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7-4 Secure Socket Layer (SSL)
Secure Sockets Layer or SSL is a security feature that will provide a secure communication path between a host and client through the use of authentication,digital
signatures and encryption.These security functions are implemented through the use of a ciphersuite,which is a security string that determines the exact
cryptographic parameters, specific encryption algorithms and key sizes to be used for an authentication session and consists of three levels:
1. Key Exchange:The first part of the ciphersuite string specifies the public key algorithm to be used.This Switch utilizes the Rivest Shamir Adleman
(RSA) public key algorithm and the Digital Signature Algorithm (DSA),specified here as the
DHE DSS Diffie-Hellman (DHE) public key algorithm.This
is the first authentication process between client and host as they “exchange keys” in looking for a match and therefore authentication to be accepted
to negotiate encryptions on the following level.
2.
Encryption:The second part of the ciphersuite that includes the encryption used for encrypting the messages sent between client and host.The
Switch supports two types of cryptology algorithms:
Stream Ciphers – There are two types of stream ciphers on the Switch,
RC4 with 40-bit keys and RC4 with 128-bit keys.These keys are used to encrypt
messages and need to be consistent between client and host for optimal use.
CBC Block Ciphers – CBC refers to Cipher Block Chaining,which means that a portion of the previously encrypted block of encrypted text is used
in the encryption of the current block.The Switch supports the
3DES EDE encryption code defined by the Data Encryption Standard (DES) to create
the encrypted text.
3. Hash Algorithm:This part of the ciphersuite allows the user to choose a message digest function which will determine a Message Authentication
Code.This Message Authentication Code will be encrypted with a sent message to provide integrity and prevent against replay attacks.The Switch
supports two hash algorithms,
MD5 (Message Digest 5) and SHA (Secure Hash Algorithm).
These three parameters are uniquely assembled in four choices on the Switch to create a three-layered encryption code for secure communication between the
server and the host.The user may implement any one or combination of the ciphersuites available, yet different ciphersuites will affect the security level and the
performance of the secured connection.The information included in the ciphersuites is not included with the Switch and requires downloading from a third
source in a file form called a
certificate.This function of the Switch cannot be executed without the presence and implementation of the certificate file and can be
do
wnloaded to the Switch by utilizing a TFTP server.The Switch supports SSLv3 and TLSv1.Other versions of SSL may not be compatible with this Switch and
may cause problems upon authentication and transfer of messages from client to host.
Download Certificate
This window is used to download a certificate file for the SSL function on the Switch from a TFTP server.The certificate file is a data record used for
authenticating devices on the network.It contains information on the owner,keys for authentication and digital signatures.Both the server and the client must
have consistent certificate files for optimal use of the SSL function.The Switch only supports certificate files with .der file extensions.
To view the following window,click Security Management > Secure Socket Layer (SSL) > Download Certificate:
Figure 7- 21.Download Certificate window
To download certificates,set the following parameters and click
Apply.
P
a
r
ameter Description
Cer
tificate T
ype
Enter the type of cer
tificate to be do
wnloaded.
This type r
efers to the server responsible for issuing
cer
tificates.This field has been limited to
local f
or this firmware release.
Server IP Enter the IP address of the TFTP server where the certificate files are located.
Certificate File Name Enter the path and the filename of the certificate file to download.This file must have a .der extension.(Ex.
c:/cer
t.der).
Key File Name Enter the path and the filename of the key file to download.This file must have a .der extension (Ex.
c:/pkey.der).
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Allied Telesyn AT-9724TS High-Density Layer 3 Stackable Gigabit Ethernet Switch