Code Signing vs SSL/TLS Certificates: Differences & When You Need Both

Code signing and SSL/TLS certificates are among the most commonly used mechanisms in the public key infrastructure (PKI). Code signing certificates secure software while SSL/TLS certificates encrypt communication. Both play a fundamental role in facilitating trust and strengthening modern cybersecurity practices.

Both align with the X.509 standard established by the International Telecommunication Union, which defines how public keys are distributed and how identities are verified. Although code signing and SSL/TLS certificates serve distinct functions, they are often not a matter of either—or for today’s enterprises. Many organizations require both to address different layers of risk. Understanding their differences helps organizations deploy the right certificates for the right reasons.

What is the difference between a code signing certificate and an SSL certificate?

Code signing certificates confirm that software comes from known publishers while also verifying that software has not been altered. SSL/TLS certificates provide encryption and authentication to protect data exchanged between browsers and servers. 

Code signing safeguards software and application integrity, while SSL/TLS protects information in transit. 

What is a code signing certificate?

Code signing verifies identities by digitally signing executable files and scripts. This process is carried out through code signing certificates. Issued by certificate authorities (CAs), code signing certificates are credentials that bind verified identities to cryptographic keys. This allows software developers and publishers to sign software and executables to confirm they haven’t been modified since release. 

During signing, code is converted into a digital fingerprint using a hash function, locked using the publisher’s private key, and optionally timestamped to preserve the signature’s validity even after the certificate expires. Properly signed software reduces "unknown publisher" warnings and can help establish SmartScreen reputation over time.

Benefits of code signing certificates include verified publisher identities, reduced risk of unauthorized code modification and supply chain attacks, and fewer security warnings, which can improve installation rates. On a broad scale, code signing supports brand protection by signaling that software is authentic and free of tampering. Through code signing, cryptography strengthens software integrity and overall security. 

Types of code signing certificates

Code signing certificates are available in two main formats: 

• Organization Validation (OV)
• Extended Validation (EV) 

OV code signing certificates offer faster issuance and baseline validation, while EV code signing certificates offer the highest level of security. 

What is an SSL/TLS certificate?

The legacy cryptographic protocol known as Secure Sockets Layer (SSL) was originally intended to secure data exchanged between browsers and servers. This has since been deprecated in favor of Transport Layer Security (TLS) protocol, but the term SSL is still widely used to convey the need for encrypted and authenticated web connections.

SSL/TLS certificates are digital certificates used to verify identities and facilitate encryption so that data cannot be intercepted or altered in transit. For websites, these certificates enable HTTPS (HyperText Transfer Protocol Secure) and activate padlocks or tune icons within browser address bars.

Cryptographic handshakes play a critical role in establishing SSL/TLS protection. These handshakes confirm identities and create shared session keys. The handshake process ensures that all data exchanged between the browser and the server is encrypted.

Benefits of SSL/TLS certificates include authenticated communication and data confidentiality. These form the basis for trust in digital communication, strengthening security posture along with overall brand reputation. 

Types of SSL/TLS certificates

SSL certificates can take many forms, categorized based on validation level and according to the number of domains or subdomains they are meant to secure. Examples of SSL/TLS certificates include:

• Domain validation (DV). Verifying that the applicant controls the domain in question, DV SSL certificates involve a streamlined vetting process that facilitates baseline protection.
• Organization validation (OV). Meant to confirm applicant identities, OV SSL certificates add targeted verification checks to provide a higher level of validation.
• Extended validation (EV). After clearing DV and OV benchmarks, EV SSL certificates extend the validation process through background checks and legal documentation. They offer the highest level of security and are the industry standard for eCommerce websites. 
• Single Domain. Offering a cost-effective solution to secure a single website, single domain SSL/TLS certificates are preferred when protection is only needed for a single hostname.
• Multi-Domain. Also known as SAN certificates, these can secure multiple domains and subdomains, including completely unrelated domains.
• Wildcard. Designed to secure a primary domain along with unlimited subdomains, wildcard certificates offer flexible and cost-effective protection.

Comparing code signing and SSL/TLS certificates in depth

Primary purpose and security application

Code signing uses digital signatures to ensure software integrity while SSL/TLS encrypts data in transit. Both rely on public-key cryptography, but serve distinct functions: code signing establishes trust within the software while SSL/TLS brings trust to connections. 

Targeted threats and mitigation

Code signing and SSL/TLS certificates both serve critical security functions: together, they establish end-to-end trust, impacting the entire software lifecycle. Their differences largely come down to where protection is provided:

• Tampering and unknown publisher warnings. Code signing confirms that the code received is the code originally produced, ensuring that signed software has not been altered before reaching end users. This prevents unknown publisher warnings because any file modification would break the digital signature and invalidate the publisher’s verified identity.
• Supply chain attacks. If threat actors infiltrate development environments, they can exploit trust-based relationships. They may insert malicious code or modify update packages in a way that appears legitimate. Code signing helps mitigate this risk by cryptographically linking software to verified publisher identities and protecting private keys with FIPS-compliant hardware to reduce the risk of unauthorized signing and release of tampered code.
• Data interception. Promoting end-to-end data security through encrypted connections, SSL/TLS certificates prevents unauthorized individuals from viewing or altering data in transit.
• Browser 'not secure' warnings. Today’s browsers warn users when a site lacks a valid SSL certificate. This undermines user trust and can harm search engine rankings while also reflecting significant security risks: connections without SSL are vulnerable to impersonation and session hijacking.

Destructive attacks tied to compromised code include the NotPetya attack of 2017 (involving a malicious update delivered via Ukrainian accounting software) and the SolarWinds Orion attack (involving a supply chain compromise that prompted widespread infiltration). 

Many attacks have been tied to SSL/TLS issues; the 2017 Equifax data breach, for example, involved an expired SSL/TLS certificate that disabled a key monitoring system, allowing attackers to remain undetected.  

When do you need both?

Organizations that develop software may require both code signing and SSL/TLS certificates, particularly if software is distributed via websites or customer portals. Without code signing, organizations lack cryptographic assurance of software integrity and publisher identity. Even if properly signed, however, software distribution remains vulnerable without SSL/TLS certificates. Licensing details or customer information could potentially be compromised if allowed to move through networks without encryption.

Together, code signing and SSL/TLS certificates support Zero Trust models, which eliminate implied trust and mandate verification for software, networks, and identities. Through code signing, organizations avoid trusting software by default, while SSL/TLS prevents implicit trust in connections or communication paths. 

Secure and manage SSL and code signing certificates at scale

Businesses rely on code signing certificates to protect software integrity and SSL/TLS certificates to secure communications and data in transit. As a leading certificate authority (CA), Sectigo offers a full range of code signing and SSL/TLS certificates to support organizations across both use cases.

As certificate volumes grow and validity periods shrink, managing both of these types of digital certificates across complex or distributed environments becomes increasingly difficult. Without centralized oversight, expired or inconsistently deployed certificates can create security gaps. Manual tracking quickly becomes unsustainable, making automation increasingly important to maintain continuity and trust.

Sectigo delivers both the certificates and the management platform organizations need to operate at scale. Sectigo Certificate Manager (SCM) centralizes and automates certificate lifecycle management (CLM), streamlining discovery, issuance, and renewals.

Sources

https://csrc.nist.gov/glossary/term/x_509_public_key_certificate

https://www.cisa.gov/sites/default/files/publications/defending_against_software_supply_chain_attacks_508.pdf

https://www.wired.com/story/notpetya-cyberattack-ukraine-russia-code-crashed-the-world/

https://www.sectigo.com/root-causes/root-causes-309-what-is-key-attestation-for-code-signing