workaround to fix #420, based on https://stackoverflow.com/questions/28411153/jsch-suppressed-java-lang-classnotfoundexception-lorg-ietf-jgss-oid/28965796#28965796 and https://github.com/zeapo/Android-Password-Store/issues/49

src/java/JavaFileStorage/app/src/main/java/keepass2android/javafilestorage/SftpStorage.java

@@ -322,6 +322,9 @@ public class SftpStorage extends JavaFileStorageBase {
 		UserInfo ui = new SftpUserInfo(ci.password);
 		session.setUserInfo(ui);
 
+		session.setConfig("PreferredAuthentications",
+				"password,publickey");
+
 		session.connect();
 
 		Channel channel = session.openChannel("sftp");