I run

sftp -i privatekeyfile sftp_user@MY_ENDPOINT

and am asked for the password for my endpoint

sftp_user@MY_ENDPOINT's password: 

What password am I supposed to supply here ?

Others have mentioned using my ssh password b

I run

sftp -i privatekeyfile sftp_user@MY_ENDPOINT

and am asked for the password for my endpoint

sftp_user@MY_ENDPOINT's password: 

What password am I supposed to supply here ?

Others have mentioned using my ssh password but I am denied access with ""

I generated my key file with ssh-keygen -P "" keyname

For context, I want to setup an ftp server with access to S3 in order to share data with external customers.