SSH public key authentication && SSH key for github && Switch GIT remote repo from https to ssh

 SSH public key authentication

https://www.ssh.com/academy/ssh/public-key-authentication

Each SSH key pair includes two keys:

• A public key that is copied to the SSH server(s). Anyone with a copy of the public key can encrypt data which can then only be read by the person who holds the corresponding private key. Once an SSH server receives a public key from a user and considers the key trustworthy, the server marks the key as authorized in its authorized_keys file. Such keys are called authorized keys.

• A private key that remains (only) with the user. The possession of this key is proof of the user's identity. Only a user in possession of a private key that corresponds to the public key at the server will be able to authenticate successfully. The private keys need to be stored and handled carefully, and no copies of the private key should be distributed. The private keys used for user authentication are called identity keys.

After authetication, remote server creates symmetric key and encrypt with public key to send to user, user can decrpyt using private key, then data exchange is encrypted by symmetric key (Like SSL)

https://superuser.com/questions/383732/how-does-ssh-encryption-work

Here are some practical examples, Assume Key A was kept a secret and is therefor the private key and Key B was posted in a publicly accessible place and therefor is the public key.

So if you want to send a message to everyone and you want them to verify that it came from you and was unaltered while it was being delivered, you would send your message and include a hash of the message encrypted with Key A. Then anyone who has Key B can decrypt the hash, compare it to the message they received, and verify that the message came from you (due to the fact that only a person with Key A could have generated the encrypted payload that successfully decrypted hash, and because you are the only person with Key A it could only come from you). This is called Signing.

Now lets say someone wants to send you a secret message but does not want to reveal who they are. They can encrypt their message with a symmetric key (as Zoredache mentioned symmetric is much cheaper to do) then take that key and encrypt it with Key B and send it to you. Because only Key A can Decrypt something that was encrypted with Key B no other person can see what is in the message that was sent to you. This is how normal encryption works and how SSH exchanges data.

SSH key for github

SSH Keys for GitHub

Objectives

• Explain what an SSH key is
• Generate your own SSH key pair
• Add your SSH key to your GitHub account
• Learn how to use your SSH key in your GitHub workflow

Why Use an SSH Key?

When working with a GitHub repository, you'll often need to identify yourself to GitHub using your username and password. An SSH key is an alternate way to identify yourself that doesn't require you to enter you username and password every time.

SSH keys come in pairs, a public key that gets shared with services like GitHub, and a private key that is stored only on your computer. If the keys match, you're granted access.

The cryptography behind SSH keys ensures that no one can reverse engineer your private key from the public one.

Generating an SSH key pair

The first step in using SSH authorization with GitHub is to generate your own key pair.

You might already have an SSH key pair on your machine. You can check to see if one exists by moving to your .ssh directory and listing the contents.

$ cd ~/.ssh
$ ls

If you see id_rsa.pub, you already have a key pair and don't need to create a new one.

If you don't see id_rsa.pub, use the following command to generate a new key pair. Make sure to replace your@email.com with your own email address.

$ ssh-keygen -o -t rsa -C "your@email.com"

(The -o option was added in 2014; if this command fails for you, just remove the -o and try again)

When asked where to save the new key, hit enter to accept the default location.

Generating public/private rsa key pair.
Enter file in which to save the key (/Users/username/.ssh/id_rsa):

You will then be asked to provide an optional passphrase. This can be used to make your key even more secure, but for this lesson you can skip it by hitting enter twice.

Enter passphrase (empty for no passphrase):

Enter same passphrase again:

When the key generation is complete, you should see the following confirmation:

Your identification has been saved in /Users/username/.ssh/id_rsa.
Your public key has been saved in /Users/username/.ssh/id_rsa.pub.
The key fingerprint is:
01:0f:f4:3b:ca:85:d6:17:a1:7d:f0:68:9d:f0:a2:db your@email.com
The key's randomart image is:
+--[ RSA 2048]----+
|                 |
|                 |
|        . E +    |
|       . o = .   |
|      . S =   o  |
|       o.O . o   |
|       o .+ .    |
|      . o+..     |
|       .+=o      |
+-----------------+

The random art image is an alternate way to match keys but we won't be needing this.

Add your public key to GitHub

We now need to tell GitHub about your public key. Display the contents of your new public key file with cat:

$ cat ~/.ssh/id_rsa.pub

The output should look something like this:

ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEA879BJGYlPTLIuc9/R5MYiN4yc/YiCLcdBpSdzgK9Dt0Bkfe3rSz5cPm4wmehdE7GkVFXrBJ2YHqPLuM1yx1AUxIebpwlIl9f/aUHOts9eVnVh4NztPy0iSU/Sv0b2ODQQvcy2vYcujlorscl8JjAgfWsO3W4iGEe6QwBpVomcME8IU35v5VbylM9ORQa6wvZMVrPECBvwItTY8cPWH3MGZiK/74eHbSLKA4PY3gM4GHI450Nie16yggEg2aTQfWA1rry9JYWEoHS9pJ1dnLqZU3k/8OWgqJrilwSoC5rGjgp93iu0H8T6+mEHGRQe84Nk1y5lESSWIbn6P636Bl3uQ== your@email.com

Copy the contents of the output to your clipboard.

Login to github.com and bring up your account settings by clicking the tools icon.

Select SSH Keys from the side menu, then click the Add SSH key button.

Name your key something whatever you like, and paste the contents of your clipboard into the Key text box.

Finally, hit Add key to save. Enter your github password if prompted.

####Using Your SSH Key

Going forward, you can use the SSH clone URL when copying a repo to your local machine.

This will allow you to bypass entering your username and password for future GitHub commands.

Switch git remote repo from https to ssh

git remote set-url origin git@github.com:username/repo-name-here.git

https://gist.github.com/m14t/3056747

https://help.learn.co/en/articles/493023-how-to-switch-github-remote-from-https-to-ssh