Link Encryption is a security technique used to protect data as it travels across a communication network. In link encryption, data is encrypted at each point (or “hop”) between source and destination, including routers and switches. This means that as data moves from one network node to the next, it is decrypted and then re-encrypted at every intermediate device. The primary goal of link encryption is to secure data transmissions over potentially insecure or untrusted networks, such as the internet or wide area networks (WANs).

One of the key advantages of link encryption is that it encrypts not only the payload (actual content) but also the header and routing information, thereby preventing attackers from analyzing traffic patterns or accessing metadata. This makes it particularly useful in scenarios where complete transmission confidentiality is required, such as in military or government communications.

However, a notable drawback is that data is exposed in plaintext at each intermediate node where it is decrypted before being re-encrypted. This introduces potential vulnerabilities if any of the nodes are compromised. In contrast, end-to-end encryption only decrypts data at the final destination, ensuring that the message remains confidential throughout the journey, even if intermediary nodes are untrusted.

Link encryption is typically implemented at the data link or network layer of the OSI model, often in hardware, for performance reasons. Protocols and technologies that support link encryption include IPsec (when configured in tunnel mode), MACsec, and secure VPNs.

In summary, link encryption is a foundational network security method that ensures data confidentiality and integrity across communication links. While it provides broad protection for data in transit, it must be complemented with other security measures to safeguard the entire network infrastructure.