Oct20notes
Cryptography from a Computer Perspective
A quick intro:
- crypto algorithm subcategories
- Symmetric cipher (substitution/permutation)
- Asymmetric cipher (Public/private keys)
- Hash functions
Tools:
- SSL/TLS
- ssh
- Using ssh without passwords
First we generate a key (leave file and passphrase empty by default):
mdhcp125:~ gabe$ ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/Users/gabe/.ssh/id_rsa):
/Users/gabe/.ssh/id_rsa already exists.
Overwrite (y/n)? y
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /Users/gabe/.ssh/id_rsa.
Your public key has been saved in /Users/gabe/.ssh/id_rsa.pub.
The key fingerprint is:
b7:b3:f4:5d:11:9a:f8:80:a3:d5:8b:3c:ad:90:08:75 gabe@mdhcp125.marlboro.edu
Next, copy your public key over to host you wish to connect to (in this case, cs):
mdhcp125:~ gabe$ scp .ssh/id_rsa.pub glein@cs:
glein@cs's password:
id_rsa.pub 100% 408 0.4KB/s 00:00
mdhcp125:~ gabe$ ssh glein@cs
glein@cs's password:
Linux cs 2.6.12-10-686-smp #1 SMP Fri Sep 15 16:47:57 UTC 2006 i686 GNU/Linux
Welcome to cs.marlboro.edu
As of Aug 30 2006 we're running Ubuntu on an Athlon 64 X2. Go figure.
Last login: Fri Oct 13 11:47:22 2006 from mdhcp11.marlboro.edu
If you don't have any other public keys stored on the host yet, you can rename the public key "authorized_keys" and move it to the .ssh directory. Otherwise you can use ">>" to append the key to the file.
glein@cs:~$ mv id_rsa.pub .ssh/authorized_keys
- Other common protocols: PGP/GnuPG
- The Weakest Link: human error
- (Lack of) authentication
- Misuse
