Why is a code-signing certificate needed and how does it work

4 months ago
nikolay
2 minutes

How a code-signing certificate works

1. What is a Code Signing Certificate?

  • A digital certificate issued to software developers.
  • It allows you to digitally sign applications, drivers, and scripts, proving:
    • The file really comes from your company/developer.
    • The file has not been modified since it was signed.

2. Why is it needed?

  • User trust: during installation, users see the publisher name instead of “Unknown Publisher”.
  • Security: ensures the software was not tampered with or infected.
  • System requirements:
    • Windows SmartScreen, macOS Gatekeeper, and browsers check for valid signatures.
    • Drivers on Windows must be code-signed.
  • Company reputation: signed software is less likely to be flagged by antivirus tools.

3. How does it work?

  1. Developer obtains a certificate from a Certificate Authority (CA)
    • e.g., DigiCert, Sectigo, GlobalSign.
    • The CA verifies the developer’s identity or company.
  2. The software is signed with the certificate (via tools like signtool, osslsigncode, or IDE integration).
  3. When launched, the OS checks the signature:
    • Is the certificate valid and trusted?
    • Has the file been modified since signing?
  4. If valid – the user sees: “Publisher: [Company Name]” instead of a warning.

4. Types of Code Signing Certificates

  • Standard Code Signing
    • Certificate stored as a file (PFX).
    • Suitable for most applications.
  • Extended Validation (EV) Code Signing
    • Delivered on a hardware token (USB key).
    • Higher trust level (instantly removes Windows SmartScreen warnings).

5. Examples of usage

  • Signing Windows applications (EXE, MSI).
  • Signing drivers.
  • Signing scripts (PowerShell, Java, Python).
  • Signing mobile apps (Android, sometimes iOS).

✅ Conclusion:
A Code Signing certificate is the “passport” of your software.
It builds user trust, protects against tampering, and ensures compatibility with modern security requirements.