What is SSL/TLS? Meaning, Types, and Benefits
SSL/TLS are encryption protocols that authenticate and protect communication between any two parties on the internet.
SSL/TLS are defined as encryption protocols that authenticate and protect communication between any two parties on the internet. SSL stands for secure sockets layer, and TLS for transport security layer. This article explains SSL/TLS in detail.
Table of Contents
What is SSL/TLS?
SSL/TLS are encryption protocols that authenticate and protect communication between any two parties on the internet. SSL stands for secure sockets layer. TLS stands for transport layer security.
SSL is the predecessor of TLS, though the terminologies are used interchangeably today. Any mention of SSL/TLS or just SSL usually translates to the latest version of TLS.
Encryption is coding messages so that only the sender and the intended receiver understand them. This communication could be between people, servers, organizations, or government agencies. Encryption protocols lay out both sides’ structure, tools, and rules. Ciphers are the techniques or algorithms used to do the actual encryption and decryption based on the agreed protocol.
The first recorded use of encryption dates back to 500 B.C. The Spartans of ancient Greece used a tool called a Scytale for encrypting military dispatches. The Scytale was a cylinder of agreed-upon dimensions. A strip of parchment was wound upon this cylinder, and the message was written across each loop. When unraveled, the parchment would not make sense unless the reader rewound it across another cylinder of the same length and circumference.
In this case, the mode of encryption is the Scytale. The encryption protocol consists of cylinder measurements and the width of the parchment strip. The cipher is the act of winding and unwinding the strip over the cylinder in a specific direction.
Most historical mentions of encryption and encryption protocols involve war or military communications. The field of cryptography was also created in the context of the military.
Why SSL/TLS?
Today, encryption is used in everyday communication, not just in military scenarios. Radicati’s 2021 Email statistics report forecasts that 347 billion emails will be sent every day in 2023. According to a 2022 report by Statista’s research department, around 180 zettabytes of data will be created by 2025, from the 64.2 zettabyte-volume in 2020.
These numbers make sense. The average individual does everything from streaming music to banking on online applications. Governments are increasingly moving their systems online to be more efficient and accessible. Every sector, be it healthcare or education, runs on applications hooked to the cloud.
For example, corporations use software for everyday functions, like Slack and Google Workspace, for collaboration. They use cloud-based SaaS solutions for independent sections of their operations, such as Salesforce for customer relationship management (CRM).
With many applications and use cases, sensitive data is almost constantly in transit. This leaves a broad attack surface for Personally Identifiable Information (PII) to be poached by cybercriminals. PII can be used for blackmail, fraud, or even identity theft.
At a corporate level, unsecured intercepted data can contain trade secrets, sensitive employee information, or, worse, customer data.
This is where SSL and TLS come in. These encryption protocols, like the Scytale, provide a way to encrypt and transfer data between a web client (typical browsers such as Google Chrome) and a web server (where applications like Youtube and Venmo are hosted).
Netscape first introduced SSL in 1995. It was designed to encrypt traffic that moved using the Hypertext transfer protocol (HTTP). Browsers use HTTP to render websites on user devices. They are the starting point of all communication between the client and the application’s servers.
After three version releases of SSL, an upgraded protocol named Transport layer security (TLS) was released. Currently, version 1.3 is the most secure and efficient so far. TLS 1.3 has changed in the supported ciphers and fixes to the known security vulnerabilities of the previous versions.
HTTPS (Hypertext transfer protocol secure) is an extension of HTTP that uses SSL or TLS. A user who sees HTTPS can be assured that all data they enter into the website will be encrypted when sent to the backend server.
See More: What Is Cybersecurity? Definition, Importance, Threats, and Best Practices
How SSL/TLS works
The SSL certificate
SSL/TLS communication is bound by SSL certificates. An SSL certificate is a digital identity card that allows browsers to verify the website’s authenticity. They are issued by a certificate authority (CA).
A certificate authority is an impartial third party that verifies the authenticity of the websites requiring encrypted data transmission. Once verified, they provide the applying organization’s digital SSL certificate and keep a copy themselves. DigiCert and Comodo are two certificate authorities among an extensive list.
The SSL certificate contains the following:
- The website’s domain and subdomain names
- Associated organization’s name
- Details of the issuing CA
- Issue and expiry dates of the certificate
- The public key of the registered website
We will look into how these public keys work in the next section.
Organizations can use HTTPS across all their pages when hosting a website. Domain providers typically enable these certificates. If not, there are also services like Let’s Encrypt that offer free SSL/TLS certificates.
The TLS Handshake
Once the certificate is in place, SSL/TLS protocols take over all communication. This happens by first establishing the TLS handshake.
The TLS handshake is when the client and server agree to which encryption protocols and ciphers to use. In this scenario, the sender is the browser and the receiver is the website hosted on a server. They are called the ‘client’ and the ‘server’.
The server that hosts the website installs the SSL certificate that has been issued to it. It is provided to all clients asking for a connection.
The first step of a TLS handshake is the client’s ‘hello’. This is done by the client sending the SSL/TLS version it supports and the cipher suites it can use.
The server checks if it also supports the same encryption protocol versions and ciphers. If it does, the server says ‘hello’ back by sending the certificate. This serves as proof of identity. The client knows it has been connected to the correct server. The certificate also contains the public key.
Symmetric and Asymmetric encryption
To understand the rest of the TLS handshake, it is crucial to understand symmetric and asymmetric encryption.
Symmetric encryption uses a single secret key to encrypt and decrypt messages using the chosen cipher. It is akin to a lock and key. Anyone with a copy of the key can unlock the door. This aspect of symmetric encryption makes it easier to execute, taking up minimal CPU load. But this also makes it less secure.
Asymmetric encryption uses two keys – a public key and a private key. The public key is only used to encrypt. The private key is only used to decrypt. The private key is a closely guarded secret, while the public key is distributed to all who need to communicate with the receiver.
Senders encrypt their messages with the public key. The public and private keys are coupled and can only work with each other. This means that only the private key can decrypt this message.
Asymmetric encryption is much more secure than symmetric because there is no storage or transmission of the secret key. But it also requires complex mathematical calculations, which take up a significant CPU load.
The beauty of SSL/TLS lies in the fact that it uses a combination of both symmetric and asymmetric encryption. It leverages the strengths of both encryption methodologies, making the process secure and less time-consuming.
Within the TLS handshake, once the client verifies the details established in the certificate, it creates a random string sequence. This is the pre-master key. The client encrypts this using the server’s public key and sends it over.
The server decrypts this string, uses the agreed-upon cipher, and generates the ‘master’ key or the session key.
This way, the client and server use asymmetric encryption to exchange the temporary, secret session key.
Now, the server uses this key to encrypt a ‘finished’ message to signal the end of the handshake. The client verifies if it can decrypt this message using its own version of the generated session key.
If successful, the user can see the padlock appear on the browser (the client) next to the URL. The session has been established. From this point on, it is only symmetric encryption. The session key is used to encrypt all communication between the client and server.
This session key is time-bound. It stops working after a pre-configured time or if the client closes the connection, usually by exiting the web page. When the user connects to the website, the TLS handshake ensues again, and a new session key is established.
This is a high-level overview of how TLS works. With this understanding, it is easy to see why SSL/TLS is crucial, especially for websites and applications where personal data is transferred.
See More: What Is a Security Vulnerability? Definition, Types, and Best Practices for Prevention
Features of SSL/TLS
SSL/TLS is the backbone of modern internet communication. Every business requires an online presence, and a secure online presence comes with SSL certificates. The main features of TLS that are leveraged by organizations and individuals alike are:
1. It authenticates the business servers
SSL certificates are unique to the registered website. The asymmetric portion of the TLS handshake ensures that all data transfer happens between the client and the intended business server. This considerably reduces man-in-the-middle attacks.
2. SSL/TLS is easy to install and execute
TLS encryption happens through an established and streamlined process. Most web server hosts have a service to register for valid SSL certificates. They also walk websites through the minimal configuration required for the complete setup. The website owner does not need to trawl through various services to install and maintain the HTTPS status.
3. It is homogenous
SSL/TLS implementation is standard and works the same way across various clients and browsers. Since it doesn’t vary from client to client, the server and the user need not focus on tailoring it to suit multiple environments.
4. It reinforces the integrity of the communication
Besides encrypting every message using the secret session key created in the TLS handshake, SSL/TLS also ensures hashing. Hashing is compressing any given data into a sequence of a specific length. Two identical sets of data always produce identical hashed strings.
SSL/TLS appends hashed versions of every communication at the end before encryption. When the receiver gets the message, it uses the same hashing algorithm to check if it gets identical results. If it gets a different hashed string from the one attached to the message, it means the message has been tampered with. This way, the integrity of the communication is verified.
5. SSL/TLS is flexible
With SSL/TLS, it is assumed that all clients and servers do not support a single cipher, hashing algorithm, or authentication mechanism. One of the first steps of the TLS handshake is to choose these algorithms based on what is mutually supported by both client and server.
6. TLS allows users to gauge security
Most browsers today provide visual insight into the SSL implementation of every website it loads. Users can view details of the SSL certificate and gather information on how secure the website is.
See More: What Is Web Application Security? Definition, Testing, and Best Practices
Types of SSL Certificates
All SSL/TLS communication revolves around the certificates. Two types of authorities can issue these certificates:
1. Root certificate authority: This is the highest CA, which does not issue SSL certificates directly to the applying clients. Root CAs issue certificates to intermediate certificate authorities.
2. Intermediate certificate authority: These authorities issue the acquired certificates to applying servers or to other intermediate CAs.
Certificates are issued at multiple levels as a matter of security. If a particular CA is compromised, all certificates issued by that CA are invalidated. Certificates issued by other CAs continue working.
SSL certificates can be classified based on the number of domains or subdomains to be supported and the scope of certificate coverage.
Based on the number of domains it supports, SSL/TLS certificates can be classified into:
1. Single-domain certificate: This certificate secures only a particular domain or a subdomain link. For example, if www.spiceworks.com uses a single-domain certificate, one cannot use it to secure community.spiceworks.com.
2. Multi-domain certificate: One multi-domain certificate can be used to secure multiple domains and subdomains. For example, one such type of certificate can be used to secure www.spiceworks.com, community.spiceworks.com, and www.spiceworks.co.uk.
3. Wildcard certificate: A wildcard is a single-character symbol that represents a placeholder. In this case, the wildcard character is an asterisk (*) and is usually mentioned in the wildcard certificate in the website URL. For example, if a wildcard certificate is issued to ‘*.spiceworks.com’, it secures www.spiceworks.com, community.spiceworks.com, and any other subdomains that one may, such as blogs.spiceworks.com.
Based on the scope of coverage, SSL certificates can be categorized into:
1. Domain-validated (DV) certificate: The certificate is issued by the CA by verifying if the applicant controls the requested domain. It only mentions the domain name but no business name. The DV certificate ensures secure encryption but cannot be used to validate business identity. These certificates are easy to obtain, typically within a few hours of application.
2. Organization-validated (OV) certificate: Organization-validated certificates are issued by the CA after verifying the domain and the corresponding business. It verifies basic business information as well as its claim to the domain.
3. Extended validated (EV) certificate: EV certificates provide users with the highest level of assurance. The CA verifies if the business is legally and operationally valid. It even checks physical location for proof of existence. This certificate takes a couple of days to issue and is considered more trustworthy than DV and OV certificates.
See More: What Is Endpoint Encryption? Definition, Architecture and Best Practices
Benefits and Challenges of SSL/TLS
As with every other technology, several benefits and challenges are associated with using SSL/TLS.
Benefits
- SSL has numerous security applications
Communication encrypted by SSL cannot be eavesdropped on. Man-in-the-middle attacks become more complicated, as do a host of other methods of cyber attacks.
- It is easy to implement
SSL/TLS is structured in a flexible yet uniform manner. This makes it easy to install. There are numerous certificate authorities, and the process for acquiring a certificate is pretty straightforward. It also requires no effort from the user’s side, which makes for a smooth user experience.
- It works across multiple clients with minimal configuration changes
All modern browsers and client services support SSL/TLS. Administrators need not make platform-specific changes to ensure that SSL works across them.
- It bundles authentication with encryption
The SSL certificate validates that a website belongs to the proper organization. Besides, the cocktail of symmetric and asymmetric encryption allows for the seamless bundling of authentication and encryption.
- It improves SEO ranking
Big search engines, such as Google, have open policies that state that they give better SEO ranking to HTTPS-enabled websites than HTTP websites. So an SSL implementation could push an organization’s website to the top of search results.
- It enables compliance with industry regulations
All industries have started focusing on data privacy. Regulations such as HIPAA and PCI DSS require user data to be encrypted. Organizations that do not comply face hefty fines.
Challenges
- Cybercriminals are quick at exploiting vulnerabilities
Each version of SSL and TLS had vulnerabilities, prompting the release of the next version. Since there is no way to force all clients to use up-to-date versions, cybercriminals can still exploit these communications. For example, the Padding Oracle On Downgraded Legacy Encryption (POODLE) attack is known to affect browsers that still support only till SSL 3.0.
- Traffic visibility is a problem
SSL encrypts – it does not discriminate between ordinary traffic and malicious traffic. This makes it easier for attackers to pass through traffic inspection software. Encryption makes it more challenging to spot command and control traffic. One way to protect against this exploitation is to decrypt all incoming traffic at the entry-level. This, however, is not an easy solution considering the scale and density of information being transferred.
- Ethical considerations come up when looking into decryption issues
Scalability is not the only problem with decryption. The whole point of encryption is to keep sensitive data away from prying eyes, and decrypting, even if for security, may defeat the entire purpose of SSL/TLS. Besides, such decryption can be a direct violation of industry regulations.
- Migration from HTTP to HTTPS can cause temporary complications
Migration to HTTPS requires altering entries in Google’s Webmaster. This causes a temporary drop in traffic. Most websites run on plugins, and all plugins may not support SSL. This is particularly true with custom form submissions. All components and assets of the website – be it videos, survey plugins, animations, or just images – must also come from an HTTPS source. If not, the browser warns users that the website has content that isn’t secure.
See More: What Is Vulnerability Management? Definition, Lifecycle, Policy, and Best Practices
Takeaway
There is no denying that there are a few challenges that come with using SSL/TLS encryption protocols. One must remember that these small costs, such as the slight time lag from the initial handshake, pale compared to the costs of a breach and regulatory fines. Implementing SSL/TLS must be one of the first security measures of every company trying to beef up IT security.
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