TLS/SSL
TLS (Transport Layer Security) and its predecessor SSL (Secure Sockets Layer) are cryptographic protocols that encrypt data transmitted between clients and servers.
§ 1 Definition
TLS/SSL is the encryption layer that secures the vast majority of internet traffic. SSL (Secure Sockets Layer) was originally developed by Netscape in the 1990s. SSL version 3.0 was the last release before the protocol was renamed to TLS (Transport Layer Security) and standardized by the IETF. SSL is deprecated and insecure. Modern systems use TLS 1.2 or 1.3. People still say "SSL certificate" out of habit, but they almost always mean a TLS certificate. TLS provides three guarantees: encryption (no one can read the data), authentication (you confirm the server's identity via a certificate chain), and integrity (data cannot be modified in transit without detection). These guarantees are what make e-commerce, online banking, and private communication possible.
§ 2 How it works
The TLS handshake begins when a client connects. The server presents its certificate, which includes a public key and is signed by a Certificate Authority (CA). The client verifies the certificate chain against its trust store. The two parties negotiate a cipher suite and exchange key material (via Diffie-Hellman key exchange in modern TLS). Once a shared session key is established, all further communication is encrypted symmetrically. TLS 1.3 reduced the handshake from two round trips to one, significantly reducing latency.
§ 3 Certificate management
Certificates have expiration dates (typically 90 days with Let's Encrypt, up to 1 year with paid CAs). Automated renewal is standard practice. Certificates can be revoked if compromised via CRL (Certificate Revocation List) or OCSP (Online Certificate Status Protocol). Wildcard certificates cover `*.example.com` but not `example.com` itself.
§ 4 Common misconception
An SSL certificate does not make your website "trustworthy." It only proves that you control the domain, not that you are a legitimate business or that your site is safe to use. Extended Validation (EV) certificates once claimed to provide business validation, but browsers no longer display them differently. They are not worth the extra cost.
§ 5 Note
§ 6 In code
```bash
# Check TLS certificate details
openssl s_client -connect example.com:443 -servername example.com
```§ 7 Common questions
- Q. What is the difference between SSL and TLS?
- A. SSL is the deprecated predecessor. TLS is the modern standard. People still say SSL out of habit.
- Q. Do I need a TLS certificate for every subdomain?
- A. No. A wildcard certificate covers `*.example.com`. For individual domains, use a multi-domain certificate or automate with Let's Encrypt.
- TLS encrypts data in transit, providing confidentiality, authentication, and integrity.
- SSL is deprecated. Use TLS 1.2 or TLS 1.3.
- TLS certificates are free via Let's Encrypt. Automation is standard.
Atomic Glue implements TLS with modern cipher suites, automated renewal, and strict security headers. See our trust and security page for details.
Get in touchTLS (Transport Layer Security) and its predecessor SSL (Secure Sockets Layer) are cryptographic protocols that encrypt data transmitted between clients and servers.
Category: Web Development (also: Security, Infrastructure)
Author: Atomic Glue Team
## Definition
TLS/SSL is the encryption layer that secures the vast majority of internet traffic. SSL (Secure Sockets Layer) was originally developed by Netscape in the 1990s. SSL version 3.0 was the last release before the protocol was renamed to TLS (Transport Layer Security) and standardized by the IETF. SSL is deprecated and insecure. Modern systems use TLS 1.2 or 1.3. People still say "SSL certificate" out of habit, but they almost always mean a TLS certificate. TLS provides three guarantees: encryption (no one can read the data), authentication (you confirm the server's identity via a certificate chain), and integrity (data cannot be modified in transit without detection). These guarantees are what make e-commerce, online banking, and private communication possible.
## How it works
The TLS handshake begins when a client connects. The server presents its certificate, which includes a public key and is signed by a Certificate Authority (CA). The client verifies the certificate chain against its trust store. The two parties negotiate a cipher suite and exchange key material (via Diffie-Hellman key exchange in modern TLS). Once a shared session key is established, all further communication is encrypted symmetrically. TLS 1.3 reduced the handshake from two round trips to one, significantly reducing latency.
## Certificate management
Certificates have expiration dates (typically 90 days with Let's Encrypt, up to 1 year with paid CAs). Automated renewal is standard practice. Certificates can be revoked if compromised via CRL (Certificate Revocation List) or OCSP (Online Certificate Status Protocol). Wildcard certificates cover `*.example.com` but not `example.com` itself.
## Common misconception
An SSL certificate does not make your website "trustworthy." It only proves that you control the domain, not that you are a legitimate business or that your site is safe to use. Extended Validation (EV) certificates once claimed to provide business validation, but browsers no longer display them differently. They are not worth the extra cost.
## Note
TLS 1.0 and 1.1 are deprecated. TLS 1.2 is the minimum acceptable version. TLS 1.3 offers better performance and security. Check your server configuration with tools like SSL Labs.
## In code
## Common questions Q: What is the difference between SSL and TLS? A: SSL is the deprecated predecessor. TLS is the modern standard. People still say SSL out of habit. Q: Do I need a TLS certificate for every subdomain? A: No. A wildcard certificate covers `*.example.com`. For individual domains, use a multi-domain certificate or automate with Let's Encrypt.
## Key takeaways
- TLS encrypts data in transit, providing confidentiality, authentication, and integrity.
- SSL is deprecated. Use TLS 1.2 or TLS 1.3.
- TLS certificates are free via Let's Encrypt. Automation is standard.
## Related entries
- [HTTPS](atomicglue.co/glossary/https)
- [HTTP](atomicglue.co/glossary/http)
- [IP Address](atomicglue.co/glossary/ip-address)
Last updated June 2026. Permalink: atomicglue.co/glossary/tls-ssl