Link encryption is a security method that encrypts data at each hardware point along the way, hiding the entire transmission from interception. It encrypts packet header information and is useful for secure data transmissions. However, it suffers on public networks and keys must be held across multiple devices. Super encryption is a workaround that encrypts data payload at the application layer and uses end-to-end encryption.
Link encryption is a security method used on communications networks to transmit encrypted data between individual computers. With this method, the data is encrypted and decrypted by each piece of hardware along the way, such as network routers or other specialized devices. When the communication link is encrypted in this way, the entire data transmission is hidden from other encryption schemes where the transmission can still be intercepted. The method may also be referred to as link-level encryption or link-level encryption. That’s because everything happens at the bottom layer of the Open Systems Interconnection (OSI) model, known as the data link layer.
When data packets leave the network interface, the entire packet, the data groups sent over the network connections, is encrypted. Link encryption is unique in this way because the packet header information, which contains source and destination address information, is encrypted along with the actual data payload. Secure packets are then sent across the line until they encounter another device along the way, at which point the header is decrypted and checked for address information. If the packets have not yet arrived at their destination, they are re-encrypted and sent on their way.
This is useful for keeping the transmission safe from someone trying to tap the line or capture packets for analysis. An attacker has no way of knowing who the data came from, where it was headed, and the path they traveled along the way. The process is also usually free of human errors because it all happens automatically, saving the user from having to remember to encrypt their communications, facilitating regular and large data transmissions that need to be secure.
There are some shortcomings in the approach. Link encryption suffers greatly on public networks like the Internet. Many who use the method will only use it on leased and leased lines, where you can get more control over your hardware along the way. This also means that the keys used to encrypt and decrypt data must be held across multiple devices, making each point along the path potentially vulnerable should an attacker gain access to one of the devices along the way.
Another workaround is a method known as super encryption, which is used to encrypt the data payload at the application layer from the user, then the remaining header information is encrypted as it goes out onto the larger network. The additional method in a super encryption is known as end-to-end encryption. The main difference between encrypting a link, therefore, is that the end-to-end method allows data to traverse an unsecured network for some time since the keys for encryption and decryption are known at each end of the transfer . The addressing and routing information in the headers is still visible to an interceptor, but the core data payload remains secure. In superencrypted cases, however, where both end-to-end and link encryption are used, data rarely needs to go beyond a local router before entering the encrypted link for transport.
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