what is ssh linux

What is ssh linux?

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

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

The ssh client can use XSHELL, Securecrt, Mobaxterm and other tools to connect

The working mechanism of SSH

When the server starts, it generates a key (768bit public key). The local ssh client sends a connection request to the ssh server, and the server checks the connection. Click on the data and IP address sent by the client, and send the key (768bits) to the client after confirming it is legal. At this time, the client combines the local private key (256bit) and the server's public key (768bit) into a key pair key (1024bit) ), 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 implant malicious code

2.SSH2 adds a Diffe_Hellman mechanism to confirm the correctness of the connection. Each time the data is During transmission, the server will check the correctness of the data source to avoid hacker intrusion.

SSH2 supports RSA and DSA keys

DSA: digital signature Algorithm Digital signature

RSA: can both digitally sign and encrypt

Summary of SSH knowledge

1.SSH is a secure encryption protocol, used to remotely connect to Linux servers

2. The default port of SSH is 22, and the security protocol version is SSH2

3. The SSH server mainly includes 2 service functions: SSH connection and SFTP server. , learning address:

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