I used Private key once with SFTP sites using Oracle's Java features (I used this in PLSQL developer), as shown below, and it worked fine.
conn = new Connection(SFTP_site_IP_Address);
File keyfile = new File(RSA_Path); // where it contains the RSA key
boolean tKeyAuthentication = true;
isAuthenticated = conn.authenticateWithPublicKey(inUser_ID, keyfile, null);
Now I need to connect to a different SFTP site, but they said I need not only a private key, but also a certificate (which was provided by them)
My question is, what function to call to initiate the SFTP connection using both RSA key and digital certificate?
I did my research on Google, couldn't find what I need,