Code signing best practices for generating and storing private keys in a secure manner.

DigiCert recommends that developers take precautions with the code signing process and the private key associated with their signing certificate.

Recommendations:

  • Limit access to keys

    Maintain access controls to and accounting of code signing keys and limit their distribution. This will help enforce strict accountability for key use.

  • Physically secure the key storage device in a locked container

    • Ensure key storage devices are not left on desks, in unlocked drawers, or where they can be easily taken or copied.

    • Keep the device storing the private key in a locked desk drawer or cabinet or otherwise behind locked doors.

  • Use a strong password for private key

    Choose a strong password for the private key. We require having at least sixteen (16) characters that are randomly generated containing uppercase letters, lowercase letters, numbers, and symbols to transport private keys. Words in a dictionary, derivatives of user-IDs, common character sequences (e.g., "123456"), proper names, geographical locations, common acronyms, slang, family member names, birthdays, etc. are not to be used.

  • Secure storage for private key

    Securely store a private key using a FIPS 140-2 Level 2 certified cryptographic device. Export of the private key is not allowed by these cryptographic devices. Most of these devices include multi-factor authentication.

  • Test Signing certificate vs Release Signing certificate

    Microsoft recommends using a separate Test signing certificate to sign prerelease code. The Test signing certificate should only be trusted in the test environment. Test signing certificates can be a self-signed certificate or come from an internal test CA.

For more information, Microsoft provides a best practices document on code-signing.