At the heart of your business’s digital security lies the SSL certificate. Often recognized by the padlock icon in a web browser’s address bar and the transition from “http” to “https,” SSL certificates are the invisible guardians that encrypt data, authenticate identities, and foster the trust essential for your organization’s online success.
Understanding the basics of SSL certificates is crucial for anyone involved in operating a website, managing online security, or simply engaging with the internet in a safe and informed manner.
What is Secure Sockets Layer (SSL)?
Secure Sockets Layer (SSL) is a foundational protocol designed to establish an encrypted link between a web server and a web browser, ensuring that all data passed between them remains private and integral. While the term “SSL” is widely used, it’s important to note that the technology has evolved significantly. The modern standard is Transport Layer Security (TLS), which is the successor to SSL, offering enhanced security features and addressing vulnerabilities found in older SSL versions. Despite this evolution, the term “SSL certificate” is commonly and often interchangeably used with TLS certificates to refer to the digital certificates that enable these secure connections.
An SSL/TLS certificate acts as a digital passport for a website. It contains identifying information about the website owner, the server’s public encryption key, and is digitally signed by a trusted third party known as a Certificate Authority (CA). The certificate verifies the identity of the website and enables the browser to establish an encrypted connection with the server. This process is vital for protecting sensitive information such as login credentials, credit card numbers, and personal data from interception by malicious actors. While over 90% of phishing websites now utilize HTTPS, leveraging free SSL certificates to appear more credible, a properly issued and managed SSL certificate provides a robust layer of trust and security for legitimate websites.
How does SSL/TLS work?
SSL/TLS relies on a sophisticated interplay of cryptography and a trusted third-party system known as Public Key Infrastructure (PKI). When a user’s browser connects to a website secured with an SSL/TLS certificate, a process called the “SSL handshake” occurs. This handshake is a multi-step negotiation that establishes a secure communication channel before any sensitive data is exchanged.
The process begins with the browser sending a “client hello” message to the web server, indicating the supported TLS versions and cipher suites (encryption algorithms). The server responds with a “server hello,” selecting the TLS version and cipher suite it will use and presenting its SSL certificate. This certificate is crucial because it contains the server’s public key. The browser then verifies the authenticity of the certificate by checking its digital signature against the CA’s public key (which is pre-installed in most browsers). If the certificate is valid and trusted, the browser uses the server’s public key to encrypt a randomly generated “session key.” This encrypted session key is sent back to the server. The server, possessing the corresponding private key, decrypts the session key. From this point forward, both the browser and the server use this shared, symmetric session key to encrypt and decrypt all subsequent data exchanged between them. This combination of asymmetric cryptography for the initial key exchange and symmetric cryptography for the actual data transfer is highly efficient and secures the communication against eavesdropping and tampering.
How do SSL certificates work?
SSL certificates are the cornerstone of secure communication over the internet, enabling websites to encrypt data and authenticate their identity. At their core, these certificates are digital files that bind a cryptographic key pair — a public key and a private key — to an organization’s or individual’s verified identity information. This identity information typically includes the domain name, organization name, location, and the validity period of the certificate.
The process of obtaining an SSL certificate involves a trusted Certificate Authority (CA) verifying the applicant’s identity. The rigor of this verification depends on the type of certificate. Once issued, the certificate is installed on the web server. When a user’s browser attempts to access the secure website (indicated by “https”), it initiates the SSL handshake, as described previously. The browser uses the public key embedded in the SSL certificate to verify the server’s identity and establish an encrypted connection. The server uses its corresponding private key, which remains securely stored on the server, to decrypt information sent by the browser and to decrypt the session key proposed by the browser. This entire mechanism ensures that the data transmitted is encrypted and that the user is communicating with the legitimate website, not an imposter.
Protects private data
One of the most critical functions of an SSL certificate is the protection of private data. Websites handle an immense amount of sensitive information, including personal identifiers, financial details, login credentials, and confidential business data. Without encryption, this data is transmitted in plain text, making it vulnerable to interception by cybercriminals who can easily read and misuse it. An SSL certificate encrypts this data in transit, rendering it unreadable to anyone who might try to intercept it. This encryption is vital for preventing Man-in-the-Middle (MITM) attacks, where an attacker positions themselves between the user and the website to snoop on or alter communications. By securing the connection, SSL certificates ensure that sensitive information remains confidential and protected from unauthorized access.
Strengthen customer confidence
The presence of an SSL certificate is a strong signal to users that a website is secure and trustworthy. Browsers visually indicate a secure connection through the padlock icon in the address bar and the “https” prefix. This visual cue is a universally recognized symbol of safety, assuring visitors that their personal and financial information will be handled securely. For e-commerce sites, this trust is paramount; a lack of SSL can lead to a significant increase in cart abandonment as users hesitate to provide payment details on an unsecured site. Conversely, a secure connection builds confidence, enhances brand reputation, and encourages users to engage more freely with the website’s content and services. In an online environment where trust can be fragile, the visible assurance of an SSL certificate is a powerful tool for fostering customer loyalty and encouraging repeat business.
Supports regulatory compliance
Many industries and jurisdictions have stringent regulations regarding data privacy and security, such as the Payment Card Industry Data Security Standard (PCI DSS) for handling credit card information, and general data protection regulations like GDPR and CCPA. These regulations often mandate the encryption of sensitive personal data transmitted over networks. SSL/TLS certificates are a fundamental requirement for meeting these compliance obligations, particularly for any website that collects, processes, or stores personal identifiable information (PII) or financial data. Failure to comply can result in severe penalties, including substantial fines, legal action, and significant reputational damage. Implementing SSL certificates is a proactive and essential step for organizations to demonstrate due diligence in protecting user data and adhere to the legal frameworks governing data security.
Improve SEO
Search engines, most notably Google, prioritize websites that provide a secure browsing experience. Since 2014, HTTPS has been a confirmed ranking signal, meaning that websites using SSL/TLS certificates tend to rank higher in search engine results pages (SERPs) compared to their HTTP counterparts. This algorithmic preference is part of a broader effort to encourage webmasters to adopt more secure practices and provide a safer internet for users. Furthermore, modern browsers actively flag HTTP websites as “Not Secure,” which can deter visitors and negatively impact user experience. By securing a website with an SSL certificate, businesses not only improve their search engine rankings but also avoid potential negative user perceptions, driving more organic traffic and enhancing overall online visibility.
What are the key principles in SSL/TLS certificate technology?
SSL/TLS certificate technology is built upon several fundamental cryptographic principles that ensure secure and authenticated communication. These principles work in concert to create a robust system for establishing trust and protecting data integrity.
Encryption
Encryption is the process of transforming readable data (plaintext) into an unreadable format (ciphertext) using an algorithm and a key. This ensures that even if data is intercepted, it cannot be understood without the correct decryption key. SSL/TLS utilizes two types of encryption: asymmetric and symmetric. Asymmetric encryption, using a public and private key pair, is employed during the initial handshake to securely exchange a symmetric session key. Symmetric encryption, which uses a single, shared key, is then used for the bulk of the data transmission because it is significantly faster and more efficient.
Public key
A public key is one part of a cryptographic key pair. It is freely shareable and is used to encrypt data. Anyone can use a website’s public key, found within its SSL certificate, to encrypt a message that only the corresponding private key can decrypt. This ensures that data sent to the server is unreadable by anyone other than the intended recipient.
Private key
The private key is the other half of the cryptographic key pair and is kept secret by the certificate holder (usually the web server). It is used to decrypt data that has been encrypted with the corresponding public key. The private key is also essential for digitally signing the SSL certificate itself, proving the CA’s authentication of the certificate holder’s identity.
Authentication
Authentication is the process of verifying the identity of a party involved in a communication. In the context of SSL/TLS, authentication ensures that the website the user is connecting to is indeed the legitimate entity it claims to be. This is achieved through the SSL certificate, which is issued by a trusted CA after performing a series of validation checks. The browser verifies the certificate’s digital signature, confirming that it was issued by a trusted CA and has not been tampered with, thereby authenticating the server’s identity.
Digital signature
A digital signature is used to verify the authenticity and integrity of a digital document or message. In SSL/TLS, Certificate Authorities (CAs) use their private key to digitally sign the SSL certificates they issue. When a browser receives an SSL certificate, it uses the CA’s public key to verify this signature. A successful verification confirms that the certificate has not been altered since it was issued by the CA and that the CA vouches for the identity of the certificate holder. This process is fundamental to establishing trust in the certificate and, by extension, in the website it represents.
Who validates SSL/TLS certificates?
The validation of SSL/TLS certificates is performed by trusted third-party organizations known as Certificate Authorities (CAs). CAs are independent entities accredited by organizations like the CA/Browser Forum. Their primary role is to verify the identity of the applicant requesting a certificate before issuing it.
The rigor of the verification process varies depending on the type of certificate being requested, ranging from a simple domain ownership check to extensive organizational vetting. Major CAs include DigiCert, Sectigo (formerly Comodo CA), GlobalSign, and Let’s Encrypt (a non-profit CA). Their digital signatures on issued certificates are embedded within operating systems and web browsers, allowing these platforms to trust and validate the certificates presented by websites.
What are the types of SSL/TLS certificates?
SSL/TLS certificates are categorized based on the level of identity verification performed by the Certificate Authority (CA) and the scope of coverage they provide to domains and subdomains. There are several different types of certificates. Understanding them is important when it comes to selecting the most appropriate certificate for a specific website’s needs.
Extended validation certificates
Extended Validation (EV) certificates represent the highest level of assurance. Obtaining an EV certificate involves a rigorous and standardized vetting process conducted by the CA. This process requires the CA to verify the applicant’s legal, physical, and operational existence through multiple documentation checks and follow-up communications. Historically, EV certificates were recognized by a prominent green address bar in browsers, although browser interfaces have evolved. They are best suited for organizations handling highly sensitive transactions or those requiring the utmost level of trust, such as financial institutions and large e-commerce platforms. While they offer the strongest validation, they are also the most expensive and time-consuming to obtain.
Organization validation certificates
Organization Validation (OV) certificates offer a moderate level of assurance. The CA verifies the applicant’s domain ownership and confirms the existence and identity of the organization through documentation and direct contact. While not as stringent as EV validation, OV certificates provide a higher degree of trust than Domain Validation (DV) certificates. When a user clicks on an OV certificate, they can view verified information about the organization, including its name and location. These certificates are suitable for businesses, e-commerce sites, and other organizations that want to demonstrate a verified identity to their customers without the extensive vetting required for EV certificates.
Domain validation certificates
Domain Validation (DV) certificates are the most basic and widely used type of SSL certificate. The CA’s verification process for DV certificates is automated and primarily focuses on confirming that the applicant has control over the domain name for which the certificate is being issued. This is typically done through email verification, DNS records, or HTTP file validation. DV certificates encrypt communication but do not provide verified information about the organization operating the website. They are a cost-effective and quick solution for blogs, informational websites, and smaller businesses that need to secure their domain and establish an encrypted connection but do not need to convey a high level of organizational trust.
Single domain SSL/TLS certificates
A Single Domain SSL/TLS certificate is designed to secure a single, fully qualified domain name. For example, a certificate issued for www.example.com would secure that specific domain but would not automatically cover its subdomains like blog.example.com or mail.example.com, nor would it cover other domains like anothersite.com. These certificates are straightforward to obtain and install, making them a popular choice for websites with a single online presence that require basic encryption.
Wildcard SSL/TLS certificates
Wildcard SSL/TLS certificates offer a more flexible solution for securing multiple subdomains under a single main domain. A wildcard certificate for *.example.com will secure all direct subdomains of example.com, such as www.example.com, blog.example.com, mail.example.com, and shop.example.com. However, it does not secure the root domain (example.com) unless explicitly included, and it does not cover subdomains of subdomains (e.g., test.mail.example.com). Wildcard certificates simplify management by using a single certificate for multiple subdomains, reducing the complexity of managing individual certificates. It’s important to note that a single wildcard certificate cannot cover multiple different domains.
Multi-domain SSL/TLS certificates
Multi-domain SSL/TLS certificates, also known as Subject Alternative Name (SAN) certificates or Unified Communications Certificates (UCC), provide the greatest flexibility. They allow you to secure multiple, distinct domain names and subdomains with a single certificate. For instance, a single multi-domain certificate could secure www.example.com, example.org, mail.anothersite.net, and blog.yourbusiness.io. These certificates are ideal for businesses with multiple online properties or individuals managing several websites. They can typically secure up to 100 domain names, offering a streamlined approach to protecting a diverse web presence.
Best Practices for Managing SSL/TLS Certificates
Effective management of SSL/TLS certificates is crucial to maintaining website security and preventing service disruptions. As certificates have expiry dates, proactive management is essential.
Automate discovery and inventory of all certificates
A fundamental step in effective certificate management is having a clear and comprehensive inventory of all deployed certificates across the organization’s infrastructure. This includes identifying the certificate, its associated domains, expiration date, type, and issuing CA. Manual tracking is prone to errors and oversights. Implementing automated discovery tools that continuously scan networks and servers can provide an up-to-date and accurate inventory, ensuring no certificate is missed or forgotten.
Implement automated renewal and revocation workflows
Certificate expiry is a leading cause of website downtime, so automating the renewal process is important. This involves setting up alerts well in advance of expiration and, ideally, integrating with CAs to automatically renew certificates. Similarly, automated workflows for revoking compromised or no-longer-needed certificates are essential for maintaining security hygiene.
Centralize certificate lifecycle management and visibility
Managing certificates across distributed environments can be complex. Centralizing certificate lifecycle management through a dedicated platform provides a single pane of glass for visibility and control. This allows security teams to monitor certificate status, manage renewals, track issuances, and enforce policies across the entire organization, significantly reducing the risk of errors and security gaps.
Shorten certificate lifespans and align with DNS-based validation
Industry best practices and browser policies are increasingly pushing for shorter certificate lifespans, typically around 13 months, to reduce the window of vulnerability should a private key be compromised. Aligning certificate issuance and renewal processes with automated DNS-based validation methods further streamlines this. DNS validation is generally faster and more efficient for automated renewal compared to email or file-based methods, especially with shorter lifespans.
Integrate DNS hygiene and domain-control validation (DCV) with certificate management
Strong DNS hygiene is foundational to secure certificate management. Ensuring that domain records are accurate and properly managed is crucial for successful automated Domain-Control Validation (DCV). Integrating DCV processes with certificate management tools ensures that domain ownership can be quickly and reliably verified during issuance and renewal, bolstering the overall security posture and simplifying the process.
Continuously monitor, audit, and proactively remediate issues
Effective certificate management is an ongoing process, not a one-time task. Continuous monitoring of certificates for compliance, expiration, and potential security vulnerabilities is essential. Regular audits of certificate inventory, issuance practices, and access controls help identify weaknesses. Proactive remediation of any detected issues — whether it’s an expiring certificate, a misconfiguration, or a potential compromise — is vital to maintaining a robust security posture and preventing incidents.
Secure your online presence with Digicert
In the digital realm, establishing and maintaining trust is critical for any organization. SSL/TLS certificates serve as indispensable tools, providing the fundamental layers of encryption and authentication necessary for secure online communication. From safeguarding sensitive user data against interception to bolstering customer confidence through visible security indicators, the importance of SSL certificates cannot be overstated. Their role in regulatory compliance and SEO further solidifies their position as a non-negotiable component of any modern website’s security infrastructure.
UltraDNS provides the authoritative DNS backbone organizations need for scale, reliability, and security. When combined with DigiCert’s certificate lifecycle management solutions, businesses can automate issuance, validation, and renewal, while ensuring DNS records propagate quickly and accurately across the internet. This synergy simplifies operations, reduces risk, and keeps digital trust intact across every connection.
Learn more about UltraDNS and how UltraDNS and DigiCert CLM work together to strengthen certificate management from the very first CSR.
