3Com 4210 PWR, Configuration Manual

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36
SSH C
ONFIGURATION
SSH Overview
Introduction to SSH Secure Shell (SSH) is a protocol that provides secure remote login and other
security services in insecure network environments. In an SSH connection, data are
encrypted before being sent out and decrypted after they reach the destination.
This prevents attacks such as plain text password interception. Besides, SSH also
provides powerful user authentication functions that prevent attacks such as DNS
and IP spoofing.
SSH adopts the client-server model. The device can be configured as an SSH client
or an SSH server. In the former case, the device establishes a remote SSH
connection to an SSH server. In the latter case, the device provides connections to
multiple clients.
Furthermore, SSH can also provide data compression to increase transmission
speed, take the place of Telnet or provide a secure "channel" for FTP.
c
CAUTION: Currently, the Switch 4210 device supports only SSH2. when
functioning as either an SSH client or an SSH server. Unless otherwise noted, SSH
refers to SSH2 throughout this document.
Algorithm and Key Algorithm is a set of transformation rules for encryption and decryption.
Information without being encrypted is known as plain text, while information
that is encrypted is known as cipher text. Encryption and decryption are performed
using a string of characters called a key, which controls the transformation
between plain text and cipher text, for example, changing the plain text into
cipher text or cipher text into plain text.
Figure 119 Encryption and decryption
Key-based algorithm is usually classified into symmetric key algorithm and
asymmetric key algorithm.
Asymmetric Key
Algorithm
Asymmetric key algorithm means that a key pair exists at both ends. The key pair
consists of a private key and a public key. The public key is effective for both ends,
Encryption
Key
Decryption
Cipher text
Plain text
Key
Plain text Encryption
Key
Decryption
Cipher text
Plain text
Key
Plain text