');
  await signedData.propset_ContentEncoding(plugin.CADESCOM_BASE64_TO_BINARY);
  await signedData.propset_Content(documentBase64);

  const signature = await signedData.SignCades(
    signer,
    plugin.CADESCOM_CADES_BES,
    true
  );

  return signature;
}

Signature Formats

Cloud QES via CryptoPro DSS

No CSP installation on the user's computer required:

// Initialize signing via DSS API
async function initDssSignature(documentHash, userPhone) {
  const response = await fetch('https://dss.cryptopro.ru/SignServer/rest/api/CreateTransactionHash', {
    method: 'POST',
    headers: {
      'Authorization': `Bearer ${process.env.DSS_ACCESS_TOKEN}`,
      'Content-Type': 'application/json',
    },
    body: JSON.stringify({
      Signature: {
        Parameters: {
          CadesType: 1,
          HashAlgorithm: 'GOST3411-2012-256',
        },
        Content: { IsDetached: true, HashValue: documentHash },
      },
      OperationID: crypto.randomUUID(),
    }),
  });

  const { TransactionID } = await response.json();
  await sendConfirmationSms(userPhone, TransactionID);
  return TransactionID;
}

// Confirm with SMS code
async function confirmDssSignature(transactionId, smsCode) {
  const response = await fetch('https://dss.cryptopro.ru/SignServer/rest/api/ConfirmSignature', {
    method: 'POST',
    body: JSON.stringify({ TransactionID: transactionId, ConfirmationCode: smsCode }),
  });

  const { Signature } = await response.json();
  return Signature;
}

Signature Verification

async function verifySignature(documentBytes, signatureBase64) {
  const plugin = await cadesplugin;
  const signedData = await plugin.CreateObjectAsync('CAdESCOM.CadesSignedData');
  await signedData.propset_ContentEncoding(plugin.CADESCOM_BASE64_TO_BINARY);
  await signedData.propset_Content(Buffer.from(documentBytes).toString('base64'));

  await signedData.VerifyCades(signatureBase64, plugin.CADESCOM_CADES_BES, true);

  const signers = await signedData.Signers;
  const signer = await signers.Item(1);
  const cert = await signer.Certificate;
  const certInfo = await cert.SubjectName;

  return {
    valid: true,
    signerName: certInfo,
    signedAt: await signer.SigningTime,
  };
}

Legal Requirements

• The certificate must be issued by an accredited CA (registry on the Ministry of Digital Development website)
• The CSP must be certified by the FSB (Federal Law No. 63-FZ "On Electronic Signature")
• Additional requirements for real estate transactions, notarial acts
• Storage of QES-signed documents — at least the statute of limitations (3–10 years)

What's Included in QES Integration

• Audit of the current electronic document flow scheme
• Selection of the appropriate method: plugin, cloud, or combined
• UI development for certificate selection and signature display
• Integration with CryptoPro Browser Plugin or DSS API
• Testing on all target browsers (Chrome, Yandex, Firefox, Safari)
• User training and documentation
• Technical support after launch

Timeline

Integration with CryptoPro Browser Plugin: UI, certificate list, CAdES-BES signing — 7–10 days. Cloud QES via CryptoPro DSS with SMS confirmation — 7–10 days. Signature verification with certificate check — 3–5 days. Full turnkey project — from 14 business days. In 90% of cases, we meet the 14-day deadline.

Request a demonstration of QES on your project — get an engineer consultation. Get a consultation — we will select the optimal solution for your business and prepare a commercial proposal.

Web Application Security: HTTPS, CSP, XSS, CSRF, WAF, DDoS Protection

A website breach rarely looks like in movies. More often it's: a bot finds an unprotected /admin/export endpoint, downloads the customer database, and closes the connection. Or: through an outdated WordPress plugin, a web shell is uploaded, and the server starts sending spam. Or quieter: an XSS in a comment field allows stealing admin session cookies, unnoticed for months. We have analyzed dozens of such cases — each vulnerability could have been fixed at the development or audit stage.

Web application security is not a single setting. It's layers of protection, each closing a separate class of attacks. Order an audit — we'll assess the project and deliver a turnkey plan within 2–4 weeks.

How do we ensure comprehensive web application security?

HTTPS and Proper TLS Configuration

HTTPS is the minimum mandatory level. But having an SSL certificate and having a properly configured TLS are different things.

In Nginx/Apache configuration we check:

• Protocols: only TLS 1.2 and TLS 1.3, SSLv3 and TLS 1.0/1.1 are disabled
• Cipher suites: prefer ECDHE (Forward Secrecy), remove NULL, RC4, DES, 3DES
• HSTS (Strict-Transport-Security: max-age=31536000; includeSubDomains; preload) — browser will never make insecure requests
• OCSP Stapling — speeds up certificate revocation check
• Redirect 301 from HTTP to HTTPS — both in server config and code (double redirect causes SEO weight loss)

Check: SSL Labs (ssllabs.com/ssltest) should show A or A+. If B, the configuration is weak.

Let's Encrypt + Certbot for production is standard. Automatic renewal via certbot renew in cron. Wildcard certificates for subdomains via DNS-01 challenge.

Content Security Policy: The Most Powerful and Complex Protection

CSP is an HTTP header that tells the browser which sources are allowed to load resources. A properly configured CSP completely blocks most XSS attacks, even if the vulnerability exists in the code.

The problem: breaking the site with an incorrect CSP is easy. default-src 'none' — and fonts, images, JS stop working. So we start with Content-Security-Policy-Report-Only — CSP logs violations but does not block anything. We monitor reports for 2–4 weeks, refine the policy, then switch to enforcement mode.

Example of a real policy for a site with Google Analytics, Google Fonts, and Stripe:

Content-Security-Policy:
  default-src 'self';
  script-src 'self' https://www.googletagmanager.com https://js.stripe.com 'nonce-{random}';
  style-src 'self' https://fonts.googleapis.com 'unsafe-inline';
  font-src 'self' https://fonts.gstatic.com;
  frame-src https://js.stripe.com;
  img-src 'self' data: https://www.google-analytics.com;
  connect-src 'self' https://api.stripe.com https://www.google-analytics.com;
  report-uri /csp-report;

nonce — a random string generated server-side per request. Inline scripts with the correct nonce are allowed; without nonce, they are blocked. This completely breaks XSS via <script>alert(1)</script>.

'unsafe-inline' in style-src is a compromise for inline styles. It's better to remove it by moving all styles to CSS files, but that requires refactoring.

Why XSS Remains the Most Common Vulnerability?

XSS (Cross-Site Scripting) — injection of JS code through user input. According to OWASP, XSS is in the top 3 web application vulnerabilities. Three types:

Protection: never insert user input into HTML without escaping. In PHP — htmlspecialchars() with ENT_QUOTES. In Laravel Blade templates — {{ $var }} is safe, {!! $var !!} is dangerous. In React — {variable} is safe, dangerouslySetInnerHTML is dangerous. For Rich Text — use htmlpurifier on PHP or DOMPurify in the browser.

CSRF: Protecting Forms and APIs

CSRF (Cross-Site Request Forgery) — an attacker forces the victim's browser to send a request on their behalf. Example: a user is logged into a bank, opens a malicious page, which makes fetch('https://bank.ru/transfer?to=evil&amount=50000') — if the bank is unprotected, money is transferred.

CSRF tokens — standard protection for forms: the server generates a random token, stores it in the session, and inserts it as a hidden field in the form. On POST request, the token is verified. The attacker does not know the token. Laravel does this automatically with @csrf.

SameSite cookies — modern protection: SameSite=Strict or SameSite=Lax prevents the browser from sending cookies in cross-site requests. Works in all modern browsers.

API without sessions (JWT, Bearer tokens) — CSRF is irrelevant if the token is not stored in a cookie (but in the Authorization header or localStorage). However, localStorage is vulnerable to XSS — so for sensitive data, HttpOnly cookies with SameSite are preferable.

WAF and DDoS Protection

WAF (Web Application Firewall) filters HTTP traffic for attacks: SQL injection, XSS, path traversal, known exploit patterns. Options:

• Cloudflare WAF — cloud-based, OWASP Top 10 rules out of the box, custom rules via expressions. Managed Rules automatically block new threats.
• ModSecurity (Nginx/Apache) — self-hosted, OWASP Core Rule Set (CRS). Flexible but requires tuning and monitoring of false positives.
• AWS WAF — for infrastructure on AWS, integrates with CloudFront and ALB.

DDoS protection. Cloudflare at L3/L4/L7 is the de facto standard for most sites. Automatic mitigation of volumetric attacks, Under Attack Mode during active attacks. For critical infrastructure — Cloudflare Magic Transit or specialized solutions (Qrator, StormWall for the Russian market).

Rate Limiting at the application level — an additional layer. Laravel ThrottleRequests middleware: 60 requests per minute per IP for general endpoints, 5 for /login and /password/reset. Redis as a counter store — mandatory for horizontally scalable systems (otherwise limits are not synchronized between servers).

Other Mandatory Measures

Security headers. Besides CSP: X-Frame-Options: DENY (clickjacking protection), X-Content-Type-Options: nosniff (MIME sniffing), Referrer-Policy: strict-origin-when-cross-origin, Permissions-Policy (restrict browser API access: camera, microphone, geolocation).

SQL injection. Prepared statements everywhere. No concatenation of user input into SQL strings. ORM (Eloquent, Doctrine) protects by default. $wpdb->prepare() in WordPress is mandatory.

Dependency updates. composer audit and npm audit in CI/CD pipeline. Dependabot or Renovate for automatic PRs with updates. Critical CVEs — patch within 24 hours.

Secrets and configuration. .env — never in Git. Secrets in production — via CI/CD environment variables (GitHub Secrets, GitLab CI Variables) or HashiCorp Vault. Leak detection: git-secrets, truffleHog in pre-commit hooks.

How We Work

1. Audit — code scanning, configuration review, dependency analysis, manual business logic verification.
2. Planning — vulnerability remediation plan, stack selection (CSP, WAF, rate limiting).
3. Implementation — TLS setup, CSP configuration, headers, Rate Limiting, WAF.
4. Testing — re-penetration test, load testing, false positive check.
5. Deployment and Monitoring — enable production CSP, set up alerts, train the team.

What's Included

• Report with found vulnerabilities and recommendations (PDF + code snippets)
• Ready TLS configuration (Nginx/Apache)
• CSP policy with Report-Only and production versions
• WAF and Rate Limiting setup
• Dependency update plan
• Access to monitoring tools (Sentry, Datadog)
• 30 days of post-audit support (consultations, fixes)

Timeline and Cost

The budget is calculated individually — contact us for a project evaluation.