MiracleLinux8.8 ; SSH public key cryptography setting

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SSH public key cipher setting

SSH public key cipher setting

1.Create a key pair

Create a public/private key pair for a user connecting to a Linux server using OpenSSH.
Use ssh-keygen to create the key pair.
The creation of a public/private key pair must be done as a user with remote login privileges.

If you do not specify the destination and file name, id_ed25519 and id_ed25519.pub will be created in /home/(user name)/.ssh/. On the way, enter the password for the key.

# su – <user name>
$  ssh-keygen -t ed25519
Generating public/private ed25519 key pair.
Enter file in which to save the key (/home/huong/.ssh/id_ed25519):
Created directory '/home/huong/.ssh'.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/huong/.ssh/id_ed25519.
Your public key has been saved in /home/huong/.ssh/id_ed25519.pub.
The key fingerprint is:
SHA256:nIJyadLBDmXJoozL8K2TGA6yXzPSV181nbT3R3+QSVE huong@localhost.localdomain
The key's randomart image is:
+--[ED25519 256]--+
|   .o.        o+E|
|  .+o        ..+o|
|o...o         *o+|
|+. + + . .   . ++|
|ooo.B . S   .   =|
|=..*.  o . .    o|
|++.o= .   .      |
|o.+o +           |
| ...             |
+----[SHA256]-----+

# su – <user name>

$ ssh-keygen -t ed25519

Generating public/private ed25519 key pair.

Enter file in which to save the key (/home/huong/.ssh/id_ed25519):

Created directory '/home/huong/.ssh'.

Enter passphrase (empty for no passphrase):

Enter same passphrase again:

Your identification has been saved in /home/huong/.ssh/id_ed25519.

Your public key has been saved in /home/huong/.ssh/id_ed25519.pub.

The key fingerprint is:

SHA256:nIJyadLBDmXJoozL8K2TGA6yXzPSV181nbT3R3+QSVE huong@localhost.localdomain

The key's randomart image is:

+--[ED25519 256]--+

| .o. o+E|

| .+o ..+o|

|o...o *o+|

|+. + + . . . ++|

|ooo.B . S . =|

|=..*. o . . o|

|++.o= . . |

|o.+o + |

| ... |

+----[SHA256]-----+

$ cat ~/.ssh/id_ed25519.pub >> ~/.ssh/authorized_keys
$ chmod 600 ~/.ssh/authorized_keys
$ chmod 700 ~/.ssh/

$ cat ~/.ssh/id_ed25519.pub >> ~/.ssh/authorized_keys

$ chmod 600 ~/.ssh/authorized_keys

$ chmod 700 ~/.ssh/

2.Private Key Login Settings

$ su -
# vi /etc/ssh/sshd_config
Delete "#" at the beginning of the line per line 49
Before change)
#PubkeyAuthentication yes
After the change)
PubkeyAuthentication yes

$ su -

# vi /etc/ssh/sshd_config

Delete "#" at the beginning of the line per line 49

Before change)

#PubkeyAuthentication yes

After the change)

PubkeyAuthentication yes

SSH restart

# systemctl restart sshd.service

1	# systemctl restart sshd.service

Copy the private key to the client PC (using WinSCP) Configure WinSCP settings
①Start WinSCP, set the following in "New Site", and click "Save".
Host name :　Server IP address
Port number :　 SSH port number
User name :　User name
Password : 　User password

Name the connection with any name.

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).

3.Change to log in only with private key

# vi /etc/ssh/sshd_config
■Per Line 69
Add "PasswordAuthentication no" under "#PasswordAuthentication yes"
#PasswordAuthentication yes
PasswordAuthentication no

# vi /etc/ssh/sshd_config

■Per Line 69

Add "PasswordAuthentication no" under "#PasswordAuthentication yes"

#PasswordAuthentication yes

PasswordAuthentication no

SSH restart

# systemctl restart sshd.service

1	# systemctl restart sshd.service

4.Creating a private key using PuTTYgen

Launch Winscp and start run PuTTYgen from Tools

Click Load [ Open File Dialog ], change the file type to [ All Files (. Change the file type to [ All Files (. *) ] and load the private key id_ed25519 transferred from the Linux server.