Software
Crestron
e-Control
®
Secure Sockets Layer
Crestron 2-Series control systems are the first in the AV industry to provide built-in
support for SSL,
S
ecure
S
ockets
L
ayer, the de facto standard for protecting Web-
based communication between clients and servers. SSL is a protocol that provides a
secure channel for communication between two machines. The secure channel is
transparent, which means that it passes the data through, unchanged. The data is
encrypted between the client and the server, but the data that one end writes is
exactly what the other end reads. The SSL protocol uses TCP as the medium of
transport.
SSL ensures that the connection between a Web browser and Web server is secure by
providing
authentication
and
encryption
. Authentication confirms that servers, and
sometimes clients, are who they say they are. Encryption creates a secure “tunnel”
between the two, which prevents unauthorized access to the system.
The secure tunnel that SSL creates is an encrypted connection that ensures that all
information sent between the client and server remains private. SSL also provides a
mechanism for detecting if someone has altered the data in transit. If at any point
SSL detects that a connection is not secure, it will terminate the connection and the
client and server will have to establish a new, secure connection.
SSL uses both
public-key
and
symmetric key
encryption techniques. Public keys are
a component of public-key cryptographic systems. The sender of a message uses a
public key to encrypt data; the recipient of the message can only decrypt the data
with the corresponding private key. Public keys are known to everybody, while
private keys are secret and only known to the recipient of the message. Since only the
server has access to its private key, only the server can decrypt the information. This
is how the information remains confidential and tamper-proof while in transit across
the network.
An SSL transaction consists of two distinct parts: the key exchange, and the bulk data
transfer. The SSL Handshake Protocol handles key exchange and the SSL Record
Protocol handles the bulk data transfer.
The key exchange (SSL handshake protocol) begins with an exchange of messages
called the SSL handshake. During the handshake, the server authenticates itself to the
client using public-key encryption techniques. Then the client and the server create a
set of symmetric keys that they use during that session to encrypt and decrypt data
and to detect if someone has tampered with the data. Symmetric key encryption is
much faster than public-key encryption, while public-key encryption provides strong
authentication techniques.
Once the key exchange is complete, the client and the server use this session key to
encrypt all communication between them. They do this encryption with a
cipher
, or
symmetric key encryption algorithm, such as RC4 or DES. This is the function of the
SSL Record Protocol. There are two types of ciphers, symmetric and asymmetric.
Symmetric ciphers require the same key for encryption and decryption, whereas with
asymmetric ciphers, data can be encrypted using a public key, but decrypted using a
private key.
SSL supports a variety of ciphers that it uses for authentication, transmission of
certificates, and establishing session keys. SSL-enabled devices can be configured to
support different sets of ciphers, called
cipher suites
.
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Crestron e-Control®
Reference Guide – DOC. 6052
