What is sshlinux-linux operation and maintenance

What is ssh linux?

SSH (remote connection tool) connection principle: ssh service is a daemon process (demon), the system monitors the connection of the client in the background, and the process of the ssh server is called sshd, which is responsible for real-time monitoring of the client Request (IP 22 port), including the exchange of public keys and other information.

The ssh server consists of 2 parts: openssh (provides ssh service) openssl (provides encryption program)

The ssh client can be connected with XSHELL, Securecrt, Mobaxterm and other tools

The working mechanism of SSH

When the server starts up, it generates a key (768bit public key), and the local ssh client sends a connection request to ssh The server, the server checks the data and IP address sent by the connection point client, and sends the key (768bits) to the client after confirming that it is legal. At this time, the client combines the local private key (256bit) and the server’s public key (768bit) into an encrypted key. The key pair key (1024bit) is sent back to the server, and the connection is established through key-pair data transmission.

SSH encryption technology

Encryption technology: transmission process, data encryption.

1.SSH1 does not verify the client’s secret key, and it is easy to be implanted with malicious code

2.SSH2 adds a Diffe_Hellman mechanism to confirm the correctness of the connection. During data transmission, the Server will check the correctness of the data source to avoid hacking.

SSH2 supports RSA and DSA keys

DSA: digital signature Algorithm digital signature

RSA: both digital signature and encryption

SSH knowledge summary

1.SSH is a secure encryption protocol for remote connection to Linux servers

2. The default port of SSH is 22, safe The protocol version is SSH2

3. The SSH server mainly includes two service functions: SSH connection and SFTP server

4. The SSH client includes ssh connection commands and remote copy scp commands, etc.

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