code: public static void convertFile(File keyFile, String passphrase,
  			String comment, int toFormat, File toFile) throws IOException,
  			InvalidPassphraseException {
  
  		SshPrivateKeyFile pub = parse(new FileInputStream(keyFile));
  
  		createFile(pub.toKeyPair(passphrase), passphrase, comment, toFormat,
  				toFile);
  	}
docs: Take a file in any of the supported public key formats and convert to the
  requested format.
  
  @param keyFile
  @param toFormat
  @param toFile
  @throws IOException
  @throws InvalidPassphraseException