I need to automate ssh-keygen -t rsa with out a password i.e. Enter at the prompt. To generate a SSH keypair without being prompted for a passphrase you can do. Public key authentication can allow you to log into remote systems via SSH without a password. Even though you will not need a password to log into a system, you will need to have access to the key.

Jun 22, 2012 SSH keys provide a more secure way of logging into a virtual private server with SSH than using a password alone. With SSH keys, users can log into a server without a password. This tutorial explains how to generate, use, and upload an SSH Key Pair. Jun 13, 2019. Nov 20, 2008 Note: This has added the key displayed by ssh-add -L Three Minor Annoyances of ssh-copy-id. Following are few minor annoyances of the ssh-copy-id. Default public key: ssh-copy-id uses /.ssh/identity.pub as the default public key file (i.e when no value is passed to option -i). Instead, I wish it uses iddsa.pub, or idrsa.pub, or identity.

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This article or section needs expansion.

Reason: The intro and Background section ignore the server perspective. (Discuss in Talk:SSH keys#)

SSH keys can serve as a means of identifying yourself to an SSH server using public-key cryptography and challenge-response authentication. The major advantage of key-based authentication is that in contrast to password authentication it is not prone to brute-force attacks and you do not expose valid credentials, if the server has been compromised.[1]

Furthermore SSH key authentication can be more convenient than the more traditional password authentication. When used with a program known as an SSH agent, SSH keys can allow you to connect to a server, or multiple servers, without having to remember or enter your password for each system.

Key-based authentication is not without its drawbacks and may not be appropriate for all environments, but in many circumstances it can offer some strong advantages. A general understanding of how SSH keys work will help you decide how and when to use them to meet your needs.

This article assumes you already have a basic understanding of the Secure Shell protocol and have installed the openssh package.

2Generating an SSH key pair
- 2.1Choosing the authentication key type
- 2.2Choosing the key location and passphrase
3Copying the public key to the remote server
4SSH agents
- 4.1ssh-agent
- 4.3Keychain
- 4.4x11-ssh-askpass
- 4.5pam_ssh
5Troubleshooting

Background

SSH keys are always generated in pairs with one known as the private key and the other as the public key. The private key is known only to you and it should be safely guarded. By contrast, the public key can be shared freely with any SSH server to which you wish to connect.

If an SSH server has your public key on file and sees you requesting a connection, it uses your public key to construct and send you a challenge. This challenge is an encrypted message and it must be met with the appropriate response before the server will grant you access. What makes this coded message particularly secure is that it can only be understood by the private key holder. While the public key can be used to encrypt the message, it cannot be used to decrypt that very same message. Only you, the holder of the private key, will be able to correctly understand the challenge and produce the proper response.

Generate Ssh Key Windows

This challenge-response phase happens behind the scenes and is invisible to the user. As long as you hold the private key, which is typically stored in the ~/.ssh/ directory, your SSH client should be able to reply with the appropriate response to the server.

A private key is a guarded secret and as such it is advisable to store it on disk in an encrypted form. When the encrypted private key is required, a passphrase must first be entered in order to decrypt it. While this might superficially appear as though you are providing a login password to the SSH server, the passphrase is only used to decrypt the private key on the local system. The passphrase is not transmitted over the network.

Generating an SSH key pair

An SSH key pair can be generated by running the ssh-keygen command, defaulting to 3072-bit RSA (and SHA256) which the ssh-keygen(1) man page says is 'generally considered sufficient' and should be compatible with virtually all clients and servers:

The randomart image was introduced in OpenSSH 5.1 as an easier means of visually identifying the key fingerprint.

Note: You can use the -a switch to specify the number of KDF rounds on the password encryption.

You can also add an optional comment field to the public key with the -C switch, to more easily identify it in places such as ~/.ssh/known_hosts, ~/.ssh/authorized_keys and ssh-add -L output. For example:

will add a comment saying which user created the key on which machine and when.

Choosing the authentication key type

OpenSSH supports several signing algorithms (for authentication keys) which can be divided in two groups depending on the mathematical properties they exploit:

DSA and RSA, which rely on the practical difficulty of factoring the product of two large prime numbers,
ECDSA and Ed25519, which rely on the elliptic curve discrete logarithm problem. (example)

Elliptic curve cryptography (ECC) algorithms are a more recent addition to public key cryptosystems. One of their main advantages is their ability to provide the same level of security with smaller keys, which makes for less computationally intensive operations (i.e. faster key creation, encryption and decryption) and reduced storage and transmission requirements.

OpenSSH 7.0 deprecated and disabled support for DSA keys due to discovered vulnerabilities, therefore the choice of cryptosystem lies within RSA or one of the two types of ECC.

#RSA keys will give you the greatest portability, while #Ed25519 will give you the best security but requires recent versions of client & server[2]^{[dead link 2020-04-02 ⓘ]}. #ECDSA is likely more compatible than Ed25519 (though still less than RSA), but suspicions exist about its security (see below).

Note: These keys are used only to authenticate you; choosing stronger keys will not increase CPU load when transferring data over SSH.

RSA

ssh-keygen defaults to RSA therefore there is no need to specify it with the -t option. It provides the best compatibility of all algorithms but requires the key size to be larger to provide sufficient security.

Minimum key size is 1024 bits, default is 3072 (see ssh-keygen(1)) and maximum is 16384.

If you wish to generate a stronger RSA key pair (e.g. to guard against cutting-edge or unknown attacks and more sophisticated attackers), simply specify the -b option with a higher bit value than the default:

Be aware though that there are diminishing returns in using longer keys.[3][4] The GnuPG FAQ reads: 'If you need more security than RSA-2048 offers, the way to go would be to switch to elliptical curve cryptography — not to continue using RSA'.[5]

On the other hand, the latest iteration of the NSA Fact Sheet Suite B Cryptography^{[dead link 2020-04-02 ⓘ]} suggests a minimum 3072-bit modulus for RSA while '[preparing] for the upcoming quantum resistant algorithm transition'.[6]

ECDSA

The Elliptic Curve Digital Signature Algorithm (ECDSA) was introduced as the preferred algorithm for authentication in OpenSSH 5.7. Some vendors also disable the required implementations due to potential patent issues.

There are two sorts of concerns with it:

Political concerns, the trustworthiness of NIST-produced curves being questioned after revelations that

Linux Generate Ssh Key No Password