I have not opened up my Minecraft launcher for nearly a year. However, when I updated to Minecraft 1.6.2 and the new launcher recently, every server I attempt to connect to seems to have some kind of problem, leaving me with this every time I try to connect to any server:

Screenshot of the disconnection screen. It reads "Disconnected by Server: BadPaddingException : Blocktype mismatch: 0 @ sun.security.rsa.RSAPadding:328".

I have checked and double checked every server and they are definitely up to date and my internet connection is working. I also guarantee you that my launcher is the official Minecraft launcher and I am playing online with a premium account.

Why is this issue cropping up? What does the text mean and how can I fix this?

  • 6
    That exception has to do with a failed exchange of encryption keys. Are these "offline" servers, or are you maybe using an unofficial launcher? Sep 10, 2013 at 2:49
  • 4
    I am using the official Minecraft launcher from mojang. As for if these servers are offline, I suspected this too but I tried about 10 large servers I do not think that they would all be offline at the same time
    – David Toh
    Sep 10, 2013 at 7:02
  • 1
    "Offline" servers are also called cracked servers in Minecraft. They allow people to join without signing into Mojang's central servers with an authorized and paid-for account.
    – oKtosiTe
    Sep 10, 2013 at 9:08
  • 2
    By "the official Minecraft launcher from mojang", do you mean the same one from pre-1.6 versions? Because the old launcher was replaced by a new one within the last six months or so. Sep 10, 2013 at 10:50
  • 1
    @BillyMailman This is the new launcher; you can't play 1.6.2 in the old launcher.
    – Unionhawk
    Sep 10, 2013 at 18:20

3 Answers 3


I've googled BadPaddingException and this is what it means: the wrong key was used to decrypt the data. It is an error for Minecraft to fix, so what you should do is report a bug to Mojang and they should fix it in later updates.


Try one of these things. if minecraft doesnt work after doing these things you might have a modded client or some kind of virus.

  1. Check all minecraft files with anti-virus if anyone of them has a virus delete it then run minecraft

  2. Delete all minecraft files than redownload it from the official website

  3. If theres any type of internet proxy or restriction then remove it

  4. Try playing it at home and not work / school / public library there might be a restriction at those places

  5. Try it on another computer


Delete the Minecraft files by going to the Start Menu then Run, and type %appdata% and then delete the .minecraft folder. Then start the launcher, log in, and it will update all your files.

Be careful! This will delete your worlds, so back them up first! Back them up by copying the saves folder inside .minecraft to your Desktop before deleting anything. After that, delete the .minecraft folder. Once the files are updated, go to AppData, double click .minecraft, delete the saves folder, then copy your backup of the saves folder from your Desktop to the .minecraft folder.

  • 4
    How does this resolve the issue? It sounds more like it just forces a reinstall. That might fix it, but there's no real explanation of what's going on.
    – Frank
    Sep 13, 2013 at 18:53
  • 6
    There is no need to Capitalise Every Word or use ALL CAPS FOR EMPHASIS. I've done an edit to make this more readable. Sep 13, 2013 at 18:55

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .