Ssh Private Key Example

On execution, we are prompted to specify a file in which to save the private key, the default being /home/user/.ssh/idrsa; here idrsa is the name of our Private Key file. You can always specify a different path and name for the Private Key file. For our demonstration, we shall use the default configuration. Step 2: Provide A Passphrase (Optional).

  1. Ssh Private Key File Example
  2. Ssh-rsa Private Key Example
  3. Example Of Ssh Key

Private keys allow the users to login to SSH without a password. This is considered a safe practice in some cases while also discards the need to remember multiple passwords.

In this tutorial, we would learn how to generate our own SSH Key Pair on our local machine and then configure our Server to use the same for authentication when trying to connect over SSH.

Steps to Login to SSH Without A Password

Let’s go over the process step-by-step to login to SSH without a password. If you’re new, you can start by reading more about how to connect to a remote host using SSH. If you’re ready, let’s get started.

Basic example The following ssh-keygen command generates 4096-bit SSH RSA public and private key files by default in the /.ssh directory. If an SSH key pair. SSH stands for Secure Shell and is a method used to establish a secure connection between two computers. SSH works by authenticating based on a key pair, with a private key being on a remote server and the corresponding public key on a local machine. When the keys match, access is granted to the remote user. Adding an Arbitrary Key. To add an arbitrary private key, give the path of the key file as an argument to ssh-add. For example, ssh-add /.ssh/tatu-aws-key. Would add the file /.ssh/tatu-aws-key. Keys with Passphrases. If the key being added has a passphrase, ssh-add will run the ssh-askpass program to.

Step 1: Generate SSH Key Pair

On our local machine, we can generate a SSH Key Pair with the following command :

On execution, we are prompted to specify a file in which to save the private key, the default being /home/user/.ssh/id_rsa ; here id_rsa is the name of our Private Key file. You can always specify a different path and name for the Private Key file. For our demonstration, we shall use the default configuration.

Step 2: Provide A Passphrase (Optional)

Next, we are presented with a prompt that asks us for a passphrase that can be used to protect the SSH Private Key from unauthorized access.

However, this field is optional and if left empty, it stores the Private Key file without any protection. In our example, we would leave this field empty. After this, we would have successfully generated our Key Pair. We are also presented with a ‘fingerprint’ and ‘visual fingerprint’ of our key which we need not save.

Step 3: Configure the Server To Use Our Private Key

At this point, we should have the following two files under /home/user/.ssh :

  • id_rsa : Our SSH Private Key
  • id_rsa.pub : Our SSH Public Key
Linux ssh keygen examples

Take note of the permissions of the private key ( id_rsa ). SSH Private Key files should ALWAYS HAVE 600 PERMISSIONS! If not, change its permission to the said value using the chmod command:

Key

Next, we need to configure our Server to use our private key for login. Now this can be done manually by logging into the Server and configuring stuff manually but there’s a tool ssh-copy-id which does all the hard work for us !

Hence, to configure our Server to use our private key, simply run :

Here,

  • USER is the username we want to login as onto the server
  • IP is the IP address of our Server

And with that, we can now simply SSH into our Server with :

If you had previously specified a passphrase, you will get a prompt asking for the same :

Private

Note that if you are not using the default path and file names then you need to specify the private key file using the -i flag as follows :

Thus we successfully SSH’d into our machine using our PRIVATE KEY !

Conclusion

And with that, we were able to login to SSH without a password on our Linux machine. It’s an easy and more secure way of logging in as it locks you to log in from specific IP addresses. If you’re interested in learning more on Linux topics, continue to follow LinuxForDevices.

Documentation » Getting Started » Protocols » SSH »

In every SSH/SFTP connection there are four keys (or two key-pairs) involved. This article explains a difference between them and what keys an SFTP client user needs to care about.

Private

The SSH employs a public key cryptography. A public-key cryptography, also known as asymmetric cryptography, is a class of cryptographic algorithms which requires two separate keys, one of which is secret (or private) and one of which is public.1 Together they are known as a key-pair. In SSH, the public key cryptography is used in both directions (client to server and server to client), so two key pairs are used. One key pair is known as a host (server) key, the other as a user (client) key.

A user private key is key that is kept secret by the SSH user on his/her client machine. The user must never reveal the private key to anyone, including the server (server administrator), not to compromise his/her identity.

To protect the private key, it should be generated locally on a user’s machine (e.g. using PuTTYgen) and stored encrypted by a passphrase. The passphrase should be long enough (that’s why it’s called passphrase, not password) to withstand a brute-force attack for a reasonably long time, in case an attacker obtains the private key file.

Different file formats are used to store private keys. WinSCP supports PuTTY format, with .ppk extension.

A user public key is a counterpart to user private key. They are generated at the same time. The user public key can be safely revealed to anyone, without compromising user identity.

To allow authorization of the user on a server, the user public key is registered on the server. In the most widespread SSH server implementation, the OpenSSH, file ~/.ssh/authorized_keys is used for that.

Ssh Private Key File Example

Learn more about public key authentication in general and how to setup authentication with public keys.

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A host private key is generated when the SSH server is set up. It is safely stored in a location that should be accessible by a server administrator only. The user connecting to the SSH server does not need to care about host private key in general.

Ssh-rsa Private Key Example

A host public key is a counterpart to host private key. They are generated at the same time. The host public key can be safely revealed to anyone, without compromising host identity.

Example Of Ssh Key

To allow authorizing the host to the user, the user should be provided with host public key in advance, before connecting. The client application typically prompts the user with host public key on the first connection to allow the user to verify/authorize the key. The host public key is then saved and verified automatically on further connections. The client application warns the user, if the host key changes.

  1. The text is partially copied from Wikipedia article on Public-key cryptography. The text is licensed under GNU Free Documentation License.Back