Intro

I wanted to make some sort of companion tool/app for the original Nintendo Wii and whilst trying to come up with an app idea, I came across the Wii Parental Control Reset Tool that was created by Hector Martin back in 2008: https://marcan.github.io/wii-parental-reset-tool/ and decided to try and make a desktop app version of it.

Parental Controls on the Nintendo Wii were used to set a ‘Highest Game Rating Allowed’ setting where you could choose an ESRB rating of games you would like to be accessed by the console i.e. “Everyone 10+” rating could be set as the highest game rating allowed, preventing you from playing “Mature” 17+ games on the console such as Resident Evil 4. You could also restrict other settings such as purchasing, messaging, internet access, news etc.

These controls are protected by a 4 digit PIN and security question. If you cannot remember the PIN and don’t know the answer to the security question, the Wii will display an 8 digit confirmation number for you. You could provide this to Nintendo support back in the day but I’m not sure if they will still support you nowadays given the Wii’s age.

If you ever buy a Nintendo Wii secondhand with parental controls, the only way of unlocking it is by using Hector Martin’s tool which he made after reverse engineering this whole process and made the source code publicly available.

Note – for the correct master key to be generated, the date must be correct on the Nintendo Wii.

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App

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How it works

I’ve made this app in Xojo so it’s cross platform (runs on macOS & Windows) and it will work offline (as the process doesn’t require internet access) Also, it doesn’t use any external libraries & doesn’t ask you for the date as that is done in the background.

From what I understand based off Hector Martin’s source code, below is how the master key is generated based off the confirmation number you get from the Wii:

Data	Example	Values Used
8 digit confirmation number	12345678	Last 4 digits: 5678
Today’s Date	April 20th	Written as 4 digits: 0420

The 8 digit string then becomes 0420 + 5678 = 04205678

Step 1 (CRC32)

The CRC32 algorithm takes each number’s ASCII code one by one and mixes it using a fixed set of rules starting with this number: 4,294,967,295 (as it’s the highest number in 32 binary digits)

04205678 > CRC32 outputs: -189,176,431

Step 2 (XOR)

This step has 2 parts, the negative number is converted into a positive number by a simple subtraction step (using the highest number in 32 binary digits again, we minus the negative number from that):

• 4,294,967,296 − 189,176,431 = 4,105,790,865

The next step is using XOR, which is used to compare 2 numbers in binary. You XOR the number against 43690 which is a fixed number Nintendo hard-coded into the Wii)

• 4,105,790,865 XOR 43690 = 4,105,817,915

Step 3 (Adding)

You simply add 5313 in this step. Again, it’s a fixed number Nintendo hard-coded into the Wii:

• 4,105,817,915 + 5313 = 4,105,823,228

Step 4 (Modulo)

The last step is to chop the number down to 5 digits using Modulo. This means, you divide it by 100,000 and then use the remainder:

• 4,105,823,228 ÷ 100,000 = 41,058

The remainder is: 23228 – that is the master key

As mentioned at the top of the post, it is important that the date is correct on the Wii before running this tool.