common security technique

aarklon

i have read the following in a book

at the bottom of the TCP/IP structure , in the physical and data link layers,you can encrypt data on the wire. this is one of the most common security technique used in communications.

can any one give a brief explanation of how this is done ?



Dave

The big problem with encrypting entire packets is that you give hackers a big clue because they know the physical structure of parts of the packet.If you know that the first N bytes follow recognized patterns then it can make life easier.

Think WiFi for an example.


Blackrose

I don't see a point in encrypting on the physical layer? you can view the actual transmission technique and modulation techniques as a kind of encryption i guess?

But every layer can perform encryption, each layer receives data from the layer above, and at the Data link layer, as long as both the sender and receiver can agree on a common way to scramble the data,any kind of encryption can be done. However it is a really bad idea to use complex methods on data link layer.

It is much more common to have the encryption up the top layers,closer to the actual data.. There is little point in encrypting in your application/network layer, and have that packet encrypted again in data link. The bottom layers are really only responsible for delivering data to adjacent nodes.