Your Guide to Secure Code Signing

Software truly serves as the backbone of nearly every industry and personal interaction in our lives. Whether it’s the apps on your phone or the operating systems that keep our essential infrastructure running smoothly, the integrity and authenticity of software are incredibly important.

This is where code signing comes into play—it’s a vital security measure that acts like a digital seal of approval, giving users confidence that the software they download, and use is completely legitimate and hasn’t been altered in any way. Code signing process typically uses robust cryptographic algorithms like RSA (Rivest–Shamir–Adleman) and ECC (Elliptic Curve Cryptography) to ensure this security. 

When a software lacks proper code signing, it loses its credibility as it can’t provide proof for its source, which makes it easily vulnerable to tampering, which may result in malware distribution, phishing attacks, and serious reputational harm for developers and organizations. We’ve seen just how serious this can be with real-world incidents like the SolarWinds attack (attackers messed with trusted software before it even reached users), the MSI Data Theft (private keys were compromised for MSI’s firmware across 57 products), and many more. 

Now, let’s dive into the essentials of secure code signing together! We’ll explore its benefits, potential drawbacks, and share best practices to strengthen your software supply chain. 

Benefits of Code Signing

Code signing is a cryptographic process that authenticates executable files, scripts, and software artifacts by applying a digital signature. This signature is created using a private key and a cryptographic hash of the software. When users run signed software, their operating system verifies the signature with the public key. 

Implementing secure code signing practices offers a multitude of benefits for both software developers and end-users: 

Verifiable origin and integrity

Code signing establishes a secure link between software and its creator. If an attacker compromises the build pipeline or distribution channel to inject malicious code, the digital signature becomes invalid, alerting to tampering. The verification process checks the digital signature against the software’s unique hash to make sure nothing has been altered since it was signed. This makes it difficult for the attackers to execute advanced supply chain attacks with legitimate software.

Bypassing security warnings and blocks

Modern operating systems and browsers, such as Windows SmartScreen, macOS Gatekeeper, and Chrome’s download protection, check for digital signatures. Unsigned software triggers aggressive security warnings, “unknown publisher” alerts, or is blocked. Secure code signing enables smooth installations without user intervention, greatly improving download-to-install conversion rates. It’s important to remember that while code signing confirms the software hasn’t been tampered with and comes from a verified publisher, it doesn’t guarantee the software itself is completely safe or free of vulnerabilities. 

Comply with industry standards

Many industries, especially those handling sensitive data (e.g., healthcare, finance), face strict regulatory requirements regarding software integrity, authenticity, and security. Code signing is essential for compliance with standards like NIST Cybersecurity Framework, SOC 2, HIPAA, PCI DSS, and ISO 27001. Beyond just meeting these regulations, different platforms also enforce code signing in their own ways; for instance, Apple requires macOS apps to undergo a process called ‘notarization’ to ensure they’re checked and signed, and Windows drivers similarly often need to be signed by Microsoft to function correctly. 

Best Practices for Secure Code Signing 

To really unlock the benefits of code signing, organizations should embrace a set of important practices and strategies. These aren’t just friendly suggestions; they’re essential steps for ensuring the integrity and trustworthiness of your software. 

Let’s learn about these key practices, their benefits, and the repercussions of not following them:

Protocol	Benefit	Repercussions of Not Following
Secure Private Key Storage (HSMs)	Private key protection is crucial for code signing. Storing them in certified Hardware Security Modules (HSMs), which are tamper-proof and prohibit private key export, provides strong protection against theft. Using HSMs also provides a strong key backup and disaster recovery strategy to ensure you can still access your keys even if an HSM fails or is lost.	Storing private keys on general-purpose computers (e.g., developer workstations) makes them vulnerable to theft. A compromised key can sign malicious code, resulting in malware distribution and reputational damage.  This risk is also present if your keys aren’t strong enough because you’ve chosen outdated algorithms or too-small key sizes, like 1024-bit RSA, making them easier for attackers to break. Furthermore, even when using specialized hardware like Hardware Security Modules (HSMs), if they don’t meet strict certifications like FIPS 140-2, they might not provide the expected level of security, leaving your valuable keys exposed to similar dangers.
Timestamping	A timestamp verifies that the code was signed during the certificate’s validity, ensuring the signature stays valid even after expiration. Timestamping typically follows the RFC 3161 protocol standard, adding an extra layer of trust and longevity to your code’s digital signature, making it vital for long-term software validation.	Without a timestamp, expired code signing certificates render all previously signed software untrusted, causing warnings and potentially blocking execution. This forces users to download new versions, increasing support overhead.
Strict Access Controls and Least Privilege	Limiting access to code signing keys and systems to only authorized personnel with defined roles (Role-Based Access Control – RBAC) minimizes the attack surface.	Unrestricted access increases the risk of insider threats or external attackers gaining control of the signing process, leading to unauthorized or malicious code being signed. To prevent this, it’s crucial to set up strict Role-Based Access Control (RBAC) policies. This ensures only specific, authorized people get the exact permissions they need for each part of the signing process, greatly reducing the chance of unauthorized access and its serious consequences.
Regular Key Rotation	Periodically rotating code signing keys and using unique keys for different releases or projects reduces the impact of a single key compromise.	If one key is used for all releases and is compromised, all software signed with that key becomes untrusted, potentially requiring mass revocation and re-signing, impacting a vast user base. To significantly reduce this, it’s recommended to use different keys for each product or module whenever that’s feasible.
Code Review and Virus Scanning	Thoroughly reviewing and virus scanning all code before it is signed ensures that no vulnerabilities or malicious elements are present in the source.	Accidentally signing vulnerable or malicious code can lead to security breaches, compromise user data, and severely damage the organization’s brand and legal standing.
Centralized Certificate Management	A centralized system for managing all code signing certificates (issuance, deployment, renewal, revocation) provides complete visibility and control over the signing infrastructure.	Without centralized management, organizations can lose track of their certificates, leading to expired certificates, compliance violations, and a lack of oversight over who is signing what. On the other side, a centralized system makes it easy to keep tabs on all your certificates and keys, enabling automated alerts for upcoming expirations, setting up triggers for renewal, and comprehensive reporting.
Monitoring and Auditing	Implementing robust logging and auditing of all code signing activities, like who signed what, when, from where, allows for prompt detection of suspicious activity and analysis in case of a breach. To make these logs even more powerful for security monitoring and incident response, it’s highly recommended that they be integrated with SIEM (Security Information and Event Management) platforms such as Splunk, Grafana, Prometheus, and many more.	Inadequate monitoring, unauthorized signings, or key compromises can go unnoticed for extended periods, allowing attackers to cause significant damage. It also makes incident response and accountability difficult.
Segregation of Test and Production Signing	Maintaining separate infrastructure, keys, and certificates for test-signing and release-signing environments prevents test compromises from affecting production code.	A less secure test environment could be exploited to compromise production signing keys, leading to widespread malicious code distribution.
Certificate Revocation Policies	Having a clear and efficient process for revoking compromised or unnecessary certificates is critical to mitigate damage quickly. To make this process fast and effective, it’s highly recommended that automated support for Certificate Revocation Lists (CRLs) and Online Certificate Status Protocol (OCSP) be implemented.	If a compromised certificate cannot be swiftly revoked, attackers can continue to sign and distribute malicious software under a trusted identity, prolonging the impact of the breach.

How can Encryption Consulting Help?

Navigating the challenges of secure code signing can be overwhelming for organizations, particularly those with distributed development teams and varied software ecosystems. Specialized solutions, such as Encryption Consulting’s CodeSign Secure, help address these issues.  

CodeSign Secure is a powerful platform that makes the code signing lifecycle smoother and more secure. It helps organizations follow the best practices we’ve talked about. Let’s look at some of its important features that will help you strategize and protect your organization’s security. 

1. FIPS 140-2 Level 3 HSM for Secure Key Storage

   Our CodeSign Secure prioritizes key security by leveraging FIPS 140-2 Level 3 certified Hardware Security Modules (HSMs). This ensures that your private signing keys are generated, stored, and used in a highly secure, tamper-resistant environment, meeting stringent industry standards.

2. Client-Side Hashing and Secure Timestamps

   Our platform uses client-side hashing, generating the code hash on your machine with the help of our custom KSP (Key Storage Provider), which is designed to work seamlessly with Microsoft’s Cryptography Next Generation (CNG) framework, allowing it to handle your private keys securely during the signing process and leverage Windows’ modern cryptographic features. Along with secure timestamps, CodeSign Secure ensures your digital signatures’ integrity and longevity, even after certificate expiration.

3. Multi-Format Signing Capabilities

   Modern development environments deal with a wide array of file types. Our solution supports signing for various formats, including .exe, .dll, .jar, .apk, .dmg, Docker containers, firmware binaries, and more. This flexibility ensures that all your software artifacts can be securely signed within multiple OS platforms such as Windows, Linux, and macOS. 

4. Auditing and Reporting

   CodeSign Secure offers comprehensive auditing and reporting features, providing detailed logs of all signing events, facilitating compliance checks and incident response, and ensuring accountability. 

5. Policy Enforcement and Granular Access Control

   Our platform allows organizations to establish and implement rigorous code signing policies. It features detailed Role-Based Access Control (RBAC), enabling administrators to designate who can sign, what can be signed, when, and under which conditions. 

Encryption Consulting’s CodeSign Secure empowers you and your organizations to manage your code signing processes with confidence and also helps automate critical security measures, minimize human error, and build a strong foundation of trust in your software. Whether you’re a growing SMB, a large enterprise, or operating in highly regulated sectors like automotive, healthcare, or fintech, CodeSign Secure is designed to meet your specific needs. 

CodeSign Secure and PQC

The looming threat of quantum computers presents a significant challenge to current cryptographic algorithms like RSA and ECC, which form the backbone of today’s code signing. But the transition to quantum-resistant cryptography is no longer a distant future. Our CodeSign Secure solution is fully equipped to integrate and utilize the newly approved Post-Quantum Cryptography (PQC) algorithms. 

We have been at the forefront of tracking NIST’s PQC standardization efforts and have successfully integrated the quantum-resistant signature algorithms, such as ML-DSA and LMS, directly into CodeSign Secure, meaning organizations will now be able to: 

• Sign their software with NIST-approved quantum-resistant algorithms 
• Implement hybrid signing strategies, i.e., combining traditional algorithms (like RSA or ECC) with a quantum-resistant one (like ML-DSA or LMS) within the same software package, giving you strong security now and against future quantum threats. 

CodeSign Secure with PQC establishes your organization as a leader in cybersecurity, showing a commitment to the integrity and authenticity of your software supply chain. Adopting this technology now is a smart, proactive move, especially for securing long-lifecycle firmware or addressing national security concerns, as it protects your software against the quantum computer threats of the future, right now. 

Conclusion

In this interconnected world, secure code signing is essential for any organization developing or distributing software. By understanding core principles, adopting best practices, and using advanced solutions like CodeSign Secure, developers and businesses can protect their software from tampering, enhance user trust, and safeguard their reputation online. 

Remember, the goal is not just to sign code, but to sign it securely. By adhering to strong protocols, protecting your private keys, and staying vigilant to cyber threats, you can ensure that your digital creations remain authentic, untampered, and a source of confidence for every user.