On an EOSIOblockchain, the principle identifier for a user is an account name, rather than public key. An account can be controlled through public key/private key pairs. By default, an account name is 12 characters long, and must be made up of the lowercase letters a through z, and the numbers 1 through 5. There is a mechanism to obtain shorter account names, through Namespace Bidding. An account can have many different permissions associated to different actions that can be done on the EOS network. These permissions are controlled through various private keys, or specific authorities can be delegated to other accounts.