Software Code Signing

Cryptography · Axiom Academy

REAL WORLD Software Code Signing How digital signatures protect the software you download every day Imagine you're downloading a popular application. How do you know the file you're getting is: Authentic - actually from the developer, not an imposter? Unmodified - hasn't been tampered with during download? Safe - doesn't contain malware injected by attackers? This is where code signing comes in - a cryptographic solution that billions of people rely on every day without realizing it. Code signing uses asymmetric cryptography (public-key cryptography) to create a digital signature that proves who created the software. (Actual signatures are much longer - this is truncated for display) Certificate Authorities: The Trust Foundation Anyone can create a key pair and sign software. But how do users know they can trust that signature? This is where Certificate Authorities (CAs) come in. Getting a Code Signing Certificate: Every major operating system has its own code signing implementation, but they all serve the same purpose: protecting users from malicious software. Microsoft's system for signing .exe, .dll, and driver files Required for macOS and iOS apps distributed via App Store Signs .apk files, required for Google Play distribution GPG signatures for .deb and .rpm packages What happens when you download unsigned software on Windows? Code signing directly impacts the user experience. Here's what happens when users download software:

This is the written version of the interactive lesson above. See the full Cryptography course.