Asymmetric Key Algorithm; Ssh Operating Process - H3C S5600 SERIES Operation Manual

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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 1-1 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, while the private key is effective only for

the local end. Normally you cannot use the private key through the public key.

Asymmetric key algorithm encrypts data using the public key and decrypts the data using the private

key, thus ensuring data security.

You can also use the asymmetric key algorithm for data signature. For example, user 1 adds his

signature to the data using the private key, and then sends the data to user 2. User 2 verifies the

signature using the public key of user 1. If the signature is correct, this means that the data originates

from user 1.

Both Revest-Shamir-Adleman Algorithm (RSA) and Digital Signature Algorithm (DSA) are asymmetric

key algorithms. RSA is used for data encryption and signature, whereas DSA is used for adding

Currently, SSH supports both RSA and DSA.

The session establishment between an SSH client and the SSH server involves the following five

Table 1-1 Stages in establishing a session between the SSH client and server

Version negotiation

Key and algorithm negotiation

SSH1 and SSH2 are supported. The two parties negotiate

a version to use.

SSH supports multiple algorithms. The two parties

negotiate an algorithm for communication.

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