Public Key Cryptology

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What is Public Key Cryptography? From Wikipedia.

Using OpenSSH

OpenSSH.org

Create Keys

On the client computer:

  • Change to your home directory
 cd ~
  • If it doesn't already exist, create a directory and set permissions
 mkdir ~/.ssh
 chmod 700 ~/.ssh
  • Generate a private/public key pair
 ssh-keygen -b 2048 -t rsa -f ~/.ssh/id_rsa
  • Enter a quality password when requested
    • For automated sessions, use an empty password (remember this is a security risk)
  • The ~/.ssh now has two new files, one named id_rsa and one named id_rsa.pub
  • Now, distribute the public key anywhere that your identity needs to be verified.

Distribute Keys

On the host computer:

  • Copy you public key from the client to the host.
  • Change to your home directory
 cd ~
  • If it doesn't already exist, create a directory and set permissions
 mkdir ~/.ssh
 chmod 700 ~/.ssh
  • Append the public key to the authorized_keys file
 cd ~/.ssh
 cat id_rsa.pub >> authorized_keys

The resulting authorized keys file should look something like this:

 ssh-rsa NLGlkn0j-this-is-the-key-nlsdh9== user@clientname.tld
 ssh-rsa Glkn0j-this-is-another-key-nsd5h= user@anotherclient.tld
 .
 .
 .

Connect from Client to Host

Test the connection

 ssh user@hostname.tld -i ~/.ssh/id_rsa

Enter the passphrase to open the private key when requested.

References