All encryptions for the GameShark can be selected from the GameShark menu item in the Input or Output menu. The GameShark requires a bit of a history lesson explain some of the discrepancies in its versions.
The GameShark has undergone some rather severe shifts during its lifetime. It was formerly marketed by Interact in North America, and was a rebranded version of Datel's Action Replay software. Around 2002 or 2003, Interact went bankrupt, and the trademark was sold to MadCatz. At that time, Datel decided to market the Action Replay in North America without the rebranding, and MadCatz partnered with Fire LTD. to produce the new GameShark, which is rebranded Xploder software. To make things more confusing, the Xploder used to be rebranded as CodeBreaker in North America. Fire apparently ended their partnership there, as the GameShark brand seemed more lucrative. This has led to a great deal of overlap between several devices. It confuses many consumers terribly. Especially since older devices developed under dissolved partnerships are no longer supported by anyone, despite the fact that the products and most of the companies still exist in some form.
Because of these rather opaque business dealings, there are four fairly distinct versions of the GameShark, and one huge shift after version 2, when the device's developer changed. That is why the GameShark submenus contain an extra level of identification, though the extra depth mostly serves to assist people who probably will not have bothered to read the help.
All versions of the GameShark, except Interact Version 1 support unencrypted codes. It is not necessary for you to encrypt codes for use with it. Interact Version 2 does require a special key code to process unencrypted codes, which is described in its section.
The GameShark submenu
The Interact submenu
The GameShark Version 1 is a rebranded version of Datel's Action Replay Version 1. You can work with it by following the same instructions. Choosing the GameShark -> Interact -> Version 1 option has the same effect as choosing Action Replay -> Version 1.
HUGE NOTE: For some silly reason, the latest versions of MadCatz's software are also referred to as GameShark 1.x. I believe the latest such version is 1.3. You need to check the manufacturer's name on your software before deciding to follow this link. The MadCatz 1.x versions are also usally named "GameShark 2 CheatCodes".
The GameShark Version 2 is a rebranded version of Datel's Action Replay Version 2. You can work with it by following the same instructions. Choosing the GameShark -> Interact -> Version 2 option has the same effect as choosing Action Replay -> Version 2.
The note above for Version 1 may some day apply to Version 2, if MadCatz does any more releases.
The MadCatz submenu
GameShark Version 3+
The time has come for confusion. The GameShark Version 3 is the first version distributed MadCatz. It is simply a rebranded version of Fire's Xploder software. There is a slight discrepancy in the version, as the GameShark 3 was actually the first software released using this particular revision of Fire's device. GameShark Version 3 roughly equates to Xploder Version 4, and GameShark Version 4 is more or less identical to Xploder Version 4. With the release of Version 5 of both devices, the version numbers were mostly in sync. However, what should have been GameShark Version 6 was called GameShark2 CheatCodes Version 1.0 (the latests is version 1.3), and Xploder has yet to advance beyond Version 5. Just check your manufacturer if that is confusing to you. If your GameShark is distributed by MadCatz, or made by Fire/Blaze, then you have a version 3+.
If you have any GameShark version 3, 4, 5, or any GameShark2 CheatCodes version, you can encrypt codes for it using the instructions for Xploder 4+. Choosing the GameShark -> MadCatz -> Version 3 - 4 option has the same effect as choosing Xploder -> Version 4.
Encrypting for Xploder Version 4+
GameShark Version 5+ (Includes GameShark2 CheatCodes Version 1.x and Up)
The encryption for this device is the same as for the Version 3. There is one minor difference in the codes however. With this version, a verifier line was introduced that contains a CRC (checksum) of the entire code. On all the versions I have tested, this verifier is optional. If for some reason you need or want to create it, you can select the appropriate menu item for it. The verifier lines begin with 76 and are created automatically. Choosing the GameShark -> MadCatz -> Version 5+ option has the same effect as choosing Xploder -> Version 5+.
If you need further instructions, see the section for Xploder Version 5.