common security technique

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Hi all,

  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 ?

Re: common security technique

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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 recognised patterns then it can
make life easier.

Think WiFi for an example.
mail da (without the space)
So many gadgets, so little time

Re: common security technique

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 datalink 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..

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