Cryptography Reference
In-Depth Information
resource through a network without having to know if the resource is
remote or local, a feature called
network transparency
. It will style itself
after the user's particular desires such as email message formatting. This
layer also deals with resource allocation and problem partitioning. The
presentation layer provides the top layer with familiar local representation
of data, which is independent of the format used on the network.
Analysis
:
Network Connections
embodya set of independent protocols,
each in a different layer. The top layer, the applications layer, consisting of user
applications programs, is the only variable layer. Each layer uses the layer one
step below it and provides a service to the layer one step above it. Each of
the network's components on a given host uses protocols applicable to its layer
to communicate with its analogous component in another host. Such layered
protocols are sometimes known as
peer-to-peer protocols
.
One large advantage of layered protocols is that the mechanism for delivering
information from one layer to another is specified clearly as part of the protocol's
definition. Also, changes within a protocol layer are prevented from affecting
the other layers. This vastly simplifies the task of designing and maintaining
network communication systems.
SSL Protocol — Simplified
Now we describe SSL, mentioned earlier in the section. SSL is an Internet
protocol that provides authenticityand secrecyfor session-based communica-
tion. It provides a secure channel on the client/server model using a secret
sharing scheme. The securitymodel of SSL is that it encrpts the channel by
enciphering the bits that go through that channel. As mentioned earlier, SSL
began with Netscape who originated it and in 1996, theyhanded over the spec-
ifications of SSL to IETF who worked to standardize the SSL version 3 model,
which had been released in 1995. In 1999, the TLS working group released TLS
version 1, which has now become the IETF standards-track variant of the SSL
version 3 protocol (see [68]). The cryptographic power of SSL/TLS is that it
operates at the transport level so HTTP runs on top of SSL, called HTTPS.
To understand the layers of SSL, we must introduce the names of the two
main subprotocols to be discussed in detail below: (1) the handshake protocol;
which operates above the (2) record protocol. This is illustrated below.
HTTP
SSL Handshake Protocol
SSL Record Protocol
TCP
IP
Data Link Layer
Physical Layer
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