ssh & sshd

[linux learner <linuxlearner03@yahoo.com>]

hi all,

i just started using sshd on my two debian boxes at
home. 

i understand that i can log into any computer that has
my public key in ~/.ssh/authorized_keys 

but when i log into my computer running sshd it
automatically adds me to the authorized_keys list for
that user. How do i turn it off?

Also, what is the function of private key locking pass
phrase? 

Say i am physically logged into my home account and my
pub and private keys are in ~/.ssh/ now when i log
into a remote host, i give my log in and password on
the remote host and it logs me in and if my public key
isn?t there in authorized_keys list it is added, my
private key pass phrase is never asked, is this
normal?

thanks for the patience n everything!

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