What is TLS?
TLS stands for Transport Layer Security. It is a cryptographic protocol used to transmit data securely over networks, such as the internet or internal networks.
TLS provides:
- Encryption (Encryptie): data becomes unreadable to third parties
- Authentication: verification of the identity of communication partners
- Integrity: detection of changes or tampering with transmitted data
TLS is the successor to SSL (Secure Sockets Layer), which is now considered outdated and insecure.
🔒 What is TLS used for?
| Application | Description |
|---|---|
| Web traffic | HTTPS = HTTP over TLS (secure browsing) |
| VPN | TLS is used in SSL VPNs or OpenVPN |
| SCADA/PLC communication | Secure communication in modern OT protocols (e.g. OPC UA) |
| Email security | Encryption of email via TLS (SMTP, IMAP, POP3) |
| Remote access | Authentication and encryption when logging in remotely |
⚙️ How does TLS work?
- Handshake: client and server exchange certificates
- Key exchange: a shared session key is agreed
- Encrypted session: from then on, all communication is encrypted
- Verification: certificates ensure that you know who you are talking to
📌 TLS in OT environments
- TLS is increasingly used in modern industrial protocols, such as:
- OPC UA over TLS
- MQTT over TLS (in IIoT applications)
- REST APIs between MES or BMS and IT/Cloud
TLS is an important part of Defense in Depth and protects data in transit.
🚫 Common misconceptions
- TLS ≠ VPN: TLS only secures the transmission, not network access
- Self-signed certificates are less trustworthy than CA-validated ones
- TLS 1.0 and 1.1 are outdated – use at least TLS 1.2 or TLS 1.3
📌 In summary
TLS is a fundamental security protocol that enables encrypted communication. It is essential in both IT and OT for protecting data against eavesdropping and manipulation.