Rockman DASH: Great Adventure on 5 Islands & Rockman Tennis Preserved in Full

Hey Mega Man fans! This is RockmanCosmo, the leader of SciLab Secrets – the team working to preserve lost Rockman games released on Japanese feature phones. In December, we announced that we preserved eight lost Rockman games, including the entirety of Rockman EXE: Phantom of Network and Legend of Network. Today, I am happy to announce that we have preserved the entirety of Rockman DASH: Great Adventure on 5 Islands and Rockman Tennis. Read on for more details and how you can play them right now!

How and Where to Play The Games

The lone DoCoMo Java (DoJa) emulator available is embedded within DoCoMo's official DoJa 5.1 SDK. Collaborating with team member LNRC, I created a portable version of this emulator housing the Rockman games. You can download it here. Extract the file to a folder with no spaces or special characters. Follow the steps in the readme closely; all resources are included. 

Please note that the SDK's emulator isn't flawless—it encounters performance glitches with 3D games and audio stuttering when there's several objects on screen. In 5 Islands, this audio issue can be resolved by accessing the options menu through the maps menu to reset the audio. To play 5 Islands smoothly, I also recommend using an application like Joy2Key to play with a controller. In the meantime, team member XerTheSquirrel is developing SquirrelJME, an inclusive Java Micro Edition emulator to support DoJa apps. Once completed, these games will operate on a more stable framework.

The Decryption Process

Our copies of 5 Islands and Rockman Tennis originated from a Panasonic P-06C. Its owner moved the entirety of the game to a microSD card before moving out of Japan. When our team first obtained 5 Islands’ game files, they were encrypted with the C2 (Cryptomeria) cipher and CPRM. Our team had to crack this encryption, something that had never been done before. Broadly speaking, there are three items needed to crack the encryption: an s-box, a device key, and a bind ID. The universal s-box was found two years ago by team member usernameak. Last October, team member GoodTofuFriday employed a bruteforce method using a program by usernameak and XerTheSquirrel to derive a universal device key. 

Usernameak deduced that the bind ID could be derived from the SD card’s device unique key (separate from the device key). As such, the device unique key can be bruteforced, but usernameak’s tool was bruteforcing against 56 bits of known plaintext with a 56-bit key. Therefore, the device unique key’s bruteforcing process was more about ruling out potential keys than finding one. In addition, this key was not universal like the s-box and device key. After three days of bruteforcing and one false positive, team members XerTheSquirrel and GoodTofuFriday found a device unique key on December 30th! Using this key, we were able to decrypt Rockman Tennis and the fifth chapter of 5 Islands, becoming the first decrypted i-mode games on an SD card. 

But 5 Islands’ other four islands remained encrypted, leading us to a revelation! The device unique key was per SVC folder, meaning it is per application that owns the game files. The rest of 5 Islands' chapters were in a different SVC folder because they were additional data owned by the 5 Islands game itself. Initially, we believed that we had to do another bruteforcing effort. But on February 24th, usernameak made a groundbreaking discovery. The second device unique key was identical to the other key, save for the bottom 32 bits! Suddenly, the rest of 5 Islands had been decrypted, finally preserving it.

The Games

 

Released in 2007, Rockman Tennis is a tennis game starring the cast of the Classic series! There are seven playable characters, including an unlockable X! Each character has their own special move that can be performed when its meter is filled. For example, Mega Man unleashes a powerful charge shot… while Shadow Man clones the ball (isn’t that cheating?). There are also four cups with varying court types. With multiple skill upgrades from Auto’s shop, this game has more depth than some may imagine!

   

Rockman DASH: Great Adventure on 5 Islands was released episodically in 2008. Each island has seven missions, along with shops and NPCs. There are many hidden items in the ruins, allowing for Roll to craft and upgrade special weapons. Denise Marmalade from The Misadventures of Tron Bonne even makes an appearance on Ilks Island, serving as its police officer! With full 3D gameplay and charming cutscenes, 5 Islands makes few concessions for a Mega Man Legends phone game. Despite the controls getting a little wonky (partially due to the poor emulation), this game is a must-play for Legends fans!

Conclusion

The past three years have been an incredible journey for the SciLab Secrets team. We have gone from securing PoN and LoN in January 2021 to preserving them and six other lost Rockman games in February 2024. I would like to thank the entire SciLab Secrets team for their perseverance and assistance. Here’s a list of the team members who would like to be publicly listed. I would also like to thank the entire Mega Man community for their support, including donating to our team via two past fundraisers. The raised funds were used to purchase research equipment and test phones. We are still working to preserve the KDDI phone versions of PoN and LoN, including the KDDI-exclusive Battler’s Tower addon for PoN. So this will not be the last you hear from SciLab Secrets! I hope you look forward to our progress with those games. If you have any questions about the games, do not hesitate to reach out to me via Twitter or the resources linked on my website.