Ubuntu Server23.04 ; SSH connection with public key cryptography

SSH connection with authentication using public key cryptography

 Creation of public and private key pairs

Create a public/private key pair for a user connecting to the Linux server using OpenSSH.
Use ssh-keygen to create key pairs.
This time, we will create a key set using the RSA cipher used in the SSH protocol Version 2.
Creation of public/private key pairs is performed with remote login user privileges (huong).
If you do not specify the destination and file name, id_ed25519,id_ed25519.pub will be created in /home/huong/.ssh/. On the way, enter the password for the key.

Save the created private key id_ed25519 to an appropriate location on windows using winSCP.
Start Winscp and click [New Session].

Host name : IP address of the server
Port number : SSH port
User name : Server login user
Password : Password for the same user

Site name : any name
Click "OK"

After confirming the server, click "Login".

Click "Update" when the following screen appears

Password of the logged-in user in the Password field

When connected, the right column is the server side and the left column is the PC (Windows) side.
Save the file "id_ed25519" in the .ssh directory to an appropriate location on Windows in the left column.

Editing SSH Configuration File

Edit the SSH configuration file to disable password authentication.
This time, use su - to become root instead of a normal user.

How to connect with Tera Term
Start Tera Term and select "File" menu "New connection"

Host : IP address of the server
TCP port : SSH port number

If you get the following security warning "Replace…. "Check

User name : Login user name
Password : Password specified when creating a public/private key pair

Under "Use RSA/DSA/ECDSA/ED25519 key to log in", set "id_ed25519" saved in Windows to "Private key file:" and click "OK

Creating a private key using PuTTYgen

Start Winscp and launch Run Puttygen from "Tools".

Select the appropriate server

Click Load

The [ Open File Dialog ] will open, change the file type to [ All Files (. Change the file type to [ All Files (. *) ] and load the private key id_ed25519 that was transferred from the Linux server.

The password is the password set in "Creating a public and private key pair" above

Click on "Save private key"

Save the file with the extension ".ppk" in the same place as "id_ed25519" saved earlier on the Windows side under the name "id_ed25519.ppk".

Select the appropriate server and click "Edit"

Click on "Advanced"

Open the "Authentication" menu and specify "id_ed25519.ppk" saved in Windows for "Private key file"

Click "Save"

Click on "Login"

The password is the password set in "Creating a public and private key pair" above

When connecting with Tera Term, use the following
Use RSA/DSA/ECDSA/…" Specify "id_ed25519.ppk" saved in windows in the "Use RSA/DSA/ECDSA/…" field.

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