Please read FAQ:
https://winscp.net/eng/docs/faq_passphrase

If that does not help, come back.

To be more specific, i am listing the command used in automation process

Script used for authenticate
open username@ipaddress:portno -privatekey=mykey.ppk

Authentication is requested after this command, but is there any way that the passphrase of the private key can be provided in the same command. Or is there any other work around?

Hi,

How could i give the pass phrase in automatic mode while authenticating through private key.

Thanks in advance.