How to create an SSH key pair in Linux/Mac/Windows(Cygwin/OpenSSH)

Warning: If your SSH private key is leaked, your account will be misused by the third-party. Please secure your private key with setting the passphrase.

SSH key pair creation method in Linux / Mac / Windows (Cygwin or OpenSSH) is as follows.
Please check man ssh-keygen command for key type difference.
There are correspondence / unsupported types depending on the version of openssh.

ecdsa key type:

$ ssh-keygen -t ecdsa

RSA key type:

$ ssh-keygen -t rsa

ed25519 key type:

$ ssh-keygen -t ed25519

When you execute one of the above commands, you will be asked for the save location as follows.
If there is special circumstance to avoid, such as the same filename is already used for other purpose, just press Enter key to use the default value.
(If you are already using SSH key pair for other sites, you can reuse the same file for TSUBAME)

Generating public/private keytype key pair.
Enter file in which to save the key $HOME/.ssh/id_keytype: (No need to type filename)[Enter]

Then you will be prompted for a passphrase, so enter it.

Enter passphrase (empty for no passphrase): (Set passphrase; What you type will not appear in screen) [Enter]

Re-enter your passphrase for confirmation.

Enter same passphrase again: (Enter the same passphrase again for confirmation; What you type will not appear in screen) [Enter]

A key pair is created and saved to two files. The upper line shows the location of private key, and the lower line shows that of public key. Register the public key via TSUBAME portal.

our identification has been saved in $HOME/.ssh/id_keytype
Your public key has been saved in $HOME/.ssh/
The key fingerprint is:
SHA256:random number:username@hostname
The key's randomart image is:
(Some text specific to the generated key pair will be shown)

Check the file with the following command.

$ ls ~/.ssh/ -l
drwx------  2 user group     512 Oct  6 10:50 .
drwx------ 31 user group    4096 Oct 6 10:41 ..
-rw-------  1 user group     411 Oct 6 10:50 private_key
-rw-r--r--  1 user group      97 Oct 6 10:50 public_key


$ chmod 700 ~/.ssh
$ chmod 600 ~/.ssh/private_key