The last challenge called "Ultimate" is a challenge composed by several sub-challenge. To validate this challenge, it's necessary to validate the sub-challenge in a specific way.
The goal of this challenge is to summarize all the different exploit approached during this project and using scenariow featuring these exploits.
The first sub challenge named "Gumpy" is a challenge using the underflow exploit.
A character named "Gumpy" want some water for that the user will have to provide him water. However he can't give him only 20 unit of water at the same time and he is limited to a certain amount of water in total.
The second sub challenge called "ItSDoneIn2Sec" is a challenge using a principle of this language, the gas.
The goal of this challenge is to find the good amount of gas to send during the transaction so that the remaining gas modulo 984 be equal to 0. If it's the case, so the challenge is validated, in the other case it's not.
The third challenge called "House" is a challenge using the exploit of reading the storages variables.
The goal of this challenge is to unlock the front door of the house, to do that we need to find the good amount of ethers to send et the password.
Le fourth challenge called "Subway" is a challenge using the re-entrancy exploit. To pass the security of the subway, a subway ticket is mandatory, to buy one you need to credit your client account. For each security passgae some of the price of the ticket is refund directly to the customer.
The goal of this challenge is to empty all of the ethers of the contract.
Once the four challenge are validated in a specific order that we can'n know, the main challenge is validated too.