Knife bootstrapping is not working in say ssh authentication fails

command which i use :- knife bootstrap --ssh-user ec2-user --sudo -i node.pem -N node1

error :-

Are you sure you want to continue connecting
? (Y/N) Y
WARN: [SSH] PTY requested: stderr will be merged into stdout
WARN: [SSH] connection failed, terminating (#<Net::SSH::AuthenticationFailed: Authentication failed for user x.x.x.x
ERROR: Train::Transports::SSHFailed: SSH session could not be established

please help i am new to chef