Chuck Nemeth

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======SSH Key Management======

This page is meant to assist in setting up and maintaining SSH keys.

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=====SSH Directory Permissions=====

<code bash>
chmod 700 ~/.ssh
chmod 644 ~/.ssh/authorized_keys
chmod 644 ~/.ssh/known_hosts
chmod 644 ~/.ssh/config
chmod 600 ~/.ssh/id_ed25519
chmod 644 ~/.ssh/id_ed25519.pub
chmod 600 ~/.ssh/id_rsa
chmod 644 ~/.ssh/id_rsa.pub
</code>

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=====Generating SSH Keys=====
====ED25519====
  * Change to ''%%~/.ssh%%'':<code bash>
cd ~/.ssh
</code>
  * Generate an **Ed25519** ssh key:<code bash>
ssh-keygen -t ed25519 -a 256
</code>
  * Generate an **Ed25519** ssh key with a specific name:<code bash>
ssh-keygen -f <keyname> -t ed25519 -a 256
</code>

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====RSA====
  * Change to ''%%~/.ssh%%'':<code bash>
cd ~/.ssh
</code>
  * Generate a **RSA** ssh key:<code bash>
ssh-keygen -t rsa -b 4096 -o -a 256
</code>
  * Generate a **RSA** ssh key with a specific name:<code bash>
ssh-keygen -f <keyname> -t rsa -b 4096 -o -a 256
</code>

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=====Verifying SSH Keys=====
====Verify SSH Key Password====
  * Change to ''%%~/.ssh%%'':<code bash>
cd ~/.ssh
</code>
  * Verify password:<code bash>
ssh-keygen -y -f id_ed25519
</code>
  * Upon entering successful passphrase, it prints the pubkey:<code bash>
Enter passphrase: 
ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIJAZcdEIpPbJal7CEsIpaHzBEjs/8nedIvDA/sDlvqll chuck@gaming
</code>
  * Enter the wrong passphrase:<code bash>
ssh-keygen -y -f id_ed25519
Enter passphrase: 
Load key "id_ed25519": incorrect passphrase supplied to decrypt private key
</code>

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====Verify SSH Private Key Matches Public Key====
  * Change to ''%%~/.ssh%%'':<code bash>
cd ~/.ssh
</code>
  * Verify ssh key matches it's private key:<code bash>
ssh-keygen -l -f id_ed25519; ssh-keygen -l -f id_ed25519.pub
</code>
  * Output should match:<code bash>
256 SHA256:W5o5+DV3Jaba4txzQ58gZuIZvZD44McIU7tV9I4LZpw chuck@gaming (ED25519)
256 SHA256:W5o5+DV3Jaba4txzQ58gZuIZvZD44McIU7tV9I4LZpw chuck@gaming (ED25519)
</code>

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=====Modifying SSH Keys=====

====Change SSH Key Password====
  * Change to ''%%~/.ssh%%'':<code bash>
cd ~/.ssh
</code>
  * Change password:<code bash>
ssh-keygen -p -f id_ed25519
</code>

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====Change SSH Key Comment====
  * Change to ''%%~/.ssh%%'':<code bash>
cd ~/.ssh
</code>
  * Change comment (email):<code bash>
ssh-keygen -c -f id_ed25519
Enter passphrase: 
Key now has comment 'chuck@hostname'
Enter new comment: user@newname
The comment in your key file has been changed.
</code>

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=====SSH-Agent=====
  * Add the key to the ssh-agent.<code bash>
ssh-add keyname
</code>
  * Add the key to the server using the credentials from the config file.<code bash>
ssh-copy-id -i keyname servername
</code>

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=====Links=====
  * https://manpages.debian.org/stable/openssh-client/ssh.1.en.html
  * https://manpages.debian.org/stable/openssh-client/ssh-keygen.1.en.html
  * https://manpages.debian.org/stable/openssh-client/ssh-add.1.en.html
  * https://manpages.debian.org/stable/openssh-client/ssh-copy-id.1.en.html