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Using and Managing AWS – Part 6: SSH Key Pairs

May 26th, 2009

Generate Your Keys

Now that you have chosen your instance, but before starting you actually start your instance, you need to generate your key pairs. The keypairs are SSH keypairs. A later post will explain SSH in greater detail but the keys come in a pair because there is both public and private components.

SSH is a Secure SHell. This is a command prompt like a DOS box or a telnet connection. However, unlike DOS and Telnet, it is very secure. The private key is the local machine’s secret password. The public key is shared to any host that the local machine will connect to.

The host is able to create a query after seeing the public key that only someone with the private key could answer. The private key is never shared but the host is convinced that it is talking to the person (or machine) that is says it is.

This may sound confusing but it is actually very secure. It’s is much better than passwords that can be hacked or accidentally given away.

Amazon supports SSH and secure communications out of the box. If you choose to revert to simple protocols such as telnet and ftp and to password authentication, you may do so. However, your first connection to any instance started through AWS will have to be via SSH. Amazon makes it easy to be secure but gives you the option of making it less secure.

So at least one pair of keys needs to be generated. Each tool set that you choose will create the files in a different way. If you are running the command line tools, you will run the ec2-add-keypair program. If running ElasticFox or CloudStudio, you will have a button on the GUI. However you create the keypair, the end result is that you will end up with a file that tends in a .pem format.

When running SSH (and the tools) from a Windows client, you will need to convert the .pem file to a PuTTY formatted key file. PuTTY, like SSH will be documented in greater detail in a near future post. Review that post for tips on Converting SSH to PuTTY.

You choose an instance’s keypair when you start it and you cannot change that after it is running. Generate your key pair and getting working first.

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