Introduction

Protocol Obfuscation is a feature which causes eMule to obfuscate or "hide" its protocol when communicating with other clients or servers. Without obfuscation, each eMule communication has a given structure which can be easily recognized and identified as an eMule packet by any observer. If this feature is turned on, the whole eMule communication appears like random data on the first look and an automatic identification is no longer easily possible. This helps against situations were the eMule Protocol is unjustly discriminated or even completely blocked from a network by identifying its packets.
It is however important to note what Obfuscation is not intended to do: It will not increase your anonymity, it will not make you "invisible" in any way and it will also not protect you effective against eavesdroppers. Also if your network admin has a good legal reason to block eMule (for example a restricted company network), bypassing it may cause you other unwanted consequences.
Obfuscation is currently available for ED2k TCP and UDP, Server TCP and UDP and Kad TCP communication. Kad UDP packets are not yet obfuscatable.

Settings

By default, each eMule client (>= 0.47b) supports obfuscated connections to other clients, but doesn't actively requests them. If your ISP is not discriminating the ED2K Protocol you do not need to change anything and still help other users which may need obfuscation. Otherwise your have the following options which can be found in the Security Options page:

Enable Protocol Obfuscation:

If you think that eMule is throttled on your network, you should enable this function. Whenever possible eMule will use obfuscated connections and will ask other clients to do the same when connecting to your client. When connecting to a server, eMule will try to establish an obfuscated connection first and only if this fails choose a normal one. There are in general no disadvantages by using this option, except insignificant higher CPU usage and very few bytes more overhead, so you can't really do anything wrong by enabling this setting.

Allow obfuscated connections only:

If you enable this option, eMule will only establish and accept obfuscated connections. Clients which do not support obfuscations are ignored, incoming plaintext connections rejected and the automatic server connect will only allow obfuscated connections to a server. You should only choose this setting if you know that the ED2K Protocol is completely blocked on your network, otherwise you will loose sources and therefore slow down your eMule. However if you know that eMule is blocked, then enabling this option is recommended, because it saves connection tries which are guaranteed to fail and therefore would waste time, overhead and resources.

Disable support for obfuscated connections:

If for some reason you want to disable the whole obfuscation feature completely you can choose this option. In general for most users there is no reason nor advantage in doing this.

Graphic Interface

Protocol Obfuscation is pretty transparent for the user, so you most likely won't see much of it. There are some indicators added however so you know what your eMule is doing:

You can see if another client supports obfuscation by opening the Client Details dialog and check the Obfuscation line. "Supported" means that this client supports obfuscation, but it won't be used (for example because you both choosed not to in your settings), while "Enabled" means that the other client supports it and it will be used when connecting to (or from) him.

Sometimes you will see a key symbol on the icon of a client as shown above. This means that there exists an obfuscated connection to this client at the moment. If there is no key, this doesn't mean he doesn't support obfuscation - he might be just not connected to you at this time.

When you are connected to a server, the MyInfo box informs you, if you use an obfuscated connection or not.