EC2 Key Pairs:

• EC2 key pairs are two cryptographically secure keys that are used by AWS to authenticate a client when logging into an EC2 instance.
• Each key pair consists of a public key and a private key.
• AWS stores the public key on the instance, and you are responsible for storing the private key.

To log into an EC2 instance, you must create and authenticate with a key pair:

• Linux instances have no password, and you use a key pair to log in (using SSH).
• With Windows instances, you use a key pair to obtain the administrator password and then log in using RDP (remote desktop protocol).
• During the creation process of an EC2 instance, you are required to either create a new key pair OR use an existing key pair - which will be tied to the instance.
• The private key is available for download and stored on your local device, however, it is only available once (in the form of a .pem file).

For SSH login to Linux instance:

• You will most likely need to change permissions on the .pem file before you can use it to login via SSH.
• This is done by running the following command "chmod 400 [key name].pem".