CompTIA Security+ Exam Notes

CompTIA Security+ Exam Notes
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Thursday, October 16, 2025

Code Signing Explained: How Digital Signatures Secure Your Software

 Code Signing

Code signing is a security technique used to verify the authenticity and integrity of software, scripts, or executables. It involves digitally signing code with a cryptographic signature to assure users that the code has not been altered or tampered with since it was signed, and that it comes from a trusted source.

Why Code Signing Matters
Code signing helps:
  • Prevent malware: Ensures the code hasn’t been modified by malicious actors.
  • Build trust: Users and systems can verify the publisher’s identity.
  • Enable secure distribution: Operating systems and browsers often block unsigned or improperly signed code.
  • Support compliance: Required in many regulated industries.
How Code Signing Works
1. Generate a key pair:
  • The developer or organization creates a public/private key pair.
  • The private key is used to sign the code.
  • The public key is included in a digital certificate issued by a Certificate Authority (CA).
2. Sign the code:
  • A hash of the code is created.
  • The hash is encrypted with the private key to create a digital signature.
  • The signature and certificate are attached to the code.
3. Verify the signature:
  • When the code is run or installed, the system:
    • Decrypts the signature using the public key.
    • Recalculates the hash of the code.
    • Compares the two hashes to ensure integrity.
    • Checks the certificate to verify the publisher.
Common Use Cases
  • Software installers (.exe, .msi)
  • Mobile apps (iOS and Android)
  • Browser extensions
  • PowerShell scripts
  • Drivers and firmware
Benefits
  • Authenticity: Confirms the publisher's identity.
  • Integrity: Detects tampering or corruption.
  • User confidence: Reduces the number of security warnings during installation.
  • Platform compatibility: Required by Windows, macOS, and mobile platforms.
Risks and Considerations
  • Stolen certificates: If a private key is compromised, attackers can sign malware.
  • Expired certificates: May cause warnings or installation failures.
  • Improper implementation: Can lead to false trust or broken verification.

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