Deleted the authorized_keys file and got into a problem

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http://unix.stackexchange.com – I was trying to send files from suppose machine A to machine B. For that, I created a public-private key pair using "ssh-keygen -t rsa" in machine A.Then I sent the id_rsa.pub file to the machine B and I added that with the authorized_keys file there. It was working fine while sending from machine A to B, I was not being prompted for the password. While doing some other experiments with this I accidently deleted authorized_keys files. Now again when I started the above procedure its not working.How to recover that? I am also interested to know is it possible to send files both way round withou (HowTos)