Puttygen SSH public key

Using public key authentication instead of a password ensures a much higher level of security when using SSH to sign into your server. After generating a public and private key pair, the private key is kept on the computer you log in from and the public key is kept on the server you want to log in to (in this case, the server hosting your PSU webspace and Unix home directory). This makes your login process more secure, because authentication requires something that you have (your private key) as well as something that you know (your public key's passphrase).

Creating a Public and Private Key Pair

PuTTY is an SSH client for Windows that comes with a program called PuTTYgen, a key generation utility that will produce a private and public key pair. For more information about obtaining and setting up PuTTY, go to Secure Shell (SSH).

Once you have PuTTY installed on your computer, you can create a public and private key pair with PuTTYgen by following these steps:

  1. Select the Start button in the bottom left-hand corner of your desktop.
  2. Select All Programs, then PuTTY.
  3. Select PuTTYgen.
  4. In the program window that comes up, change "Number of bits…" from 1024 to 4096.
  5. For "Type of key to generate, " select "SSH-2 RSA".
  6. Select the Generate button.
  7. Move your mouse around the blank area to generate randomness and fill the status bar.
  8. Wait while the key is generated, then enter the following information:
  9. Key comment: You may leave the default comment, which contains the key type and the date it was generated, or change it to something else. Another common format is your name and the name of the computer (ex: "john@john-pc"). The comment is displayed whenever PuTTY asks you for your passphrase.
  10. Key passphrase: Enter a strong passphrase here. PuTTY documentation recommends avoiding a "song lyric, quotation or other well-known sentence". Try to create a passphrase of 10 to 30 characters with word breaks, mixed case, number, and special characters (ex: "VikingS $CORE another ^g0al^"). You also have the option of leaving the passphrase blank, but this will save your key unencrypted. Do not forget your passphrase, as there is no way to recover it.
  11. Confirm passphrase: Enter the same passphrase you just created.
  • Select "Save private key".
  • In the dialog box that appears, select a directory to save your private key, type in a file name, and select Save.
  • Select "Save public key".
  • In the dialog box that appears, select a directory to save your public key, type in a file name and add ".pub" to the end, then select Save.
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