I believe this has been mentioned before in a similar thread, but you'll need to have the private key file in
OpenSSH format. You can use a program named 'PuttyGen' to load the private key file, then "Export"
that to a new file in OpenSSH format. Once you do that, use the newly exported file as you're key file
parameter and see how things go.
The key was generated from WInscp Putty Key Generater, if you see the header in the post
there are 3 different kind of key that Winscp Generate
I am afraid that CF8 only support certain key type from OpenSSH and they are not the same as WinSCP's Putty Key?
and SSH-2 DSA
this the the key in the header in the ppk file
Very true, but in the version of PuttyGen that I use (release 0.60), there is a menu option called [Conversions], and under that is an option [Export OpenSSH key]. Load your private key file, then select that option and try the resulting file with your CFFTP call. I actually did this earlier this week and it works just fine with CF8. You can not use the file you would normally save with PuttyGen, you must use the one you "export".
p.s. Just to be clear, I generated a new key pair as "SSH-2 RSA", then exported it as an OpenSSH key file. After installing the public key portion on the SFTP server, I used the exported (not the saved) private key file in the CFFTP tag, and all is working correctly. If you try and use the saved SSH-2 RSA file, you'll get the "invaid privatekey" error.