During implementations of the SFTP listener, you may be prompted to accept a public key from a SFTP server. In this scenario, you must ensure that the private key file being specified for the SFTP listener is generated using OpenSSH key format. Otherwise, the SFTP listener will be unable to open the file. Usually, private key files that are generated for PuTTY interfaces have a .ppk file extension. You must convert the private key file to OpenSSH key format by using the PuTTY Key Generator tool, which can be downloaded from the following website:
Once you download the PuTTY Key Generator tool, perform the following steps.
To convert a private key to the OpenSSH key format using the PuTTY Key Generator tool:
The Save private key as dialog box opens, as shown in the following image.