Difference between revisions of "Making an ssh key"

From PrgmrWiki
(PuTTY (Windows Only))
(Key Generation)
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Terminal comes installed with OS X.
Terminal comes installed with OS X.
=== Key Generation ===
=== Key Generation ===
<li>Check for existing keys before beginning:
Check for existing keys before beginning:
ls -la ~/.ssh
ls -la ~/.ssh
If there is no key you already want to use, generate a new key with:
If there is no key you already want to use, generate a new key as shown in the following sections.
$ ssh-keygen -t rsa -b 4096
Generating public/private rsa key pair.
Enter file in which to save the key (/home/<user>/.ssh/id_rsa): /home/<user./.ssh/<keyname>
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/<user>/.ssh/<keyname>.
Your public key has been saved in /home/<user>/.ssh/<keyname>.pub.
The key fingerprint is:
The key's randomart image is:
+--[ RSA 4096]----+
|.oo.o.  o      |
|...+ .  . o      |
| .=.= .. .      |
|  .+.+..  .      |
|  ...  SE o . . |
|    .    . o +  |
|            +  |
|              .  |
If you use the default key filename /home/<user>/.ssh/id_rsa , ssh will try to use it automatically.
We support rsa, dsa, dss, and also ecdsa (on newer servers only). We recommend at least 2048 bits in your key (or 256 for ecdsa). We do not yet support ed25519. You can choose an alternate algorithm by using the -t flag.
== Generating an SSH Key in Windows ==
== Generating an SSH Key in Windows ==

Revision as of 21:43, 30 August 2020

Programs have different options for the ssh public key format. We use the OpenSSH key format. It is safe to share your public key with anyone. Never share your private key!

OpenSSH (Linux, Windows Cygwin) and Terminal (OS X)

    Linux Installation Instructions

    If openssh is not already installed, on Debian/Ubuntu try
    aptitude install openssh-client
    or on Redhat/CentOS
    yum install openssh-clients
    or download the portable source from openssh.org and compile it. When OpenSSH is setup you can generate a key and try to login.

    Windows Installation Instructions

    Install cygwin from https://cygwin.com and select the openssh package.

    OS X Installation Instructions

    Terminal comes installed with OS X.

    Key Generation

    Check for existing keys before beginning:

    ls -la ~/.ssh

    If there is no key you already want to use, generate a new key as shown in the following sections.

    Generating an SSH Key in Windows

    Windows 10 has an OpenSSH client (ssh-keygen) installed by default. We recommend using this tool if possible. However if not then see instructions for PuTTY below.

    Prgmr.com supports several SSH key algorithms. In order from the most to least-widely supported:

  1. RSA: An old algorithm based on the difficulty of factoring large numbers. we recommend a key size of 4096 bits. All SSH clients support this algorithm, and this is the most generally useful algorithm.
  2. ECDSA: We recommend always using it with 521 bits (that's not a typo!). Most SSH clients now support this algorithm
  3. ED25519 - This is a relatively new algorithm in OpenSSH. It is not as widely supported as RSA and ECDSA. However we do support it, and it is highly secure.

    Using the Native Win 10 SSH Client

    1. First, verify that the Windows SSH client is installed on your computer. Press the Windows logo key on your keyboard or click on the Start Menu. Type cmd. Right-click on the Windows Command Prompt and select Run as administrator.
    2. In the command line, type ssh and Enter. If the client is installed, then Windows will return a short summary of command-line options.
    3. In the command line, enter ssh-keygen to use the default values (Algorithm RSA, keysize 2048 bits). To select a different algorithm and keysize, use the -t and -b options, as shown below.
      • ssh-keygen -t rsa -b 4096
      • ssh-keygen -t ecdsa -b 521
      • ssh-keygen -t ed25519
    4. In all cases, Windows will return a default directory and filename under which to save the private key. If you wish to use a different name and path then enter it with the -f <filename> option, as in ssh-keygen -f ~/<filename> -t ed25519. (This example uses the tilde (~) notation for your Windows home directory.)
    5. Windows then requires a password or passphrase to encrypt the keys. Use a strong password for this.

    Once all the required information is entered, Windows will return the location of your public and private keys, the key hash, and other information.

    Installing PuTTY

    Download the PuTTY installer and install it. These are the keys for verifying the signature.

    Key Generation with PuTTY

    1. Run PuTTYgen
    2. Click "Generate" to generate a key
    3. Enter a passphrase for the private key.
    4. Save the private key.
    5. Copy/paste the "OpenSSH authorized_keys" text to a separate public key file. The contents of this file (typically starting with ssh-rsa or ssh-dss) is what you need to use when either signing up or changing the key for a VM.

    The config settings to access the management console are at Management Console#Logging in via PuTTY

    Commercial SSH Clients

    These are links to tutorials for the given client. We do not have personal experience with any of these clients.