Debian12.5 ; SSH connection using public key cryptography

Create public and private key pairs

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

Use Winscp or other means to save the private key (~/.ssh/id_ed25519) in an appropriate location on Windows.
Start Winscp
Host name  : Server IP Address
Port number : SSH Port
User name : Server Login User
Password : Password for the same user

Site name : Name the connection with any name.
Click "OK"

Click "Login" to return to the following screen.

If the following screen appears, click "Update".

In the following screen, enter the user's password in the "Pasword" field.

The following screen will appear. Copy id_ed25519 in the /home/user/.ssh directory to any location on the windows side (select id_ed25519 and drag & copy it to the left side).

Change to log in only with private key

Edit the SSH configuration file to disable password authentication.
su - to become root.

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

Host : Server IP Address
TCP port : SSH Port number

If you get the following security warning "Replace.... "check the box and "Continue".

User name : Login username
Password :Password specified in the creation of a public/private key pair
Check the "Use RSA/DSA...." checkbox. and in the "Private key file" field, specify the "id_ed25519" that you just saved in windows.

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 (*. *)] and load the private key id_ed25519 transferred from the Linux server.

Enter the passphrase you entered when you created the private key on the server side

Click the [ Save private key ] button to save the private key.

Save it here as id_ed25519.ppk (in Windows).

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
Specify "id_ed25519.ppk" saved in windows

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